The influence of alloying and fabrication techniques on the mechanical properties, biodegradability and biocompatibility of zinc: A comprehensive review

Optimal submicron roughness for balancing degradation behavior, immune modulation, and microbial adhesion on zinc-based barrier membranes

Metallic zinc (Zn) has been demonstrated to be a promising alternative to barrier membrane materials for guided bone regeneration. Surface roughness significantly affects the properties of degradable Zn-based metals, especially within the Janus micro-environments of tissue regeneration. However, the effects of optimal surface roughness on Zn remain unknown. In this study, pure Zn surfaces were fabricated with three roughness scales: nano (Sa < 0.1 μm), submicron (Sa: 0.5-1.0 μm), and micron (Sa > 1.0 μm). Submicron-scale pure Zn exhibited a moderate degradation rate in simulated body fluids, and no deep corrosion pits appeared on the surface. By contrast, the degradation rate of nano-surface pure Zn decreased significantly, while localized corrosion tended to appear on micron surfaces. In addition, the degradation rate of Zn with different roughness was overall accelerated in artificial saliva, accompanied by varying degradation morphologies. Co-culturing with submicron samples inhibited macrophage polarization to the M1 phenotype. Nano-scale surfaces promoted macrophage polarization towards the M1 phenotype and exhibited significantly reduced antibacterial rates compared to rougher surfaces. These findings demonstrate that submicron-scale pure Zn could be an optimal choice for barrier membrane surfaces.

Biodegradability, biocompatibility, and mechanical behavior of additively manufactured zinc scaffolds

Zinc is a promising material for biodegradable scaffolds due to its biocompatible nature and suitable degradation rate. However, its low mechanical strength limits its use in load-bearing applications. This study aims to address this challenge by optimizing the process parameters of pure zinc using laser-based powder bed fusion and designing zinc scaffolds with tailored structures. Scaffolds based on five different unit cell types (Diamond, gyroid, primitive, Fischer-Kock S, and I-WP) were designed and fabricated using the optimized process parameters. The resulting scaffolds were evaluated for mechanical properties, degradation behavior, and cytocompatibility evaluation. Results show that I-WP and primitive scaffolds exhibited superior mechanical properties with compressive yield strength of 36.1 ± 1.2 MPa and 33.5 ± 1.4 MPa, respectively. While all scaffolds displayed a degradation rate within the range of 0.14-0.15 mm/year, the I-WP and primitive design exhibited a slightly higher degradation rate (0.15 mm/year) compared to the gyroid, diamond, and Fischer Koch S scaffolds (0.14 mm/year). Zinc itself demonstrated excellent cytocompatibility, as evidenced by in vitro MTT assay and cell morphology studies. Unit cell morphology also could accelerate proliferation, where MG-63 cells formed bridges between the unit cell walls in Fischer Koch S scaffolds. Considering the targeted application (mandible or jawbone healing) and evaluating all findings, scaffolds with I-WP and primitive designs and wall thicknesses of 500 μm (S01) emerged as the most promising candidates in mandible healing injuries.

380 MPa-30% grade biodegradable Zn-Mn-Mg-Ca alloy: Bimodal grain structure, large work-hardening strain, and enhanced biocompatibility

Strain softening is a common issue for high-strength biodegradable Zn alloys. We developed Zn-0.6Mn-0.05Mg-0.05Ca alloy with a bimodal grain structure by extrusion and caliber rolling, refer to as ZMMC063 (CRD). The alloy exhibits the best strength-ductility synergy among Zn-Mn based alloys, which shows a yield strength of 386 MPa, an ultimate tensile strength of 443 MPa, and an elongation rate of 31%. This is the first 380 MPa-30% grade Zn-Mn based alloy, surpassing the previous reported Zn alloy with 320 MPa-20% grade. Its work-hardening strain reaches as high as 11.6%, which is 4 times greater than that of other 300 MPa Zn-Mn based alloys. This is owing to hetero-deformation induced strengthening effect of the bimodal grain. Additionally, it demonstrates for the first time that micro-galvanic corrosion happens between coarse and fine Zn grains, thereby accelerating degradation of the alloy. This provides a feasible protocol for controlling degradation of Zn alloys. Compared with the extruded Zn-0.6Mn-0.05Mg-0.05Ca alloy, refer to as ZMMC063 (HE), the increased release of Mg2+ and Ca2+ ions in ZMMC063 (CRD) improves tolerance of MC3T3-E1 cells to Zn2+. Consequently, ZMMC063 (CRD) shows higher antibacterial abilities against E. coli and S. aureus, meanwhile much less toxicity to MC3T3-E1 cells. Synergistic effect of Zn2+, Mg2+ and Ca2+ ions promote expression of ALP, COl-1, OCN and Runx-2, so that ZMMC063 (CRD) exhibits better ability to induce osteogenic differentiation. This paper suggests that ZMMC063 (CRD) is a promising candidate for orthopedic implants. STATEMENT OF SIGNIFICANCE: Previously the highest yield strength-elongation level of Zn-Mn based alloys is 320 MPa-20% grade. At such a high strength, the alloys' work-hardening strain (Ewh) values are below 4%. To further improve comprehensive properties of Zn-Mn based alloys, 380 MPa-30% grade Zn-0.6Mn-0.05Mg-0.05Ca alloy with bimodal grain structure is developed by extrusion and caliber rolling. The alloy's Ewh reaches as high as 11.6%, due to the hetero-deformation induced effect of bimodal grain structure. Additionally, micro-galvanic corrosion happens between bimodal grains, which accelerates the alloy's degradation. In vitro studies show that the alloy exhibits enhanced antibacterial activity, good cytocompatibility, and promising osteogenic effect, indicating that it is a promising candidate for orthopedic implants.

Machine Learning Prediction of the Corrosion Rate of Zinc-Based Alloys Containing Copper, Lithium, Magnesium, and Silver

Implementation of machine learning (ML) techniques in materials science often requires large data sets. However, a proper choice of features and regression methods allows the construction of accurate ML models able to work with a relatively small data set. In this work, an extensive, although still limited, experimental data set of corrosion-related properties of Zn-based alloys used in biomedicine was created. On the basis of this data set, a robust and accurate model was built to predict the corrosion behavior of Zn-based alloys. This work highlights the effectiveness of ML methods for assessing the corrosion behavior of Zn-based alloys, which can facilitate their application in bioimplants.

Incorporation of cerium oxide nanoparticles into the micro-arc oxidation layer promotes bone formation and achieves structural integrity in magnesium orthopedic implants

Biodegradable metals offer significant advantages by reducing the need for additional surgeries following bone fixation. These materials, with their optimal mechanical and degradable properties, also mitigate stress-shielding effects while promoting biological processes essential for healing. This study investigated the in vitro and in vivo biocompatibility of ZK60 magnesium alloy coated with a micro-arc oxidative layer incorporated with cerium oxide nanoparticles in orthopedic implants. The results demonstrated that the magnesium substrate undergoes gradual degradation, effectively eliminating long-term inflammation during bone formation. The micro-arc oxidative coating forms a dense ceramic layer, acting as a protective barrier that reduces corrosion rates and enhances the biocompatibility of the magnesium substrate. The incorporation of cerium oxide nanoparticles improves the tribological properties of the coating, refining degradation patterns and improving osteogenic characteristics. Furthermore, cerium oxide nanoparticles enhance bone reconstruction by facilitating appropriate interconnections between newly formed bone and native bone tissue. Consequently, cerium oxide nanoparticles contribute to favorable biosafety outcomes and exceptional bone remodeling capabilities by supporting bone healing and sustaining a prolonged degradation process, ultimately achieving dynamic equilibrium in bone formation. STATEMENT OF SIGNIFICANCE: This study comprehensively examined the incorporation of cerium oxide nanoparticles into biodegradable magnesium through a micro-arc oxidative process for use in orthopedic implants. This study conducted a comprehensive analysis involving material characterization, biodegradability testing, in vitro osteogenesis assays, and in vivo implantation, highlighting the potential benefits of the distinctive properties of cerium oxide nanoparticles. This research emphasizes the ability of cerium oxide nanoparticles to enhance the biodegradability of magnesium and facilitate remarkable bone regeneration, suggesting promising advantages for additive materials in orthopedic implants.

Next-Generation Approaches for Biomedical Materials Evaluation: Microfluidics and Organ-on-a-Chip Technologies

Biological evaluation of biomedical materials faces constraints imposed by the limitations of traditional in vitro and animal experiments. Currently, miniaturized and biomimetic microfluidic technologies and organ-on-chip systems have garnered widespread attention in the field of drug development. However, their exploration in the context of biomedical material evaluation and medical device development remains relatively limited. In this review, a summary of existing biological evaluation methods, highlighting their respective advantages and drawbacks is provided. The application of microfluidic technologies in the evaluation of biomedical materials, emphasizing the potential of organ-on-chip systems as highly biomimetic in vitro models in material evaluation is then focused. Finally, the challenges and opportunities associated with utilizing organ-on-chip systems to evaluate biomedical materials in the field of material evaluation are discussed. In conclusion, the integration of advanced microfluidic technologies and organ-on-chip systems presents a potential paradigm shift in the biological assessment of biomedical materials, offering the prospective of more accurate and predictive in vitro models in the development of medical devices.

Insights into heat treatments of biodegradable Mg-Y-Nd-Zr alloys in clinical settings: Unveiling roles of β' and β1 nanophases and latent in vivo hydrogen evolution

Heat treatment serves as a viable strategy to effectively mitigate the intense corrosion of biodegradable WE43 alloys. However, limited comprehension of the passivation mechanisms underlying heat treatment and the dilemma to quantitatively examine the evolution of hydrogen gas in vivo introduce uncertainties in designing heat treatments for developing clinically applicable WE43. This work aims to advance this knowledge by applying cutting-edge atom probe tomography to provide atomic-scale insights into the passivation roles of rare earth (RE)-rich β1 (Mg3(Y, Nd)) and β' (Mg12NdY) nanophases induced by T6 heat treatment at 250 °C, and employing machine learning-based image analysis techniques to quantitatively unveil WE43's in vivo gas evolution during a 12-week implantation. It was found that nanosized β1 and β' phases can effectively improve WE43's corrosion resistance by inducing an accelerated passivation effect on the surface and confining the distribution of hydrogen ions in the matrix. Female rats presented slightly higher corrosion rates than male rats in weeks 1 and 4 but lower hydrogen gas volumes in vivo, while male rats possessed a superior ability to metabolise hydrogen gas in vivo. Notably, latent gas evolution against the corrosion rates was found which peaked at week 4 and subsided at week 12 despite the gradually decreased corrosion rates from week 1 to 12. This study offers insights for engineering heat treatments to develop clinically applicable WE43 with acceptable corrosion rates and in vivo gas generation at various implantation stages. STATEMENT OF SIGNIFICANCE: The study aimed to reveal the role of β1 and β' nanophases on the good corrosion resistance of WE43. The influence of these nanophases on WE43's corrosion performance has not been totally understood. Similarly, the understanding of hydrogen gas evolution as it relates to the magnesium implant's corrosion rate lacks clarity. Atom probe tomography (APT) indicates β1 and β' nanophases trap hydrogen, removing H2 from the lattice and disabling its catalytic role in Mg oxidation. Machine learning-aided analyses of computed tomography (CT) scan images indicate latent gas evolution, contradicting the monotonic in vivo H2 evolution that is widely accepted.

Fabrication and performance of Zinc-based biodegradable metals: From conventional processes to laser powder bed fusion

Zinc (Zn)-based biodegradable metals (BMs) fabricated through conventional manufacturing methods exhibit adequate mechanical strength, moderate degradation behavior, acceptable biocompatibility, and bioactive functions. Consequently, they are recognized as a new generation of bioactive metals and show promise in several applications. However, conventional manufacturing processes face formidable limitations for the fabrication of customized implants, such as porous scaffolds for tissue engineering, which are future direction towards precise medicine. As a metal additive manufacturing technology, laser powder bed fusion (L-PBF) has the advantages of design freedom and formation precision by using fine powder particles to reliably fabricate metallic implants with customized structures according to patient-specific needs. The combination of Zn-based BMs and L-PBF has become a prominent research focus in the fields of biomaterials as well as biofabrication. Substantial progresses have been made in this interdisciplinary field recently. This work reviewed the current research status of Zn-based BMs manufactured by L-PBF, covering critical issues including powder particles, structure design, processing optimization, chemical compositions, surface modification, microstructure, mechanical properties, degradation behaviors, biocompatibility, and bioactive functions, and meanwhile clarified the influence mechanism of powder particle composition, structure design, and surface modification on the biodegradable performance of L-PBF Zn-based BM implants. Eventually, it was closed with the future perspectives of L-PBF of Zn-based BMs, putting forward based on state-of-the-art development and practical clinical needs.

Study on the Bioactivity Response of the Newly Developed Zn-Cu-Mn/Mg Alloys for Biodegradable Implant Application

Scaffolds play a crucial role in bone tissue engineering to support the defect area through bone regeneration and defect reconstruction. Promising tissue regeneration without negative repercussions and avoidance of the lifelong presence inside the body make bioresorbable metals prosper in the field of regenerative medicine. Recently, Zn and its alloys have emerged as promising biodegradable materials for their moderate degradation rate and satisfactory biocompatibility. Nevertheless, it is very challenging for cells to adhere and grow over the Zn surface alone, which influences the tissue-implant integration. In this study, an attempt has been made to systematically investigate the bioactivity responses in terms of in vitro hemocompatibility, cytotoxicity, antibacterial activity, and in vivo biocompatibility of newly developed Zn-2Cu-0.5Mn/Mg alloy scaffolds with different surface roughness. The rough surface of Zn-2Cu-0.5Mg shows the highest degradation rate of 0.16 mm/yr. The rough surface exhibits a prominent role in the adsorption of protein, further enhancing cell adhesion. Concentration-dependent alloy extract shows the highest cell proliferation for 12.5% of the extract with a maximum cell viability of 101% in Zn-2Cu-0.5Mn and 108% in Zn-2Cu-0.5Mg after 3 d. Acceptable hemolysis percentages (less than 5%) with promising anticoagulation properties are observed for all of the conditions. Enhanced antibacterial (Staphylococcus aureus and Escherichia coli) activity due to a significant effect of ions illustrates the maximum killing effect on the bacterial colony for the rough Zn-2Cu-0.5Mg alloy. In addition, it is observed that for rough Zn-2Cu-0.5Mn/Mg alloys, the inflammatory response is minimal after subcutaneous implantation, and neo-bone tissue forms in the defect areas of the rat femur with satisfactory biosafety response. The osseointegration property of the Zn-2Cu-0.5Mg alloy is comparable to that of the Zn-2Cu-0.5Mn alloy. Therefore, the rough surface of the Zn-2Cu-0.5Mg alloy has the potential to enhance biocompatibility and promote better osseointegration activity with host tissues for various biomedical applications.

The effect of Silver addition and deformation parameters on mechanostructure, biodegradation, antimicrobial and mechanical properties of Zn-based biodegradable alloys

Although low mechanical properties, Zinc (Zn) alloy systems with Copper (Cu) and Silver (Ag) as alloying elements have strong biocompatibility and biodegradability characteristics. This study examined the effects of rolling parameters and Ag alloying on the mechanical, biodegradable, and final structure of an alloy based on Zn. Comparing treated and untreated specimens, the addition of Ag led to a considerable improvement in both hardness and compressive strength. The produced alloys with varying amounts of Ag (between 1 and 4 wt%) were cold rolled at 400-800 r/min and friction coefficients between 0.3 and 0.5. The alloys' ultimate strength rose with an increase in rolling speed for Zn1Cu4Ag, and hardness and compressive strengths rose to 80HV and 470 MPa, respectively. It was demonstrated that rolling force rose somewhat with Ag concentration but significantly increased with rolling speed and friction. E. Coli and S. aureus were used to assess the biodegradable alloys' antibacterial properties. For the Zn-1Cu-2Ag alloy, the inclusion of Ag resulted in a considerable (50%) rise in antibacterial activity that exceeded the effects seen in other alloy systems.

Preparation, Mechanical Properties, and Degradation Behavior of Zn-1Fe-xSr Alloys for Biomedical Applications

As biodegradable materials, zinc (Zn) and zinc-based alloys have attracted wide attention owing to their great potential in biomedical applications. However, the poor strength of pure Zn and binary Zn alloys limits their wide application. In this work, a stir casting method was used to prepare the Zn-1Fe-xSr (x = 0.5, 1, 1.5, 2 wt.%) ternary alloys, and the phase composition, microstructure, tensile properties, hardness, and degradation behavior were studied. The results indicated that the SrZn13 phase was generated in the Zn matrix when the Sr element was added, and the grain size of Zn-1Fe-xSr alloy decreased with the increase in Sr content. The ultimate tensile strength (UTS) and Brinell hardness increased with the increase in Sr content. The UTS and hardness of Zn-1Fe-2Sr alloy were 141.65 MPa and 87.69 HBW, which were 55.7% and 58.4% higher than those of Zn-1Fe alloy, respectively. As the Sr content increased, the corrosion current density of Zn-1Fe-xSr alloy increased, and the charge transfer resistance decreased significantly. Zn-1Fe-2Sr alloy had a degradation rate of 0.157 mg·cm-2·d-1, which was 118.1% higher than the degradation rate of Zn-1Fe alloy. Moreover, the degradation rate of Zn-1Fe-xSr alloy decreased significantly with the increase in immersion time.

Nanoparticle-Enabled Zn-0.1Mg Alloy with Long-Term Stability, Refined Degradation, and Favorable Biocompatibility for Biodegradable Implant Devices

Zinc-based alloys, specifically Zn-Mg, have garnered considerable attention as promising materials for biodegradable implants due to their favorable mechanical strength, appropriate corrosion rate, and biocompatibility. Nevertheless, the alloy's lack of mechanical stability and integrity, resulting from ductility loss induced by age hardening at room temperature, hampers its practical bioapplication. In this study, ceramic nanoparticles have been successfully incorporated into the Zn-Mg alloy system, leading to a significant improvement in long-term stability as well as mechanical strength and ductility. In addition, this study represents the first investigation of Zn-based nanocomposites both in vitro and in vivo to comprehend the influence of nanoparticles on the degradation behavior and biocompatibility of the Zn system. The findings indicate that the incorporation of WC nanoparticles effectively refines and stabilizes the degradation behavior of Zn-Mg without negatively impacting the cytocompatibility of the alloy. The subcutaneous implantation and femoral implantation further prove the benefits of nanoparticle incorporation and found no negative effects. Collectively, Zn-Mg-WC nanocomposites yield great potential for implant usage.

A Critical Review of Biodegradable Zinc Alloys toward Clinical Applications

Biodegradable zinc (Zn) alloys stand out as promising contenders for biomedical applications due to their favorable mechanical properties and appropriate degradation rates, offering the potential to mitigate the risks and expenses associated with secondary surgeries. While current research predominantly centers on the in vitro examination of Zn alloys, notable disparities often emerge between in vivo and in vitro findings. Consequently, conducting in vivo investigations on Zn alloys holds paramount significance in advancing their clinical application. Different element compositions and processing methods decide the mechanical properties and biological performance of Zn alloys, thus affecting their suitability for specific medical applications. This paper presents a comprehensive overview of recent strides in the development of biodegradable Zn alloys, with a focus on key aspects such as mechanical properties, toxicity, animal experiments, biological properties, and molecular mechanisms. By summarizing these advancements, the paper aims to broaden the scope of research directions and enhance the understanding of the clinical applications of biodegradable Zn alloys.

Mechanical properties, corrosion behavior, and in vitro and in vivo biocompatibility of hot-extruded Zn-5RE (RE = Y, Ho, and Er) alloys for biodegradable bone-fixation applications

Biodegradable Zn alloys have significant application potential for hard-tissue implantation devices owing to their suitable degradation behavior and favorable biocompatibility. Nonetheless, pure Zn and its alloys in the as-cast state are mechanically instable and low in strength, which restricts their clinical applicability. Here, we report the exceptional mechanical, corrosion, and biocompatibility properties of hot-extruded Zn-5RE (wt.%, RE = rare earth of Y; or Ho; or Er) alloys intended for use in biodegradable bone substitutes. The microstructural characteristics, mechanical behavior, corrosion resistance, cytocompatibility, osteogenic differentiation, and capacity of osteogenesis in vivo of the Zn-5RE alloys are comparatively investigated. The Zn-5Y alloy demonstrates the best tensile properties, encompassing a 138 MPa tensile yield strength, a 302 MPa ultimate tensile strength, and 63% elongation, while the Zn-5Ho alloy shows the highest compression yield strength of 260 MPa and Vickers hardness of 104 HV. The Zn-5Er alloy shows a 126 MPa tensile yield strength, a 279 MPa ultimate tensile strength, 52% elongation, a 196 MPa compression yield strength, and a 101 HV Vickers microhardness. Further, the Zn-5Er alloy has a 130 µm per year corrosion rate in electrochemical tests and a 26 µm per year degradation rate in immersion tests, which is the lowest among the tested alloys. It also has the best in vitro osteogenic differentiation ability and capacity for osteogenesis and osteointegration in vivo after implantation in rat femurs among the Zn-5RE alloys, indicating promising potential in load-bearing biodegradable internal bone-fixation applications. STATEMENT OF SIGNIFICANCE: This work reports the exceptional mechanical, corrosion, and biocompatibility properties of hot-extruded (HE) Zn-5 wt.%-rare earth (Zn-5RE) alloys using single yttrium (Y), holmium (Ho), and erbium (Er) alloying for biodegradable bone-implant applications. Our findings demonstrate that the HE Zn-5Er alloy showed σuts of 279 MPa, tensile yield strength of 126 MPa, elongation of 51.6%, compression yield strength of 196 MPa, and microhardness of 101.2 HV. Further, HE Zn-5Er showed the lowest electrochemical corrosion rate of 130 µm/y and lowest degradation rate of 26 µm/y, and the highest in vitro osteogenic differentiation ability, in vivo osteogenesis, and osteointegration ability after implantation in rat femurs among the Zn-5RE alloys, indicating promising potential in load-bearing biodegradable internal bone-fixation applications.

Biodegradable PMMA coated Zn-Mg alloy with bimodal grain structure for orthopedic applications - A promising alternative

The study examines the impact of microstructure and polymethyl methacrylate (PMMA) grafting on the degradability of Zn-Mg alloys. The mechanical properties of a Zn alloy containing 0.68 wt% Mg and extruded at 200 °C are enhanced for degradable load-bearing applications, addressing a crucial need in the field. The material exhibits a bimodal grain size distribution that is random texture, consisting of secondary phases, grains, and sub-grains. With an elongation to failure of 16 %, the yield and ultimate tensile strengths are 325.9 and 414.5 MPa, respectively, and the compressive yield strength is 450.5 MPa. The "grafting-from" method was used to coat a few micrometers thick of PMMA on both bulk and scaffold Zn alloys to mitigate the corrosion rate. The last one is a porous structure, with a porosity of 65.8 %, considered as in the first approach of an orthopedic implant. After being immersed for 720 h, the PMMA-grafted bulk alloy's corrosion rate decreased from 0.43 to 0.25 mm/y. Similarly, the scaffold alloy's corrosion rate reduced from 1.24 to 0.49 mm/y. These results indicate that the method employed could be used for future orthopedic applications.

Research Progress on Laser Powder Bed Fusion Additive Manufacturing of Zinc Alloys

Zinc, along with magnesium and iron, is considered one of the most promising biodegradable metals. Compared with magnesium and iron, pure Zn exhibits poor mechanical properties, despite its mild biological corrosion behavior and beneficial biocompatibility. Laser powder bed fusion (LPBF), unlike traditional manufacturing techniques, has the capability to rapidly manufacture near-net-shape components. At present, although the combination of LPBF and Zn has made great progress, it is still in its infancy. Element loss and porosity are common processing problems for LPBF Zn, mainly due to evaporation during melting under a high-energy beam. The formation quality and properties of the final material are closely related to the alloy composition, design and processing. This work reviews the state of research and future perspective on LPBF zinc from comprehensive assessments such as powder characteristics, alloy composition, processing, formation quality, microstructure, and properties. The effects of powder characteristics, process parameters and evaporation on formation quality are introduced. The mechanical, corrosion, and biocompatibility properties of LPBF Zn and their test methodologies are introduced. The effects of microstructure on mechanical properties and corrosion properties are analyzed in detail. The practical medical application of Zn is introduced. Finally, current research status is summarized together with suggested directions for advancing knowledge about LPBF Zn.

Biodegradable Zn-2Cu-0.5Zr alloy promotes the bone repair of senile osteoporotic fractures via the immune-modulation of macrophages

Delayed bone-healing of senile osteoporotic fractures remains a clinical challenge due to the alterations caused by aging in bone and immune systems. The novel biomaterials that address the deficiencies in both skeletal cells and immune systems are required to effectively treat the bone injuries of older patients. Zinc (Zn) has shown promise as a biodegradable material for use in orthopedic implants. To address the bone-healing deficiencies in elderly patients with bone injuries, we developed a biodegradable Zn-based alloy (Zn-2Cu-0.5Zr) with enhanced mechanical properties, including a yield strength of 198.7 MPa and ultimate tensile strength of 217.6 MPa, surpassing those of pure Zn and Zn-2Cu alloys. Cytotoxicity tests conducted on bone marrow mesenchymal stem cells (BMSCs) and MC3T3-E1 cells demonstrated that the extracts from Zn-2Cu-0.5Zr alloy exhibited no observable cytotoxic effects. Furthermore, the extracts of Zn-2Cu-0.5Zr alloy exhibited significant anti-inflammatory effects through regulation of inflammation-related cytokine production and modulation of macrophage polarization. The improved immune-osteo microenvironment subsequently contributed to osteogenic differentiation of BMSCs. The potential therapeutic application of Zn-2Cu-0.5Zr in senile osteoporotic fracture was tested using a rat model of age-related osteoporosis. The Zn-2Cu-0.5Zr alloy met the requirements for load-bearing applications and accelerated the healing process in a tibial fracture in aged rats. The imaging and histological analyses showed that it could accelerate the bone-repair process and promote the fracture healing in senile osteoporotic rats. These findings suggest that the novel Zn-2Cu-0.5Zr alloy holds potential for influencing the immunomodulatory function of macrophages and facilitating bone repair in elderly individuals with osteoporosis.

An adaptive biodegradable zinc alloy with bidirectional regulation of bone homeostasis for treating fractures and aged bone defects

Healing of fractures or bone defects is significantly hindered by overactivated osteoclasts and inhibited osteogenesis in patients with abnormal bone metabolism. Current clinical approaches using titanium alloys or stainless steel provide mechanical support but have no biological effects on bone regeneration. Therefore, designing and fabricating degradable metal materials with sufficient mechanical strength and bidirectional regulation of both osteoblasts and osteoclasts is a substantial challenge. Here, this study first reported an adaptive biodegradable Zn-0.8 Mg alloy with bidirectional regulation of bone homeostasis, which promotes osteogenic differentiation by activating the Pi3k/Akt pathway and inhibits osteoclast differentiation by inhibiting the GRB2/ERK pathway. The anti-osteolytic ability of the Zn-0.8 Mg alloy was verified in a mouse calvarial osteolysis model and its suitability for internal fracture fixation with high-strength screws was confirmed in the rabbit femoral condyle fracture model. Furthermore, in an aged postmenopausal rat femoral condyle defect model, 3D printed Zn-0.8 Mg scaffolds promoted excellent bone regeneration through adaptive structures with good mechanical properties and bidirectionally regulated bone metabolism, enabling personalized bone defect repair. These findings demonstrate the substantial potential of the Zn-0.8 Mg alloy for treating fractures or bone defects in patients with aberrant bone metabolism.

Quaternary Zinc Alloys with Magnesium, Calcium and Strontium after Hydrostatic Extrusion-Microstructure and Its Impact on Mechanical and Corrosion Properties

The development of bioabsorbable implants from Zn alloys is one of the main interests in the new generation of biomaterials. The main drawbacks of Zn-based materials are their insufficient mechanical properties. In the presented studies, a quaternary alloy composed of zinc with magnesium (0.2-1 wt. %), calcium (0.1-0.5 wt. %) and strontium (0.05-0.5 wt. %) was prepared by gravity casting followed by hot extrusion and then by hydrostatic extrusion. Microstructural characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis was performed. The mechanical properties were examined, using static tensile tests. Corrosion properties were analyzed using immersion tests. Samples were immersed in Hanks' solution (temperature = 37 °C, pH = 7.4) for 14 days. All alloys were subjected after corrosion to SEM observations on the surface and cross-section. The corrosion rate was also calculated. The microstructure of the investigated quaternary alloy consists of the α-Zn grains and intermetallic phases Mg2Zn11, CaZn13 and SrZn13 with different grain sizes and distribution, which impacted both mechanical and corrosion properties. Thanks to the alloying by the addition of Mg, Ca, and Sr and plastic deformation using hydrostatic extrusion, outstanding mechanical properties were obtained along with improvement in uniformity of corrosion rate.

Mimicking the mechanical properties of cortical bone with an additively manufactured biodegradable Zn-3Mg alloy

Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg2Zn11 phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60 %. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. STATEMENT OF SIGNIFICANCE: Our study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics.

Development and characterization of ZnxCuyTizMo alloys for biomedical applications: A high-throughput gradient continuous casting approach

The limited mechanical properties of pure Zn, such as its low strength and ductility, hinder its application as a material for biodegradable implants. Addressing this challenge, the current study focuses on the development of biodegradable Zn-based alloys, employing innovative alloy design and processing strategies. Here, alloys with compositions ranging from 0.02 to 0.10 weight percent (wt%) Cu, 1.22 to 1.80 wt% Ti, and 0.04 to 0.06 wt% Mo were produced utilizing a high-throughput gradient continuous casting process. This study highlights three specific alloys: Zn1.82Cu0.10Ti0.05Mo (HR8), Zn0.08Cu1.86Ti0Mo (HR7), and Zn1.26Cu0.13Ti0.06Mo (HR6), which were extensively evaluated for their microstructure, mechanical properties, electrochemical performance, potential as bioimplants, and cytotoxicity. These alloys were found to exhibit enhanced mechanical strength, optimal degradation rates, and superior biocompatibility, evidenced by in-vivo experiments with SD rats, positioning them as promising candidates for medical implants. This research not only introduces a significant advancement in biodegradable alloy development but also proposes an efficient method for their production, marking a pivotal step forward in biomedical engineering. STATEMENT OF SIGNIFICANCE: The limited mechanical properties of pure Zn have hindered its application in biodegradable implants. Our research primarily focuses on the alloy design and process strategies of biodegradable Zn-based alloys. We explore the ZnCuxTixMox alloys. This study introduces a high-throughput experimental approach for efficient screening of multi-component alloy systems with optimal properties. The ZnCuxTixMox alloys were designed and processed through gradient continuous casting, followed by homogenization and hot rolling. Our findings indicate that the Zn1.82Cu0.10Ti0.05Mo alloy demonstrates superior tensile, mechanical, and corrosion properties post hot rolling. The study suggests that Zn0.13Cu1.26Ti0.06Mo, Zn0.08Cu1.86Ti0Mo, and Zn1.82Cu0.10Ti0.05Mo alloys hold significant potential as biodegradable materials.

Advances in biodegradable materials: Degradation mechanisms, mechanical properties, and biocompatibility for orthopedic applications

Mg-based and Zn-based biodegradable materials have the potential to become the next-generation implant materials to treat bone diseases, because of their desired degradation and mechanical properties. This article reviews the status of these implant materials. The required properties of biodegradable materials such as biodegradability, mechanical properties, and biocompatibility for performance evaluation were briefly discussed. The influence of fabrication techniques, microstructure, alloying elements, and post-processing techniques on the properties of Mg and Zn-based materials was addressed. The degradation mechanism by dissolution, oxidation, and interaction with human body cells was discussed. The biocompatibility of Mg and Zn-based biodegradable materials was analyzed. The significance of in vitro and in vivo biocompatibility testing was highlighted, emphasizing the superiority of in vivo results over cell line studies. This article identifies the many Mg and Zn-based biodegradable materials and summarizes the key findings.

Structural and temporal dynamics analysis of zinc-based biomaterials: History, research hotspots and emerging trends

Objectives

To examine the 16-year developmental history, research hotspots, and emerging trends of zinc-based biodegradable metallic materials from the perspective of structural and temporal dynamics.

Methods

The literature on zinc-based biodegradable metallic materials in WoSCC was searched. Historical characteristics, the evolution of active topics and development trends in the field of zinc-based biodegradable metallic materials were analyzed using the bibliometric tools CiteSpace and HistCite.

Results

Over the past 16 years, the field of zinc-based biodegradable metal materials has remained in a hotspot stage, with extensive scientific collaboration. In addition, there are 45 subject categories and 51 keywords in different research periods, and 80 papers experience citation bursts. Keyword clustering anchored 3 emerging research subfields, namely, #1 plastic deformation #4 additive manufacturing #5 surface modification. The keyword alluvial map shows that the longest-lasting research concepts in the field are mechanical property, microstructure, corrosion behavior, etc., and emerging keywords are additive manufacturing, surface modification, dynamic recrystallization, etc. The most recent research on reference clustering has six subfields. Namely, #0 microstructure, #2 sem, #3 additive manufacturing, #4 laser powder bed fusion, #5 implant, and #7 Zn-1Mg.

Conclusion

The results of the bibliometric study provide the current status and trends of research on zinc-based biodegradable metallic materials, which can help researchers identify hot spots and explore new research directions in the field.

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

A biodegradable Zn-5Gd alloy with biomechanical compatibility, cytocompatibility, antibacterial ability, and in vitro and in vivo osteogenesis for orthopedic applications

Zinc (Zn) and some of its alloys are recognized as promising biodegradable implant materials due to their acceptable biocompatibility, facile processability, and moderate degradation rate. Nevertheless, the limited mechanical properties and stability of as-cast Zn alloys hinder their clinical application. In this work, hot-rolled (HR) and hot-extruded (HE) Zn-5 wt.% gadolinium (Zn-5Gd) samples were prepared by casting and respectively combining with hot rolling and hot extrusion for bone-implant applications. Their microstructure evolution, mechanical properties, corrosion behavior, cytotoxicity, antibacterial ability, and in vitro and in vivo osteogenesis were systematically evaluated. The HR and HE Zn-5Gd exhibited significantly improved mechanical properties compared with those of their pure Zn counterparts and the HR Zn-5Gd showed a unique combination of tensile properties with an ultimate tensile strength of ∼311.6 MPa, yield strength of ∼236.5 MPa, and elongation of ∼40.6%, all of which are greater than the mechanical properties required for bone-implant materials. The HR and HE Zn-5Gd showed higher corrosion resistance than their pure Zn counterpart in Hanks' solution and the HE Zn-5Gd had the lowest corrosion rate of 155 µm/y measured by electrochemical corrosion and degradation rate of 26.9 µm/y measured by immersion testing. The HR and HE Zn-5Gd showed high cytocompatibility toward MC3T3-E1 and MG-63 cells, high antibacterial effects against S. aureus, and better in vitro osteogenic activity than their pure Zn counterparts. Furthermore, the HE Zn-5Gd exhibited better in vivo biocompatibility, osteogenesis, and osteointegration ability than pure Zn and pure Ti. STATEMENT OF SIGNIFICANCE: This work reports the mechanical properties, corrosion behaviors, cytocompatibility, antibacterial ability, in vitro and in vivo osteogenesis of biodegradable Zn-Gd alloy for bone-implant applications. Our findings demonstrate that the hot-rolled (HR) Zn-5Gd showed a unique combination of tensile properties with an ultimate tensile strength of ∼311.6 MPa, yield strength of ∼236.5 MPa, and elongation of ∼40.6%. The HR and HE Zn-5Gd showed higher corrosion resistance than their pure Zn counterpart in Hanks' solution. The HR and HE Zn-5Gd showed high cytocompatibility toward MC3T3-E1 and MG-63 cells, good antibacterial effects against S. aureus, and better in vitro osteogenic activity. Furthermore, the HE Zn-5Gd exhibited better in vivo biocompatibility, osteogenesis, and osteointegration ability than pure Zn and pure Ti.

Osteogenesis or Apoptosis-Twofold Effects of Zn2+ on Bone Marrow Mesenchymal Stem Cells: An In Vitro and In Vivo Study

Zinc (Zn) is a bioabsorbable metal that shows great potential as an implant material for orthopedic applications. Suitable concentrations of zinc ions promote osteogenesis, while excess zinc ions cause apoptosis. As a result, the conflicting impacts of Zn2+ concentration on osteogenesis could prove to be significant problems for the creation of novel materials. This study thoroughly examined the cell viability, proliferation, and osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) cultured in various concentrations of Zn2+ in vitro and validated the osteogenesis effects of zinc implantation in vivo. The effective promotion of cell survival, proliferation, migration, and osteogenic differentiation of bone marrow mesenchymal stem cell (BMSCs) may be achieved at a low concentration of Zn2+ (125 μM). The excessively high concentration of zinc ions (>250 μM) not only reduces BMSCs' viability and proliferation but also causes them to suffer apoptosis due to the disturbed zinc homeostasis and excessive Zn2+. Moreover, transcriptome sequencing was used to examine the underlying mechanisms of zinc-induced osteogenic differentiation with particular attention paid to the PI3K-AKT and TGF-β pathways. The present investigation elucidated the dual impacts of Zn2+ microenvironments on the osteogenic characteristics of rBMSCs and the associated processes and might offer significant insights for refining the blueprint for zinc-based biomaterials.

Characterization of hFOB 1.19 Cell Line for Studying Zn-Based Degradable Metallic Biomaterials

In vitro testing is the first important step in the development of new biomaterials. The human fetal osteoblast cell line hFOB 1.19 is a very promising cell model; however, there are vast discrepancies in cultivation protocols, especially in the cultivation temperature and the presence of the selection reagent, geneticin (G418). We intended to use hFOB 1.19 for the testing of Zn-based degradable metallic materials. However, the sensitivity of hFOB 1.19 to zinc ions has not yet been studied. Therefore, we compared the toxicity of zinc towards hFOB 1.19 under different conditions and compared it with that of the L929 mouse fibroblast cell line. We also tested the cytotoxicity of three types of Zn-based biomaterials in two types of media. The presence of G418 used as a selection reagent decreased the sensitivity of hFOB 1.19 to Zn2+. hFOB 1.19 cell line was more sensitive to Zn2+ at elevated (restrictive) temperatures. hFOB 1.19 cell line was less sensitive to Zn2+ than L929 cell line (both as ZnCl2 and extracts of alloys). Therefore, the appropriate cultivation conditions of hFOB 1.19 during biomaterial testing should be chosen with caution.

Biocompatibility and osteogenic potential of choline phosphate chitosan-coated biodegradable Zn1Mg

Zinc alloys have demonstrated considerable potentials as implant materials for biodegradable vascular and orthopedic applications. However, the high initial release of Zn2+ can trigger intense immune responses that impede tissue healing. To address this challenge and enhance the osteogenic capacity of zinc alloys, the surface of Zn1Mg was subjected to CO2 plasma modification (Zn1Mg-PP) followed by grafting with choline phosphate chitosan (Zn1Mg-PP-PCCs). This study aims to investigate the in vitro and in vivo biocompatibility of the surface-modified Zn1Mg. The effect of the surface modification on the inflammatory response and osteogenic repair process was investigated. Compared with unmodified Zn1Mg, the degradation rate of Zn1Mg-PP-PCCs was significantly decreased, avoiding the cytotoxicity triggered by the release of large amounts of Zn2+. Moreover, PCCs significantly enhanced the cell-material adhesion, promoted the proliferation of osteoblasts (MC3T3-E1) and upregulated the expression of key osteogenic factors in vitro. Notably, the in vivo experiments revealed that the surface modification of Zn1Mg suppressed inhibited the expression of inflammatory cytokines, promoting the secretion of anti-inflammatory factors, thereby reducing inflammation and promoting bone tissue repair. Furthermore, histological analysis of tissue sections exhibited strong integration between the material and the bone, along with well-defined new bone formation and reduced osteoclast aggregation on the surface. This was attributed to the improved immune microenvironment by PCCs, which promoted osteogenic differentiation of osteoblasts. These findings highlight that the preparation of PCCs coatings on zinc alloy surfaces effectively inhibited ion release and modulated the immune environment to promote bone tissue repair. STATEMENT OF SIGNIFICANCE: Surface modification of biodegradable Zn alloys facilitates the suppression of intense immune responses caused by excessive ion release concentrations from implants. We modified the surface of Zn1Mg with choline phosphate chitosan (PCCs) and investigated the effects of surface modification on the inflammatory response and osteogenic repair process. In vitro results showed that the PCCs coating effectively reduced the degradation rate of Zn1Mg to avoid cytotoxicity caused by high Zn2+ concentration, favoring the proliferation of osteoblasts. In addition, in vivo results indicated that Zn1Mg-PP-PCCs attenuated inflammation to promote bone repair by modulating the release of inflammation-related factors. The surface-modified Zn1Mg implants demonstrated strong osseointegration, indicating that the PCCs coating effectively modulated the immune microenvironment and promoted bone healing.

Additively Manufactured Zn-2Mg Alloy Porous Scaffolds with Customizable Biodegradable Performance and Enhanced Osteogenic Ability

The combination of bioactive Zn-2Mg alloy and additively manufactured porous scaffold is expected to achieve customizable biodegradable performance and enhanced bone regeneration. Herein, Zn-2Mg alloy scaffolds with different porosities, including 40% (G-40-2), 60% (G-60-2), and 80% (G-80-2), and different unit sizes, including 1.5 mm (G-60-1.5), 2 mm (G-60-2), and 2.5 mm (G-60-2.5), are manufactured by a triply periodic minimal surface design and a reliable laser powder bed fusion process. With the same unit size, compressive strength (CS) and elastic modulus (EM) of scaffolds substantially decrease with increasing porosities. With the same porosity, CS and EM just slightly decrease with increasing unit sizes. The weight loss after degradation increases with increasing porosities and decreasing unit sizes. In vivo tests indicate that Zn-2Mg alloy scaffolds exhibit satisfactory biocompatibility and osteogenic ability. The osteogenic ability of scaffolds is mainly determined by their physical and chemical characteristics. Scaffolds with lower porosities and smaller unit sizes show better osteogenesis due to their suitable pore size and larger surface area. The results indicate that the biodegradable performance of scaffolds can be accurately regulated on a large scale by structure design and the additively manufactured Zn-2Mg alloy scaffolds have improved osteogenic ability for treating bone defects.

Full-thickness osteochondral defect repair using a biodegradable bilayered scaffold of porous zinc and chondroitin sulfate hydrogel

The regeneration of osteochondral tissue necessitates the re-establishment of a gradient owing to the unique characteristics and healing potential of the chondral and osseous phases. As the self-healing capacity of hyaline cartilage is limited, timely mechanical support during neo-cartilage formation is crucial to achieving optimal repair efficacy. In this study, we devised a biodegradable bilayered scaffold, comprising chondroitin sulfate (CS) hydrogel to regenerate chondral tissue and a porous pure zinc (Zn) scaffold for regeneration of the underlying bone as mechanical support for the cartilage layer. The photocured CS hydrogel possessed a compressive strength of 82 kPa, while the porous pure Zn scaffold exhibited a yield strength of 11 MPa and a stiffness of 0.8 GPa. Such mechanical properties are similar to values reported for cancellous bone. In vitro biological experiments demonstrated that the bilayered scaffold displayed favorable cytocompatibility and promoted chondrogenic and osteogenic differentiation of bone marrow stem cells. Upon implantation, the scaffold facilitated the simultaneous regeneration of bone and cartilage tissue in a porcine model, resulting in (i) a smoother cartilage surface, (ii) more hyaline-like cartilage, and (iii) a superior integration into the adjacent host tissue. Our bilayered scaffold exhibits significant potential for clinical application in osteochondral regeneration.

Mechanical Properties and Corrosion Rate of ZnAg3 as a Novel Bioabsorbable Material for Osteosynthesis

Osteosynthesis in fracture treatment typically uses hardware that remains in the patient's body, which brings a permanent risk of negative side effects such as foreign body reactions or chronic inflammation. Bioabsorbable materials, however, can degrade and slowly be replaced by autologous bone tissue. A suitable material is requested to offer great biocompatibility alongside excellent mechanical properties and a reasonable corrosion rate. Zinc-silver alloys provide these characteristics, which makes them a promising candidate for research. This study investigated the aptitude as a bioabsorbable implant of a novel zinc-silver alloy containing 3.3 wt% silver (ZnAg3). Here, the tensile strength as well as the corrosion rate in PBS solution (phosphate buffered solution) of ZnAg3 were assessed. Furthermore, shear tests, including fatigue and quasi-static testing, were conducted with ZnAg3 and magnesium pins (MAGNEZIX®, Syntellix AG, Hannover, Germany), which are already in clinical use. The detected corrosion rate of 0.10 mm/year for ZnAg3 was within the proposed range for bioabsorbable implants. With a tensile strength of 237.5 ± 2.12 MPa and a shear strength of 144.8 ± 13.2 N, ZnAg3 satisfied the mechanical requirements for bioabsorbable implants. The fatigue testing did not show any significant difference between ZnAg3 and magnesium pins, whereas both materials withstood the cyclic loading. Thus, the results support the assumption that ZnAg3 is qualified for further investigation.

Research progress and perspective of metallic implant biomaterials for craniomaxillofacial surgeries

Craniomaxillofacial bone serves a variety of functions. However, the increasing number of cases of craniomaxillofacial bone injury and the use of selective rare implants make the treatment difficult, and the cure rate is low. If such a bone injury is not properly treated, it can lead to a slew of complications that can seriously disrupt a patient's daily life. For example, premature closure of cranial sutures or skull fractures can lead to increased intracranial pressure, which can lead to headaches, vomiting, and even brain hernia. At present, implant placement is one of the most common approaches to repair craniomaxillofacial bone injury or abnormal closure, especially with biomedical metallic implants. This review analyzes the research progress in the design and development of degradable and non-degradable metallic implants in craniomaxillofacial surgery. The mechanical properties, corrosion behaviours, as well as in vitro and in vivo performances of these materials are summarized. The challenges and future research directions of metallic biomaterials used in craniomaxillofacial surgery are also identified.

Advances in Aerogels Formulations for Pulmonary Targeted Delivery of Therapeutic Agents: Safety, Efficacy and Regulatory Aspects

Aerogels are the 3D network of organic, inorganic, composite, layered, or hybrid-type materials that are used to increase the solubility of Class 1 (low solubility and high permeability) and Class 4 (poor solubility and low permeability) molecules. This approach improves systemic drug absorption due to the alveoli's broad surface area, thin epithelial layer, and high vascularization. Local therapies are more effective and have fewer side effects than systemic distribution because inhalation treatment targets the specific location and raises drug concentration in the lungs. The present manuscript aims to explore various aspects of aerogel formulations for pulmonary targeted delivery of active pharmaceutical agents. The manuscript also discusses the safety, efficacy, and regulatory aspects of aerogel formulations. According to projections, the global respiratory drug market is growing 4-6% annually, with short-term development potential. The proliferation of literature on pulmonary medicine delivery, especially in recent years, shows increased interest. Aerogels come in various technologies and compositions, but any aerogel used in a biological system must be constructed of a material that is biocompatible and, ideally, biodegradable. Aerogels are made via "supercritical processing". After many liquid phase iterations using organic solvents, supercritical extraction, and drying are performed. Moreover, the sol-gel polymerization process makes inorganic aerogels from TMOS or TEOS, the less hazardous silane. The resulting aerogels were shown to be mostly loaded with pharmaceutically active chemicals, such as furosemide-sodium, penbutolol-hemisulfate, and methylprednisolone. For biotechnology, pharmaceutical sciences, biosensors, and diagnostics, these aerogels have mostly been researched. Although aerogels are made of many different materials and methods, any aerogel utilized in a biological system needs to be made of a substance that is both biocompatible and, preferably, biodegradable. In conclusion, aerogel-based pulmonary drug delivery systems can be used in biomedicine and non-biomedicine applications for improved sustainability, mechanical properties, biodegradability, and biocompatibility. This covers scaffolds, aerogels, and nanoparticles. Furthermore, biopolymers have been described, including cellulose nanocrystals (CNC) and MXenes. A safety regulatory database is necessary to offer direction on the commercialization potential of aerogelbased formulations. After that, enormous efforts are discovered to be performed to synthesize an effective aerogel, particularly to shorten the drying period, which ultimately modifies the efficacy. As a result, there is an urgent need to enhance the performance going forward.

In vitro long-term antibacterial performance and mechanism of Zn-doped micro-arc oxidation coatings

Micro-arc oxidation (MAO) coatings containing 2.86 wt%, 5.83 wt% and 8.81 wt% Zn (Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt%) were separately fabricated on Ti6Al4V alloys using EDTA-ZnNa2 electrolytes. In vitro antibacterial examination exhibits that the antibacterial rates of Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt% against Staphylococcus aureus (S. aureus) are 76.0 %, 100.0 % and 99.2 %, respectively. Reactive oxygen species (ROS) level of MAO samples is significantly higher than that of the untreated Ti6Al4V. Zn-containing coatings especially Zn-5.83 wt% induces the strongest oxidative stress on S. aureus due to relatively high released Zn2+ concentration. Moreover, qPCR analysis shows that MAO samples inhibit the icaADBC transcription and result in the down-regulation of PIA production, thereby mitigating biofilm formation. After immersion in simulated body fluid (SBF) for 3, 8 and 14 d, the antibacterial rate of Zn-5.83 wt% is 84.7 %, 63.2 % and 12.5 % respectively, and ROS level of MAO samples is also significantly higher than that of the untreated Ti6Al4V even after 14 d of immersion, suggesting that the antibacterial performance of MAO samples can last a relatively long immersion period and exhibit large application potential in orthopedic clinic.

Recent Advances in Biodegradable Green Electronic Materials and Sensor Applications

As environmental issues have become the dominant agenda worldwide, the necessity for more environmentally friendly electronics has recently emerged. Accordingly, biodegradable or nature-derived materials for green electronics have attracted increased interest. Initially, metal-green hybrid electronics are extensively studied. Although these materials are partially biodegradable, they have high utility owing to their metallic components. Subsequently, carbon-framed materials (such as graphite, cylindrical carbon nanomaterials, graphene, graphene oxide, laser-induced graphene) have been investigated. This has led to the adoption of various strategies for carbon-based materials, such as blending them with biodegradable materials. Moreover, various conductive polymers have been developed and researchers have studied their potential use in green electronics. Researchers have attempted to fabricate conductive polymer composites with high biodegradability by shortening the polymer chains. Furthermore, various physical, chemical, and biological sensors that are essential to modern society have been studied using biodegradable compounds. These recent advances in green electronics have paved the way toward their application in real life, providing a brighter future for society.

Development of Zn-2Cu-xMn/Mg Alloys for Orthopedic Applications: Mechanical Performance to In Vitro Degradation under Different Physiological Environments

Zinc (Zn) and its alloys are considered futuristic biodegradable materials for their acceptable mechanical properties, suitable corrosion rate, and good biocompatibility. In this study, we report newly developed biodegradable Zn-2Cu-xMn/Mg (x = 0, 0.1, and 0.5) alloys, aiming to achieve good mechanical strength with excellent elongation, desirable wear resistance, and suitable corrosion rate. The effect of Mn/Mg addition on the structural, mechanical, wear, and degradation behaviors of the Zn-2Cu-xMn/Mg alloys was thoroughly investigated. Degradation and tribological behaviors of the alloys were explored in the presence of simulated body fluid (SBF), Dulbecco's modified Eagle medium (DMEM), and DMEM with a 10% fetal bovine serum (FBS) solution. Alloy elements and hot rolling improve their mechanical properties significantly due to precipitation hardening, grain refinement, and solid solution strengthening owing to the formation of MnZn13 and Mg2Zn11 phases. Among all the alloys, the Zn-2Cu-0.5Mn alloy achieved the highest ultimate tensile strength (UTS) of ∼405 MPa and yield strength (YS) of ∼293 MPa with an excellent elongation of ∼51%. The corrosion behavior of the alloys as determined by a potentiodynamic polarization study under different solutions follows the sequence Zn-2Cu < Zn-2Cu-0.5Mn < Zn-2Cu-0.1Mn < Zn-2Cu-0.1Mg < Zn-2Cu-0.5Mg. The corrosion rate by immersion testing for 30 and 90 days also follows the same sequence. The corrosion rate in different solutions follows the order SBF > DMEM + 10%FBS > DMEM. The addition of Mn/Mg also improves the wear resistance and slows the wear rate under wet conditions. The bending test results also indicate the highest bending strength of ∼375 MPa for the Zn-2Cu-0.5Mn alloy, among all the alloys. The bending and tensile strengths deteriorate continuously after the immersion for 30 and 90 days in the solution of SBF, DMEM, and DMEM + 10%FBS. Therefore, the Zn-2Cu-xMn/Mg (x = 0.1 and 0.5) alloys can be considered potential biodegradable implant materials.

Biocompatibility and antibacterial activity of MgO/Ca3(PO4)2 composite ceramic scaffold based on vat photopolymerization technology

Recent advancements in medical technology and increased interdisciplinary research have facilitated the development of the field of medical engineering. Specifically, in bone repair, researchers and potential users have placed greater demands on orthopedic implants regarding their biocompatibility, degradation rates, antibacterial properties, and other aspects. In response, our team developed composite ceramic samples using degradable materials calcium phosphate and magnesium oxide through the vat photopolymerization (VP) technique. The calcium phosphate content in each sample was, respectively, 80 %, 60 %, 40 %, and 20 %. To explore the relationship between the biocompatibility, antibacterial activity, and MgO content of the samples, we cultured them with osteoblasts (MC3T3-E1), Escherichia coli (a gram-negative bacterium), and Staphylococcus aureus (a gram-positive bacterium). Our results demonstrate that as the MgO content of the sample increases, its biocompatibility improves but its antibacterial activity decreases. Regarding the composite material samples, the 20 % calcium phosphate content group exhibited the best biocompatibility. However, after 0.5 h of co-cultivation, the antibacterial rates of all groups except the 20 % calcium phosphate content group co-cultured with S. aureus exceed 80 %. Furthermore, after 3 h, the antibacterial rates against E. coli exceed 95 % in all groups. This is because higher levels of MgO correspond to lower pH values and Mg2+ concentrations in the cell and bacterial culture solutions, which ultimately promote cell and bacterial proliferation. This elevates the biocompatibility of the samples, albeit at the expense of their antimicrobial efficacy. Thus, modulating the MgO content in the composite ceramic samples provides a strategy to develop gradient composite scaffolds for better control of their biocompatibility and antibacterial performance during different stages of bone regeneration.

Corrosion-tailoring, osteogenic, anti-inflammatory, and antibacterial aspirin-loaded organometallic hydrogel composite coating on biodegradable Zn for orthopedic applications

Zn and its alloys are receiving increasing interest for biodegradable orthopedic implant applications owing to their moderate corrosion rate and the potential functionality of Zn2+. However, their non-uniform corrosion behavior and insufficient osteogenic, anti-inflammatory, and antibacterial properties do not meet the comprehensive requirements of orthopedic implants in clinical use. Herein, an aspirin (an acetylsalicylic acid, ASA, 10, 50, 100, and 500 mg/L)-loaded carboxymethyl chitosan (CMC)/gelatin (Gel)-Zn2+ organometallic hydrogel composite coating (CMC/Gel&Zn2+/ASA) was fabricated on a Zn surface via an alternating dip-coating method, aiming to obtain a material with these comprehensive properties improved. The organometallic hydrogel composite coatings, ca. 12-16 μm in thickness, showed compact, homogeneous, and micro-bulge structured surface morphology. The coatings protected well the Zn substrate from pitting/localized corrosion and contained the release of the bioactive components, Zn2+ and ASA, in a sustained and stable manner in long-term in vitro immersions in Hank's solution. The coated Zn showed greater ability to promote proliferation and osteogenic differentiation for MC3T3-E1 osteoblasts, and better anti-inflammatory capacity when compared with uncoated Zn. Additionally, this coating displayed excellent antibacterial activity against both Escherichia coli (>99 % antibacterial rate) and Staphylococcus aureus (>98 % antibacterial rate). Such appealing properties can be attributed to the compositional nature of the coating, namely the sustained release of Zn2+ and ASA, as well as the surface physiochemical properties because of its unique microstructure. This organometallic hydrogel composite coating can be considered a promising option for the surface modification of biodegradable Zn-based orthopedic implants among others.

3D printing for bone regeneration: challenges and opportunities for achieving predictability

3D printing offers attractive opportunities for large-volume bone regeneration in the oro-dental and craniofacial regions. This is enabled by the development of CAD-CAM technologies that support the design and manufacturing of anatomically accurate meshes and scaffolds. This review describes the main 3D-printing technologies utilized for the fabrication of these patient-matched devices, and reports on their pre-clinical and clinical performance including the occurrence of complications for vertical bone augmentation and craniofacial applications. Furthermore, the regulatory pathway for approval of these devices is discussed, highlighting the main hurdles and obstacles. Finally, the review elaborates on a variety of strategies for increasing bone regeneration capacity and explores the future of 4D bioprinting and biodegradable metal 3D printing.

Mechanical properties, corrosion and degradation behaviors, and in vitro cytocompatibility of a biodegradable Zn-5La alloy for bone-implant applications

Zinc (Zn) and its alloys are used in bone-fixation devices as biodegradable bone-implant materials due to their good biosafety, biological function, biodegradability, and formability. Unfortunately, the clinical application of pure Zn is hindered by its insufficient mechanical properties and slow degradation rate. In this study, a Zn-5 wt.% lanthanum (Zn-5La) alloy with enhanced mechanical properties, suitable degradation rate, and cytocompatibility was developed through La alloying and hot extrusion. The hot-extruded (HE) Zn-5La alloy showed ultimate tensile strength of 286.3 MPa, tensile yield strength of 139.7 MPa, elongation of 35.7%, compressive yield strength of 262.7 MPa, and microhardness of 109.7 HV. The corrosion resistance of the HE Zn-5La in Hanks' and Dulbecco's modified Eagle medium (DMEM) solutions gradually increased with prolonged immersion time. Further, the HE Zn-5La exhibited an electrochemical corrosion rate of 36.7 μm/y in Hanks' solution and 11.4 μm/y in DMEM solution, and a degradation rate of 49.5 μm/y in Hanks' solution and 30.3 μm/y in DMEM solution, after 30 d of immersion. The corrosion resistance of both HE Zn and Zn-5La in DMEM solution was higher than in Hanks' solution. The 25% concentration extract of the HE Zn-5La showed a cell viability of 106.5%, indicating no cytotoxicity toward MG-63 cells. We recommend the HE Zn-5La alloy as a promising candidate material for biodegradable bone-implant applications. STATEMENT OF SIGNIFICANCE: This work reports the mechanical properties, corrosion and degradation behaviors, in vitro cytocompatibility and antibacterial ability of biodegradable Zn-5La alloy for bone-implant applications. Our findings demonstrate that the hot-extruded (HE) Zn-5La alloy showed an ultimate tensile strength of 286.3 MPa, a yield strength of 139.7 MPa, an elongation of 35.7%, compressive yield strength of 262.7 MPa, and microhardness of 109.7 HV. HE Zn-5La exhibited appropriate degradation rates in Hanks' and DMEM solutions. Furthermore, the HE Zn-5La alloy showed good cytocompatibility toward MG-63 and MC3T3-E1 cells and greater antibacterial ability against S. aureus.

An Overview of Scaffolds and Biomaterials for Skin Expansion and Soft Tissue Regeneration: Insights on Zinc and Magnesium as New Potential Key Elements

The utilization of materials in medical implants, serving as substitutes for non-functional biological structures, supporting damaged tissues, or reinforcing active organs, holds significant importance in modern healthcare, positively impacting the quality of life for millions of individuals worldwide. However, certain implants may only be required temporarily to aid in the healing process of diseased or injured tissues and tissue expansion. Biodegradable metals, including zinc (Zn), magnesium (Mg), iron, and others, present a new paradigm in the realm of implant materials. Ongoing research focuses on developing optimized materials that meet medical standards, encompassing controllable corrosion rates, sustained mechanical stability, and favorable biocompatibility. Achieving these objectives involves refining alloy compositions and tailoring processing techniques to carefully control microstructures and mechanical properties. Among the materials under investigation, Mg- and Zn-based biodegradable materials and their alloys demonstrate the ability to provide necessary support during tissue regeneration while gradually degrading over time. Furthermore, as essential elements in the human body, Mg and Zn offer additional benefits, including promoting wound healing, facilitating cell growth, and participating in gene generation while interacting with various vital biological functions. This review provides an overview of the physiological function and significance for human health of Mg and Zn and their usage as implants in tissue regeneration using tissue scaffolds. The scaffold qualities, such as biodegradation, mechanical characteristics, and biocompatibility, are also discussed.

Biomaterials combined with ADSCs for bone tissue engineering: current advances and applications

In recent decades, bone tissue engineering, which is supported by scaffold, seed cells and bioactive molecules (BMs), has provided new hope and direction for treating bone defects. In terms of seed cells, compared to bone marrow mesenchymal stem cells, which were widely utilized in previous years, adipose-derived stem cells (ADSCs) are becoming increasingly favored by researchers due to their abundant sources, easy availability and multi-differentiation potentials. However, there is no systematic theoretical basis for selecting appropriate biomaterials loaded with ADSCs. In this review, the regulatory effects of various biomaterials on the behavior of ADSCs are summarized from four perspectives, including biocompatibility, inflammation regulation, angiogenesis and osteogenesis, to illustrate the potential of combining various materials with ADSCs for the treatment of bone defects. In addition, we conclude the influence of additional application of various BMs on the bone repair effect of ADSCs, in order to provide more evidences and support for the selection or preparation of suitable biomaterials and BMs to work with ADSCs. More importantly, the associated clinical case reports and experiments are generalized to provide additional ideas for the clinical transformation and application of bone tissue engineering loaded with ADSCs.

A Comprehensive Review of the Current Research Status of Biodegradable Zinc Alloys and Composites for Biomedical Applications

Zinc (Zn)-based biodegradable materials show moderate degradation rates in comparison with other biodegradable materials (Fe and Mg). Biocompatibility and non-toxicity also make them a viable option for implant applications. Furthermore, Pure Zn has poor mechanical behavior, with a tensile strength of around 100-150 MPa and an elongation of 0.3-2%, which is far from reaching the strength required as an orthopedic implant material (tensile strength is more than 300 MPa, elongation more than 15%). Alloy and composite fabrication have proven to be excellent ways to improve the mechanical performance of Zn. Therefore, their alloys and composites have emerged as an innovative category of biodegradable materials. This paper summarizes the most important recent research results on the mechanical and biological characteristics of biodegradable Zn-based implants for orthopedic applications and the most commonly added components in Zn alloys and composites.

The Influence of Manganese Addition on the Properties of Biodegradable Zinc-Manganese-Calcium Alloys

This study focuses on the preparation and characterization of zinc-based alloys containing magnesium, calcium, and manganese. The alloys were prepared by the melting of pure elements, casting them into graphite molds, and thermo-mechanically treating them via hot extrusion. The phase compositions of the samples were analyzed using X-ray diffraction technique and SEM/EDX analysis. The analysis confirmed that in addition to the Zn matrix, the materials are reinforced by the CaZn₁₃, MgZn_2, and Mn-based precipitates. The mechanical properties of the alloys were ascertained by tensile, compressive, and bending tests, measurement of the samples microhardness and elastic modulus. The results indicate that an increase in Mn content leads to an increase in the maximum stress experienced under both tension and compression. However, the plastic deformation of the alloys decreases with increasing Mn content. This study provides valuable insights into the microstructural changes and mechanical behavior of zinc-based alloys containing magnesium, calcium, and manganese, which can be used to design alloys for specific biomedical applications.

Additive manufacturing of vascular stents

With the advancement of additive manufacturing (AM), customized vascular stents can now be fabricated to fit the curvatures and sizes of a narrowed or blocked blood vessel, thereby reducing the possibility of thrombosis and restenosis. More importantly, AM enables the design and fabrication of complex and functional stent unit cells that would otherwise be impossible to realize with conventional manufacturing techniques. Additionally, AM makes fast design iterations possible while also shortening the development time of vascular stents. This has led to the emergence of a new treatment paradigm in which custom and on-demand-fabricated stents will be used for just-in-time treatments. This review is focused on the recent advances in AM vascular stents aimed at meeting the mechanical and biological requirements. First, the biomaterials suitable for AM vascular stents are listed and briefly described. Second, we review the AM technologies that have been so far used to fabricate vascular stents as well as the performances they have achieved. Subsequently, the design criteria for the clinical application of AM vascular stents are discussed considering the currently encountered limitations in materials and AM techniques. Finally, the remaining challenges are highlighted and some future research directions are proposed to realize clinically-viable AM vascular stents. STATEMENT OF SIGNIFICANCE: Vascular stents have been widely used for the treatment of vascular disease. The recent progress in additive manufacturing (AM) has provided unprecedented opportunities for revolutionizing traditional vascular stents. In this manuscript, we review the applications of AM to the design and fabrication of vascular stents. This is an interdisciplinary subject area that has not been previously covered in the published review articles. Our objective is to not only present the state-of-the-art of AM biomaterials and technologies but to also critically assess the limitations and challenges that need to be overcome to speed up the clinical adoption of AM vascular stents with both anatomical superiority and mechanical and biological functionalities that exceed those of the currently available mass-produced devices.

Exploring the Influence of Biologically Relevant Ions on the Corrosion Behavior of Biodegradable Zinc in Physiological Fluids

This work presents a study on the influence of biologically relevant ions on the corrosion of zinc (Zn) in physiological fluids. Electrochemical techniques were used to investigate the degradation of pure Zn exposed to different physiological electrolytes containing chlorides, carbonates, sulfates, and phosphates. The corrosion behavior of Zn in the solutions over a 7-day period was also assessed. SEM, EDS, and FTIR were used to analyze corrosion products. With respect to corrosion, the most aggressive ions are chlorides, which induce localized corrosion, while carbonates and phosphates reduce the corrosive attack of the chloride on Zn while inducing uniform corrosion. Sulfates reduce the corrosion rate by disrupting Zn's passive layer. The overall corrosion rate of Zn changed in each electrolyte depending on the nature of the solution and the corrosion product formed. These findings will be useful in predicting the in-service behavior of future biodegradable Zn medical implants.

Development, Processing and Aging of Novel Zn-Ag-Cu Based Biodegradable Alloys

The use of biodegradable materials for implants is a promising strategy to overcome known long-term clinical complications related to permanent implants. Ideally, biodegradable implants support the damaged tissue for a certain period and then degrade, while the physiological function of the surrounding tissue is restored. Although Mg-based alloys nearly ideally lend themselves to biodegradable implants, a few critical shortcomings promoted the development of alternative alloy systems. Due to their reasonably good biocompatibility, moderate corrosion rate without hydrogen evolution and adequate mechanical properties, increasing attention has been paid to Zn alloys. In this work, precipitation-hardening alloys in the system Zn-Ag-Cu were developed relying on thermodynamic calculations. After casting the alloys, their microstructures were refined by thermomechanical treatment. The processing was tracked and directed, respectively, by routine investigations of the microstructure, associated with hardness assessments. Although microstructure refinement increased the hardness, the material proved to be susceptible to aging as the homologous temperature of zinc is at 0.43 T_m. Besides mechanical performance and corrosion rate, long-term mechanical stability is another crucial factor that must be taken into consideration to ensure the safety of the implant and thus requires a profound understanding of the aging process.

Analysis of Degradation Products of Biodegradable ZnMgY Alloy

Biodegradable metallic materials are increasingly gaining ground in medical applications. Zn-based alloys show a degradation rate between those recorded for Mg-based materials with the fastest degradation rate and Fe-based materials with the slowest degradation rate. From the perspective of medical complications, it is essential to understand the size and nature of the degradation products developed from biodegradable materials, as well as the stage at which these residues are eliminated from the body. This paper presents investigations conducted on the corrosion/degradation products of an experimental material (ZnMgY alloy in cast and homogenized state) after immersion tests in three physiological solutions (Dulbecco's, Ringer's and simulated body fluid (SBF)). Scanning electron microscopy (SEM) was used to highlight the macroscopic and microscopic aspects of corrosion products and their effects on the surface. An X-ray energy dispersive detector (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) provided general information about the compounds based on their non-metallic character. The pH of the electrolyte solution was recorded for 72 h during immersion. The pH variation of the solution confirmed the main reactions proposed for the corrosion of ZnMg. The agglomerations of corrosion products were on the micrometer scale, mainly oxides, hydroxides and carbonates or phosphates. The corrosion effects on the surface were homogeneously spread, with a tendency to connect and form cracks or larger corrosion zones, transforming the pitting corrosion pattern into a generalized one. It was noticed that the alloy's microstructure strongly influences the corrosion characteristics.

Microstructural and Electrochemical Influence of Zn in MgCaZn Biodegradable Alloys

In recent years, biodegradable materials have included magnesium alloys with homogenous disintegration and a controllable degradation rate. Utilized in medical applications, biodegradable materials based on magnesium have been widely explored throughout the years. It is well-known that alloying Mg with biocompatible and non-toxic elements increases the biodegradability of surgical alloys. The purpose of this study was to examine the microstructure and the electrochemical response (corrosion resistance) of a new experimental Mg-based biodegradable alloy-Mg-0.5%Ca with additions of Zn as follows: 0.5, 1.5, and 3.0 wt.% in order to control the corrosion rate. Immersion tests were performed for different periods in a simulated body fluid electrolyte solution at 37 °C, and the mass loss was appreciated in order to calculate the corrosion rate (CR). The investigation led to the discovery of a dendritic Mg solid solution, a lamellar Mg₂Ca compound, and a MgZn₂ intermetallic phase. Scanning electron microscopy, optical microscopy, and energy dispersive spectroscopy were used for surface analysis after the immersion and electro-corrosion resistance tests. The metallic and ceramic compounds that detached themselves from the sample and passed into the solution were evaluated using the SEM-EDS system. All samples presented a generalized electro-corrosion with anodic and cathodic reactions of similar intensity. The corrosion rate was similar regardless of the percentage of zinc, with a smaller value for a higher than 3 wt.% Zn percentage based on the more protective zinc oxide that appeared on the surface.

The effects of atomic percentage and size of Zinc nanoparticles, and atomic porosity on thermal and mechanical properties of reinforced calcium phosphate cement by molecular dynamics simulation

This study used the molecular dynamics (MD) simulation method to assess the effects of different percentages of NPs, sizes, and percentages of porosity on reinforced cement thermal behavior (TB) and mechanical behavior (MB) of samples. The temperature and kinetic energy (KE) converged to 300 K and 35.42 eV after 10 ns, which indicated the thermodynamic equilibrium and the atomic stability in the structures. Increasing the NPs percentage from 1% to 3% increased the maximum temperature from 1364 to 1405 K. By further increasing it to 5%, it was reduced to 1361 K. As the radius of Zn NPs increased to 16 Å, the ultimate strength (US) and Young's Modulus (YM) increased from 1.07 to 0.19 MPa to 1.2 and 0.22 MPa. The increase in the NPs' radius to 16 Å caused an increase in the maximum temperature from 1405 to 1455 K, maintaining atomic stability. As the porosity increased from 1% to 5%, the US and YM reduced from 0.91 to 0.17 MPa to 0.81 and 0.15 MPa. As the porosity increased from 1% to 5%, the maximum temperature was reduced from 1400 K to 1384 K. According to the results, Zn NPs' percentage and size effectively improved the MB of the final cement.