A functionalized TiO2/Mg2TiO4 nano-layer on biodegradable magnesium implant enables superior bone-implant integration and bacterial disinfection

Enhancing corrosion resistance of biodegradable magnesium with dicalcium phosphate dihydrate and Chlorella sp. biomass

Magnesium shows promise as a material for temporary fixation, yet its rapid corrosion poses health risks due to metal ion release. To mitigate these concerns, a biofunctionalization approach involving dicalcium phosphate dihydrate (DCPD) compounds and Chlorella sp. biomass was employed via electrodeposition, silanization, and dip-coating. Surface characterization using XRD, FTIR, and SEM confirmed successful deposition and immobilization. Corrosion behavior was assessed through electrochemical, immersion, and atomic absorption tests, revealing improved resistance and reduced Mg2+ ion release. The coatings demonstrated significant enhancement in corrosion resistance, guarding against pitting and cracks. The findings suggest the potential of Mg/DCPD and Mg/DCPD/microalgae coatings in addressing corrosion-related risks in temporary fixation applications, promising improved biocompatibility and longevity for medical implants.

SrTiO3 Nanotube-Based "Pneumatic Nanocannon" for On-Demand Delivery of Antibacterial and Sustained Osseointegration Enhancement

Infection and aseptic loosening caused by bacteria and poor osseointegration remain serious challenges for orthopedic implants. The advanced surface modification of implants is an effective strategy for addressing these challenges. This study presents a "pneumatic nanocannon" coating for titanium orthopedic implants to achieve on-demand release of antibacterial and sustained release of osteogenic agents. SrTiO3 nanotubes (SrNT) were constructed on the surface of Ti implants as "cannon barrel," the "cannonball" (antibiotic) and "propellant" (NH4HCO3) were codeposited into SrNT with assistance of mussel-inspired copolymerization of dopamine and subsequently sealed by a layer of polydopamine. The encapsulated NH4HCO3 within the nanotubes could be thermally decomposed into gases under near-infrared irradiation, propelling the on-demand delivery of antibiotics. This coating demonstrated significant efficacy in eliminating typical pathogenic bacteria both in planktonic and biofilm forms. Additionally, this coating exhibited a continuous release of strontium ions, which significantly enhanced the osteogenic differentiation of preosteoblasts. In an implant-associated infection rat model, this coating demonstrated substantial antibacterial efficiency (>99%) and significant promotion of osseointegration, along with alleviated postoperative inflammation. This pneumatic nanocannon coating presents a promising approach to achieving on-demand infection inhibition and sustained osseointegration enhancement for titanium orthopedic implants.

Construction of antibacterial bone implants and their application in bone regeneration

Bacterial infection represents a prevalent challenge during the bone repair process, often resulting in implant failure. However, the extensive use of antibiotics has limited local antibacterial effects at the infection site and is prone to side effects. In order to address the issue of bacterial infection during the transplantation of bone implants, four types of bone scaffold implants with long-term antimicrobial functionality have been constructed, including direct contact antimicrobial scaffold, dissolution-penetration antimicrobial scaffold, photocatalytic antimicrobial scaffold, and multimodal synergistic antimicrobial scaffold. The direct contact antimicrobial scaffold involves the physical penetration or disruption of bacterial cell membranes by the scaffold surface or hindrance of bacterial adhesion through surface charge, microstructure, and other factors. The dissolution-penetration antimicrobial scaffold releases antimicrobial substances from the scaffold's interior through degradation and other means to achieve local antimicrobial effects. The photocatalytic antimicrobial scaffold utilizes the absorption of light to generate reactive oxygen species (ROS) with enhanced chemical reactivity for antimicrobial activity. ROS can cause damage to bacterial cell membranes, deoxyribonucleic acid (DNA), proteins, and other components. The multimodal synergistic antimicrobial scaffold involves the combined use of multiple antimicrobial methods to achieve synergistic effects and effectively overcome the limitations of individual antimicrobial approaches. Additionally, the biocompatibility issues of the antimicrobial bone scaffold are also discussed, including in vitro cell adhesion, proliferation, and osteogenic differentiation, as well as in vivo bone repair and vascularization. Finally, the challenges and prospects of antimicrobial bone implants are summarized. The development of antimicrobial bone implants can provide effective solutions to bacterial infection issues in bone defect repair in the foreseeable future.

The development of magnesium-based biomaterials in bone tissue engineering: A review

Bone regeneration is a vital clinical challenge in massive or complicated bone defects. Recently, bone tissue engineering has come to the fore to meet the demand for bone repair with various innovative materials. However, the reported materials usually cannot satisfy the requirements, such as ideal mechanical and osteogenic properties, as well as biocompatibility at the same time. Mg-based biomaterials have considerable potential in bone tissue engineering owing to their excellent mechanical strength and biosafety. Moreover, the biocompatibility and osteogenic activity of Mg-based biomaterials have been the research focuses in recent years. The main limitation faced in the applications of Mg-based biomaterials is rapid degradation, which can produce excessive Mg2+ and hydrogen, affecting the healing of the bone defect. In order to overcome the limitations, researchers have explored several ways to improve the properties of Mg-based biomaterials, including alloying, surface modification with coatings, and synthesizing other composite materials to control the degradation rate upon implantation. This article reviewed the osteogenic mechanism and requirement for appropriate degradation rate and focused on current progress in the biomedical use of Mg-based biomaterials to inspire more clinical applications of Mg in bone regeneration in the future.

Investigation of In Vitro Cytocompatibility of Zinc-Containing Coatings Developed on Medical Magnesium Alloys

In a neutral solution, we investigated the effects of Na2[ZnEDTA] concentrations at 0, 6, 12, 18, and 24 g/L on surface morphology, chemical composition, degradation resistance, and in vitro cytocompatibility of micro-arc oxidation (MAO) coatings developed on WE43 (Mg-Y-Nd-Zr) magnesium alloys. The results show that the enhanced Na2[ZnEDTA] concentration increased the Zn amount but slightly decreased the degradation resistance of MAO-treated coatings. Among the zinc-containing MAO samples, the fabricated sample in the base solution added 6 g/L Na2[ZnEDTA] exhibits the smallest corrosion current density (6.84 × 10-7 A·cm-2), while the sample developed in the solution added 24 g/L Na2[ZnEDTA] and contains the highest Zn content (3.64 wt.%) but exhibits the largest corrosion current density (1.39 × 10-6 A·cm-2). Compared to untreated WE43 magnesium alloys, zinc-containing MAO samples promote initial cell adhesion and spreading and reveal enhanced cell viability. Coating degradation resistance plays a more important role in osseogenic ability than Zn content. Among the untreated WE43 magnesium alloys and the treated MAO samples, the sample developed in the base solution with 6 g/L Na2[ZnEDTA] reveals the highest ALP expression at 14 d. Our results indicate that the MAO samples formed in the solution with Na2[ZnEDTA] promoted degradation resistance and osseogenesis differentiation of the WE43 magnesium alloys, suggesting potential clinic applications.

Magnesium Alloys in Orthopedics: A Systematic Review on Approaches, Coatings and Strategies to Improve Biocompatibility, Osteogenic Properties and Osteointegration Capabilities

There is increasing interest in using magnesium (Mg) alloy orthopedic devices because of their mechanical properties and bioresorption potential. Concerns related to their rapid degradation have been issued by developing biodegradable micro- and nanostructured coatings to enhance corrosion resistance and limit the release of hydrogen during degradation. This systematic review based on four databases (PubMed®, Embase, Web of Science™ and ScienceDirect®) aims to present state-of-the-art strategies, approaches and materials used to address the critical factors currently impeding the utilization of Mg alloy devices. Forty studies were selected according to PRISMA guidelines and specific PECO criteria. Risk of bias assessment was conducted using OHAT and SYRCLE tools for in vitro and in vivo studies, respectively. Despite limitations associated with identified bias, the review provides a comprehensive analysis of preclinical in vitro and in vivo studies focused on manufacturing and application of Mg alloys in orthopedics. This attests to the continuous evolution of research related to Mg alloy modifications (e.g., AZ91, LAE442 and WE43) and micro- and nanocoatings (e.g., MAO and MgF2), which are developed to improve the degradation rate required for long-term mechanical resistance to loading and excellent osseointegration with bone tissue, thereby promoting functional bone regeneration. Further research is required to deeply verify the safety and efficacy of Mg alloys.

Recent advances in nanoantibiotics against multidrug-resistant bacteria

Multidrug-resistant (MDR) bacteria-caused infections have been a major threat to human health. The abuse of conventional antibiotics accelerates the generation of MDR bacteria and makes the situation worse. The emergence of nanomaterials holds great promise for solving this tricky problem due to their multiple antibacterial mechanisms, tunable antibacterial spectra, and low probabilities of inducing drug resistance. In this review, we summarize the mechanism of the generation of drug resistance, and introduce the recently developed nanomaterials for dealing with MDR bacteria via various antibacterial mechanisms. Considering that biosafety and mass production are the major bottlenecks hurdling the commercialization of nanoantibiotics, we introduce the related development in these two aspects. We discuss urgent challenges in this field and future perspectives to promote the development and translation of nanoantibiotics as alternatives against MDR pathogens to traditional antibiotics-based approaches.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Surface Modification of Titanium Implants by Metal Ions and Nanoparticles for Biomedical Application

Implant surface modification can improve osseointegration and reduce peri-implant inflammation. Implant surfaces are modified with metals because of their excellent mechanical properties and significant functions. Metal surface modification is divided into metal ions and nanoparticle surface modification. These two methods function by adding a finishing metal to the surface of the implant, and both play a role in promoting osteogenic, angiogenic, and antibacterial properties. Based on this, the nanostructural surface changes confer stronger antibacterial and cellular affinity to the implant surface. The current paper reviews the forms, mechanisms, and applications of nanoparticles and metal ion modifications to provide a foundation for the surface modification of implants.

Composite Nanocoatings of Biomedical Magnesium Alloy Implants: Advantages, Mechanisms, and Design Strategies

The rapid degradation of magnesium (Mg) alloy implants erodes mechanical performance and interfacial bioactivity, thereby limiting their clinical utility. Surface modification is among the solutions to improve corrosion resistance and bioefficacy of Mg alloys. Novel composite coatings that incorporate nanostructures create new opportunities for their expanded use. Particle size dominance and impermeability may increase corrosion resistance and thereby prolong implant service time. Nanoparticles with specific biological effects may be released into the peri-implant microenvironment during the degradation of coatings to promote healing. Composite nanocoatings provide nanoscale surfaces to promote cell adhesion and proliferation. Nanoparticles may activate cellular signaling pathways, while those with porous or core-shell structures may carry antibacterial or immunomodulatory drugs. Composite nanocoatings may promote vascular reendothelialization and osteogenesis, attenuate inflammation, and inhibit bacterial growth, thus increasing their applicability in complex clinical microenvironments such as those of atherosclerosis and open fractures. This review combines the physicochemical properties and biological efficiency of Mg-based alloy biomedical implants to summarize the advantages of composite nanocoatings, analyzes their mechanisms of action, and proposes design and construction strategies, with the purpose of providing a reference for promoting the clinical application of Mg alloy implants and to further the design of nanocoatings.

An osteogenic magnesium alloy with improved corrosion resistance, antibacterial, and mechanical properties for orthopedic applications

The aim of this study was to develop a novel biodegradable magnesium (Mg) alloy for bone implant applications. We used scandium (Sc; 2 wt %) and strontium (Sr; 2 wt %) as alloying elements due to their high biocompatibility, antibacterial efficacy, osteogenesis, and protective effects against corrosion. In the present work, we also examined the effect of a heat treatment process on the properties of the Mg-Sc-Sr alloy. Alloys were manufactured using a metal casting process followed by heat treatment. The microstructure, corrosion, mechanical properties, antibacterial activity, and osteogenic activity of the alloy were assessed in vitro. The results showed that the incorporation of Sc and Sr elements controlled the corrosion, reduced the hydrogen generation, and enhanced mechanical properties. Furthermore, alloying with Sc and Sr demonstrated a significantly enhanced antibacterial activity and decreased biofilm formation compared to control Mg. Also, culturing Mg-Sc-Sr alloy with human bone marrow-derived mesenchymal stromal cells showed a high degree of biocompatibility (>90% live cells) and a significant increase in osteoblastic differentiation in vitro shown by Alizarin red staining and alkaline phosphatase activity. Based on these results, the Mg-Sc-Sr alloy heat-treated at 400°C displayed optimal mechanical properties, corrosion rate, antibacterial efficacy, and osteoinductivity. These characteristics make the Mg-Sc-Sr alloy a promising candidate for biodegradable orthopedic implants in the fixation of bone fractures such as bone plate-screws or intramedullary nails.

Facile and versatile strategy for fabrication of highly bacteriostatic and biocompatible SLA-Ti surfaces with the regulation of Mg/Cu coimplantation ratio for dental implant applications

The low bactericidal activity and poor osteogenic activity of Ti limit the use of this metal in dental implants by increasing the risk of their periimplantitis-induced failure. To address this problem, we herein surface-modify biomedical Ti through the plasma immersion coimplantation of Mg and Cu ions and examine the physicochemical properties and bio-/hemocompatibility of the resulting materials as well as their activity against periimplantitis-causing bacteria, namely Streptococcus mutans and Porphyromonas gingivalis. The reactive oxygen species release (ROS) was assessed via the 2'7'-dichlorodihydrofluorescein diacetate (DCFH-DA) assay. The best-performing sample Mg/Cu（8/10）-Ti promotes cell proliferation and initial cell adhesion while exhibiting high hydrophilicity, outstanding activity against the aforementioned pathogens, and good bio-/hemocompatibility. Additionally, higher levels of cellular ROS generation in S. mutans and P. gingivalis could provide insight into the antibacterial mechanisms involved in Mg/Cu（8/10）-Ti. Thus, Mg/Cu coimplantation is concluded to endow the Ti surface with high bacteriostatic activity and biocompatibility, paving the way to the widespread use of Ti-based dental implants.

Biological Scaffolds Assembled with Magnetic Nanoparticles for Bone Tissue Engineering: A Review

Superparamagnetic iron oxide nanoparticles (SPION) are widely used in bone tissue engineering because of their unique physical and chemical properties and their excellent biocompatibility. Under the action of a magnetic field, SPIONs loaded in a biological scaffold can effectively promote osteoblast proliferation, differentiation, angiogenesis, and so on. SPIONs have very broad application prospects in bone repair, bone reconstruction, bone regeneration, and other fields. In this paper, several methods for forming biological scaffolds via the biological assembly of SPIONs are reviewed, and the specific applications of these biological scaffolds in bone tissue engineering are discussed.

Biodegradable Mg-Sc-Sr Alloy Improves Osteogenesis and Angiogenesis to Accelerate Bone Defect Restoration

Magnesium (Mg) and its alloys are considered to be biodegradable metallic biomaterials for potential orthopedic implants. While the osteogenic properties of Mg alloys have been widely studied, few reports focused on developing a bifunctional Mg implant with osteogenic and angiogenic properties. Herein, a Mg-Sc-Sr alloy was developed, and this alloy's angiogenesis and osteogenesis effects were evaluated in vitro for the first time. X-ray Fluorescence (XRF), X-ray diffraction (XRD), and metallography images were used to evaluate the microstructure of the developed Mg-Sc-Sr alloy. Human umbilical vein/vascular endothelial cells (HUVECs) were used to evaluate the angiogenic character of the prepared Mg-Sc-Sr alloy. A mix of human bone-marrow-derived mesenchymal stromal cells (hBM-MSCs) and HUVEC cell cultures were used to assess the osteogenesis-stimulating effect of Mg-Sc-Sr alloy through alkaline phosphatase (ALP) and Von Kossa staining. Higher ALP activity and the number of calcified nodules (27% increase) were obtained for the Mg-Sc-Sr-treated groups compared to Mg-treated groups. In addition, higher VEGF expression (45.5% increase), tube length (80.8% increase), and number of meshes (37.9% increase) were observed. The Mg-Sc-Sr alloy showed significantly higher angiogenesis and osteogenic differentiation than pure Mg and the control group, suggesting such a composition as a promising candidate in bone implants.

Development of degradable magnesium-based metal implants and their function in promoting bone metabolism (A review)

Background

Use of degradable magnesium (Mg)-based metal implants in orthopaedic surgeries can avoid drawbacks associated with subsequent removal of the non-degradable metallic implants, reducing cost and trauma of patients. Although Mg has been applied in the clinic for orthopaedic treatment, the use of Mg-based metal implants is largely in the research phase. But its application is potentially beneficial in this context as it has been shown that Mg can promote osteogenesis and inhibit osteoclast activity.

Methods

A systematic literature search about “degradable magnesium (Mg)-based metal implants” was performed in PubMed and Web of Science. Meanwhile, relevant findings have been reviewed and quoted.

Results

In this review, we summarize the latest developments in Mg-based metal implants and their role in bone regeneration. We also review the various molecular mechanisms by which Mg ions regulate bone metabolic processes, including osteogenesis, osteoclast activity, angiogenesis, immunity, and neurology. Finally, we discuss the remaining research challenges and opportunities for Mg-based implants and their applications.

Conclusion

Currently, establishment of the in vitro and in vivo biological evaluation systems and phenotypic modification improvement of Mg-based implants are still needed. Clarifying the functions of Mg-based metal implants in promoting bone metabolism is beneficial for their clinical application.

The Translational potential of this article

All current reviews on Mg-based implants are mainly concerned with the improvement of Mg alloy properties or the progress of applications. However, there are few reviews that provides a systematic narrative on the effect of Mg on bone metabolism. This review summarized the latest developments in Mg-based metal implants and various molecular mechanisms of Mg ions regulating bone metabolism, which is beneficial to further promote the translation of Mg based implants in the clinic and is able to provide a strong basis for the clinical application of Mg based implants.

Growth inhibition of bacterial pathogens by photo-catalyst process of nano-alloys FeCuNi doped TiO2 under ultraviolet irradiation

This study reports the application of FeCuNi nano-alloy doped TiO₂ synthesized via the sol-gel method as an antibacterial with a sterilization rate greater than 95% under ultra-violet (UV) irradiation. The performance was characterized using X-ray diffraction (XRD), thermal analysis (TG-DTA), scanning electron microscope (SEM-EDX), and transmission electron microscope (TEM). The results showed that the sterilization process of FeCuNi–TiO₂ in cell suspension of Escherichia coli, Staphylococcus aureus and Bacillus subtilis increased the effectiveness of UV irradiation at wavelength (λ) ≥ 385 nm after 120 min. The optimum growth inhibition of FeCuNi–TiO₂ was observed in the concentrations 1.5 g/L of E. coli, 1.5 g/L of S. aureus and 2.0 g/L of B. subtilis. The highest antimicrobial efficiency of FeCuNi–TiO₂ powder was provided by a particle size of 16.8 nm, surface area of 70.98 m²/g. The increased antimicrobial activity in multiplied-three doped ions was related to the increase of illumination energy of UV absorption in the photo-catalyst process. The inhibition mechanism reaction of the three species of bacteria cell affects the lipid peroxidation process at the microbe cell’s wall. This was indicated by the formation of malondialdehyde (MDA). Lipid oxidation was based on the reaction of 2-thiobarbituric acid (TBARS) as an indicator of primary and secondary oxidation.

High-efficient engineering of osteo-callus organoids for rapid bone regeneration within one month

Large bone defects that cannot form a callus tissue are often faced with long-time recovery. Developmental engineering-based strategies with mesenchymal stem cell (MSC) aggregates have shown enhanced potential for bone regeneration. However, MSC aggregates are different from the physiological callus tissues, which limited the further endogenous osteogenesis. This study aims to achieve engineering of osteo-callus organoids for rapid bone regeneration in cooperation with bone marrow-derived stem cell (BMSC)-loaded hydrogel microspheres (MSs) by digital light-processing (DLP) printing technology and stepwise-induction. The printed MSC-loaded MSs aggregated into osteo-callus organoids after chondrogenic induction and showed much higher chondrogenic efficiency than that of traditional MSC pellets. Moreover, the osteo-callus organoids exhibited stage-specific gene expression pattern that recapitulated endochondral ossification process, as well as a synchronized state of cell proliferation and differentiation, which highly resembled the diverse cell compositions and behaviors of developmentally endochondral ossification. Lastly, the osteo-callus organoids efficiently led to rapid bone regeneration within only 4 weeks in a large bone defect in rabbits which need 2-3 months in previous tissue engineering studies. The findings suggested that in vitro engineering of osteo-callus organoids with developmentally osteogenic properties is a promising strategy for rapid bone defect regeneration and recovery.

Magnesium for Implants: A Review on the Effect of Alloying Elements on Biocompatibility and Properties

An attempt is made to cover the whole of the topic of biodegradable magnesium (Mg) alloys with a focus on the biocompatibility of the individual alloying elements, as well as shed light on the degradation characteristics, microstructure, and mechanical properties of most binary alloys. Some of the various work processes carried out by researchers to achieve the alloys and their surface modifications have been highlighted. Additionally, a brief look into the literature on magnesium composites as also been included towards the end, to provide a more complete picture of the topic. In most cases, the chronological order of events has not been particularly followed, and instead, this work is concentrated on compiling and presenting an update of the work carried out on the topic of biodegradable magnesium alloys from the recent literature available to us.

Enhanced anti-corrosion and biocompatibility of a functionalized layer formed on ZK60 Mg alloy via hydroxyl (OH-) ion implantation

Magnesium and its alloys have piqued the interest of researchers due to their promising mechanical properties and biocompatibility. Moreover, the excessively fast corrosion rate of Mg alloys impedes their development in biomedical fields. Inspired by conventional ion implantation, a less-toxic functional group (hydroxyl) is used as the ion source to bombard the ZK60 Mg alloy surface to form a functionalized oxide layer. The surface characterization, corrosion resistance, and biocompatibility are systematically investigated before and after hydroxyl ion implantation. A smoother surface mainly constituted of hydroxide/oxide is formed for the treated samples. The formed functionalized layer significantly improves the corrosion resistance of the ZK60 Mg alloy substrate and the proliferation of MC3T3-E1 cells, as demonstrated by electrochemical, immersion, and in vitro cytocompatibility tests. In summary, less-toxic functional ion implantation can be an effective strategy for preventing corrosion of Mg alloy implants and promoting their biocompatibility.

Enhanced healing process of tooth sockets using strontium-doped TiO2

Prevention of residual ridge resorption is important for tooth socket healing in clinical treatment. As a well known biomaterial, titanium dioxide (TiO₂) has been reported to show desirable bone regeneration capability. On the other hand, strontium plays a role in maintaining normal function in organisms and balancing bone remodeling. Hence, we synthesized strontium-doped titanium dioxide mesoporous nanospheres functionalized with amino-group using diphenyl diisocyanate. After incorporation with segmented polyurethane, the obtained injectable SPU/Sr-TiO₂/MDI nanocomposite adhesive showed satisfactory antibacterial activity and cell nontoxicity. This nanocomposite was used for tooth socket healing, and greatly promoted the formation of new bone tissue in the tooth extraction socket.

Effects of Zinc, Magnesium, and Iron Ions on Bone Tissue Engineering

Large-sized bone defects are a great challenge in clinics and considerably impair the quality of patients' daily life. Tissue engineering strategies using cells, scaffolds, and bioactive molecules to regulate the microenvironment in bone regeneration is a promising approach. Zinc, magnesium, and iron ions are natural elements in bone tissue and participate in many physiological processes of bone metabolism and therefore have great potential for bone tissue engineering and regeneration. In this review, we performed a systematic analysis on the effects of zinc, magnesium, and iron ions in bone tissue engineering. We focus on the role of these ions in properties of scaffolds (mechanical strength, degradation, osteogenesis, antibacterial properties, etc.). We hope that our summary of the current research achievements and our notifications of potential strategies to improve the effects of zinc, magnesium, and iron ions in scaffolds for bone repair and regeneration will find new inspiration and breakthroughs to inspire future research.

Recent Advances in Transition-Metal Based Nanomaterials for Noninvasive Oncology Thermal Ablation and Imaging Diagnosis

With the developments of nanobiotechnology and nanomedicine, non-invasive thermal ablation with fewer side effects than traditional tumor treatment methods has received extensive attention in tumor treatment. Non-invasive thermal ablation has the advantages of non-invasiveness and fewer side effects compared with traditional treatment methods. However, the clinical efficiency and biological safety are low, which limits their clinical application. Transition-metal based nanomaterials as contrast agents have aroused increasing interest due to its unique optical properties, low toxicity, and high potentials in tumor diagnosis. Transition-metal based nanomaterials have high conversion efficiency of converting light energy into heat energy, good near-infrared absorption characteristics, which also can targetedly deliver those loaded drugs to tumor tissue, thereby improving the therapeutic effect and reducing the damage to the surrounding normal tissues and organs. This article mainly reviews the synthesis of transition-metal based nanomaterials in recent years, and discussed their applications in tumor thermal ablation and diagnosis, hopefully guiding the development of new transition metal-based nanomaterials in enhancing thermal ablation.

GSK-3β suppression upregulates Gli1 to alleviate osteogenesis inhibition in titanium nanoparticle-induced osteolysis

Wear particle-induced periprosthetic osteolysis (PPO) have become a major reason of joint arthroplasty failure and secondary surgery following joint arthroplasty and thus pose a severe threat to global public health. Therefore, determining how to effectively suppress particle-induced PPO has become an urgent problem. The pathological mechanism involved in the PPO signaling cascade is still unclear. Recently, the interaction between osteogenic inhibition and wear particles at the implant biological interface, which has received increasing attention, has been revealed as an important factor in pathological process. Additionally, Hedgehog (Hh)-Gli1 is a crucial signaling cascade which was regulated by multiple factors in numerous physiological and pathological process. It was revealed to exert a crucial part during embryonic bone development and metabolism. However, whether Hh-Gli1 is involved in wear particle-induced osteogenic inhibition in PPO remains unknown. Our present study explored the mechanism by which the Hh-Gli1 signaling cascade regulates titanium (Ti) nanoparticle-induced osteolysis. We found that Hh-Gli1 signaling was dramatically downregulated upon Ti particle treatment. Mechanistically, glycogen synthesis kinase 3β (GSK-3β) activation was significantly increased in Ti particle-induced osteogenic inhibition via changes in GSK-3β phosphorylation level and was found to participate in the posttranslational modification and degradation of the key transcription factor Gli1, thus decreasing the accumulation of Gli1 and its translocation from the cytoplasm to the nucleus. Collectively, these findings suggest that the Hh-Gli1 signaling cascade utilizes a GSK3β-mediated mechanism and may serve as a rational new therapeutic target against nanoparticle-induced PPO.

Construction of a magnesium hydroxide/graphene oxide/hydroxyapatite composite coating on Mg–Ca–Zn–Ag alloy to inhibit bacterial infection and promote bone regeneration

The improved corrosion resistance, osteogenic activity, and antibacterial ability are the key factors for promoting the large-scale clinical application of magnesium (Mg)-based implants. In the present study, a novel nanocomposite coating composed of inner magnesium hydroxide, middle graphene oxide, and outer hydroxyapatite (Mg(OH)₂/GO/HA) is constructed on the surface of Mg-0.8Ca–5Zn-1.5Ag by a combined strategy of hydrothermal treatment, electrophoretic deposition, and electrochemical deposition. The results of material characterization and electrochemical corrosion test showed that all the three coatings have high bonding strength, hydrophilicity and corrosion resistance. In vitro studies show that Mg(OH)₂ indeed improves the antibacterial activity of the substrate. The next GO and GO/HA coating procedures both promote the osteogenic differentiation of MC3T3-E1 cells and show no harm to the antibacterial activity of Mg(OH)₂ coating, but the latter exhibits the best promoting effect. In vivo studies demonstrate that the Mg alloy with the composite coating not only ameliorates osteolysis induced by bacterial invasion but also promotes bone regeneration under both normal and infected conditions. The current study provides a promising surface modification strategy for developing multifunctional Mg-based implants with good corrosion resistance, antibacterial ability and osteogenic activity to enlarge their biomedical applications.

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A Mg(OH)₂/GO/HA composite coating with high bonding strength was constructed on the surface of Mg–Ca–Zn–Ag alloy.

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The outer HA layer with excellent osteogenic activity recovered the high corrosion resistance of inner Mg(OH)₂ layer.

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The Mg(OH)₂/GO/HA composite coating promoted new bone regeneration significantly under both normal and infected conditions.

A bimetallic load-bearing bioceramics of TiO2 @ ZrO2 integrated polycaprolactone fibrous tissue construct exhibits anti bactericidal effect and induces osteogenesis in MC3T3-E1 cells

Bioactive mesoporous binary metal oxide nanoparticles allied with polymeric scaffolds can mimic natural extracellular matrix because of their self-mineralized functional matrix. Herein, we developed fibrous scaffolds of polycaprolactone (PCL) integrating well-dispersed TiO₂@ZrO₂ nanoparticles (NPs) via electrospinning for a tissue engineering approach. The scaffold with 0.1 wt% of bioceramic (TiO₂@ZrO₂) shows synergistic effects on physicochemical and bioactivity suited to stem cell attachment/proliferation. The bioceramics-based scaffold shows excellent antibacterial activity that can prevent implant-associated infections. In addition, the TiO₂@ZrO₂ in scaffold serves as a stem cell microenvironment to accelerate cell-to-cell interactions, including cell growth, morphology/orientation, differentiation, and regeneration. The NPs in PCL exert superior biocompatibility on MC3T3-E1 cells inducing osteogenic differentiation. The ALP activity and ARS staining confirm the upregulation of bone-related proteins and minerals suggesting the scaffolds exhibit osteoinductive abilities and contribute to bone cell regeneration. Based on this result, the bimetallic oxide could become a novel bone ceramic tailor TiO₂@ZrO₂ composite tissue-construct and keep potential nanomaterials-based scaffold for bone tissue engineering strategy.

Biomass Microcapsules with Stem Cell Encapsulation for Bone Repair

Bone defects caused by trauma, tumor, or osteoarthritis remain challenging due to the lack of effective treatments in clinic. Stem cell transplantation has emerged as an alternative approach for bone repair and attracted widespread attention owing to its excellent biological activities and therapy effect. The attempts to develop this therapeutic approach focus on the generation of effective cell delivery vehicles, since the shortcomings of direct injection of stem cells into target tissues. Here, we developed a novel core-shell microcapsule with a stem cell-laden core and a biomass shell by using all-aqueous phase microfluidic electrospray technology. The designed core-shell microcapsules showed a high cell viability during the culture procedure. In addition, the animal experiments exhibited that stem cell-laden core-shell microcapsules have good biocompatibility and therapeutic effect for bone defects. This study indicated that the core-shell biomass microcapsules generated by microfluidic electrospray have promising potential in tissue engineering and regenerative medicine.

Mg/Cu-doped TiO2 nanotube array: A novel dual-function system with self-antibacterial activity and excellent cell compatibility

Many studies were conducted to change the surface morphology and chemical composition of Ti implants for the improvement of antibacterial ability and osseointegration between medical Ti and surrounding bone tissue. In this study, we successfully prepared a novel dual-function coating on pure Ti surface, i.e. Cu and Mg-co-doped TiO₂ nanotube (TN) coating, by combining anodisation and hydrothermal treatment (HT), which could act as a delivery platform for the sustained release of Cu and Mg ions. Results showed that the amounts of Cu and Mg were about 5.43 wt%-6.55 wt% and 0.69 wt%-0.73 wt%, respectively. In addition, the surface morphology of Cu and Mg-co-doped TN (CuMTN) coatings transformed into nanoneedles after HT for 1 h. Compared with TN, CuMTN had no change in roughness and remarkable improved hydrophilicity. Antibacterial tests revealed that CuMTN had an antibacterial rate of more than 93% against Escherichia coli and Staphylococcus aureus, thereby showing excellent antibacterial properties. In addition, CuMTN could induce the formation of apatite well after being immersed in simulated body fluid, showing good biological activity. Preosteoblasts (MC3T3-E1) cultured on CuMTN-coated Ti demonstrated better proliferation and osteogenic differentiation than pristine and as-anodised specimens. To the best of our best knowledge, this study had successfully attempted to combine anodisation and HT, introduce Cu/Mg elements and functionalise Ti-based implant surfaces with enhanced hydrophilicity, osteogenesis and antimicrobial properties that can meet clinical needs for the first time.

Ba/Mg co-doped hydroxyapatite/PLGA composites enhance X-ray imaging and bone defect regeneration

Hydroxyapatite (HA) is the most commonly used orthopedic implant material. In recent years, the emergence of cationic doped hydroxyapatite has revealed more possibilities for the biological application of HA. Conventional HA does not promote new bone formation because of its poor osteoinductive activity, and has a similar density to that of bone, leading to difficulty in distinguishing both via imaging. Magnesium ions are useful for regulating the cellular behavior and promoting bone regeneration. Ba ion related compounds, such as BaSO₄, have a strong X-ray shielding effect. In this study, Ba/Mg@HA was synthesized to prepare Ba/Mg@HA/PLGA composites, and we aimed to investigate if Ba/Mg@HA/PLGA composites enhanced bone repair on osteoblasts and tibial defects, as well as the X-ray and CT imaging ability of bone implants in rats. The in vitro experimental results showed that the Ba/Mg@HA/PLGA composites significantly improved the attachment and osteogenic differentiation of MC3T3-E1 cells. These include the promotion of mineral deposition, enhancement of alkaline phosphatase activity, upregulation of OCN and COL-1 gene expression, and increase in COL-1 and OCN protein expression in a time- and concentration-dependent manner. The in vivo experimental results showed that the Ba/Mg@HA/PLGA composites significantly increased the rate of bone defect healing and the expression of BMP-2 and COL-1 in the bones of rats. X-ray and CT imaging results showed that the Ba/Mg@HA/PLGA composites enhanced the X-ray imaging ability. These findings indicate that the Ba/Mg@HA/PLGA composites can effectively promote bone formation and improve the X-ray and CT imaging abilities to a certain extent.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

Transmembrane charge (ion/electron) transfer is essential for maintaining cellular homeostasis and is involved in many biological processes, from protein synthesis to embryonic development in organisms. Designing implant devices that can detect or regulate cellular transmembrane charge transfer is expected to sense and modulate the behaviors of host cells and tissues. Thus, charge transfer can be regarded as a bridge connecting living systems and human-made implantable devices. This review describes the mode and mechanism of charge transfer between organisms and nonliving materials, and summarizes the strategies to endow implants with charge-transfer regulating or monitoring abilities. Furthermore, three major charge-transfer controlling systems, including wired, self-activated, and stimuli-responsive biomedical implants, as well as the design principles and pivotal materials are systematically elaborated. The clinical challenges and the prospects for future development of these implant devices are also discussed.

3D-Printing Biodegradable PU/PAAM/Gel Hydrogel Scaffold with High Flexibility and Self-Adaptibility to Irregular Defects for Nonload-Bearing Bone Regeneration

A three-dimensional (3D) printed biodegradable hydrogel scaffold with a strong self-expanding ability to conform to the contour of irregular bone defects and be closely adjacent to host tissues is reported herein. The scaffold has a triple cross-linked network structure consisting of photo-cross-linked polyacrylamide (PAAM) and polyurethane (PU) as the primary IPN network and chemical cross-linked gelatin (Gel) as the secondary network, which confers the scaffold with good mechanical properties. The addition of PU in the polymerization process of acrylamide (AAM) can improve the ultraviolet (UV) photocuring efficiency of the hydrogel and incorporate abundant hydrogen bonds between the PAAM copolymer chain and the PU chain. The results show that the hydrogel scaffold contains regular structures with smooth morphology, excellent dimensional stability, and uniform aperture. The degradation rate of the hydrogel scaffold is controllable through adjusting cross-linking agents and can be up to about 60% after degradation for 28 days. More importantly, the rapid self-inflating characteristic of the scaffold in water, that is, the volume of hydrogel scaffold can increase to about 8 times that of their own in an hour and can generate a slight compressive stress on the surrounding host tissue, thus stimulating the reconstruction and growth of new bone tissues. The in vitro experiment indicates that the scaffold is nontoxic and biocompatible. The in vivo experiment shows that the PU/PAAM/Gel chemically cross-linked scaffold displays the desirable osteogenic capability. This UV-curable 3D printed self-adaptive and degradable hydrogel scaffold holds great potential for nonload-bearing bone repair.

Advanced Strategies of Biomimetic Tissue-Engineered Grafts for Bone Regeneration

The failure to repair critical-sized bone defects often leads to incomplete regeneration or fracture non-union. Tissue-engineered grafts have been recognized as an alternative strategy for bone regeneration due to their potential to repair defects. To design a successful tissue-engineered graft requires the understanding of physicochemical optimization to mimic the composition and structure of native bone, as well as the biological strategies of mimicking the key biological elements during bone regeneration process. This review provides an overview of engineered graft-based strategies focusing on physicochemical properties of materials and graft structure optimization from macroscale to nanoscale to further boost bone regeneration, and it summarizes biological strategies which mainly focus on growth factors following bone regeneration pattern and stem cell-based strategies for more efficient repair. Finally, it discusses the current limitations of existing strategies upon bone repair and highlights a promising strategy for rapid bone regeneration.

Novel Inorganic Nanomaterial-Based Therapy for Bone Tissue Regeneration

Extensive bone defect repair remains a clinical challenge, since ideal implantable scaffolds require the integration of excellent biocompatibility, sufficient mechanical strength and high biological activity to support bone regeneration. The inorganic nanomaterial-based therapy is of great significance due to their excellent mechanical properties, adjustable biological interface and diversified functions. Calcium-phosphorus compounds, silica and metal-based materials are the most common categories of inorganic nanomaterials for bone defect repairing. Nano hydroxyapatites, similar to natural bone apatite minerals in terms of physiochemical and biological activities, are the most widely studied in the field of biomineralization. Nano silica could realize the bone-like hierarchical structure through biosilica mineralization process, and biomimetic silicifications could stimulate osteoblast activity for bone formation and also inhibit osteoclast differentiation. Novel metallic nanomaterials, including Ti, Mg, Zn and alloys, possess remarkable strength and stress absorption capacity, which could overcome the drawbacks of low mechanical properties of polymer-based materials and the brittleness of bioceramics. Moreover, the biodegradability, antibacterial activity and stem cell inducibility of metal nanomaterials can promote bone regeneration. In this review, the advantages of the novel inorganic nanomaterial-based therapy are summarized, laying the foundation for the development of novel bone regeneration strategies in future.

In vitro and in vivo antibacterial performance of Zr & O PIII magnesium alloys with high concentration of oxygen vacancies

The effects of dual Zr and O plasma immersion ion implantation (Zr & O PIII) on antibacterial properties of ZK60 Mg alloys are systematically investigated. The results show that a hydrophobic, smooth, and ZrO₂-containing graded film is formed. Electrochemical assessment shows that the corrosion rate of the plasma-treated Mg alloy decreases and the decreased degradation rate is attributed to the protection rendered by the surface oxide. In vitro and in vivo antibacterial tests reveal Zr & O PIII ZK60 presents higher antibacterial rate compared to Zr PIII ZK60 and untreated control. The hydrophobic and smooth surface suppresses bacterial adhesion. High concentration of oxygen vacancies in the surface films are determined by X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS) and electron paramagnetic resonance (EPR) and involved in the production of reactive oxygen species (ROS). The higher level of ROS expression inhibits biofilm formation by down-regulating the expression of icaADBC genes but up-regulating the expression of icaR gene. In addition, Zr & O PIII improves cell viability and initial cell adhesion confirming good cytocompatibility. Dual Zr & O PIII is a simple and practical means to expedite clinical acceptance of biodegradable magnesium alloys.

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A ZrO₂-containing graded film with high concentration of oxygen vacancies was formed via PIII.

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S. aureus adhesion was suppressed due to enhanced hydrophobicity and decreased roughness.

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High concentration of oxygen vacancies lead to the upregulation of ROS expression.

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ROS mediates biofilm-associated genes expression to inhibit biofilm formation in vitro and in vivo.

Regulation of extracellular bioactive cations in bone tissue microenvironment induces favorable osteoimmune conditions to accelerate in situ bone regeneration

The design of orthopedic biomaterials has gradually shifted from “immune-friendly” to “immunomodulatory,” in which the biomaterials are able to modulate the inflammatory response via macrophage polarization in a local immune microenvironment that favors osteogenesis and implant-to-bone osseointegration. Despite the well-known effects of bioactive metallic ions on osteogenesis, how extracellular metallic ions manipulate immune cells in bone tissue microenvironments toward osteogenesis and subsequent bone formation has rarely been studied. Herein, we investigate the osteoimmunomodulatory effect of an extracellular bioactive cation (Mg²⁺) in the bone tissue microenvironment using custom-made poly lactic-co-glycolic acid (PLGA)/MgO-alendronate microspheres that endow controllable release of magnesium ions. The results suggest that the Mg²⁺-controlled tissue microenvironment can effectively induce macrophage polarization from the M0 to M2 phenotype via the enhancement of anti-inflammatory (IL-10) and pro-osteogenic (BMP-2 and TGF-β1) cytokines production. It also generates a favorable osteoimmune microenvironment that facilitates the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. The in vivo results further verify that a large amount of bony tissue, with comparable bone mineral density and mechanical properties, has been generated at an early post-surgical stage in rat intramedullary bone defect models. This study demonstrates that the concept of in situ immunomodulated osteogenesis can be realized in a controlled magnesium tissue microenvironment.

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Controlled release of Mg²⁺ was achieved by the microfluidic electrosprayed PLGA/MgO-alendronate microspheres.

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PLGA/MgO-alendronate microspheres with satisfied osteoimmunomodulatory properties accelerated bone regeneration in vivo.

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Extracellular Mg²⁺ induced macrophage switch to M2 phenotype with enhanced expressions of IL-10, BMP-2 and TGF-β1.

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Osteoimmune microenvironment favourably upregulated the osteogenic expressions of BMSCs.

Osteogenesis, angiogenesis and immune response of Mg-Al layered double hydroxide coating on pure Mg

Layered double hydroxides (LDHs) are widely studied to enhance corrosion resistance and biocompatibility of Mg alloys, which are promising bone implants. However, the influence of LDH coating on the osteointegration of Mg implants lacks of a systematic study. In this work, Mg-Al LDH coating was prepared on pure Mg via hydrothermal treatment. The as-prepared Mg-Al LDH coated Mg exhibited better in vitro and in vivo corrosion resistance than bare Mg and Mg(OH)2 coated Mg. In vitro culture of mouse osteoblast cell line (MC3T3-E1) suggested that Mg-Al LDH coated Mg was more favorable for its osteogenic differentiation. In vitro culture of HUVECs revealed that cells cultured in the extract of Mg-Al LDH coated Mg showed superior angiogenic behaviors. More importantly, the immune response of Mg-Al LDH coated Mg was studied by in vitro culturing murine-derived macrophage cell line (RAW264.7). The results verified that Mg-Al LDH coated Mg could induce macrophage polarize to M2 phenotype (anti-inflammatory). Furthermore, the secreted factor in the macrophage-conditioned culture medium of Mg-Al LDH group was more suitable for the bone differentiation of rat bone marrow stem cells (rBMSCs) and the angiogenic behavior of human umbilical vein endothelial cells (HUVECs). Finally, the result of femoral implantation suggested that Mg-Al LDH coated Mg exhibited better osteointegration than bare Mg and Mg(OH)2 coated Mg. With favorable in vitro and in vivo performances, Mg-Al LDH is promising as protective coating on Mg for orthopedic applications.

Effects of Various Polishing Techniques on the Surface Characteristics of the Ti-6Al-4V Alloy and on Bacterial Adhesion

Ti-6Al-4V, although widely used in dental materials, causes peri-implant inflammation due to the long-term accumulation of bacteria around the implant, resulting in bone loss and eventual failure of the implant. This study aims to overcome the problem of dental implant infection by analyzing the influence of Ti-6Al-4V surface characteristics on the quantity of accumulated bacteria. Ti-6Al-4V specimens, each with different surface roughness are produced by mechanical, chemical, and electrolytic polishing. The surface roughness, surface contact angle, surface oxygen content, and surface structure were measured via atomic force microscopy (AFM), laser scanning confocal microscopy (LSCM), drop shape analysis (using sessile drop), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The micro and macro surface roughness are 10.33–120.05 nm and 0.68–2.34 μm, respectively. The surface X direction and Y direction contact angle are 21.38°–96.44° and 18.37°–92.72°, respectively. The surface oxygen content is 47.36–59.89 at.%. The number of colonies and the optical density (OD) are 7.87 × 106–17.73 × 106 CFU/mL and 0.189–0.245, respectively. The bacterial inhibition were the most effective under the electrolytic polishing of Ti-6Al-4V. The electrolytic polishing of Ti-6Al-4V exhibited the best surface characteristics: the surface roughness of 10 nm, surface contact angle of 92°, and surface oxygen content of 54 at.%, respectively. This provides the best surface treatment of Ti-6Al-4V in dental implants.

Properties of Titanium Oxide Coating on MgZn Alloy by Magnetron Sputtering for Stent Application

Constructing surface coatings is an effective way to improve the corrosion resistance and biocompatibility of magnesium alloy bioabsorbable implants. In this present work, a titanium oxide coating with a thickness of about 400 nm was successfully prepared on a MgZn alloy surface via a facile magnetron sputtering route. The surface features were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the contact angle method. The corrosion behavior and biocompatibility were evaluated. The results indicated that the amorphous TiO2 coating with a flat and dense morphology was obtained by magnetron-sputtering a titanium oxide target. The corrosion current density decreased from 1050 (bare MgZn alloy) to 49 μA/cm2 (sample with TiO2 coating), suggesting a significant increase in corrosion resistance. In addition, the TiO2 coating showed good biocompatibilities, including significant reduced hemolysis and platelet adhesion, and increased endothelial cell viability and adhesion.

Biodegradable magnesium alloy with eddy thermal effect for effective and accurate magnetic hyperthermia ablation of tumors

Magnetic hyperthermia therapy (MHT) is able to ablate tumors using an alternating magnetic field (AMF) to heat up magnetocaloric agents (e.g. magnetic nanoparticles) administered into the tumors. For clinical applications, there is still a demand to find new magnetocaloric agents with strong AMF-induced heating performance and excellent biocompatibility. As a kind of biocompatible and biodegradable material, magnesium (Mg) and its alloys have been extensively used in the clinic as an implant metal. Herein, we discovered that the eddy thermal effect of the magnesium alloy (MgA) could be employed for MHT to effectively ablate tumors. Under low-field-intensity AMFs, MgA rods could be rapidly heated, resulting in a temperature increase in nearby tissues. Such AMF-induced eddy thermal heating of MgA could not only be used to kill tumor cells in vitro, but also be employed for effective and accurate ablation of tumors in vivo. In addition to killing tumors in mice, we further demonstrated that VX₂ tumors of much larger sizes growing in rabbits after implantation of MgA rods could also be eliminated after exposure to an AMF, illustrating the ability of MgA-based MHT to kill large-sized tumors. Moreover, the implanted MgA rods showed excellent biocompatibility and ∼20% of their mass was degraded within three months. Our work thus discovered for the first time that non-magnetic biodegradable MgA, an extensively used implant metal in clinic, could be used for effective magnetic thermal ablation of tumors under a low-field-intensity AMF. Such a strategy could be readily translated into clinical use.

Robust Biomimetic Hierarchical Diamond Architecture with a Self-Cleaning, Antibacterial, and Antibiofouling Surface

Biofouling is a worldwide problem from healthcare to marine exploration. Aggressive biofouling, wear, and corrosion lead to severe deterioration in function and durability. Here, micro- and nanostructured hierarchical diamond films mimicking the morphology of plant leaves were developed to simultaneously achieve superhydrophobicity, antibacterial efficacy, and marine antibiofouling, combined with mechanical and chemical robustness. These coatings were designed and successfully constructed on various commercial substrates, such as titanium alloys, silicon, and quartz glass via a chemical vapor deposition process. The unique surface structure of diamond films reduced bacteria attachment by 90-99%. In the marine environment, these biomimetic diamond films significantly reduced more than 95% adhesion of green algae. The structured diamond films retained mechanical robustness, superhydrophobicity, and antibacterial efficacy under high abrasion and corrosive conditions, exhibiting at least 20 times enhanced wear resistance than the bare commercial substrates even after long-term immersion in seawater.

A biodegradable multifunctional nanofibrous membrane for periodontal tissue regeneration

Biomaterial-based membranes represent a promising therapeutic option for periodontal diseases. Although conventional periodontal membranes function greatly in preventing the ingrowth of both fibroblasts and epithelial cells as well as connective tissues, they are not capable of promoting periodontal tissue regeneration. Here, we report a multifunctional periodontal membrane prepared by electrospinning biodegradable polymers with magnesium oxide nanoparticles (nMgO). nMgO is a light metal-based nanoparticle with high antibacterial capacity and can be fully resorbed in the body. Our results showed that incorporating nMgO into poly(L-lactic acid) (PLA)/gelatin significantly improved the overall properties of membranes, including elevated tensile strength to maintain structural stability and adjusted degradation rate to fit the time window of periodontal regeneration. Acidic degradation products of PLA were neutralized by alkaline ions from nMgO hydrolysis, ameliorating pH microenvironment beneficial for cell proliferation. In vitro studies demonstrated considerable antibacterial and osteogenic properties of nMgO-incorporated membranes that are highly valuable for periodontal regeneration. Further investigations in a rat periodontal defect model revealed that nMgO-incorporated membranes effectively guided periodontal tissue regeneration. Taken together, our data indicate that nMgO-incorporated membranes might be a promising therapeutic option for periodontal regeneration. STATEMENT OF SIGNIFICANCE: Traditional clinical treatments of periodontal diseases largely focus on the management of the pathologic processes, which cannot effectively regenerate the lost periodontal tissue. GTR, a classic method for periodontal regeneration, has shown promise in clinical practice. However, the current membranes might not fully fulfill the criteria of ideal membranes. Here, we report bioabsorbable nMgO-incorporated nanofibrous membranes prepared by electrospinning to provide an alternative for the clinical practice of GTR. The membranes not only function greatly as physical barriers but also exhibit high antibacterial and osteoinductive properties. We therefore believe that this study will inspire more practice work on the development of effective GTR membranes for periodontal regeneration.

The role of magnesium in biomaterials related infections

Magnesium is currently increasing interest in the field of biomaterials. An extensive bibliography on this material in the last two decades arises from its potential for the development of biodegradable implants. In addition, many researches, motivated by this progress, have analyzed the performance of magnesium in both in vitro and in vivo assays with gram-positive and gram-negative bacteria in a very broad range of conditions. This review explores the extensive literature in recent years on magnesium in biomaterials-related infections, and discusses the mechanisms of the Mg action on bacteria, as well as the competition of Mg²⁺ and/or synergy with other divalent cations in this subject.

Tissue Engineering and Regenerative Medicine: Achievements, Future, and Sustainability in Asia

Exploring innovative solutions to improve the healthcare of the aging and diseased population continues to be a global challenge. Among a number of strategies toward this goal, tissue engineering and regenerative medicine (TERM) has gradually evolved into a promising approach to meet future needs of patients. TERM has recently received increasing attention in Asia, as evidenced by the markedly increased number of researchers, publications, clinical trials, and translational products. This review aims to give a brief overview of TERM development in Asia over the last decade by highlighting some of the important advances in this field and featuring major achievements of representative research groups. The development of novel biomaterials and enabling technologies, identification of new cell sources, and applications of TERM in various tissues are briefly introduced. Finally, the achievement of TERM in Asia, including important publications, representative discoveries, clinical trials, and examples of commercial products will be introduced. Discussion on current limitations and future directions in this hot topic will also be provided.

Multistep Instead of One-Step: A Versatile and Multifunctional Coating Platform for Biocompatible Corrosion Protection

Magnesium alloys have potential application in cardiovascular stents and orthopedic implants. However, the rapid corrosion rate of magnesium limits their clinical application. In order to improve the corrosion resistance and biocompatibility of the substrate, a protective coating is constructed by alternate immersing of MgZnMn alloy in epigallocatechin gallate (EGCG) and polyethyleneimine (PEI) solution. The conventional method is immersing magnesium alloy into a conversion solution by simple one-step immersion. In the present work, the EGCG/PEI coating is prepared by a novel alternate immersion method. The number of alternate immersions resulted in a different density of phenolic hydroxyl groups and amino groups on the surface. The corrosion resistance and bonding strength of the coating also varied with alternating immersion times. As the corrosion resistance and density of the functional groups varies, endothelial cells (ECs), smooth muscle cells (SMCs), osteoblasts, and macrophages showed a different growth state on EGCG/PEI coatings. In summary, this EGCG/PEI coating addressed the rapid corrosion rate of the magnesium alloy and can adjust its function by controlling the number of alternate immersions. The EGCG/PEI coating exhibited multifunctions: improved corrosion resistance, good compatibility with ECs and osteoblasts, and inhibition of SMC growth and inflammation, and the effective groups on the coating make it possible for further modification by grafting biomolecules. This is an effective method for preparing a multifunctional platform on biomedical magnesium alloys.