Antibacterial metals and alloys for potential biomedical implants

Understanding the antibacterial mechanism of metal surfaces

Bacterial inactivation on antibacterial metal surfaces has been widely used in medicine and daily life to inhibit infection caused by surface contact. However, the underlying antibacterial mechanism of metal surfaces has remained elusive due to a lack of comprehensive theoretical perspectives and direct evidence. Here, we propose a universal understanding of the bacteria-inactivation mechanism of metal surfaces and reveal the changes in bacterial survival behavior with time and spatial location. In terms of bacterial survival over time, we established a quantitative ion influx model and predicted four bacterial survival behaviors based on osmotic pressure changes and ion release. To demonstrate the spatial distribution of bacterial survival, we consider variations in metal antibacterial properties and electrode potentials and design five corrosion galvanic couples to cover all possible metal combinations. The results on the bacterial survival behavior over time confirm our theoretical predictions, exhibiting a dependence of bacterial viability on environmental humidity and metal toxicity. In addition, on the surfaces of galvanic couples, bacteria will experience the most pronounced decrease in viability at anodes, irrespective of the location of the antibacterial metals. This abnormal distribution pattern can be fundamentally attributed to the highest toxic-ion concentration resulting from a low pH at anodes. The consistency between our predictions and observed bacterial survival rates supports the notion that the antibacterial mechanism follows surface ion release and subsequent free-ion influx into the cytoplasm, leading to lethal biochemical reactions in bacteria. STATEMENT OF SIGNIFICANCE: Numerous studies have been conducted on developing antibacterial metals, alloys, and their related applications. However, the underlying antibacterial mechanism of metal surfaces has remained elusive. This work is the first to propose a general understanding of the antibacterial mechanism of metal surfaces, including the temporal and spatial characteristics of bacterial survival behavior. By building a theoretical model, we predicted and confirmed the shapes of the four bacterial survival curves over time. In addition, we found that bacteria have the worst viability loss at the alloy anode, even if non-antibacterial metals occupy this position. The conclusions can provide theoretical support for the antibacterial behavior of metal surfaces, including but not limited to Ag, Cu, Zn, and their corresponding alloys.

Antibacterial properties of copper-tantalum thin films: The impact of copper content and thermal treatment on implant coatings

This study evaluates the antibacterial properties and physicochemical characteristics of -tantalum-copper (Ta-Cu) coatings deposited on titanium alloy substrates using high-power magnetron sputtering. Implant-associated infections, particularly those caused by bacterial adhesion and biofilm formation, pose significant challenges in the field of orthopedic and dental implants. To address these issues, Ta-Cu coatings with varying copper content (∼3.0 wt%, ∼10 wt%, ∼17 wt% for TaCu-1, TaCu-2, and TaCu-3, respectively) and different thermal treatment conditions (400 °C, 500 °C, 600 °C) were assessed for their antibacterial efficacy against Escherichia coli, Staphylococcus aureus, Salmonella enterica, and Pseudomonas aeruginosa. The study utilized both the diffusion into agar method and the time-kill test to evaluate antibacterial activity. Results indicate that the TaCu-2 sample, particularly when annealed at 600 °C, demonstrated the highest bactericidal activity, especially against E. coli and P. aeruginosa. The findings highlight the critical role of optimizing both copper content and annealing temperature in enhancing the antibacterial properties of Cu-Ta coatings, making them promising candidates for preventing implant-associated infections.

Surface modification of AISI 316L stainless steel by applying single and multilayer coatings: Study of elastic modulus and antibacterial properties

AISI 316L stainless steel is extensively used in various fields, including medicine. In this study, in order to improve antibacterial properties, reduce elastic modulus, increase hydrophilicity and delay corrosion on the surface of AISI 316L stainless steel pieces for biomedical applications, zinc and magnesium elements were used for coating. Zn monolayer, Zn-Mg bilayer, and Zn-Mg-Zn triple coatings were deposited on AISI 316L substrates using the thermal evaporation method. Field emission scanning electron microscopy (FE-SEM) confirmed the formation of thin film coatings on the substrate. EDX analysis also indicated the presence of Zn and Mg elements in the coatings. Atomic force microscopy (AFM) results showed a reduction in the root mean square roughness in the coated specimens compared to the uncoated ones. This technique was also used to compare the force between the samples. The result of this research indicated 22.78 % increase in hydrophilicity, 31.25 % improvement in antibacterial properties and 86.67 % reduction in elastic modulus when comparing the uncoated sample with the three-layer coated sample. X-ray diffraction (XRD) revealed the intermetallic composition of Zn and Mg. The average crystallite size, determined using Scherer's equation, was 14.61, 13.15, 13.92, and 49.60 nm for the uncoated, one-layer, two-layer, and three-layer samples, respectively. Atomic absorption spectroscopy (AAS) revealed that the 24-h release of Zn2+, Mg2+, and Ni2+ ions from the samples was within the allowable range when immersed in simulated body fluid (SBF). Corrosion measurements indicated the formation of a galvanic cell due to the layers in the coated samples, and the substrate did not corrode until the coating was fully degraded.

Rethinking Biomedical Titanium Alloy Design: A Review of Challenges from Biological and Manufacturing Perspectives

Current biomedical titanium alloys have been repurposed from other industries, which has contributed to several biologically driven implant failure mechanisms. This review highlights the added value that may be gained by building an appreciation of implant biological responses at the onset of alloy design. Specifically, the fundamental mechanisms associated with immune response, angiogenesis, osseointegration and the potential threat of infection are discussed, including how elemental selection can modulate these pivotal systems. With a view to expedite inclusion of these interactions in alloy design criteria, methods to analyze these performance characteristics are also summarized. While machine learning techniques are being increasingly used to unearth complex relationships between alloying elements and material properties, much is still unknown about the correlation between composition and some bio-related properties. To bridge this gap, high-throughput methods are also reviewed to validate biological response along with cutting edge manufacturing approaches that may support rapid discovery. Taken together, this review encourages the alloy development community to rethink their approach to enable a new generation of biomedical implants intrinsically designed for a life in the body, including functionality to tackle biological challenges thereby offering improved patient outcomes.

Advances in 3D printing technology for preparing bone tissue engineering scaffolds from biodegradable materials

Introduction

Bone tissue engineering (BTE) provides an effective repair solution by implanting osteoblasts or stem cells into biocompatible and biodegradable scaffolds to promote bone regeneration. In recent years, the rapid development of 3D bioprinting has enabled its extensive application in fabricating BTE scaffolds. Based on three-dimensional computer models and specialized "bio-inks," this technology offers new pathways for customizing BTE scaffolds. This study reviews the current status and future prospects of scaffold materials for BTE in 3D bioprinting.

Methods

This literature review collected recent studies on BTE and 3D bioprinting, analyzing the advantages and limitations of various scaffold materials for 3D printing, including bioceramics, metals, natural polymers, and synthetic polymers. Key characteristics like biocompatibility, mechanical properties, and degradation rates of these materials were systematically compared.

Results

The study highlights the diverse performances of materials used in BTE scaffolds. Bioceramics exhibit excellent biocompatibility but suffer from brittleness; metals offer high strength but may induce chronic inflammation; natural polymers are biocompatible yet have poor mechanical properties, while synthetic polymers offer strong tunability but may produce acidic by-products during degradation. Additionally, integrating 3D bioprinting with composite materials could enhance scaffold biocompatibility and mechanical properties, presenting viable solutions to current challenges.

Discussion

This review summarizes recent advances in 3D bioprinting for BTE scaffold applications, exploring the strengths and limitations of various materials and proposing composite material combinations to improve scaffold performance. By optimizing material selection and combinations, 3D bioprinting shows promise for creating customized scaffolds, offering a new technical route for clinical applications of BTE. This research provides a unique perspective and theoretical support for advancing 3D bioprinting technology in bone regeneration, outlining future directions for BTE materials and 3D bioprinting technology development.

Emerging Strategies to Prevent Bacterial Infections on Titanium-Based Implants

Titanium and titanium alloys remain the gold standard for dental and orthopedic implants. These materials are heavily used because of their bioinert nature, robust mechanical properties, and seamless integration with bone. However, implant-associated infections (IAIs) remain one of the leading causes of implant failure. Eradicating an IAI can be difficult since bacteria can form biofilms on the medical implant, protecting the bacterial cells against systemic antibiotics and the host's immune system. If the infection is not treated promptly and aggressively, device failure is inevitable, leading to costly multi-step revision surgeries. To circumvent this dire situation, scientists and engineers continue to develop novel strategies to protect the surface of medical implants from bacteria. In this review, details on emerging strategies to prevent infection in titanium implants are reported. These strategies include anti-adhesion properties provided by polymers, superhydrophobic, superhydrophilic, and liquid-infused surface coatings, as well as strategies and coatings employed to lyse the bacteria. Additionally, commercially available technologies and those under preclinical trials are examined while discussing current and future trends.

Coalescence Mechanism Induced by Different Wetting States of Ti and Al Droplets on Rough Surfaces

There is currently increasing interest in droplet transportation and coalescence on rough surfaces. However, the relationship among wettability, coalescence mode, and substrate characteristics (roughness and nanopillar height) remains unclear. In this work, two coalescence modes, climbing coalescence and contacting coalescence, are first observed in the dynamic behaviors of Ti and Al droplets on rough substrates. Due to the nonsynchronized wetting state transition of the droplets, the coalescence mode with increasing substrate characteristics differs, transitioning from contacting coalescence to climbing coalescence and then returning to the contacting mode. In general, the mode of coalescence correlates closely with the respective wetting states. Typically, Ti and Al droplets coalesce in the contacting mode when they have the same wetting state, but if they have different wetting states, they coalesce in the climbing mode. Our results emphasize the complicated relationship between the surface structure and the wettability of droplets, which could provide insights into self-assembly, three-dimensional printing, and microfluidic devices.

Synergistic antimicrobial nanofiber membranes based on metal incorporated silica nanoparticles as advanced antimicrobial layers

In this post-new-normal era, the public prioritizes preventive measures over curing, which is a constructive approach to staying healthy. In this study, an innovative antimicrobial membrane material has been developed, showcasing the promising potential for various applications. The metal-doped silica nanoparticles (Ag, Cu, and Co) were incorporated into a cellulose acetate (CA) polymer-based nanofiber membrane using the electrospinning technique. The metal nanoparticles were doped into a silanol network of silica nanoparticles. The fabricated membranes underwent detailed characterization using a wide range of techniques including PXRD, FTIR, Raman, SEM, TEM, TGA, and tensile testing. These analyses provided compelling evidence confirming the successful incorporation of metal-doped silica nanoparticles (Ag, Cu, and Co) into cellulose-based nanofibers. The band gap energies of the fabricated CA mats lie below 3.00 eV, confirming that they are visible light active. The trimetallic silica nanohybrid exhibited the lowest band gap energy of 2.84 eV, proving the self-sterilizing ability of the CA mats. The DPPH assay further confirmed the best radical scavenging activity by the trimetallic silica nanohybrid incorporated nanofiber mat (91.77 ± 0.88%). The antimicrobial activity was assessed by using the bacterial ATCC strains of Staphylococcus aureus, Streptococcus pneumoniae, MRSA (Methicillin-resistant Staphylococcus aureus), Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa and fungal strains; quality control samples of Trichophyton rubrum, Microsporum gypsium, and Aspergillus niger, as well as the ATCC strain of Candida albicans. The trimetallic silica nanohybrid-incorporated CA membranes demonstrated the most significant inhibition zones. The reported findings substantiate the self-sterilizing mat's viability, affordability, efficacy against a broad spectrum of microbial strains, cost-effectiveness, and biodegradability. Furthermore, the mat serves as a dual-purpose physical and biological barrier against microbes, affirming its potential impact.

Preparation and Antibacterial Properties of Polyelectrolyte Complexed Nanoparticles Aggregated from PHMG and Sodium Caffeate

In this study, we synthesized polyelectrolyte complexed nanoparticles using an ion exchange reaction between poly(hexamethylene guanidine hydrochloride) and sodium caffeate. The morphology of the obtained antiparticle was observed by scanning electron microscopy, and FT-IR and XPS were employed for the structural characterization. The antimicrobial properties of E. coli and S. aureus were characterized through minimum inhibitory concentration (MIC), growth curve analysis, plate colony counting method, and crystal violet method. Notably, the sample showed a 100% bactericidal rate against E. coli at 0.095 μg/mL and against S. aureus at 0.375 μg/mL within 1 h, demonstrating excellent antimicrobial performance against E. coli and S. aureus. The CA-PHMG-containing acrylic resin coatings exhibited exceptional antimicrobial and antiadhesive properties when examined under an inverted fluorescence microscope, particularly at a 4% weight concentration of the antibacterial agent. This study holds vast potential for development in the field of antimicrobial coatings.

Enhancing anti-adhesion properties by designing microstructure - the microscopy and spectroscopy study of the intercellular bacterial response

This study is the first one that investigates in detail the bacterial intercellular response to the high density of crystallographic defects including vacancies created in Cu by high pressure torsion. To this aim, samples were deformed by high pressure torsion and afterward, their antibacterial properties against Staphylococcus aureus were analyzed in adhesion tests. As a reference an annealed sample was applied. To avoid the influence of surface roughness, specially elaborated conditions for surface preparation were employed, which do not introduce defects and assure comparable surface roughness. The analysis of the chemical composition and thickness of passive layers by X-ray photoelectron spectroscopy showed that they were comparable for nanostructured and micrograined samples, consisting of Cu2O and CuO, and a thickness of 6 nm. The interface bacterium-substrate was prepared by a focused ion beam and further analyzed by scanning transmission electron microscopy and energy dispersive spectroscopy. High pressure torsion processed Cu shows enhanced anti-adhesion properties while in contact with S. aureus than micrograined Cu. There is a linear correlation between luminous intensity and grain size-0.5. The bacterial intercellular defence mechanism includes the creation of Cu2O nanoparticles and the increased concentration of sulphur-rich compounds near these nanoparticles.

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.

Two decades of continuous progresses and breakthroughs in the field of bioactive ceramics and glasses driven by CICECO-hub scientists

Over the past two decades, the CICECO-hub scientists have devoted substantial efforts to advancing bioactive inorganic materials based on calcium phosphates and alkali-free bioactive glasses. A key focus has been the deliberate incorporation of therapeutic ions like Mg, Sr, Zn, Mn, or Ga to enhance osteointegration and vascularization, confer antioxidant properties, and impart antimicrobial effects, marking significant contributions to the field of biomaterials and bone tissue engineering. Such an approach is expected to circumvent the uncertainties posed by methods relying on growth factors, such as bone morphogenetic proteins, parathyroid hormone, and platelet-rich plasma, along with their associated high costs and potential adverse side effects. This comprehensive overview of CICECO-hub's significant contributions to the forefront inorganic biomaterials across all research aspects and dimensionalities (powders, granules, thin films, bulk materials, and porous structures), follows a unified approach rooted in a cohesive conceptual framework, including synthesis, characterization, and testing protocols. Tangible outcomes [injectable cements, durable implant coatings, and bone graft substitutes (scaffolds) featuring customized porous architectures for implant fixation, osteointegration, accelerated bone regeneration in critical-sized bone defects] were achieved. The manuscript showcases specific biofunctional examples of successful biomedical applications and effective translations to the market of bone grafts for advanced therapies.

Synergistic Bactericidal Effect of Zn2+ Ions and Reactive Oxygen Species Generated in Response to Either UV or X-ray Irradiation of Zn-Doped Plasma Electrolytic Oxidation TiO2 Coatings

Zn-containing TiO2-based coatings with Na, Ca, Si, and K additives were obtained by plasma electrolytic oxidation (PEO) of Ti in order to achieve an effective and broad bactericidal protection without compromising biocompatibility. A protocol has been developed for cleaning the coating surface from electrolyte residues, ensuring the preservation of the microstructure and composition of the surface layer. Using high-resolution transmission electron microscopy, three characteristic microstructural zones in the PEO-Zn coating are well documented: zone 1 with a TiO2-based nanocrystalline structure, zone 2 with an amorphous structure, and zone 3 around pores with an amorphous-nanocrystalline structure. The excellent cytocompatibility of PEO-Zn samples was confirmed by three different methods: monitoring the proliferation of MC3T3-E1 cells, assessing the viability of sheep osteoblast cells using calcein-AM staining and fluorescence microscopy, and incubation with spheroids based on primary osteoblast cells and mouse embryonic fibroblast NIH3T3 cells. The PEO-Zn coatings absorb >60% of the incident light over the UV and Vis-NIR spectral ranges. After 24 h, the PEO-Zn coatings completely inactivate four types of strains: Gram-positive Staphylococcus aureus CSA154 and ATCC29213 and Gram-negative Escherichia coli K261 and U20, and also prevent E. coli U20 and K261 biofilm formation. The superior antibacterial activity is associated with the synergistic effect of Zn2+ ions in safe concentration and reactive oxygen species (ROS) generated in response to either UV irradiation or soft short-term X-ray irradiation. The X-ray irradiation-induced ROS formation by a PEO coating is reported for the first time. The enhanced bactericidal activity after X-ray irradiation compared to UV illumination is attributed to the more intense ROS generation in the first few hours. The results obtained significantly expand the possibilities of using PEO coatings on the surfaces of titanium implants.

Probiotics functionalized with a gallium-polyphenol network modulate the intratumor microbiota and promote anti-tumor immune responses in pancreatic cancer

The intratumor microbiome imbalance in pancreatic cancer promotes a tolerogenic immune response and triggers immunotherapy resistance. Here we show that Lactobacillus rhamnosus GG probiotics, outfitted with a gallium-polyphenol network (LGG@Ga-poly), bolster immunotherapy in pancreatic cancer by modulating microbiota-immune interactions. Upon oral administration, LGG@Ga-poly targets pancreatic tumors specifically, and selectively eradicates tumor-promoting Proteobacteria and microbiota-derived lipopolysaccharides through a gallium-facilitated disruption of bacterial iron respiration. This elimination of intratumor microbiota impedes the activation of tumoral Toll-like receptors, thus reducing immunosuppressive PD-L1 and interleukin-1β expression by tumor cells, diminishing immunotolerant myeloid populations, and improving the infiltration of cytotoxic T lymphocytes in tumors. Moreover, LGG@Ga-poly hampers pancreatic tumor growth in both preventive and therapeutic contexts, and amplifies the antitumor efficacy of immune checkpoint blockade in preclinical cancer models in female mice. Overall, we offer evidence that thoughtfully designed biomaterials targeting intratumor microbiota can efficaciously augment immunotherapy for the challenging pancreatic cancer.

Nanoclay Hydrogel Microspheres with a Sandwich-Like Structure for Complex Tissue Infection Treatment

Addressing complex tissue infections remains a challenging task because of the lack of effective means, and the limitations of traditional bioantimicrobial materials in single-application scenarios hinder their utility for complex infection sites. Hence, the development of a bioantimicrobial material with broad applicability and potent bactericidal activity is necessary to treat such infections. In this study, a layered lithium magnesium silicate nanoclay (LMS) is used to construct a nanobactericidal platform. This platform exhibits a sandwich-like structure, which is achieved through copper ion modification using a dopamine-mediated metallophenolic network. Moreover, the nanoclay is encapsulated within gelatin methacryloyl (GelMA) hydrogel microspheres for the treatment of complex tissue infections. The results demonstrate that the sandwich-like micro- and nanobactericidal hydrogel microspheres effectively eradicated Staphylococcus aureus (S. aureus) while exhibiting excellent biocompatibility with bone marrow-derived mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs). Furthermore, the hydrogel microspheres upregulated the expression levels of osteogenic differentiation and angiogenesis-related genes in these cells. In vivo experiments validated the efficacy of sandwich-like micro- and nanobactericidal hydrogel microspheres when injected into deep infected tissues, effectively eliminating bacteria and promoting robust vascular regeneration and tissue repair. Therefore, these innovative sandwich-like micro- and nanobacteriostatic hydrogel microspheres show great potential for treating complex tissue infections.

Biomaterials science and surface engineering strategies for dental peri-implantitis management

Peri-implantitis is a bacterial infection that causes soft tissue inflammatory lesions and alveolar bone resorption, ultimately resulting in implant failure. Dental implants for clinical use barely have antibacterial properties, and bacterial colonization and biofilm formation on the dental implants are major causes of peri-implantitis. Treatment strategies such as mechanical debridement and antibiotic therapy have been used to remove dental plaque. However, it is particularly important to prevent the occurrence of peri-implantitis rather than treatment. Therefore, the current research spot has focused on improving the antibacterial properties of dental implants, such as the construction of specific micro-nano surface texture, the introduction of diverse functional coatings, or the application of materials with intrinsic antibacterial properties. The aforementioned antibacterial surfaces can be incorporated with bioactive molecules, metallic nanoparticles, or other functional components to further enhance the osteogenic properties and accelerate the healing process. In this review, we summarize the recent developments in biomaterial science and the modification strategies applied to dental implants to inhibit biofilm formation and facilitate bone-implant integration. Furthermore, we summarized the obstacles existing in the process of laboratory research to reach the clinic products, and propose corresponding directions for future developments and research perspectives, so that to provide insights into the rational design and construction of dental implants with the aim to balance antibacterial efficacy, biological safety, and osteogenic property.

Zinc Oxide-Based Nanomaterials for Microbiostatic Activities: A Review

The world is fighting infectious diseases. Therefore, effective antimicrobials are required to prevent the spread of microbes and protect human health. Zinc oxide (ZnO) nano-materials are known for their antimicrobial activities. Because of their distinctive physical and chemical characteristics, they can be used in medical and environmental applications. ZnO-based composites are among the leading sources of antimicrobial research. They are effective at killing (microbicidal) and inhibiting the growth (microbiostatic) of numerous microorganisms, such as bacteria, viruses, and fungi. Although most studies have focused on the microbicidal features, there is a lack of reviews on their microbiostatic effects. This review provides a detailed overview of available reports on the microbiostatic activities of ZnO-based nano-materials against different microorganisms. Additionally, the factors that affect the efficacy of these materials, their time course, and a comparison of the available antimicrobials are highlighted in this review. The basic properties of ZnO, challenges of working with microorganisms, and working mechanisms of microbiostatic activities are also examined. This review underscores the importance of further research to better understand ZnO-based nano-materials for controlling microbial growth.

Innovative wound management: creating dynamic Alg-Mg/SF hydrogels for controlled Mg2+ release in wound healing

Antibacterial hydrogels have gained considerable attention for soft tissue repair, particularly in preventing infections associated with wound healing. However, developing an antibacterial hydrogel that simultaneously possesses excellent cell affinity and controlled release of metal ions remains challenging. This study introduces an antibacterial hydrogel based on alginate modified with bisphosphonate, forming a coordination complex with magnesium ions. The hydrogel, through an interpenetrating network with silk fibroin, effectively controls the release of magnesium ions and enhances strain resistance. The Alg-Mg/SF hydrogel not only demonstrates outstanding biocompatibility and broad-spectrum antibacterial properties but also stimulates macrophages to secrete anti-inflammatory factors. This advanced Alg-Mg/SF hydrogel provides a convenient therapeutic approach for chronic wound management, showcasing its potential applications in wound healing and other relevant biomedical fields.

Design and preparation of Ti-xFe antibacterial titanium alloys based on micro-area potential difference

Fe was selected as an alloying element for the first time to prepare a new antibacterial titanium alloy based on micro-area potential difference (MAPD) antibacterial mechanism. The microstructure, the corrosion resistance, the mechanical properties, the antibacterial properties and the cell biocompatibility have been investigated in detail by optical microscopy, scanning electron microscopy, electrochemical testing, mechanical property test, plate count method and cell toxicity measurement. It was demonstrated that heat treatment had a significant on the compressive mechanical properties and the antibacterial properties. Ti-xFe (x = 3,5 and 9) alloys after 850 °C/3 h + 550 °C/62 h heat treatment exhibited strong antimicrobial properties with an antibacterial rate of more than 90% due to the MAPD caused by the redistribution of Fe element during the aging process. In addition, the Fe content and the heat treatment process had a significant influence on the mechanical properties of Ti-xFe alloy but had nearly no effect on the corrosion resistance. All Ti-xFe alloys showed non-toxicity to the MC3T3 cell line in comparison with cp-Ti, indicating that the microzone potential difference had no adverse effect on the corrosion resistance, cell proliferation, adhesion, and spreading. Strong antibacterial properties, good cell compatibility and good corrosion resistance demonstrated that Ti-xFe alloy might be a candidate titanium alloy for medical applications.

Implants coating strategies for antibacterial treatment in fracture and defect models: A systematic review of animal studies

Objective

Fracture-related infection (FRI) remains a major concern in orthopaedic trauma. Functionalizing implants with antibacterial coatings are a promising strategy in mitigating FRI. Numerous implant coatings have been reported but the preventive and therapeutic effects vary. This systematic review aimed to provide a comprehensive overview of current implant coating strategies to prevent and treat FRI in animal fracture and bone defect models.

Methods

A literature search was performed in three databases: PubMed, Web of Science and Embase, with predetermined keywords and criteria up to 28 February 2023. Preclinical studies on implant coatings in animal fracture or defect models that assessed antibacterial and bone healing effects were included.

Results

A total of 14 studies were included in this systematic review, seven of which used fracture models and seven used defect models. Passive coatings with bacteria adhesion resistance were investigated in two studies. Active coatings with bactericidal effects were investigated in 12 studies, four of which used metal ions including Ag+ and Cu2+; five studies used antibiotics including chlorhexidine, tigecycline, vancomycin, and gentamicin sulfate; and the other three studies used natural antibacterial materials including chitosan, antimicrobial peptides, and lysostaphin. Overall, these implant coatings exhibited promising efficacy in antibacterial effects and bone formation.

Conclusion

Antibacterial coating strategies reduced bacterial infections in animal models and favored bone healing in vivo. Future studies of implant coatings should focus on optimal biocompatibility, antibacterial effects against multi-drug resistant bacteria and polymicrobial infections, and osseointegration and osteogenesis promotion especially in osteoporotic bone by constructing multi-functional coatings for FRI therapy.

The translational potential of this paper

The clinical treatment of FRI is complex and challenging. This review summarizes novel orthopaedic implant coating strategies applied to FRI in preclinical studies, and offers a perspective on the future development of orthopaedic implant coatings, which can potentially contribute to alternative strategies in clinical practice.

Ultrasound-activated piezo-hot carriers trigger tandem catalysis coordinating cuproptosis-like bacterial death against implant infections

Implant-associated infections due to the formation of bacterial biofilms pose a serious threat in medical healthcare, which needs effective therapeutic methods. Here, we propose a multifunctional nanoreactor by spatiotemporal ultrasound-driven tandem catalysis to amplify the efficacy of sonodynamic and chemodynamic therapy. By combining piezoelectric barium titanate with polydopamine and copper, the ultrasound-activated piezo-hot carriers transfer easily to copper by polydopamine. It boosts reactive oxygen species production by piezoelectrics, and facilitates the interconversion between Cu2+ and Cu+ to promote hydroxyl radical generation via Cu+ -catalyzed chemodynamic reactions. Finally, the elevated reactive oxygen species cause bacterial membrane structure loosening and DNA damage. Transcriptomics and metabolomics analysis reveal that intracellular copper overload restricts the tricarboxylic acid cycle, promoting bacterial cuproptosis-like death. Therefore, the polyetherketoneketone scaffold engineered with the designed nanoreactor shows excellent antibacterial performance with ultrasound stimulation and promotes angiogenesis and osteogenesis on-demand in vivo.

Inherent Antibacterial Properties of Biodegradable FeMnC(Cu) Alloys for Implant Application

Implant-related infections or inflammation are one of the main reasons for implant failure. Therefore, different concepts for prevention are needed, which strongly promote the development and validation of improved material designs. Besides modifying the implant surface by, for example, antibacterial coatings (also implying drugs) for deterring or eliminating harmful bacteria, it is a highly promising strategy to prevent such implant infections by antibacterial substrate materials. In this work, the inherent antibacterial behavior of the as-cast biodegradable Fe69Mn30C1 (FeMnC) alloy against Gram-negative Pseudomonas aeruginosa and Escherichia coli as well as Gram-positive Staphylococcus aureus is presented for the first time in comparison to the clinically applied, corrosion-resistant AISI 316L stainless steel. In the second step, 3.5 wt % Cu was added to the FeMnC reference alloy, and the microbial corrosion as well as the proliferation of the investigated bacterial strains is further strongly influenced. This leads for instance to enhanced antibacterial activity of the Cu-modified FeMnC-based alloy against the very aggressive, wild-type bacteria P. aeruginosa. For clarification of the bacterial test results, additional analyses were applied regarding the microstructure and elemental distribution as well as the initial corrosion behavior of the alloys. This was electrochemically investigated by a potentiodynamic polarization test. The initial degraded surface after immersion were analyzed by glow discharge optical emission spectrometry and transmission electron microscopy combined with energy-dispersive X-ray analysis, revealing an increase of degradation due to Cu alloying. Due to their antibacterial behavior, both investigated FeMnC-based alloys in this study are attractive as a temporary implant material.

Fabrication of a Nanoscale Magnesium/Copper Metal-Organic Framework on Zn-Based Guided Bone Generation Membranes for Enhancing Osteogenesis, Angiogenesis, and Bacteriostasis Properties

Recently, zinc (Zn) and its alloys have demonstrated great potential as guided bone regeneration (GBR) membranes to treat the problems of insufficient alveolar bone volume and long-term osseointegration instability during dental implantology. However, bone regeneration is a complex process consisting of osteogenesis, angiogenesis, and antibacterial function. For now, the in vivo osteogenic performance and antibacterial activity of pure Zn are inadequate, and thus fabricating a platform to endow Zn membranes with multifunctions may be essential to address these issues. In this study, various bimetallic magnesium/copper metal-organic framework (Mg/Cu-MOF) coatings were fabricated and immobilized on pure Zn. The results indicated that the degradation rate and water stability of Mg/Cu-MOF coatings could be regulated by controlling the feeding ratio of Cu2+. As the coating and Zn substrate degraded, an alkaline microenvironment enriched with Zn2+, Mg2+, and Cu2+ was generated. It significantly improved calcium phosphate deposition, differentiation of osteoblasts, and vascularization of endothelial cells in the extracts. Among them, Mg/Cu1 showed the best comprehensive performance. The superior antibacterial activity of Mg/Cu1 was demonstrated in vitro and in vivo, which indicated significantly enhanced bacteriostatic activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli as compared to that of the bare sample. Bimetallic Mg/Cu-MOF coating could properly coordinate the multifunction on a Zn membrane and could be a promising platform for promoting its bone regeneration, which could pave the way for Zn-based materials to be used as barrier membranes in oral clinical trials.

In vitro and in vivo studies on biodegradable Zn porous scaffolds with a drug-loaded coating for the treatment of infected bone defect

Additively manufactured biodegradable zinc (Zn) scaffolds have great potential to repair infected bone defects due to their osteogenic and antibacterial properties. However, the enhancement of antibacterial properties depends on a high concentration of dissolved Zn2+, which in return deteriorates osteogenic activity. In this study, a vancomycin (Van)-loaded polydopamine (PDA) coating was prepared on pure Zn porous scaffolds to solve the above dilemma. Compared with pure Zn scaffolds according to comprehensive in vitro tests, the PDA coating resulted in a slow degradation and inhibited the excessive release of Zn2+ at the early stage, thus improving cytocompatibility and osteogenic activity. Meanwhile, the addition of Van drug substantially suppressed the attachment and proliferation of S. aureus and E. coli bacterial. Furthermore, in vivo implantation confirmed the simultaneously improved osteogenic and antibacterial functions by using the pure Zn scaffolds with Van-loaded PDA coating. Therefore, it is promising to employ biodegradable Zn porous scaffolds with the proposed drug-loaded coating for the treatment of infected bone defects.

Unrelenting Infection of Implanted Prosthetic Hip Joint by Corynebacterium striatum

Non-diphtherial Corynebacterial (NDC) species, while previously considered as culture contaminants, are increasingly being implicated in clinical disease and identified as causes of opportunistic infections. In cases where they grow in pure cultures, isolated from a sterile site or repeated isolations from the same patient, NDC may be labeled as clinically significant. We report here a case of non-healing infection of one of the implanted devices in a case of bilateral total hip replacement, caused by multidrug-resistant Corynebacterium striatum. Adherence to infection prevention strategies is essential for the prevention of prosthetic implant infections.

All-Natural Injectable Antibacterial Hydrogel Enabled by Chitosan and Borneol

Hydrogels with intrinsic antimicrobial capabilities based on natural strategies have been studied as a hot topic in biomedicine. Nevertheless, it is highly challenging to thoroughly develop a bacteriostatic natural hydrogel. Borneol as a traditional Chinese medicine possesses a unique broad-spectrum antibacterial activity under a membrane-breaking mechanism. In this study, a range of fully natural antibacterial hydrogels are designed and synthesized via the Schiff base cross-linking of carboxymethyl chitosan and dialdehyde dextran grafted natural borneol. The borneol with three configurations is hydrophilically modified onto dextran to boost its antibacterial activity. Also, the synergism of hydrophilic-modified borneol groups and positively charged ammonium ions of carboxymethyl chitosan make the hydrogels totally constrict the E. coli and S. aureus growth during 24 h. Furthermore, the hydrogels exhibit good in vitro cytocompatibility through cytotoxicity, protein adhesion, and hemolytic tests. In view of the injectability, the hydrogels can be delivered to the target site through a minimally invasive route. In short, this work offers a potential tactic to develop antibacterial hydrogels for the treatment of topical wound infections.

Immunomodulatory biomaterials against bacterial infections: Progress, challenges, and future perspectives

Bacterial infectious diseases are one of the leading causes of death worldwide. Even with the use of multiple antibiotic treatment strategies, 4.95 million people died from drug-resistant bacterial infections in 2019. By 2050, the number of deaths will reach 10 million annually. The increasing mortality may be partly due to bacterial heterogeneity in the infection microenvironment, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants. In addition, the complexity of the immune microenvironment at different stages of infection makes biomaterials with direct antimicrobial activity unsatisfactory for the long-term treatment of chronic bacterial infections. The increasing mortality may be partly attributed to the biomaterials failing to modulate the active antimicrobial action of immune cells. Therefore, there is an urgent need for effective alternatives to treat bacterial infections. Accordingly, the development of immunomodulatory antimicrobial biomaterials has recently received considerable interest; however, a comprehensive review of their research progress is lacking. In this review, we focus mainly on the research progress and future perspectives of immunomodulatory antimicrobial biomaterials used at different stages of infection. First, we describe the characteristics of the immune microenvironment in the acute and chronic phases of bacterial infections. Then, we highlight the immunomodulatory strategies for antimicrobial biomaterials at different stages of infection and their corresponding advantages and disadvantages. Moreover, we discuss biomaterial-mediated bacterial vaccines' potential applications and challenges for activating innate and adaptive immune memory. This review will serve as a reference for future studies to develop next-generation immunomodulatory biomaterials and accelerate their translation into clinical practice.

Core-Shell NiS@SrTiO3 Nanorods on Titanium for Enhanced Osseointegration via Programmed Regulation of Bacterial Infection, Angiogenesis, and Osteogenesis

Developing bone implants with dynamic self-adjustment of antibacterial, angiogenic, and osteogenic functions in line with a bone regenerative cascade is highly required in orthopedics. Herein, a unique core-shell nanorods array featuring a thin layer of NiS coated on each SrTiO3 nanorod (NiS@SrTiO3) was in situ constructed on titanium (Ti) through a two-step hydrothermal treatment. Under near-infrared (NIR) irradiation, the photoresponsive effect of NiS layer in synergy with the physical perforation of SrTiO3 nanorods initially enabled in vitro antibacterial rates of 96.5% to Escherichia coli and 93.1% to Staphylococcus aureus. With the degradation of the NiS layer, trace amounts of Ni ions were released, which accelerated angiogenesis by upregulating the expression of vascular regeneration-related factors, while the gradual exposure of SrTiO3 nanorods could simultaneously enhance the surface hydrophilicity in favor of cell adhesion and slowly release Sr ions to promote the proliferation and differentiation of MC3T3-E1 cells. The in vivo assessment verified not only the satisfactory antibacterial effect but also the superior osteogenic ability of the NiS@SrTiO3/Ti group with the aid of NIR irradiation, finally promoting the osseointegration of the Ti implant. The modification method endowing Ti implant with antibacterial, angiogenic, and osteogenic functions provides a new strategy to improve the long-term reliability of Ti-based devices.

Evaluation of the biocompatibility, antibacterial and anticancer effects of a novel nano-structured Fe-Mn-based biodegradable alloys in-vitro study

Scientific backgrounds

Development of nanostructured biodegradable alloys has generated a great deal of interest in the recent years as they offer promising bioactive materials for reconstruction of bony defects following traumatic fractures or surgical excision of tumors.

Objectives

The aim of the current study was to investigate the biocompatibility of Iron-Manganese -based alloys (Fe-Mn) with addition of copper (Cu), Tungsten (W) and cobalt (Co) to obtain 3 different alloys namely, Fe-Mn-Cu, Fe-Mn-W, and Fe-Mn-Co on normal oral epithelial cell line,and their possible anticancer effect on MG-63: osteosarcoma cell line.

Materials and methods

The sulforhodamine B (SRB) assay was used to assess cell viability percentage of both cell lines after exposure to discs of the proposed experimental alloys. Moreover, the antibacterial effect of such alloys against Escherichia coli (E. coli) was tested using disc diffusion susceptibility (Kirby-Bauer method) and colony suspension method.

Results

The cell viability percentage of oral epithelial cell line showed a significant increase in all the experimental groups in comparison to the control group. The highest percentage was observed in Fe-Mn-Co group, followed by Fe-Mn-W then Fe-Mn-Cu, at 24 and 72-h intervals, respectively. While the cell viability percentage of osteosarcoma cell line showed significant increase in all the experimental groups at 24-h intervals, it showed a significant drop in all the study groups at 72-h intervals. The lowest percentage was observed in Fe-Mn-Cu group, followed by Fe-Mn-W then Fe-Mn-Co. Moreover, all the examined study groups didn't show any inhibition zones against E. coli reference culture.

Conclusions

The novel nanostructured biodegradable Fe-Mn-Cu, Fe-Mn-W, and Fe-Mn-Co metal alloys exhibit good biocompatibility on oral epithelial cell lines with the enhancement of cell proliferation in a time-dependent manner that favors bone regeneration. On the other hand, all the alloys manifested possible anticancer activity against MG-63: osteosarcoma cell line. Furthermore, our study sheds the light on the importance of Co, W and Cu as promising alloying elements. However, the antibacterial activity of the examined alloys is still questionable.

Clinical relevance

The novel nanostructured biodegradable Fe-Mn-Cu, Fe-Mn-W, and Fe-Mn-Co metal alloys offer promising bioactive materials for reconstruction of bony defects following traumatic fractures or surgical excision of tumors, In addition, they could be excellent alternatives for undegradable or non-resorbable alloys that are commonly used. Moreover, they could be used as beneficial 3D printing materials to obtain patient-specific medical implants that favor bone regeneration in addition to manufacturing of plates and screws suitable for fracture fixation.

Burning question: Are there sustainable strategies to prevent microbial metal corrosion?

The global economic burden of microbial corrosion of metals is enormous. Microbial corrosion of iron-containing metals is most extensive under anaerobic conditions. Microbes form biofilms on metal surfaces and can directly extract electrons derived from the oxidation of Fe0 to Fe2+ to support anaerobic respiration. H2 generated from abiotic Fe0 oxidation also serves as an electron donor for anaerobic respiratory microbes. Microbial metabolites accelerate this abiotic Fe0 oxidation. Traditional strategies for curbing microbial metal corrosion include cathodic protection, scrapping, a diversity of biocides, alloys that form protective layers or release toxic metal ions, and polymer coatings. However, these approaches are typically expensive and/or of limited applicability and not environmentally friendly. Biotechnology may provide more effective and sustainable solutions. Biocides produced with microbes can be less toxic to eukaryotes, expanding the environments for potential application. Microbially produced surfactants can diminish biofilm formation by corrosive microbes, as can quorum-sensing inhibitors. Amendments of phages or predatory bacteria have been successful in attacking corrosive microbes in laboratory studies. Poorly corrosive microbes can form biofilms and/or deposit extracellular polysaccharides and minerals that protect the metal surface from corrosive microbes and their metabolites. Nitrate amendments permit nitrate reducers to outcompete highly corrosive sulphate-reducing microbes, reducing corrosion. Investigation of all these more sustainable corrosion mitigation strategies is in its infancy. More study, especially under environmentally relevant conditions, including diverse microbial communities, is warranted.

Profiling to Probing: Atomic force microscopy to characterize nano-engineered implants

Surface modification of implants in the nanoscale or implant nano-engineering has been recognized as a strategy for augmenting implant bioactivity and achieving long-term implant success. Characterizing and optimizing implant characteristics is crucial to achieving desirable effects post-implantation. Modified implant enables tailored, guided and accelerated tissue integration; however, our understanding is limited to multicellular (bulk) interactions. Finding the nanoscale forces experienced by a single cell on nano-engineered implants will aid in predicting implants' bioactivity and engineering the next generation of bioactive implants. Atomic force microscope (AFM) is a unique tool that enables surface characterization and understanding of the interactions between implant surface and biological tissues. The characterization of surface topography using AFM to gauge nano-engineered implants' characteristics (topographical, mechanical, chemical, electrical and magnetic) and bioactivity (adhesion of cells) is presented. A special focus of the review is to discuss the use of single-cell force spectroscopy (SCFS) employing AFM to investigate the minute forces involved with the adhesion of a single cell (resident tissue cell or bacterium) to the surface of nano-engineered implants. Finally, the research gaps and future perspectives relating to AFM-characterized current and emerging nano-engineered implants are discussed towards achieving desirable bioactivity performances. This review highlights the use of advanced AFM-based characterization of nano-engineered implant surfaces via profiling (investigating implant topography) or probing (using a single cell as a probe to study precise adhesive forces with the implant surface). STATEMENT OF SIGNIFICANCE: Nano-engineering is emerging as a surface modification platform for implants to augment their bioactivity and achieve favourable treatment outcomes. In this extensive review, we closely examine the use of Atomic Force Microscopy (AFM) to characterize the properties of nano-engineered implant surfaces (topography, mechanical, chemical, electrical and magnetic). Next, we discuss Single-Cell Force Spectroscopy (SCFS) via AFM towards precise force quantification encompassing a single cell's interaction with the implant surface. This interdisciplinary review will appeal to researchers from the broader scientific community interested in implants and cell adhesion to implants and provide an improved understanding of the surface characterization of nano-engineered implants.

Harnessing gradient gelatin nanocomposite hydrogels: a progressive approach to tackling antibacterial biofilms

Infectious wounds pose significant challenges due to their susceptibility to bacterial infections, hindering tissue repair. This study introduces gradient gelatin nanocomposite hydrogels for wound healing and antibacterial biofilm management. These hydrogels, synthesized via UV light polymerization, incorporate copper-doped polydopamine nanoparticles (PDA-Cu) and GelMA (gelatin methacrylate). The hydrogels have a unique structure with a porous upper layer and a denser lower layer, ensuring superior swelling (over than 600%) and effective contact with bacterial biofilms. In vitro experiments demonstrate their remarkable antibacterial properties, inhibiting S. aureus and E. coli biofilms by over 45% and 53%, respectively. This antibacterial action is attributed to the regulation of reactive oxygen species (ROS) production, an alternative mechanism to bacterial cell wall disruption. Moreover, the hydrogels exhibit high biocompatibility with mammalian cells, making them suitable for medical applications. In vivo evaluation in a rat wound infection model shows that the gradient hydrogel treatment effectively controls bacterial biofilm infections and accelerates wound healing. The treated wounds have smaller infected areas and reduced bacterial colony counts. Histological analysis reveals reduced inflammation and enhanced granulation tissue formation in treated wounds, highlighting the therapeutic potential of these gradient nanocomposite hydrogels. In summary, gradient gelatin nanocomposite hydrogels offer promising multifunctional capabilities for wound healing and biofilm-related infections, paving the way for innovative medical dressings with enhanced antibacterial properties and biocompatibility.

Functionally Tailored Metal-Organic Framework Coatings for Mediating Ti Implant Osseointegration

Owing to their mechanical resilience and non-toxicity, titanium implants are widely applied as the major treatment modality for the clinical intervention against bone fractures. However, the intrinsic bioinertness of Ti and its alloys often impedes the effective osseointegration of the implants, leading to severe adverse complications including implant loosening, detachment, and secondary bone damage. Consequently, new Ti implant engineering strategies are urgently needed to improve their osseointegration after implantation. Remarkably, metalorganic frameworks (MOFs) are a class of novel synthetic material consisting of coordinated metal species and organic ligands, which have demonstrated a plethora of favorable properties for modulating the interfacial properties of Ti implants. This review comprehensively summarizes the recent progress in the development of MOF-coated Ti implants and highlights their potential utility for modulating the bio-implant interface to improve implant osseointegration, of which the discussions are outlined according to their physical traits, chemical composition, and drug delivery capacity. A perspective is also provided in this review regarding the current limitations and future opportunities of MOF-coated Ti implants for orthopedic applications. The insights in this review may facilitate the rational design of more advanced Ti implants with enhanced therapeutic performance and safety.

Research progress on antibacterial activity of medical titanium alloy implant materials

Titanium and its alloys are the preferred materials for medical implants. However, easy infection is a fatal shortcoming of Ti implants. Fortunately, the ongoing development of antibacterial implant materials is a promising solution, and Ti alloys with antibacterial properties hold immense potential for medical applications. In this review, we briefly outline the mechanisms of bacterial colonization and biofilm formation on implants; discuss and classify the major antimicrobials currently in use and development, including inorganic and organic antimicrobials; and describe the important role of antimicrobials in the development of implant materials for clinical applications. Strategies and challenges related to improving the antimicrobial properties of implant materials as well as the prospects of antibacterial Ti alloys in the medical field are also discussed.

Green synthesis of copper oxide nanoparticles from Murraya koenigii and its corrosion resistivity on Ti-6Al-4V dental alloy

The present work describes green-mediated copper oxide nanoparticles as a potential corrosion inhibitor for the dental alloy Ti-6Al-4V. The salt of copper was reduced to metal nanoparticles using Murraya koenigii leaves, which helps with the agglomeration and nanocluster formation through a reduction mechanism. The current synthesis is a single-step process and is cost-effective. The synthesized nanoparticle was characterized using UV, FTIR, XRD, Zeta potential and Particle size analyzer, SEM, and EDX. The particles were then electrodeposited on Ti-6Al-4V alloy, and the corrosion resistivity in the dental medium was analyzed using Electrochemical parameters such as Corrosion current, Corrosion potential, and anodic and cathodic intercepts through the Tafel and Nyquist plots. The synthesized nanoparticles showed characteristic absorbance at 359 nm. FTIR peaks confirm the phytochemical constituents present in the Murraya koenigii that accounts for the formation of nanoparticles. The XRD predicts the crystalline nature, which is further studied using SEM and EDX. The Zeta potential and Particle size analyzer confirms the negative-negative interactive nature of the synthesized CuO NPs. The NPs showed explicit corrosion inhibition properties with an overall inhibition efficiency of 58.15% and 25.6%, respectively. The study confirms the advantage of using Copper Oxide nanoparticles as a potential coating agent in dental implant alloys in increasing its corrosion efficiency.

Silver-Containing Biomaterials for Biomedical Hard Tissue Implants

Bacterial infection caused by biomaterials is a very serious problem in the clinical treatment of implants. The emergence of antibiotic resistance has prompted other antibacterial agents to replace traditional antibiotics. Silver is rapidly developing as an antibacterial candidate material to inhibit bone infections due to its significant advantages such as high antibacterial timeliness, high antibacterial efficiency, and less susceptibility to bacterial resistance. However, silver has strong cytotoxicity, which can cause inflammatory reactions and oxidative stress, thereby destroying tissue regeneration, making the application of silver-containing biomaterials extremely challenging. In this paper, the application of silver in biomaterials is reviewed, focusing on the following three issues: 1) how to ensure the excellent antibacterial properties of silver, and not easy to cause bacterial resistance; 2) how to choose the appropriate method to combine silver with biomaterials; 3) how to make silver-containing biomaterials in hard tissue implants have further research. Following a brief introduction, the discussion focuses on the application of silver-containing biomaterials, with an emphasis on the effects of silver on the physicochemical properties, structural properties, and biological properties of biomaterials. Finally, the review concludes with the authors' perspectives on the challenges and future directions of silver in commercialization and in-depth research.

Overview of strategies to improve the antibacterial property of dental implants

The increasing number of peri-implant diseases and the unsatisfactory results of conventional treatment are causing great concern to patients and medical staff. The effective removal of plaque which is one of the key causes of peri-implant disease from the surface of implants has become one of the main problems to be solved urgently in the field of peri-implant disease prevention and treatment. In recent years, with the advancement of materials science and pharmacology, a lot of research has been conducted to enhance the implant antimicrobial properties, including the addition of antimicrobial coatings on the implant surface, the adjustment of implant surface topography, and the development of new implant materials, and significant progress has been made in various aspects. Antimicrobial materials have shown promising applications in the prevention of peri-implant diseases, but meanwhile, there are some shortcomings, which leads to the lack of clinical widespread use of antimicrobial materials. This paper summarizes the research on antimicrobial materials applied to implants in recent years and presents an outlook on the future development.

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.

Silver nanoparticle technology in orthopaedic infections

The irrational and prolonged use of antibiotics in orthopaedic infections poses a major threat to the development of antimicrobial resistance. To combat antimicrobial resistance, researchers have implemented various novel and innovative modalities to curb infections. Nanotechnology involves doping ions/metals onto the scaffolds to reach the target site to eradicate the infective foci. In this connotation, we reviewed silver nanoparticle technology in terms of mechanism of action, clinical applications, toxicity, and regulatory guidelines to treat orthopaedic infections.

Exploring the potential of metal and metal oxide nanomaterials for sustainable water and wastewater treatment: A review of their antimicrobial properties

Metallic nanoparticles (NPs) are of particular interest as antimicrobial agents in water and wastewater treatment due to their broad suppressive range against bacteria, viruses, and fungi commonly found in these environments. This review explores the potential of different types of metallic NPs, including zinc oxide, gold, copper oxide, and titanium oxide, for use as effective antimicrobial agents in water and wastewater treatment. This is due to the fact that metallic NPs possess a broad suppressive range against bacteria, viruses, as well as fungus. In addition to that, NPs are becoming an increasingly popular alternative to antibiotics for treating bacterial infections. Despite the fact that most research has been focused on silver NPs because of the antibacterial qualities that are known to be associated with them, curiosity about other metallic NPs as potential antimicrobial agents has been growing. Zinc oxide, gold, copper oxide, and titanium oxide NPs are included in this category since it has been demonstrated that these elements have antibacterial properties. Inducing oxidative stress, damage to the cellular membranes, and breakdowns throughout the protein and DNA chains are some of the ways that metallic NPs can have an influence on microbial cells. The purpose of this review was to engage in an in-depth conversation about the current state of the art regarding the utilization of the most important categories of metallic NPs that are used as antimicrobial agents. Several approaches for the synthesis of metal-based NPs were reviewed, including physical and chemical methods as well as "green synthesis" approaches, which are synthesis procedures that do not involve the employment of any chemical agents. Moreover, additional pharmacokinetics, physicochemical properties, and the toxicological hazard associated with the application of silver NPs as antimicrobial agents were discussed.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

From energy storage to pathogen eradication: unveiling the antibacterial and antiviral capacities of flexible solid-state carbon cloth supercapacitors

With the emergence of deadly viral and bacterial infections, preventing the spread of microorganisms on surfaces has gained ever-increasing importance. This study investigates the potential of solid-state supercapacitors as antibacterial and antiviral devices. We developed a low-cost and flexible carbon cloth supercapacitor (CCSC) with highly efficient antibacterial and antiviral surface properties. The CCSC comprised two parallel layers of carbon cloth (CC) electrodes assembled in a symmetric, electrical double-layer supercapacitor structure that can be charged at low potentials between 1 to 2 V. The optimized CCSC exhibited a capacitance of 4.15 ± 0.3 mF cm-2 at a scan rate of 100 mV s-1, high-rate capability (83% retention of capacitance at 100 mV s-1 compared to its value at 5 mV s-1), and excellent electrochemical stability (97% retention of the initial capacitance after 1000 cycles). Moreover, the CCSC demonstrated outstanding flexibility and retained its full capacitance even when bent at high angles, making it suitable for wearable or flexible devices. Using its stored electrical charge, the charged CCSC disinfects bacteria effectively and neutralizes viruses upon surface contact with the positive and negative electrodes. The charged CCSC device yielded a 6-log CFU reduction of Escherichia coli bacterial inocula and a 5-log PFU reduction of HSV-1 herpes virus. Antibacterial and antiviral carbon cloth supercapacitors represent a promising platform technology for various applications, including electronic textiles and electronic skins, health monitoring or motion sensors, wound dressings, personal protective equipment (e.g., masks) and air filtration systems.

Synthesis, Characterization and Antimicrobial Activity of Multiple Morphologies of Gold/Platinum Doped Bismuth Oxide Nanostructures

Bismuth oxides were synthesized from bismuth carbonate using the sol-gel method. Studies have described the formation of Bi2O3, as a precursor of HNO3 dissolution, and intermediate oxides, such as BixOy when using H2SO4 and H3PO4. The average size of the crystallite calculated from Scherrer's formula ranged from 9 to 19 nm, according to X-ray diffraction. The FTIR analysis showed the presence of specific Bi2O3 bands when using HNO3 and of crystalline phases of "bismuth oxide sulphate" when using H2SO4 and "bismuth phosphate" when using H3PO4. The TG curves showed major mass losses and specific thermal effects, delimited in four temperature zones for materials synthesized with HNO3 (with loss of mass between 24% and 50%) and H2SO4 (with loss of mass between 45% and 76%), and in three temperature zones for materials synthesized with H3PO4 (with loss of mass between 13% and 43%). Further, the thermal stability indicates that materials have been improved by the addition of a polymer or polymer and carbon. Confocal laser scanning microscopy showed decreased roughness in the series, [BixOy]N > [BixOy-6% PVA]N > [BixOy-C-6% PVA]N, and increased roughness for materials [BixOy]S, [BixOy-6% PVA]S, [BixOy-C-6% PVA]S, [BixOy]P, [BixOy-6% PVA]P and [BixOy-C-6% PVA]P. The morphological analysis (electronic scanning microscopy) of the synthesized materials showed a wide variety of forms: overlapping nanoplates ([BixOy]N or [BixOy]S), clusters of angular forms ([BixOy-6% PVA]N), pillars ([BixOy-6% PVA]S-Au), needle particles ([BixOy-Au], [BixOy-6% PVA]S-Au, [BixOy-C-6% PVA]S-Au), spherical particles ([BixOy-C-6% PVA]P-Pt), 2D plates ([BixOy]P-Pt) and 3D nanometric plates ([BixOy-C-6% PVA]S-Au). For materials obtained in the first synthesis stage, antimicrobial activity increased in the series [BixOy]N > [BixOy]S > [BixOy]P. For materials synthesized in the second synthesis stage, when polymer (polyvinyl alcohol, PVA) was added, maximum antimicrobial activity, regardless of the microbial species tested, was present in the material [BixOy-6% PVA]S. For the materials synthesized in the third stage, to which graphite and 6% PVA were added, the best antimicrobial activity was in the material [BixOy-C-6% PVA]P. Materials synthesized and doped with metal ions (gold or platinum) showed significant antimicrobial activity for the tested microbial species.

Optimization of wear behavior of heat-treated Ti-6Al-7Nb biomedical alloy by response surface methodology

Titanium-based metals are used most often in biomedical implant studies because they have good qualities like being biocompatible, not being poisonous, Osseo-integration, high specific properties, wear resistance, etc. The main goal of this work is to improve the wear resistance of Ti-6Al-7Nb biomedical metal by using a mix of Taguchi, ANOVA, and Grey Relational Analysis. The effect of changeable control process factors like applied load, spinning speed, and time on wear reaction measures like wear rate (WR), coefficient of friction (COF), and frictional force. The optimal combinations of wear rate, COF, and frictional force minimise wear characteristics. The L9 Taguchi orthogonal array was used to plan the experiments, which were done on a pin-on-disc set-up according to ASTM G99. To find the best set of control factors, Taguchi, ANOVA, and Grey relationship analysis were used. The results show that a load of 30 N, a speed of 700 rpm, and a time of 10 min are the best control settings.

Bioactive Zn-0.6Cu thin sheet for craniofacial bone repair: In vitro and in vivo evaluations

Millions of craniofacial surgeries are performed annually worldwide, and materials for craniofacial bone repair are widely needed. However, traditionally applied materials, such as titanium and polymethylmethacrylate, have some shortcomings (limited malleability, material-based toxicity, non-biodegradability, lack of bioactivity, etc.). Zinc based biodegradable metals possess superior mechanical properties, biodegradability, and bioactivity, which make them promising candidate materials. Here, we successfully fabricated Zn-0.6Cu thin sheets (thickness ≤0.5 mm, suitable for craniofacial surgery) through combined extrusion and rolling. The in vitro and in vivo performances were generally evaluated and compared to those of a commercially applied pure titanium mesh. The mechanical properties of Zn-0.6Cu sheets were superior to those of clinically used polymethyl methacrylate. They were easy to shape and would not fracture during deformation. The Zn-0.6Cu sheet exhibited a gentle degradation mode, and proper implant-derived Zn improved osteogenic differentiation of rat bone marrow mesenchymal stem cells by up-regulating expression of osteogenesis related genes (alkaline phosphatase, bone morphogenetic protein-2). Thus, it further promoted extracellular matrix mineralization by improving calcium deposition for bone formation. It also improved the expression of angiogenesis-related genes (vascular endothelial growth factor, hypoxia-inducible factor alpha). The Zn-0.6Cu sheet exhibited high osteogenic activity in a cranial defect animal model compared to a non-biodegradable pure titanium mesh. Significant surface degradation occurred after two months in vivo, and degradation products were compatible with surrounding tissues. In general, the Zn-0.6Cu thin sheet seems to be a bioactive material selection for craniofacial bone repair, which might possibly accelerate defect repair and prevent adverse complications.

Durable and rechargeable antimicrobial cotton driven by enhanced UV stability and real-time detection of biocidal factors

In this study, graphene oxide/N-halamine nanocomposite was synthesized through Pickering miniemulsion polymerization, which was then coated on cotton surface. The modified cotton exhibited excellent superhydrophobicity, which could effectively prevent microbial infestation and reduce the probability of hydrolysis of active chlorine, with virtually no active chlorine released in water after 72 h. Deposition of reduced graphene oxide nanosheets endowed cotton with ultraviolet-blocking properties, attributing to enhanced UV adsorption and long UV paths. Moreover, encapsulation of polymeric N-halamine resulted in improved UV stability, thus extending the life of N-halamine-based agents. After 24 h of irradiation, 85 % of original biocidal component (active chlorine content) was retained, and approximately 97 % of initial chlorine could be regenerated. Modified cotton has been proven to be an effective oxidizing material against organic pollutants and a potential antimicrobial substance. Inoculated bacteria were completely killed after 1 and 10 min of contact time, respectively. An innovative and simple scheme for determination of active chlorine content was also devised, and real-time inspection of bactericidal activity could be achieved to assure antimicrobial sustainability. Moreover, this method could be utilized to evaluate hazard classification of microbial contamination in different locations, thus broadening the application scope of N-halamine-based cotton fabrics.

Fit and forget: The future of dental implant therapy via nanotechnology

Unlike orthopedic implants, dental implants require the orchestration of both osseointegration at the bone-implant interface and soft-tissue integration at the transmucosal region in a complex oral micro-environment with ubiquitous pathogenic bacteria. This represents a very challenging environment for early acceptance and long-term survival of dental implants, especially in compromised patient conditions, including aged, smoking and diabetic patients. Enabling advanced local therapy from the surface of titanium-based dental implants via novel nano-engineering strategies is emerging. This includes anodized nano-engineered implants eluting growth factors, antibiotics, therapeutic nanoparticles and biopolymers to achieve maximum localized therapeutic action. An important criterion is balancing bioactivity enhancement and therapy (like bactericidal efficacy) without causing cytotoxicity. Critical research gaps still need to be addressed to enable the clinical translation of these therapeutic dental implants. This review informs the latest developments, challenges and future directions in this domain to enable the successful fabrication of clinically-translatable therapeutic dental implants that would allow for long-term success, even in compromised patient conditions.

Morphological, mechanical and antibacterial properties of Ti-Cu-N thin films deposited by sputtering DC

The problems associated with Stainless Steel 316 L (SS 316 L) orthopedic implants, when implanted in the human body, are infection, local inflammation, and the possibility of bacterial growth. In this study, SS 316 L was coated with copper-doped Titanium Nitride (Ti-Cu-N) using the DC Sputtering technique. This Ti-Cu-N film improved the antibacterial performance and mechanical properties of SS 316 L. The Ti-Cu-N films were deposited using reactive DC sputtering with an 80%:20% argon to nitrogen ratio. The source voltage and current were kept constant at 10 kV and 10 mA, respectively. X-Ray Diffraction (XRD) showed that the phases formed were TiN and Cu with FCC crystal structure. Results show that the surfaces of samples containing 44.34 wt% and 54.97 wt% Cu had antibacterial effectiveness against Staphylococcus aureus (S. Aureus). The highest hardness value of a Ti-Cu-N layer was 212.032 Vickers Hardness Number (VHN), which was an improvement of 36.63% on the raw material (155.18 VHN). Surface morphology analysis using SEM-EDS was performed on the samples before and after the antibacterial test to investigate the antibacterial mechanism of the surfaces of SS 316 L containing Ti-Cu-N against S. Aureus.

First clinical experience with posterior lumbar interbody fusion using a thermal-sprayed silver-containing hydroxyapatite-coated cage

BACKGROUND

To investigate the possibility of silver (Ag)-induced adverse events and the degree of bone fusion in posterior lumbar interbody fusion surgery using an Ag-containing hydroxyapatite (HA) lumbar interbody cage.

METHODS

An Ag-HA cage consisting of highly osteoconductive HA interfused with Ag was developed, and we applied it clinically at three university-affiliated hospitals from April 2020 to December 2020. During the 12-month postoperative observation period, Ag-related adverse events, neuropathy, and postoperative complications were investigated as indicators of safety, while clinical improvement and the fusion status were investigated as indicators of efficacy. Clinical improvement was defined as improvement beyond the minimum clinically important difference (MCID) in the numerical rating scale (NRS; 1.6) for low back and lower limb pain and the Oswestry Disability Index (ODI; 12.8).

RESULTS

We performed lumbar interbody fusion using an Ag-HA cage for 48 patients (female, n = 25; mean age, 67.5 years). The mean preoperative NRS was 6.4 (standard deviation, 1.9), while the mean preoperative ODI was 44 [12]. No adverse effects (i.e., argyria) were identified during the 12-month observation period. Surgical site infection occurred in one case, although the implant was preserved via immediate debridement. In total, 39 (81%) participants showed clinical improvement beyond MCID for both NRS and ODI. Bone fusion was achieved at 45 levels (88%) at 6 months and 48 levels (91%) at 12 months postoperatively.

CONCLUSIONS

The results of this study suggest that Ag-HA cages can be safely used in spinal fusion procedures and have the potential to prevent postoperative infections, prevent deterioration of the quality of life, and result in favorable outcomes. Larger-scale and longer-term follow-up studies will be required to corroborate these conclusions. Trial registration UMIN 000039964 (date: April 01, 2020).

Graphene oxide reinforced chitosan/polyvinyl alcohol antibacterial coatings on stainless steel surfaces exhibit superior bioactivity without human cell cytotoxicity

The study proposes an alternative therapeutics to diminish bacterial attachment in biomedical implants by modifying their surface with passive coatings. A uniform, thin-film of chitosan/polyvinyl alcohol/graphene oxide (CS/PVA/GO) was coated on 316 L stainless steel (SS) surface through spread casting followed by solvent evaporation. The abundant anchoring sites available at macromolecular interfaces of chitosan/PVA matrix facilitated a smooth, dense loading of GO. The effect of GO content on physicochemical features, antibacterial potential, and biocompatibility of coatings was thoroughly studied. The hybrid films displayed good adhesion behavior, and UV-protection ability with desired mechanical and thermal stability when coated on SS surface. Coatings manifested a 1.5-1.7 fold rise in antibacterial efficacy against Staphylococcus epidermidis and Staphylococcus aureus and exhibited a permanent biocidal response after 6 h of contact-active behaviour. We investigated a 3-fold generation of reactive oxygen species as the predominant antibacterial mechanism, which diminishes bacterial integrity by inducing protein leakage (8.5-9 fold higher) and suppressing respiratory chain activity as two secondary mechanisms. All coatings with varying GO content appeared non-haemolytic (<2%) with ultra-low cytotoxicity (<29.08%) against human hepatocellular carcinoma (HepG2) and peripheral blood mononuclear cells. The degradation rate of coatings in simulated body fluid exhibited a higher stability, indicated by a lower weight loss (69-78%) and a decrease in pH values as the GO content in coatings increased from 0.05 to 0.15 wt%. Such anti-infective coating is a step forward in inhibiting bacterial colonization on SS surfaces to extend its lifespan.