Antibacterial metals and alloys for potential biomedical implants

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.

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.

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.

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.

Investigating the Properties and Characterization of a Hybrid 3D Printed Antimicrobial Composite Material Using FFF Process: Innovative and Swift

Novel strategies and materials have gained the attention of researchers due to the current pandemic, the global market high competition, and the resistance of pathogens against conventional materials. There is a dire need to develop cost-effective, environmentally friendly, and biodegradable materials to fight against bacteria using novel approaches and composites. Fused filament fabrication (FFF), also known as fused deposition modeling (FDM), is the most effective and novel fabrication method to develop these composites due to its various advantages. Compared to metallic particles alone, composites of different metallic particles have shown excellent antimicrobial properties against common Gram-positive and Gram-negative bacteria. This study investigates the antimicrobial properties of two sets of hybrid composite materials, i.e., Cu-PLA-SS and Cu-PLA-Al, are made using copper-enriched polylactide composite, one-time printed side by-side with stainless steel/PLA composite, and second-time with aluminum/PLA composite respectively. These materials have 90 wt.% of copper, 85 wt.% of SS 17-4, 65 wt.% of Al with a density of 4.7 g/cc, 3.0 g/cc, and 1.54 g/cc, respectively, and were fabricated side by side using the fused filament fabrication (FFF) printing technique. The prepared materials were tested against Gram-positive and Gram-negative bacteria such as Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), Salmonella Poona (S. Poona), and Enterococci during different time intervals (5 min, 10 min, 20 min, 1 h, 8 h, and 24 h). The results revealed that both samples showed excellent antimicrobial efficiency, and 99% reduction was observed after 10 min. Hence, three-dimensional (3D) printed polymeric composites enriched with metallic particles can be utilized for biomedical, food packaging, and tissue engineering applications. These composite materials can also provide sustainable solutions in public places and hospitals where the chances of touching surfaces are higher.

Incorporation of Magnesium and Zinc Metallic Particles in PLGA Bi-layered Membranes with Sequential Ion Release for Guided Bone Regeneration

Guided bone regeneration (GBR) membranes are commonly used for periodontal tissue regeneration. Due to the complications of existing GBR membranes, the design of bioactive membranes is still relevant. GBR membranes with an asymmetric structure can accommodate the functional requirements of different interfacial tissues. Here, poly(lactic acid-glycolic acid) (PLGA) was selected as the matrix for preparing a bi-layered membrane with both dense and porous structure. The dense layer for blocking soft tissues was incorporated with zinc (Zn) particles, while the porous layer for promoting bone regeneration was co-incorporated with magnesium (Mg) and Zn particles. Mg/Zn-embedded PLGA membranes exhibited 166% higher mechanical strength in comparison with pure PLGA membranes and showed suitable degradation properties with a sequential ion release behavior of Mg²⁺ first and continuously Zn²⁺. More importantly, the release of Zn²⁺ from bi-layered PLGA endowed GBR membranes with excellent antibacterial activity (antibacterial rate > 69.3%) as well as good cytocompatibility with MC3T3-E1 (mouse calvaria pre-osteoblastic cells) and HGF-1 (human gingival fibroblast cells). Thus, the asymmetric bi-layered PLGA membranes embedded with Mg and Zn particles provide a simple and effective strategy to not only reinforce the PLGA membrane but also endow membranes with osteogenic and antibacterial activity due to the continuous ion release profile, which serves as a promising candidate for use in GBR therapy.

Surface Modification of Biomedical Ti-18Zr-15Nb Alloy by Atomic Layer Deposition and Ag Nanoparticles Decoration

Superelastic biocompatible alloys attract significant attention as novel materials for bone tissue replacement. These alloys are often composed of three or more components that lead to the formation of complex oxide films on their surfaces. For practical use, it is desirable to have a single-component oxide film with a controlled thickness on the surface of biocompatible material. Herein we investigate the applicability of the atomic layer deposition (ALD) technique for surface modification of Ti-18Zr-15Nb alloy with TiO₂ oxide. It was found that a 10-15 nm thick, low-crystalline TiO₂ oxide layer is formed by ALD method over the natural oxide film (~5 nm) of the Ti-18Zr-15Nb alloy. This surface consists of TiO₂ exclusively without any additions of Zr or Nb oxides/suboxides. Further, the obtained coating is modified by Ag nanoparticles (NPs) with a surface concentration up to 1.6% in order to increase the material's antibacterial activity. The resulting surface exhibits enhanced antibacterial activity with an inhibition rate of more than 75% against E. coli bacteria.

Porous Biocoatings Based on Diatomite with Incorporated ZrO2 Particles for Biodegradable Magnesium Implants

In the present work, the surface of a biodegradable Mg alloy was modified to create porous diatomite biocoatings using the method of micro-arc oxidation. The coatings were applied at process voltages in the range of 350-500 V. We have studied the influence of the addition of ZrO₂ microparticles on the structure and properties of diatomite-based protective coatings for Mg implants. The structure and properties of the resulting coatings were examined using a number of research methods. It was found that the coatings have a porous structure and contain ZrO₂ particles. The coatings were mostly characterized by pores less than 1 μm in size. However, as the voltage of the MAO process increases, the number of larger pores (5-10 μm in size) also increases. However, the porosity of the coatings varied insignificantly and amounted to 5 ± 1%. It has been revealed that the incorporation of ZrO₂ particles substantially affects the properties of diatomite-based coatings. The adhesive strength of the coatings has increased by approximately 30%, and the corrosion resistance has increased by two orders of magnitude compared to the coatings without zirconia particles.

Ti-30Nb-3Ag alloy with improved corrosion resistance and antibacterial properties for orthopedic and dental applications produced by mechanical alloying

Titanium alloys have gained popularity as a bioimplant material due to their biocompatibility, low modulus of elasticity, and increased strength. However, other issues, such as corrosion resistance, and infections can reduce the implant's lifespan. This paper aims to fabricate a new Ti-30Nb-3Ag at% alloy with enhanced in vitro corrosion and antibacterial properties by mechanical alloying (MA) followed by powder consolidation. XRD, SEM/EDX, and Vickers microhardness analyses were used to examine the phases compositions, microstructure, and microhardness, respectively. The in vitro corrosion performance of Ti-30Nb-3Ag alloy was inspected in a simulated body medium and artificial saliva. The alloy's antibacterial properties were evaluated in the gram-positive and negative bacterial medium. The results showed that after MA for 60 h, nanocrystalline β-Ti (BCC) and α-Ti (HCP) solid solutions were formed with crystallite sizes of 7.44 and 3.47 nm, respectively. The sintered sample exhibited densifications of 97%, with a microstructure composed of β-Ti, α-Ti, and a minor quantity of ultrafine Ti₂Ag phase. The microhardness result showed that Ti-30Nb-3Ag alloy possesses HV 491.5. Ti-30Nb-3Ag alloy has a potent antibacterial capability of 85.75% and 88.81% relative to Ti-6Al-4V alloy and CP-Ti, respectively. In vitro corrosion results revealed that the Ti-30Nb-3Ag alloy exhibited the widespread passive area in the investigated anodic regions and presented the highest impedance values in comparison with the commercial alloys, confirming its improved corrosion resistance performance in both studied mediums. Ti-30Nb-3Ag alloy possibly be a competitive bioimplant material for orthopedic and dental uses owing to its enhanced biocorrosion and antibacterial properties compared to commercial Ti-6Al-4V alloy and CP-Ti.

Novel Antibacterial Metals as Food Contact Materials: A Review

Food contamination caused by microorganisms is a significant issue in the food field that not only affects the shelf life of food, but also threatens human health, causing huge economic losses. Considering that the materials in direct or indirect contact with food are important carriers and vectors of microorganisms, the development of antibacterial food contact materials is an important coping strategy. However, different antibacterial agents, manufacturing methods, and material characteristics have brought great challenges to the antibacterial effectiveness, durability, and component migration associated with the use security of materials. Therefore, this review focused on the most widely used metal-type food contact materials and comprehensively presents the research progress regarding antibacterial food contact materials, hoping to provide references for exploring novel antibacterial food contact materials.

Improvement implant osseointegration through nonthermal Ar/O2 plasma

This study investigated the effects of nonthermal Ar/O₂ plasma on the osseointegration of titanium implants. Through 8 weeks' in vivo evaluation of implants inserted into femoral bones of male Sprague-Dawley rats, the new bone mineralization apposition rate (MAR) is increased by 1.87 and 2.14 times for implants of smooth machined (SM) and sand-blasted and acid-etched (SLA) after plasma treatment. The bone volume fraction (bone volume/total volume, BV/TV) and bone-implant contact (BIC) ratios are improved by 1.31, 1.26 times and 1.35, 1.15 times after 90 s plasma treatment. The improved hydrophilicity rather than implant surface morphology is believed to play a critical role for the osseointegration improvement.

Corrosion Behavior and Bio-Functions of the Ultrafine-Grained Ti6Al4V-5Cu Alloy with a Dual-Phase Honeycomb Shell Structure in Simulated Body Fluid

Titanium alloys are widely used in biomedical applications. However, cases of implant failure due to fatigue fracture and bacterial infection are common. In addition, implants are susceptible to metal ions (Al, V) released by long-term exposure to human body fluids, which causes neuropathy, mental disorders, and other diseases. Thus, development of novel materials to achieve long-term safety of implants is currently a research hotspot. Recently, our research group has developed an ultrafine-grained Ti6Al4V-5Cu alloy with a unique "dual-phase honeycomb shell" (DPHS) structure, which possesses high fatigue strength and stability. This study further affirmed its higher corrosion behavior, antibacterial properties, and cytocompatibility compared to the coarse-grained Ti6Al4V and Ti6Al4V-5Cu alloys. The ultrafine-grained structure of Ti6Al4V-5Cu having DPHS increased the proportion of phases (Cu-rich phases, β-phase, and Ti₂Cu intermetallic phase) with a lower surface potential. It was observed that the developed microstructure was conducive to a stable configuration of the oxide (passive) layer on the alloy surface. In addition, the low-phase interfacial energies of the ultrafine-grained structure with DPHS even facilitated the improvement of the denseness of the protective passive film and eventually enhanced the corrosion behavior. Besides, the fine-Cu-rich phases and the micro-galvanic couples formed between them and the matrix significantly increased the contact frequency of bacteria, thus increasing the contact sterilization efficiency of the ultrafine-grained Ti6Al4V-5Cu alloy. These results showed that the new ultrafine-grained Ti6Al4V-5Cu alloy has excellent corrosion resistance and biological functions for clinical application.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy

Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation properties. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m²h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.

Craniofacial therapy: advanced local therapies from nano-engineered titanium implants to treat craniofacial conditions

Nano-engineering-based tissue regeneration and local therapeutic delivery strategies show significant potential to reduce the health and economic burden associated with craniofacial defects, including traumas and tumours. Critical to the success of such nano-engineered non-resorbable craniofacial implants include load-bearing functioning and survival in complex local trauma conditions. Further, race to invade between multiple cells and pathogens is an important criterion that dictates the fate of the implant. In this pioneering review, we compare the therapeutic efficacy of nano-engineered titanium-based craniofacial implants towards maximised local therapy addressing bone formation/resorption, soft-tissue integration, bacterial infection and cancers/tumours. We present the various strategies to engineer titanium-based craniofacial implants in the macro-, micro- and nano-scales, using topographical, chemical, electrochemical, biological and therapeutic modifications. A particular focus is electrochemically anodised titanium implants with controlled nanotopographies that enable tailored and enhanced bioactivity and local therapeutic release. Next, we review the clinical translation challenges associated with such implants. This review will inform the readers of the latest developments and challenges related to therapeutic nano-engineered craniofacial implants.

Enhancement of Fracture Toughness in carbonate doped Hydroxyapatite based nanocomposites: Rietveld analysis and Mechanical behaviour

Highly nanocrystalline carbonated hydroxyapatite (CHAp) is synthesized by hydrothermal technique with four different stoichiometric compositions for microstructural and mechanical analysis. HAp is one of the most biocompatible material and addition of carbonate ions lead to increase in fracture toughness highly required in biomedical applications. The structural properties and its purity as single phase is confirmed by X-ray diffraction. Lattice imperfections and structural defects is investigated using XRD pattern model simulation, i.e. Rietveld's analysis. The substitution of CO₃^2- in HAp structure leads to a decrease in crystallinity which ultimately lessens crystallite size of sample as verified by XRD analysis. FE-SEM micrographs confirms the formation of nanorods with cuboidal morphology and porous structure of HAp and CHAp samples. The particle size distribution histogram validates the constant decrease in size due to carbonate addition. The mechanical testing of prepared samples revealed the increase in mechanical strength from 6.12 MPa to 11.52 MPa due to the addition of carbonate content, which leads to a rise in fracture toughness, a significant property of an implant material from 2.93 kN to 4.22 kN. The cumulative effect of CO₃^2- substitution on HAp structure and mechanical properties has been generalized for the application as biomedical implant material or biomedical smart materials.

Antimicrobial particles based on Cu2ZnSnS4 monograins

In this research, Cu₂ZnSnS₄ (CZTS) particles were successfully fabricated via the molten salt approach from the copper, zinc and tin sulphides as raw precursors. SEM analysis revealed that CZTS particles are tetragonal-shaped with sharp edges, smooth flat plane morphology, and crystal size varying from 10.8 to 28.7 µm. The phase and crystalline structure of synthesized powders were investigated using XRD analysis, which confirms the presence of a tetragonal crystal structure kesterite phase. The chemical composition of CZTS particles was evaluated by EDX spectroscopy, which identified the nearly stoichiometric composition with an averaged formula of Cu_1.88Zn_1.04SnS_3.97. The TG/DTA-MS and ICP-OES analysis showed the possible decomposition pathways and predicted their degradation rate in aqueous solutions. The CZTS particles possessed highly effective concentration and time-dependent antimicrobial properties against medically relevant bacteria and yeast strains. The CZTS particles (1 g L^-1) exhibited over 95.7 ± 1.9% killing efficiency towards M. luteus. In contrast, higher dosages (3.5 and 5 g L^-1) led to its complete inactivation and reduced the P. aeruginosa cell viability to 43.2 ± 3.2% and 4.1 ± 1.1%, respectively. Moreover, the CZTS particles (0.5 g L^-1) are responsible for causing 54.8 ± 1.8% of C. krusei and 89.7 ± 2.1% of C. parapsilosis yeasts death within the 24 h of exposure, which expanded to almost 100% when yeasts were treated with two times higher CZTS concentration (1.0 g L^-1). The mechanism of action has been proposed and evidenced by monitoring the 2',7'-dichlorofluorescein (DCF) fluorescence, which revealed that the overproduction of reactive oxygen species (ROS) is responsible for microorganism death.

Preparation of Superhydrophobic Materials and Establishment of Anticorrosive Coatings on the Tinplate Substrate by Alkylation of Graphene Oxide

Corrosion of structural parts not only reduces the service life of the equipment but also causes safety accidents, so building a long-lasting anti-corrosion coating on its surface is the key to solving this problem. Under the action of alkali catalysis, n-octyltriethoxysilane (OTES), dimethyldimethoxysilane (DMDMS), and perfluorodecyltrimethoxysilane (FTMS) hydrolyzed and polycondensed co-modified graphene oxide (GO), modified to synthesize a self-cleaning superhydrophobic material fluorosilane-modified graphene oxide (FGO). The structure, film morphology, and properties of FGO were systematically characterized. The results showed that the newly synthesized FGO was successfully modified by long-chain fluorocarbon groups and silanes. FGO presented an uneven and rough morphology on the substrate surface, the water contact angle was 151.3°, and the rolling angle was 3.9°, which caused the coating to exhibit excellent self-cleaning function. Meanwhile, the epoxy polymer/fluorosilane-modified graphene oxide (E-FGO) composite coating adhered to the carbon structural steel's surface, and its corrosion resistance was detected by the Tafel curve and EIS impedance. It was found that the current density of the 10 wt% E-FGO coating (I_corr) was the lowest (1.087 × 10^-10 A/cm²), which was approximately 3 orders of magnitude lower than that of the unmodified epoxy coating. This was primarily due to the introduction of FGO, which formed a continuous physical barrier in the composite coating and gave the composite coating excellent hydrophobicity. This method might provide new ideas for advances in steel corrosion resistance in the marine sector.