Zn/Ag micro-galvanic couples formed on titanium and osseointegration effects in the presence of S. aureus

Study on preparation and properties of silver alloy for Mongolian medicine acupuncture

The Mongolian medical silver needles often encounter issues of bending, fracturing, and blunting in clinical applications. Similarly, Mongolian warm needles can cause burns on patients due to inaccurate temperature control. In this study, we developed an Ag85Cu15 alloy specifically for acupuncture needles based on material preparation. By incorporating appropriate amounts of Mn and Ti elements, we were able to enhance the mechanical properties and biocompatibility of the acupuncture needles. Compared to commercially available silver needles, this alloy exhibited a significant increase in microhardness up to 210.2 Hv0.2 and an improved tensile strength of 880.2 MPa. Furthermore, we designed a thermoelectric effect-based temperature measurement model for precise control of the warm needle's temperature, enhancing the therapeutic effectiveness of the treatment.

What to Know about Antimicrobial Coatings in Arthroplasty: A Narrative Review

Periprosthetic joint infections (PJIs) are one of the most worrying complications orthopedic surgeons could face; thus, methods to prevent them are evolving. Apart from systemic antibiotics, targeted strategies such as local antimicrobial coatings applied to prosthetics have been introduced. This narrative review aims to provide an overview of the main antimicrobial coatings available in arthroplasty orthopedic surgery practice. The search was performed on the PubMed, Web of Science, SCOPUS, and EMBASE databases, focusing on antimicrobial-coated devices used in clinical practice in the arthroplasty world. While silver technology has been widely adopted in the prosthetic oncological field with favorable outcomes, recently, silver associated with hydroxyapatite for cementless fixation, antibiotic-loaded hydrogel coatings, and iodine coatings have all been employed with promising protective results against PJIs. However, challenges persist, with each material having strengths and weaknesses under investigation. Therefore, this narrative review emphasizes that further clinical studies are needed to understand whether antimicrobial coatings can truly revolutionize the field of PJIs.

Lithium-Modified TiO2 Surface by Anodization for Enhanced Protein Adsorption and Cell Adhesion

Promoting osseointegration is an essential step in improving implant success rates. Lithium has gradually gained popularity for promoting alkaline phosphatase activity and osteogenic gene expression in osteoblasts. The incorporation of lithium into a titanium surface has been reported to change its surface charge, thereby enhancing its biocompatibility. In this study, we applied anodization as a novel approach to immobilizing Li on a titanium surface and evaluated the changes in its surface characteristics. The objective of this study was to determine the effect of Li treatment of titanium on typical proteins, such as albumin, laminin, and fibronectin, in terms of their adsorption level as well as on the attachment of osteoblast cells. Titanium disks were acid-etched by 66 wt % H2SO4 at 120 °C for 90 s and set as the control group. The etched samples were placed in contact with an anode, while a platinum bar served as the counter electrode. Both electrodes were mounted on a custom electrochemical cell filled with 1 M LiCl. The samples were anodized at constant voltages of 1, 3, and 9 V. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) results showed no significant differences in the topography. However, the ζ potentials of the 3 V group were higher than those of the control group at a physiological pH of 7.4. Interestingly, the adsorption level of the extracellular matrix protein was mostly enhanced on the 3 V-anodized surface. The number of attached cells on the Li-anodized surfaces increased. The localization of vinculin at the tips of the stretching cytoplasmic projections was observed more frequently in the osteoblasts on the 3 V-anodized surface. Although the optimal concentration or voltage for Li application should be investigated further, this study suggests that anodization could be an effective method to immobilize lithium ions on a titanium surface and that modifying the surface charge characteristics enables a direct protein-to-material interaction with enhanced biological adhesion.

Recent Strategies and Future Recommendations for the Fabrication of Antimicrobial, Antibiofilm, and Antibiofouling Biomaterials

Biomaterials and biomedical devices induced life-threatening bacterial infections and other biological adverse effects such as thrombosis and fibrosis have posed a significant threat to global healthcare. Bacterial infections and adverse biological effects are often caused by the formation of microbial biofilms and the adherence of various biomacromolecules, such as platelets, proteins, fibroblasts, and immune cells, to the surfaces of biomaterials and biomedical devices. Due to the programmed interconnected networking of bacteria in microbial biofilms, they are challenging to treat and can withstand several doses of antibiotics. Additionally, antibiotics can kill bacteria but do not prevent the adsorption of biomacromolecules from physiological fluids or implanting sites, which generates a conditioning layer that promotes bacteria's reattachment, development, and eventual biofilm formation. In these viewpoints, we highlighted the magnitude of biomaterials and biomedical device-induced infections, the role of biofilm formation, and biomacromolecule adhesion in human pathogenesis. We then discussed the solutions practiced in healthcare systems for curing biomaterials and biomedical device-induced infections and their limitations. Moreover, this review comprehensively elaborated on the recent advances in designing and fabricating biomaterials and biomedical devices with these three properties: antibacterial (bacterial killing), antibiofilm (biofilm inhibition/prevention), and antibiofouling (biofouling inhibition/prevention) against microbial species and against the adhesion of other biomacromolecules. Besides we also recommended potential directions for further investigations.

A dual-functional PEEK implant coating for anti-bacterial and accelerated osseointegration

Polyetheretherketone (PEEK) has been widely applied in biomedical engineering. However, the unsatisfactory bioactivity essentially limits the clinical application of PEEK. In this study, a simply immersing method was proposed to fabricate a dual-functional PEEK with antibacterial properties and enhanced bone integration. Firstly, the surface of PEEK was modified with a polydopamine (PDA) coating by incubating at dopamine solution. Afterward, the PEEK-PDA was modified with manganese (Mn) and silver (Ag) ions by the soaking method to fabricate the PEEK-PDA-Mn/Ag. The physicochemical capabilities of PEEK-PDA-Mn/Ag were further explored in the ions release, wettability, morphology, and element distributions. PEEK-PDA-Mn/Ag obviously accelerated the adhesion and distribution of MC3T3-E1 cells, indicating favorable biosafety in vitro. Meanwhile, the osteogenic properties of PEEK-PDA-Mn and PEEK-PDA-Mn/Ag were proved by the increased expression of osteogenic genes, alkaline phosphatase (ALP), and mineralization in vitro. Additionally, the wide antibacterial capabilities of PEEK-PDA-Mn/Ag were proved in both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. Furthermore, the PEEK-PDA-Mn/Ag was antibacterial with capability in enhancing osseointegration in vivo. Overall, the simply immersing method can modify the surface of PEEK, giving the bioactivity, biocompatibility, and antibacterial ability to the composited PEEK, which could be applied as an orthopedic implant in clinical.

Antibacterial coatings on orthopedic implants

With the aging of population and the rapid improvement of public health and medical level in recent years, people have had an increasing demand for orthopedic implants. However, premature implant failure and postoperative complications frequently occur due to implant-related infections, which not only increase the social and economic burden, but also greatly affect the patient's quality of life, finally restraining the clinical use of orthopedic implants. Antibacterial coatings, as an effective strategy to solve the above problems, have been extensively studied and motivated the development of novel strategies to optimize the implant. In this paper, a variety of antibacterial coatings recently developed for orthopedic implants were briefly reviewed, with the focus on the synergistic multi-mechanism antibacterial coatings, multi-functional antibacterial coatings, and smart antibacterial coatings that are more potential for clinical use, thereby providing theoretical references for further fabrication of novel and high-performance coatings satisfying the complex clinical needs.

Endowing biodegradable Zinc implants with dual-function of antibacterial ability and osteogenic activity by micro-addition of Mg and Ag (≤ 0.1 wt.%)

Infection remains the devastating complications associated with surgical fixation of bones fractured during trauma. In this study, we report a low-alloyed Zn-Mg-Ag that simultaneously has optimized strength degeneration profiles during degradation, outstanding antibacterial efficacy and osteogenic activity. Our results showed that Zn-0.05Mg-0.1Ag alloy had favorable mechanical properties (UTS: 247.8 ± 1.6 MPa, Elong.: 35 ± 2.2 %) and presented a better hold of mechanical integrity than pure Zn during 28 days corrosion, 2.6 % vs. 18.7 % reduction. After one-year of natural aging, the alloy still preserved an elongation of 24.07 ± 3.84 %. As verified by microbial cultures, Zn-0.05Mg-0.1Ag alloy demonstrated high antibacterial performance against Gram-positive and Gram-negative strains, as well as antibiotic-resistant strains (MRSA) in vitro and in vivo due to the synergistic antibacterial actions of Zn²⁺ and Ag⁺. Meanwhile, Zn-Mg-Ag alloy also exhibited enhanced viability, osteogenic differentiation, and gene expressions of osteoblasts in vitro, as well as promoted osteogenic activity than pure Zn in the femoral condyle defect repair model. The co-releasing of Zn, Mg and Ag ions did not induce toxic side effects. Collectively, low alloyed Zn-0.05Mg-0.1Ag indicated long-lasting mechanical integrity during degradation, and presented the ability to synergistically inhibit bacteria and promote osteogenesis, possessing tremendous potential in treating implant-associated infections. STATEMENT OF SIGNIFICANCE: Infection after fracture fixation (IAFF) remains the most common and serious side effects of orthopedic surgery. Additionally, widespread antibiotic use contributes to the development of multi-drug resistant bacteria such as methicillin-resistant staphylococcus aureus (MRSA), which exacerbates IAFF treatment and prevention. IAFF treatment and prevention remain clinically challenging, so implants with dual antibacterial and osteogenic functions are in high demand. The antibacterial efficacy and osteogenic activity of low-alloyed Zn-Mg-Ag (≤0.1 wt.% Mg, Ag) alloys were investigated in vitro and in vivo. The results showed that micro addition of Mg and Ag could significantly improve osseointegration function, mechanical properties, and antibacterial performance. These quantification findings shed new light on the development and understanding of dual functional Zn-based orthopedic implants.

Lactoferrin network with MC3T3-E1 cell proliferation, auxiliary mineralization, antibacterial functions: A multifunctional coating for biofunctionalization of implant surfaces

Developing biocompatible, low-immunoreactive, and antibacterial implants are challenging yet fundamental to osteosynthesis. In this study, mineralization-stimulative and antibacterial networking nanostructures are assembled via amyloid-like aggregation of lactoferrin (LF) triggered by reducing the intramolecular disulfide bonds. Due to the adhesive property of their rich β-sheet architecture, the LF networks are amenable to the deposition upon the surface of various implant materials, functionalizing the implants with cell-proliferative, mineralization-stimulative, and antibacterial properties. Specifically, the abundant functional groups and amino acids exposed on the surface of LF networks provide abundant functional microdomains for subsequent mineralization of different forms of calcium ions and promote the formation of hydroxyapatite (HAp) crystals in simulated body fluids. We further demonstrate that the LF network inherits the innate antibacterial properties of LF and exerts a synergistic antibacterial ability with surface-enriched positively charged and hydrophobic amino acid residues, disrupting bacterial biofilm formation, enhancing microbial cell wall perturbation, and ultimately leading to microbial death. The results underscore the feasibility of the LF network as a multifunctional coating on bioscaffold surfaces, which may provide insight into its future applications in next-generation artificial bone implants with bacterial/biofilm clearance and bone tissue remodeling capabilities.

The Antibacterial and Cytotoxic Effects of Silver Nanoparticles Coated Titanium Implants: A Narrative Review

Nanotechnology has become an emerging research field with numerous biomedical scientific applications. Silver possesses bactericidal activities that have been harnessed for centuries; however, there is a concern about the toxic effects of silver nanoparticles. This paper aims to provide an overview of silver-treated dental implants and discuss their potential to reduce the prevalence of peri-implant diseases. An electronic search was performed using PubMed. After screening, data extraction was performed on the 45 remaining articles using inclusion and exclusion criteria. Most of the articles demonstrated that silver nanoparticles embedded in a coating layer and/or on surface-treated titanium exhibit sound antibacterial effects and biocompatibility. Most of the reviewed studies revealed that silver nanoparticles on dental implant surfaces reduced cytotoxicity but provided a prolonged antibacterial effect. The cytotoxicity and antibacterial effect are closely linked to how the silver nanoparticles are released from the titanium surfaces, where a slower release increases cell viability and proliferation. However, to improve the clinical translation, there is still a need for more studies, especially evaluating the long-term systemic effects and studies recreating the conditions in the oral cavity.

Recent Advances in Copper-Doped Titanium Implants

Titanium (Ti) and its alloys have been extensively used as implant materials in clinical practice due to their high corrosion resistance, light weight and excellent biocompatibility. However, the insufficient intrinsic osteogenic capacity of Ti and its alloys impedes bone repair and regeneration, and implant-related infection or inflammation remains the leading cause of implant failure. Bacterial infections or inflammatory diseases constitute severe threats to human health. The physicochemical properties of the material are critical to the success of clinical procedures, and the doping of Cu into Ti implants has been confirmed to be capable of enhancing the bone repair/regeneration, angiogenesis and antibacterial capability. This review outlines the recent advances in the design and preparation of Cu-doped Ti and Ti alloy implants, with a special focus on various methods, including plasma immersion implantation, magnetron sputtering, galvanic deposition, microarc oxidation and sol-gel synthesis. More importantly, the antibacterial and mechanical properties as well as the corrosion resistance and biocompatibility of Cu-doped Ti implants from different methods are systematically reviewed, and their prospects and limitations are also discussed.

A novel Ti-Au alloy with strong antibacterial properties and excellent biocompatibility for biomedical application

In order to avoid the toxic and side effects on human body of long-term dissolution of metal ions from antibacterial titanium alloys, Au element with non-toxicity and non-side effect was selected as the alloying element to prepare a new Ti-Au alloy with strong antibacterial property. We produced Ti-Au(S) sintered alloy by powder metallurgy and Ti-Au ingot alloy by ingot metallurgy, and investigated the influence of the secondary phase on the relative antimicrobial properties and antibacterial mechanism in this work. The results indicated that the aged Ti-Au(T6) alloy and Ti-Au(S) sintered alloy exhibited strong antibacterial rate against S. aureus due to the formation of Ti₃Au phases. In vitro cell culture (MC3T3 cells) experiments showed that Ti-Au alloys had good cytocompatibility and osteogenic properties. The following viewpoints of antibacterial mechanism are that the Ti₃Au destroyed the ROS homeostasis of bacteria, causing oxidative stress in bacterial cells and preventing from the biofilms formation.

Construction of multi-layered Zn-modified TiO2 coating by ultrasound-auxiliary micro-arc oxidation: Microstructure and biological property

Surfaces with desirable cytocompatibility and bactericidal ability are favoured for orthopaedic implants to stimulate osteogenic activity and to prevent implant-associated infection. In this work, we creatively introduce ultrasonic vibration (UV) to micro-arc oxidation (MAO) process and explore its influence on the microstructure, corrosion property and biological responses of Zn-modified TiO₂ coating. With the introduction of UV, a uniform surface layer with homogeneously-distributed clusters could be produced as the outer layer, which possesses a fusion band with the underlying TiO₂. The microstructural modification associated with UV results in the enhanced corrosion resistance, increased adhesive strength and improved biological performances of the resultant coating relative to that with the absence of UV. Hence, the ultrasonic auxiliary micro-arc oxidation (UMAO) is regarded as a promising surface modification method to produce Ti-based orthopaedic implants of high quality.

Self-activating anti-infection implant

Clinically, it is difficult to endow implants with excellent osteogenic ability and antibacterial activity simultaneously. Herein, the self-activating implants modified with hydroxyapatite (HA)/MoS₂ coating are designed to prevent Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) infections and accelerate bone regeneration simultaneously. The electron transfer between bacteria and HA/MoS₂ is triggered when bacteria contacted with the material. RNA sequencing data reveals that the expression level of anaerobic respiration-related genes is up-regulated and the expression level of aerobic respiration-related genes is down-regulated when bacteria adhere to the implants. HA/MoS₂ presents a highly effective antibacterial efficacy against both S. aureus and E. coli because of bacterial respiration-activated metabolic pathway changes. Meanwhile, this coating promotes the osteoblastic differentiation of mesenchymal stem cells by altering the potentials of cell membrane and mitochondrial membrane. The proposed strategy exhibits great potential to endow implants with self-activating anti-infection performance and osteogenic ability simultaneously.

Enhanced osteogenic activity and antibacterial performance in vitro of polyetheretherketone by plasma-induced graft polymerization of acrylic acid and incorporation of zinc ions

Polyetheretherketone (PEEK) has been widely used in the fields of orthopedics and trauma, but weak osteointegration and bacterial infection affect its long-term stability and repair effects. Surface modification is an effective way to improve the osteogenic and antibacterial activity of PEEK implants. In the present study, a layer of acrylic acid (AA) polymer coating loaded with zinc ions (Zn²⁺) was constructed on the surface of PEEK (PEEK-AA-Zn) using a strategy of combining plasma-induced graft polymerization with a chemical immersion technique. Successful construction of the AA coating remarkably enhanced the hydrophilicity of PEEK, and effectively loaded and released Zn²⁺. In vitro cell culture using MC3T3-E1 preosteoblasts showed that the Zn²⁺ released from PEEK-AA-Zn promoted cell proliferation and elevated gene expression levels of alkaline phosphatase (ALP), osteocalcin (OCN) and bone sialoprotein (BSP). Antibacterial tests revealed that PEEK-AA-Zn efficiently inhibited the proliferation of Staphylococcus aureus (S. aureus). These results suggest that the combined method of graft polymerization and ion incorporation endows PEEK with excellent osteogenic and antibacterial activity, which provides a wide range of possibilities for developing PEEK implants with multifunctional properties for bone tissue repair.

Anodic TiO2 Nanotubes: Tailoring Osteoinduction via Drug Delivery

TiO₂ nanostructures and more specifically nanotubes have gained significant attention in biomedical applications, due to their controlled nanoscale topography in the sub-100 nm range, high surface area, chemical resistance, and biocompatibility. Here we review the crucial aspects related to morphology and properties of TiO₂ nanotubes obtained by electrochemical anodization of titanium for the biomedical field. Following the discussion of TiO₂ nanotopographical characterization, the advantages of anodic TiO₂ nanotubes will be introduced, such as their high surface area controlled by the morphological parameters (diameter and length), which provides better adsorption/linkage of bioactive molecules. We further discuss the key interactions with bone-related cells including osteoblast and stem cells in in vitro cell culture conditions, thus evaluating the cell response on various nanotubular structures. In addition, the synergistic effects of electrical stimulation on cells for enhancing bone formation combining with the nanoscale environmental cues from nanotopography will be further discussed. The present review also overviews the current state of drug delivery applications using TiO₂ nanotubes for increased osseointegration and discusses the advantages, drawbacks, and prospects of drug delivery applications via these anodic TiO₂ nanotubes.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

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

The Synergy of Topographical Micropatterning and Ta|TaCu Bilayered Thin Film on Titanium Implants Enables Dual-Functions of Enhanced Osteogenesis and Anti-Infection

Poor osteogenesis and implant-associated infection are the two leading causes of failure for dental and orthopedic implants. Surface design with enhanced osteogenesis often fails in antibacterial activity, or vice versa. Herein, a surface design strategy, which overcomes this trade-off via the synergistic effects of topographical micropatterning and a bilayered nanostructured metallic thin film is presented. A specific microgrooved pattern is fabricated on the titanium surface, followed by sequential deposition of a nanostructured copper (Cu)-containing tantalum (Ta) (TaCu) layer and a pure Ta cap layer. The microgrooved patterns coupled with the nanorough Ta cap layer shows strong contact guidance to preosteoblasts and significantly enhances the osteogenic differentiation in vitro, while the controlled local sustained release of Cu ions is responsible for high antibacterial activity. Importantly, rat calvarial defect models in vivo further confirm that the synergy of microgrooved patterns and the Ta|TaCu bilayered thin film on titanium surface could effectively promote bone regeneration. The present effective and versatile surface design strategy provides significant insight into intelligent surface engineering that can control biological response at the site of healing in dental and orthopedic implants.

Research status of biodegradable metals designed for oral and maxillofacial applications: A review

The oral and maxillofacial regions have complex anatomical structures and different tissue types, which have vital health and aesthetic functions. Biodegradable metals (BMs) is a promising bioactive materials to treat oral and maxillofacial diseases. This review summarizes the research status and future research directions of BMs for oral and maxillofacial applications. Mg-based BMs and Zn-based BMs for bone fracture fixation systems, and guided bone regeneration (GBR) membranes, are discussed in detail. Zn-based BMs with a moderate degradation rate and superior mechanical properties for GBR membranes show great potential for clinical translation. Fe-based BMs have a relatively low degradation rate and insoluble degradation products, which greatly limit their application and clinical translation. Furthermore, we proposed potential future research directions for BMs in the oral and maxillofacial regions, including 3D printed BM bone scaffolds, surface modification for BMs GBR membranes, and BMs containing hydrogels for cartilage regeneration, soft tissue regeneration, and nerve regeneration. Taken together, the progress made in the development of BMs in oral and maxillofacial regions has laid a foundation for further clinical translation.

Antibacterial Titanium Implants Biofunctionalized by Plasma Electrolytic Oxidation with Silver, Zinc, and Copper: A Systematic Review

Patients receiving orthopedic implants are at risk of implant-associated infections (IAI). A growing number of antibiotic-resistant bacteria threaten to hamper the treatment of IAI. The focus has, therefore, shifted towards the development of implants with intrinsic antibacterial activity to prevent the occurrence of infection. The use of Ag, Cu, and Zn has gained momentum as these elements display strong antibacterial behavior and target a wide spectrum of bacteria. In order to incorporate these elements into the surface of titanium-based bone implants, plasma electrolytic oxidation (PEO) has been widely investigated as a single-step process that can biofunctionalize these (highly porous) implant surfaces. Here, we present a systematic review of the studies published between 2009 until 2020 on the biomaterial properties, antibacterial behavior, and biocompatibility of titanium implants biofunctionalized by PEO using Ag, Cu, and Zn. We observed that 100% of surfaces bearing Ag (Ag-surfaces), 93% of surfaces bearing Cu (Cu-surfaces), 73% of surfaces bearing Zn (Zn-surfaces), and 100% of surfaces combining Ag, Cu, and Zn resulted in a significant (i.e., >50%) reduction of bacterial load, while 13% of Ag-surfaces, 10% of Cu-surfaces, and none of Zn or combined Ag, Cu, and Zn surfaces reported cytotoxicity against osteoblasts, stem cells, and immune cells. A majority of the studies investigated the antibacterial activity against S. aureus. Important areas for future research include the biofunctionalization of additively manufactured porous implants and surfaces combining Ag, Cu, and Zn. Furthermore, the antibacterial activity of such implants should be determined in assays focused on prevention, rather than the treatment of IAIs. These implants should be tested using appropriate in vivo bone infection models capable of assessing whether titanium implants biofunctionalized by PEO with Ag, Cu, and Zn can contribute to protect patients against IAI.

Antibacterial and antibiofilm properties of graphene and its derivatives

Infections resulting from bacteria and biofilms have become a huge problem threatening human health. In recent years, the antibacterial and antibiofilm effects of graphene and its derivatives have been extensively studied. However, there continues to be some controversy over whether graphene and its derivatives can resist infection and biofilms. Moreover, the antibacterial mechanism and cytotoxicity of graphene and its derivatives are unclear. In the present review, antibacterial and antibiofilm abilities of graphene and its derivatives in solution, on the surface are reviewed, and their toxicity and possible mechanisms are also reviewed. Furthermore, we propose possible future development directions for graphene and its derivatives in antibacterial and antibiofilm applications.

Co-implantation of magnesium and zinc ions into titanium regulates the behaviors of human gingival fibroblasts

Soft tissue sealing around implants acts as a barrier between the alveolar bone and oral environment, protecting implants from the invasion of bacteria or external stimuli. In this work, magnesium (Mg) and zinc (Zn) are introduced into titanium by plasma immersed ion implantation technology, and their effects on the behaviors of human gingival fibroblasts (HGFs) as well as the underlying mechanisms are investigated. Surface characterization confirms Mg and Zn exist on the surface in metallic and oxidized states. Contact angle test suggests that surface wettability of titanium changes after ion implantation and thus influences protein adsorption of surfaces. In vitro studies disclose that HGFs on Mg ion-implanted samples exhibit better adhesion and migration while cells on Zn ion-implanted samples have higher proliferation rate and amounts. The results of immunofluorescence staining and real-time reverse-transcriptase polymerase chain reaction (RT-PCR) suggest that Mg mainly regulates the motility and adhesion of HGFs through activating the MAPK signal pathway whereas Zn influences HGFs proliferation by triggering the TGF-β signal pathway. The synergistic effect of Mg and Zn ions ensure that HGFs cultured on co-implanted samples possessed both high proliferation rate and motility, which are critical to soft tissue sealing of implants.

Synergistic effects of immunoregulation and osteoinduction of ds-block elements on titanium surface

Ds-block elements have been gaining increasing attention in the field of biomaterials modification, owing to their excellent biological properties, such as antibiosis, osteogenesis, etc. However, their function mechanisms are not well understood and conflicting conclusions were drawn by previous studies on this issue, which are mainly resulted from the inconsistent experimental conditions. In this work, three most widely used ds-block elements, copper, zinc, and silver were introduced on titanium substrate by plasma immersion ion implantation method to investigate the rule of ds-block elements in the immune responses. Results showed that the implanted samples could decrease the inflammatory responses compared with Ti sample. The trend of anti-inflammatory effects of macrophages on samples was in correlation with cellular ROS levels, which was induced by the implanted biomaterials and positively correlated with the number of valence electrons of ds-block elements. The co-culture experiments of macrophages and bone marrow mesenchymal stem cells showed that these two kinds of cells could enhance the anti-inflammation and osteogenesis of samples by the paracrine manner of PGE2. In general, in their steady states on titanium substrate (Cu2+, Zn2+, Ag), the ds-block elements with more valence electrons exhibit better anti-inflammatory and osteogenic effects. Moreover, molecular biology experiments indicate that the PGE2-related signaling pathway may contribute to the desired immunoregulation and osteoinduction capability of ds-block elements. These findings suggest a correlation between the number of valence electrons of ds-block elements and the relevant biological responses, which provides new insight into the selection of implanted ions and surface design of biomaterials.

Enhanced biocompatibility and osteogenic differentiation of mesenchymal stem cells of titanium by Sr-Ga clavate double hydroxides

To improve in vivo osseointegration of pure titanium implant, Sr-Ga clavate double hydroxide (CDH) coating was grown in situ on a titanium (Ti) substrate with simple hydrothermal and calcination treatments at 500 °C. The obtained coating on the Ti substrate (Ti-CDH and Ti-CDH500) was researched by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Ti-CDH exhibited a sustained release profile of metal ions and maintained a slightly alkaline environment. The CDH coating was beneficial for osteogenic differentiation of mesenchymal stem cells (MSCs), which were reflected by the results of cellular assays, including alkaline phosphatase activity (ALP), cell mineralization capability (ARS), and osteogenesis-related gene expression. Besides, Ti-CDH could effectively improve the autophagic levels in MSCs, which further promoted osteogenic differentiation of MSCs. Hence, the Ti surface with Sr-Ga CDH modification supplied a simple and effective strategy to design biomaterials for bone generation.

Engineered probiotics biofilm enhances osseointegration via immunoregulation and anti-infection

Preventing multidrug-resistant bacteria-related infection and simultaneously improving osseointegration are in great demand for orthopedic implants. However, current strategies are still limited to a combination of non-U.S. Food and Drug Administration-approved antibacterial and osteogenic agents. Here, we develop a food-grade probiotic-modified implant to prevent methicillin-resistant Staphylococcus aureus (MRSA) infection and accelerate bone integration. Lactobacillus casei is cultured on the surface of alkali heat-treated titanium (Ti) substrates and inactivated by ultraviolet irradiation to avoid sepsis induced by viable bacteria. This inactivated L. casei biofilm shows excellent 99.98% antibacterial effectiveness against MRSA due to the production of lactic acid and bacteriocin. In addition, the polysaccharides in the L. casei biofilm stimulate macrophages to secrete abundant osteogenic cytokines such as oncostatin M and improve osseointegration of the Ti implant. Inactivated probiotics modification can be a promising strategy to endow implants with both excellent self-antibacterial activity and osteointegration ability.

Antibacterial Effect of the Controlled Nanoscale Precipitates Obtained by Different Heat Treatment Schemes with a Ti-Based Nanomaterial, Ti-7.5Mo-5Cu Alloy

It is well known that copper is an excellent option for a Ti-based alloy component as a β-stabilizer that provides improved biocompatibility and antibacterial ability. The development of a Ti-based nanomaterial containing Cu is a promising strategy for addressing implant-associated infections (OII). However, the antibacterial mechanism of copper-related alloys is still unknown. There are two popular hypotheses: copper ion release sterilization and alloy contact sterilization. The main mechanism of contact sterilization may be Cu-related phase (Ti₂Cu) precipitation. Because excess copper can lead to cytotoxicity and reduce the β-Ti phase content, molybdenum needs to be added to the alloy given its well-known and widely researched β-stabilizer characteristics, which can provide satisfactory mechanical properties, wear resistance, and biocompatibility. Our study created a Ti-based nanomaterial, Ti-7.5Mo-5Cu, and performed two kinds of heat treatment schemes at different solution temperatures: 750 and 900 °C. The above schemes resulted in homogeneous and heterogeneous nucleation on the precipitation behavior of the Ti₂Cu crystal phase, which controlled its amount, distribution, and size. Finally, our results showed that Ti-7.5Mo-5Cu, especially at 900 °C, possessed excellent antibacterial ability, corrosion resistance, cytocompatibility, and induced osteogenic differentiation, indicating its potential for use as a biomedical antibacterial alloy in the future.

Intrafibrillar Mineralized Collagen-Hydroxyapatite-Based Scaffolds for Bone Regeneration

As one of the major challenges in the field of tissue engineering, large skeletal defects have attracted wide attention from researchers. Collagen (Col) and hydroxyapatite (HA), the most abundant protein and the main component in natural bone, respectively, are usually used as a biomimetic composite material in tissue engineering due to their excellent biocompatibility and biodegradability. In this study, novel intrafibrillar mineralized Col-HA-based scaffolds, constructed in either cellular or lamellar microstructures, were established through a biomimetic method to enhance the new bone-regenerating capability of tissue engineering scaffolds. Moreover, iron (Fe) and manganese (Mn), two of the essential trace elements in the body, were successfully incorporated into the lamellar scaffold to further improve the osteoinductivity of these biomaterials. It was found that the lamellar scaffolds demonstrated better osteogenic abilities compared to both in-house and commercial Col-HA-based cellular scaffolds in vitro and in vivo. Meanwhile, Fe/Mn incorporation further amplified the osteogenic promotion of the lamellar scaffolds. More importantly, a synergistic effect was observed in the Fe and Mn dual-element-incorporated lamellar scaffolds for both in vitro osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and in vivo bone regeneration loaded with fresh bone marrow cells. This study provides a simple but practical strategy for the creation of functional scaffolds for bone regeneration.

Biofunctionalization of selective laser melted porous titanium using silver and zinc nanoparticles to prevent infections by antibiotic-resistant bacteria

Antibiotic-resistant bacteria are frequently involved in implant-associated infections (IAIs), making the treatment of these infections even more challenging. Therefore, multifunctional implant surfaces that simultaneously possess antibacterial activity and induce osseointegration are highly desired in order to prevent IAIs. The incorporation of multiple inorganic antibacterial agents onto the implant surface may aid in generating synergistic antibacterial behavior against a wide microbial spectrum while reducing the occurrence of bacterial resistance. In this study, porous titanium implants synthesized by selective laser melting (SLM) were biofunctionalized with plasma electrolytic oxidation (PEO) using electrolytes based on Ca/P species as well as silver and zinc nanoparticles in ratios from 0 to 100% that were tightly embedded into the growing titanium oxide layer. After the surface bio-functionalization process, silver and zinc ions were released from the implant surfaces for at least 28 days resulting in antibacterial leaching activity against methicillin-resistant Staphylococcus aureus (MRSA). Furthermore, the biofunctionalized implants generated reactive oxygen species, thereby contributing to antibacterial contact-killing. While implant surfaces containing up to 75% silver and 25% zinc nanoparticles fully eradicated both adherent and planktonic bacteria in vitro as well as in an ex vivo experiment performed using murine femora, solely zinc-bearing surfaces did not. The minimum inhibitory and bactericidal concentrations determined for different combinations of both types of ions confirmed the presence of a strong synergistic antibacterial behavior, which could be exploited to reduce the amount of required silver ions by two orders of magnitude (i.e., 120 folds). At the same time, the zinc bearing surfaces enhanced the metabolic activity of pre-osteoblasts after 3, 7, and 11 days. Altogether, implant biofunctionalization by PEO with silver and zinc nanoparticles is a fruitful strategy for the synthesis of multifunctional surfaces on orthopedic implants and the prevention of IAIs caused by antibiotic-resistant bacteria. STATEMENT OF SIGNIFICANCE: Implant-associated infections are becoming increasingly challenging to treat due to growing antibiotic resistance against antibiotics. Here, we propose an alternative approach where silver and zinc nanoparticles are simultaneously used for the biofunctionalization of rationally designed additively manufactured porous titanium. This combination of porous design and tailored surface treatment allows us to reduce the amount of required silver nanoparticles by two orders of magnitude, fully eradicate antibiotic-resistant bacteria, and enhance the osteogenic behavior of pre-osteoblasts. We demonstrate that the resulting implants display antibacterial activity in vitro and ex vivo against methicillin-resistant Staphylococcus aureus.

Improving the corrosion resistance of micro-arc oxidation coated Mg-Zn-Ca alloy

Four additives (Na₂WO₄, nano-hydroxyapatite, K₂TiF₆ and NaF) were added into the Na₅P₃O₁₀ + NaOH + C₃H₈O₃ base electrolyte according to the orthogonal design of four factors three levels (L₉ (3⁴)). Nine different micro-arc oxidation (MAO) coatings were fabricated on Mg–2Zn–0.5Ca alloys through orthogonal experiments. The effects of four additives on the microstructure, mechanical properties, corrosion resistance and biocompatibility of MAO coatings were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), electrochemical corrosion test and in vitro degradation test. The addition of nano-hydroxyapatite and K₂TiF₆ showed self-sealing effects and contributed to the corrosion resistance of the samples significantly. The addition of 0.5 g L⁻¹ Na₂WO₄ markedly elevated the bonding strength of the coatings with the substrate. The optimal combination of factors and levels considering both mechanical properties and corrosion resistance was: 0.5 g L⁻¹ Na₂WO₄, 0 g L⁻¹ NaF, 5 g L⁻¹ n-HAp, 5 g L⁻¹ K₂TiF₆. The growth mechanism of MAO coatings combining with the visual phenomenon was discussed as well.

Large amount of micro-pores formed in MAO coatings were interconnected and sealed.

On-demand storage and release of antimicrobial peptides using Pandora's box-like nanotubes gated with a bacterial infection-responsive polymer

Background: Localized delivery of antimicrobial agents such as antimicrobial peptides (AMPs) by a biomaterial should be on-demand. Namely, AMPs should be latent and biocompatible in the absence of bacterial infection, but released in an amount enough to kill bacteria immediately in response to bacterial infection. Methods: To achieve the unmet goal of such on-demand delivery, here we turned a titanium implant with titania nanotubes (Ti-NTs) into a Pandora's box. The box was loaded with AMPs (HHC36 peptides, with a sequence of KRWWKWWRR) inside the nanotubes and "closed" (surface-modified) with a pH-responsive molecular gate, poly(methacrylic acid) (PMAA), which swelled under normal physiological conditions (pH 7.4) but collapsed under bacterial infection (pH ≤ 6.0). Thus, the PMAA-gated Ti-NTs behaved just like a Pandora's box. The box retarded the burst release of AMPs under physiological conditions because the gate swelled to block the nanotubes opening. However, it was opened to release AMPs to kill bacteria immediately when bacterial infection occurred to lowering the pH (and thus made the gate collapse). Results: We demonstrated such smart excellent bactericidal activity against a panel of four clinically important bacteria, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus. In addition, this box was biocompatible and could promote the osteogenic differentiation of human mesenchymal stem cells. Both in vitro and in vivo studies confirmed the smart "on-demand" bactericidal activity of the Pandora's box. The molecularly gated Pandora's box design represents a new strategy in smart drug delivery.

Zn-incorporation with graphene oxide on Ti substrates surface to improve osteogenic activity and inhibit bacterial adhesion

The poor osseointegration and postoperative bacterial infection are prominently responsible for the failure of titanium (Ti)-based implant in clinic. To address above issues, methacryloyl modified graphene oxide (GOMA) as zinc ions (Zn²⁺ ) reservoir and release platform was fabricated on the Ti substrates with cathode electrophoresis deposition (EPD). Afterward, phenylboronic acid (PBA) functionalization methacryloyl-gelatin (GelMA-PBA) was reacting with GOMA through in situ free-radical polymerization to prepare GO-Zn/GelMA-PBA coating. The obtained coating was confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, and Zn ions release property, respectively. in vitro cellular experiments including cell activity, alkaline phosphatase, collagen secretion, extracellular matrix (ECM) mineralization, osteogenic genes and proteins, revealed that GO-Zn/GelMA-PBA coating was beneficial for enhancing the adhesion, proliferation, and differentiation of osteoblasts. The positive results were related to the existence of gelatin, formation of boronic ester between PBA groups, and carbohydrates of osteoblasts surface. Meanwhile, antibacterial assay against Staphylococcus aureus and Pseudomonas aeruginosa confirmed that GO-Zn/GelMA-PBA coating on Ti substrates had superior antibacterial capacity, availably inhibited the bacterial adhesion, and prevented formation of biofilm. Hence, the study provides a promising strategy for designing pro-osteogenesis and antibacterial coating on Ti substrates for orthopedic applications.

Degradable magnesium-based alloys for biomedical applications: The role of critical alloying elements

Magnesium-based alloys exhibit biodegradable, biocompatible and excellent mechanical properties which enable them to serve as ideal candidate biomedical materials. In particular, their biodegradable ability helps patients to avoid a second surgery. The corrosion rate, however, is too rapid to sustain the healing process. Alloying is an effective method to slow down the corrosion rate. However, currently magnesium alloys used as biomaterials are mostly commercial alloys without considering cytotoxicity from the perspective of biosafety. This article comprehensively reviews the status of various existing and newly developed degradable magnesium-based alloys specially designed for biomedical application. The effects of critical alloying elements, compositions, heat treatment and processing technology on the microstructure, mechanical properties and corrosion resistance of magnesium alloys are discussed in detail. This article covers Mg-Ca based, Mg-Zn based, Mg-Sr based, Mg-RE based and Mg-Cu-based alloy systems. The novel methods of fabricating Mg-based biomaterials and surface treatment on Mg based alloys for potential biomedical applications are summarized.

Improved antibacterial properties of collagen I/hyaluronic acid/quaternized chitosan multilayer modified titanium coatings with both contact-killing and release-killing functions

The HACC-based multilayer could inhibit the colonization of bacteria via contact-killing and release-killing.

Antimicrobial Titanium Surface via Click-Immobilization of Peptide and Its in Vitro/Vivo Activity

The use of antimicrobial peptides (AMPs)-functionalized titanium implants is an efficient method for preventing bacterial infection. However, the attachment of AMPs to the surface of titanium implants remains a challenge. In this study, a "clickable" titanium surface was developed by using a silane coupling agent with an alkynyl group. The antimicrobial titanium implant was then constructed through the reaction between the "clickable" surface and azido-AMPs (PEG-HHC36:N₃-PEG₁₂-KRWWKWWRR) via click chemistry of Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Such an antimicrobial titanium implant, with an AMP density of 897.4 ± 67.3 ng/cm² (2.5 ± 0.2 molecules per nm²) on the surface, exhibited good and stable antimicrobial activity, inhibited 90.2% of Staphylococcus aureus and 88.1% of Escherichia coli after 2.5 h of incubation, and even inhibited 69.5% of Staphylococcus aureus after 4 days of degradation. The CCK-8 assay indicated that the antimicrobial titanium implant exhibited negligible cytotoxicity to mouse bone mesenchymal stem cells. In vivo assay illustrated that this implant could kill 78.8% of Staphylococcus aureus after 7 days. This method has great potential for the preparation of antimicrobial titanium implants and the prevention of infections in the clinic.

Effect of Local Alkaline Microenvironment on the Behaviors of Bacteria and Osteogenic Cells

The interactions between material surfaces and bacteria/cells have been widely investigated, based on which biomaterials with antibacterial and osteogenic abilities can be designed to conquer implant failures. The pH of environments is known to affect bacterial growth and bone formation/resorption, and it is possible that the antibacterial and osteogenic abilities of biomaterials can be simultaneously improved by regulating their surface alkalinity. Herein, we fabricated many kinds of films with various alkalinity levels on titanium surface to explore the effect of local alkaline microenvironments around material surfaces on the behaviors of bacteria and osteogenic cells. Both Gram-positive and -negative bacteria were cultured on sample surfaces to investigate their antibacterial effects. Cell adhesion, proliferation, and alkaline phosphatase (ALP) activities were investigated by culturing both bone mesenchymal stem cells (MSCs) and osteoblast cells on sample surfaces. The results show that an appropriate local alkaline environment can effectively inhibit the growth of both Gram-positive and -negative bacteria through inactivating ATP synthesis and inducing oxidative stress. Meanwhile, it can promote the osteogenic differentiation of bone MSCs and enhance the proliferation and ALP activities of osteoblast cells. In conclusion, material surfaces endowed with appropriate alkalinity can possess antibacterial and osteogenic properties, which provide a novel strategy to design multifunctional biomaterials for bone generation.

A facile fabrication of novel stuff with antibacterial property and osteogenic promotion utilizing red phosphorus and near-infrared light

Bone-implant materials are important for bone repairing and orthopedics surgery, which include bone plates and bone nails. These materials need to be designed not only considering its biostability and biocompatibility, but also their by-products induced infection after therapy or long-time treatment in vivo. Thus, the development of novel implant materials is quite urgent. Red phosphorus has great biocompatibility and exhibits efficient photothermal ability. Herein, a red phosphorus/IR780/arginine-glycine-asparticacid-cysteine (RGDC) coating on titanium bone-implant was prepared. The temperature sensitivity of Staphylococcus aureus biofilm is enhanced in the presence of ROS produced by IR780 with 808 nm light irradiation. With keeping the cells and tissues normal, a high antibacterial performance can be realized by near-infrared (808 nm) irradiated within 10 min at 50 °C. Besides the high effective antibacterial efficacy provided by photothermal therapy (PTT) and photodynamic therapy (PDT), the RGDC decorated surface can also possess an excellent performance in osteogenesis in vivo.

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A red phosphorus/IR780/arginine-glycine-asparticacid-cysteine (RGDC) coating on titanium bone-implant was prepared.

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The temperature sensitivity of Staphylococcus aureus biofilm is enhanced in the presence of ROS produced by IR780.

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A high antibacterial performance can be realized by near-infrared (808 nm) irradiated within 10 min at 50 °C.

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RGDC modified implants exhibit an excellent performance in osteogenesis in vivo.

Temperature-Controlled Reversible Exposure and Hiding of Antimicrobial Peptides on an Implant for Killing Bacteria at Room Temperature and Improving Biocompatibility in Vivo

Modification of implants by antimicrobial peptides (AMPs) can improve the antimicrobial activity of the implants. However, AMPs have some cytotoxicity in vivo when they are exposed at body temperature. To tackle this challenge, we propose to develop a new approach to generating a smart antimicrobial surface through exposure of AMPs on the surface. A polydopamine film was first formed on the substrates, followed by the conjugation of a temperature-sensitive polymer, poly( N-isopropylacrylamide) (pNIPAM), to the film through atom transfer radical polymerization (ATRP). Then, AMPs were conjugated to the NIPAM on the resultant pNIPAM-modified surface through a click chemistry reaction. Because of the temperature-sensitive property of pNIPAM, the AMPs motif was more exposed to the external environment at room temperature (25 °C) than at body temperature (37 °C), making the surface present a higher antimicrobial activity at room temperature than at body temperature. More importantly, such a smart behavior is accompanied with the increased biocompatibility of the surface at body temperature when compared to the substrates unmodified or modified by AMPs or pNIPAM alone. Our in vivo study further verified that pNIPAM-AMP dual modified bone implants showed increased biocompatibility even when they were challenged with the bacteria at room temperature before implantation. These results indicate that the implants are antibacterial at room temperature and can be safely employed during surgery, resulting in no infection after implantations. Our work represents a new promising strategy to fully explore the antimicrobial property of AMPs, while improving their biocompatibility in vivo. The higher exposure of AMPs at room temperature (the temperature for storing the implants before surgery) will help decrease the risk of bacterial infection, and the lower exposure of AMPs at body temperature (the temperature after the implants are placed into the body by surgery) will improve the biocompatibility of AMPs.

Surface treatment strategies to combat implant-related infection from the beginning

Orthopaedic implants are recognised as important therapeutic devices in the successful clinical management of a wide range of orthopaedic conditions. However, implant-related infections remain a challenging and not uncommon issue in patients with implanted instrumentation or medical devices. Bacterial adhesion and formation of biofilm on the surface of the implant represent important processes towards progression of infection. Given the intimate association between infection and the implant surface, adequate treatment of the implant surface may help mitigate the risk of infection. This review summarises the current surface treatment technologies and their role in prevention of implant-related infection from the beginning.

Translational potential of this article

Despite great technological advancements, the prevalence of implant-related infections remains high. Four main challenges can be identified. (i) Insufficient mechanical stability can cause detachment of the implant surface coating, altering the antimicrobial ability of functionalized surfaces. (ii) Regarding drug-loaded coatings, a stable drug release profile is of vital importance for achieving effective bactericidal effect locally; however, burst release of the loaded antibacterial agents remains common. (iii) Although many coatings and modified surfaces provide superior antibacterial action, such functionalisation of surfaces sometimes has a detrimental effect on tissue biocompatibility, impairing the integration of the implants into the surrounding tissue. (iv) Biofilm eradication at the implant surface remains particularly challenging. This review summarised the recent progress made to address the aforementioned problems. By providing a perspective on state-of-the-art surface treatment strategies for medical implants, we hope to support the timely adoption of modern materials and techniques into clinical practice.

Galvanic Displacement Synthesis of Monodisperse Janus- and Satellite-Like Plasmonic-Magnetic Ag-Fe@Fe3O4 Heterostructures with Reduced Cytotoxicity

The unique physicochemical properties of silver nanoparticles offer a large potential for biomedical application, however, the serious biotoxicity restricts their usage. Herein, nanogalvanic couple Ag-Fe@Fe3O4 heterostructures (AFHs) are designed to prevent Ag+ release from the cathodic Ag by sacrificial anodic Fe, which can reduce the cytotoxicity of Ag. AFHs are synthesized with modified galvanic displacement strategy in nonaqueous solution. To eliminate the restriction of lattice mismatch between Fe and Ag, amorphous Fe@Fe3O4 nanoparticles (NPs) are selected as seeds, meanwhile, reductive Fe can reduce Ag precursor directly even at as low as 20 °C without additional reductant. The thickness of the Fe3O4 shell can influence the amorphous properties of AFHs, and a series of Janus- and satellite-like AFHs are synthesized. A "cut-off thickness" effect is proposed based on the abnormal phenomenon that with the increase of reaction temperature, the diameter of Ag in AFHs decreases. Because of the interphase interaction and the coupling effect of Ag and Fe@Fe3O4, the AFHs exhibit unique optical and magnetic properties. This strategy for synthesis of monodisperse heterostructures can be extended for other metals, such as Au and Cu.

Antibacterial Performance of TiCaPCON Films Incorporated with Ag, Pt, and Zn: Bactericidal Ions Versus Surface Microgalvanic Interactions

It is very important to prevent bacterial colonization at the early postoperative stages. There are four major strategies and their corresponding types of antibacterial surfaces specifically designed to fight infection: bactericide release, anti-adhesion, pH-sensitive, and contact-killing. Herein, we aimed at determining the antibacterial efficiency of different types of bactericidal ions and revealing the possible contribution of surface microgalvanic effects arising from a potential difference on heterogeneous surfaces. We considered five types of TiCaPCON films, with Ag, Zn, Pt, Ag + Zn, and Pt + Zn nanoparticles (NPs) on their surface. The Ag-modified film demonstrated a pronounced antibacterial effect at a very low Ag ion concentration of 0.11 ppb in physiological solution that was achieved already after 3 h of immersion in Escherichia coli ( E. coli) bacterial culture. The Zn-containing sample also showed a noticeable antibacterial effect against E. coli and Staphylococcus aureus ( S. aureus) strains, wherein the concentration of Zn ions was 2 orders of magnitude higher (15 ppb) compared with the Ag ions. The presence of Ag NPs accelerated the leaching of Zn ion out of the TiCaPCON-Ag-Zn film, but no synergistic effect of the simultaneous presence of the two bactericidal components was observed. After the incubation of the samples with Ag, Zn, and Ag + Zn NPs in E. coli and S. aureus suspensions for 24 and 8 h, respectively, all bacterial cells were completely inactivated. The Pt-containing film showed a very low Pt ion release, and therefore the contribution of this type of ions to the total bactericidal effect could be neglected. The results of the electrochemical studies and Kelvin probe force microscopy indicated that microgalvanic couples were formed between the Pt NPs and the TiCaPCON film, but no noticeable antibacterial effect against either E. coli or S. aureus strains was observed. All ion-modified samples provided good osteoblastic cell attachment, spreading, and proliferation and therefore were concluded to be nontoxic for cells. In addition, the TiCaPCON films with Ag, Pt, and Zn NPs on their surface demonstrated good osteoconductive characteristics.

Potential antibacterial mechanism of silver nanoparticles and the optimization of orthopedic implants by advanced modification technologies

Infection, as a common postoperative complication of orthopedic surgery, is the main reason leading to implant failure. Silver nanoparticles (AgNPs) are considered as a promising antibacterial agent and always used to modify orthopedic implants to prevent infection. To optimize the implants in a reasonable manner, it is critical for us to know the specific antibacterial mechanism, which is still unclear. In this review, we analyzed the potential antibacterial mechanisms of AgNPs, and the influences of AgNPs on osteogenic-related cells, including cellular adhesion, proliferation, and differentiation, were also discussed. In addition, methods to enhance biocompatibility of AgNPs as well as advanced implants modifications technologies were also summarized.

Citrate chemistry and biology for biomaterials design

Leveraging the multifunctional nature of citrate in chemistry and inspired by its important role in biological tissues, a class of highly versatile and functional citrate-based materials (CBBs) has been developed via facile and cost-effective polycondensation. CBBs exhibiting tunable mechanical properties and degradation rates, together with excellent biocompatibility and processability, have been successfully applied in vitro and in vivo for applications ranging from soft to hard tissue regeneration, as well as for nanomedicine designs. We summarize in the review, chemistry considerations for CBBs design to tune polymer properties and to introduce functionality with a focus on the most recent advances, biological functions of citrate in native tissues with the new notion of degradation products as cell modulator highlighted, and the applications of CBBs in wound healing, nanomedicine, orthopedic, cardiovascular, nerve and bladder tissue engineering. Given the expansive evidence for citrate's potential in biology and biomaterial science outlined in this review, it is expected that citrate based materials will continue to play an important role in regenerative engineering.

Runx2/Osterix and Zinc Uptake Synergize to Orchestrate Osteogenic Differentiation and Citrate Containing Bone Apatite Formation

Citrate is essential to biomineralization of the bone especially as an integral part of apatite nanocomposite. Citrate precipitate of apatite is hypothesized to be derived from mesenchymal stem/stromal cells (MSCs) upon differentiation into mature osteoblasts. Based on ¹³C-labeled signals identified by solid-state multinuclear magnetic resonance analysis, boosted mitochondrial activity and carbon-source replenishment of tricarboxylic acid cycle intermediates coordinate to feed forward mitochondrial anabolism and deposition of citrate. Moreover, zinc (Zn²⁺) is identified playing dual functions: (i) Zn²⁺ influx is influenced by ZIP1 which is regulated by Runx2 and Osterix to form a zinc-Runx2/Osterix-ZIP1 regulation axis promoting osteogenic differentiation; (ii) Zn²⁺ enhances citrate accumulation and deposition in bone apatite. Furthermore, age-related bone loss is associated with Zn²⁺ and citrate homeostasis; whereas, restoration of Zn²⁺ uptake alleviates age-associated declining osteogenic capacity and amount of citrate deposition. Together, these results indicate that citrate is not only a key metabolic intermediate meeting the emerging energy demand of differentiating MSCs but also participates in extracellular matrix mineralization, providing mechanistic insight into Zn²⁺ homeostasis and bone formation.

Progress in TiO2 nanotube coatings for biomedical applications: a review

Titanium dioxide nanotubes (TNTs) have drawn wide attention and been extensively applied in the field of biomedicine, due to their large specific surface area, good corrosion resistance, excellent biocompatibility, and enhanced bioactivity. This review describes the preparation of TNTs and the surface modification that entrust the nanotubes with better antibacterial property and enhanced osteoblast adhesion, proliferation, and differentiation. Considering the contact between TNTs' surface and surrounding tissues after implantation, the interactions between TNTs (with properties including their diameter, length, wettability, and crystalline phase) and proteins, platelets, bacteria, and cells are illustrated. The state of the art in the applications of TNTs in dentistry, orthopedic implants, and cardiovascular stents are introduced. In particular, the application of TNTs in biosensing has attracted much attention due to its ability for the rapid diagnosis of diseases. Finally, the difficulties and challenges in the practical application of TNTs are also discussed.

Graphene oxide as a dual Zn/Mg ion carrier and release platform: enhanced osteogenic activity and antibacterial properties

Graphene oxide as an ion carrier and release platform: enhanced osteogenic activity and antibacterial properties.

Minocycline hydrochloride loaded on titanium by graphene oxide: an excellent antibacterial platform with the synergistic effect of contact-killing and release-killing

Graphene oxide loaded with minocycline hydrochloride as an excellent antibacterial platform with the synergistic effect of contact-killing and release-killing.

Immunomodulatory Effects of Calcium and Strontium Co-Doped Titanium Oxides on Osteogenesis

The effects of calcium (Ca) or strontium (Sr) on host osteogenesis and immune responses have been investigated separately. In clinical practice, these two elements may both be present around an orthopedic device, but their potential synergistic effects on osteogenesis and the immune response have not been explored to date. In this work, we investigated the immunomodulatory effects of Ca and Sr co-doped titanium oxides on osteogenesis in vitro using the mouse macrophage cell line RAW 264.7 alone and in co-culture with mouse bone mesenchymal stem cells (BMSCs), and in vivo using a mouse air-pouch model. Coatings containing Ca and Sr at different concentration ratios were fabricated on titanium substrates using micro-arc oxidation and electrochemical treatment. The in vitro and in vivo results demonstrated that the Ca and Sr concentration ratio has a marked influence on macrophage polarization. The coating with a Ca/Sr ratio of 2:1 was superior to those with other Ca and/or Sr concentrations in terms of modulating M2 polarization, which enhanced osteogenic differentiation of mouse BMSCs in co-culture. These findings suggest that the osteoimmunomodulatory effect of a titanium-oxide coating can be enhanced by modulating the concentration ratio of its components.