Antibacterial infection and immune-evasive coating for orthopedic implants

Unraveling the anti-biofouling mechanisms of slippery liquid-infused porous surface from molecular interaction perspective

Newly developed slippery liquid-infused porous surfaces (SLIPS) exhibit highly effective anti-fouling performance without harming organisms, making them a promising solution for both environmental and material protection. However, previous studies have primarily understood the anti-fouling effects of SLIPS from a mechanical perspective, neglecting the atomic interactions involved in the anti-fouling process. In this study, we combined microbiological experiments with multi-scale simulations to elucidate the microscopic mechanisms behind the unique anti-biofouling effects of SLIPS. After developing SLIPS with robust liquid-repellency, we characterized its physical and chemical properties and demonstrated its superior effectiveness in preventing Pseudomonas aeruginosa attachment. To probe the initial contact during bacterial attachment, all-atom molecular dynamics (MD) simulations were conducted, revealing that the liquid-liquid interface suppresses the effective pilin adhesion on SLIPS. Further analysis through steered MD, ab initio MD, and density functional theory calculations revealed that the flexible siloxane backbone and the non-polar nature of silicone oil molecules enhance the diffusivity of interfacial water and lead to the continuous nanoscale fluctuation of liquid-liquid interface, thus inhibiting the role of protein dynamics in promoting bio-adhesion. These novel insights into the characteristics of liquid-liquid and nano-bio interface during the anti-biofouling process of SLIPS may promote the future development of bio-inspired functional surfaces.

Nature-inspired surface modification strategies for implantable devices

Medical and implantable devices are essential instruments in contemporary healthcare, improving patient quality of life and meeting diverse clinical requirements. However, ongoing problems such as bacterial colonization, biofilm development, foreign body responses, and insufficient device-tissue adhesion hinder the long-term effectiveness and stability of these devices. Traditional methods to alleviate these issues frequently prove inadequate, necessitating the investigation of nature-inspired alternatives. Biomimetic surfaces, inspired by the chemical and physical principles found in biological systems, present potential opportunities to address these challenges. Recent breakthroughs in manufacturing techniques, including lithography, vapor deposition, self-assembly, and three-dimensional printing, now permit precise control of surface properties at the micro- and nanoscale. Biomimetic coatings can diminish inflammation, prevent bacterial adherence, and enhance stable tissue integration by replicating the antifouling, antibacterial, and adhesive properties observed in creatures such as geckos, mussels, and biological membranes. This review emphasizes the cutting-edge advancements in biomimetic surfaces for medical and implantable devices, outlining their design methodologies, functional results, and prospective clinical applications. Biomimetic coatings, by integrating biological inspiration with advanced surface engineering, have the potential to revolutionize implantable medical devices, providing safer, more lasting, and more effective interfaces for prolonged patient benefit.

Ultrashort Peptide Hydrogels Biomaterials with Potent Antibacterial Activity

For the past few decades, ultrashort peptide hydrogels have been at the forefront of biomaterials due to their unique properties like biocompatibility, tunable mechanical properties, and potent antibacterial activity. These ultrashort peptides self-assemble into a hydrogel matrix with nanofibrous networks. In this minireview, we have explored the design and self-assembly of these ultrashort peptide hydrogels by focusing on their antibacterial properties. Cationic and hydrophobic residues are incorporated to engineer the peptides, facilitating interaction with bacterial membranes and leading to membrane disruption and cell death. The hydrogels exhibit broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. Overall, this minireview highlights the potential of ultrashort peptide hydrogels as versatile and practical antibacterial biomaterials, providing a novel approach to combating bacterial infections and addressing the growing challenge of antibiotic resistance.

Ultrasound-Controllable Release of Carbon Monoxide in Multifunctional Polymer Coating for Synergetic Treatment of Catheter-Related Infections

Medical catheters are susceptible to biological contamination and pathogen invasion, leading to infection and inflammatory complications. The development of antimicrobial coatings for medical devices has emerged as a promising strategy. However, limited biological functionality and the incompatibility between bactericidal properties and biosafety remain great challenges. Herein, a multifunctional polymer coating (CPB-Ac) is created, incorporating an ultrasonic-responsive carbon monoxide release unit (CORM-Ac) and antifouling unit to treat catheter-related complications. As-synthesized CPB-Ac polymer can be stably anchored to various medical devices with arbitrary shapes and compositions via facile UV treatment. Both in vivo and vitro experiments demonstrated that this multi-functional coating exhibits anti-fouling, anti-inflammatory, and broad-spectrum antibacterial activities as well as good biosafety. During the initial implantation phase, the antifouling units of CPB-Ac coating effectively inhibit the attachment of biological contaminants, significantly reducing the risk of thrombosis and bacterial infection. Once bacterial infection occurs, ultrasonic irradiation can activate CPB-Ac coating to release CO with a much higher amount of 55.3 µm than non-ultrasound controls, therefore rapidly eliminating bacteria and alleviating inflammatory response. It is believed that the work may provide an effective method for the development of next-generation intelligent medical coatings against catheter-related complications.

Quaternary Ammonium Salt-Based Intrinsic Antibacterial Polyurethanes: Optimizing the Antibacterial Activity via Cationic Main- or Side-Chain Design in Hard Segments

Thermoplastic polyurethanes (TPUs) are one of the most appealing materials with extensive applications in biomedical fields due to their versatile mechanical properties and excellent biocompatibility. In response to the escalating challenges of bacterial infections, it is desirable to obtain TPUs with intrinsic antibacterial activity, particularly for application in biomedical devices and public places. Herein, a cationic main-/side-chain structure regulation strategy in the TPU hard segment was adopted to introduce and optimize the antibacterial activity. This was achieved by synthesizing two types of quaternary ammonium salts (QAS)-containing chain extenders, i.e., N-methyl-N-alkyl-N,N-bis(2-hydroxyethyl) ammonium bromide (Mn, where n represents the N-alkyl chain length) and N,N-dimethyl-N-alkyl-N-2,3-propylene glycol (Dn), from N-methyldiethanolamine (MDEA) and 3-dimethylamino-1,2-propanediol (DMAD), respectively. Given the structural differences between Mn and Dn, main-chain-type PU-Mn and side-chain-type PU-Dn were subsequently obtained with QAS groups in the hard segment. The N-alkyl chain length, QAS content, and main-/side-chain types were systematically investigated to optimize bactericidal properties. The results revealed that a long N-alkyl chain (from C6 to C14) increased the antibacterial activity of the chain extenders and corresponding TPU films. Besides, side-chain-type PU-Dn films showed higher contact-active antibacterial activity than that exerted by the main-chain-type PU-Mn films. Remarkably, almost 100% of Staphylococcus aureus(S. aureus) could be killed by the PU-D14 film with a low QAS content (1.6 wt %). All the TPUs showed good thermal stability with a degradation temperature of 5% mass loss (Td,5%) above 300 °C. Moreover, the TPU films displayed excellent mechanical properties with the tensile strength at break varying from 20.7 to 47.5 MPa and ultimate elongation above 1000%. All of the intrinsic antibacterial films showed negligible hemolytic activities.

Mussel-inspired bifunctional coating for long-term stability of oral implants

Peri-implantitis and osseointegration failure present considerable challenges to the prolonged stability of oral implants. To address these issues, there is an escalating demand for a resilient implant surface coating that seamlessly integrates antimicrobial features to combat bacteria-induced peri‑implantitis, and osteogenic properties to promote bone formation. In the present study, a bio-inspired poly(amidoamine) dendrimer (DA-PAMAM-NH2) is synthesized by utilizing a mussel protein (DA) known for its strong adherence to various materials. Conjugating DA with PAMAM-NH2, inherently endowed with antibacterial and osteogenic properties, results in a robust and multifunctional coating. Robust adhesion between DA-PAMAM-NH2 and the titanium alloy surface is identified using confocal laser scanning microscopy (CLSM) and attenuated total reflectance-infrared (ATR-IR) spectroscopy. Following a four-week immersion of the coated titanium alloy surface in simulated body fluid (SBF), the antimicrobial activity and superior osteogenesis of the DA-PAMAM-NH2-coated surface remain stable. In contrast, the bifunctional effects of the PAMAM-NH2-coated surface diminish after the same immersion period. In vivo animal experiments validate the enduring antimicrobial and osteogenic properties of DA-PAMAM-NH2-coated titanium alloy implants, significantly enhancing the long-term stability of the implants. This innovative coating holds promise for addressing the multifaceted challenges associated with peri‑implantitis and osseointegration failure in titanium-based implants. STATEMENT OF SIGNIFICANCE: Prolonged stability of oral implants remains a clinically-significant challenge. Peri-implantitis and osseointegration failure are two important contributors to the poor stability of oral implants. The present study developed a mussel-bioinspired poly(amidoamine) dendrimer (DA-PAMAM-NH2) for a resilient implant surface coating that seamlessly integrates antimicrobial features to combat bacteria-induced peri‑implantitis, and osteogenic properties to promote bone formation to extend the longevity of oral implants.

Antibacterial Immunonegative Coating with Biocompatible Materials on a Nanostructured Titanium Plate for Orthopedic Bone Fracture Surgery

Periprosthetic infections resulting from bacterial biofilm formation following surgical bone fracture fixation present important clinical challenges. Conventional orthopedic implant materials, such as titanium, are prone to biofilm formation. This study introduces a novel surface for orthopedic titanium plates, optimized for clinical application in human bone fractures. Leveraging nanostructure-based surface coating technology, the plate achieves an antibacterial/immunonegative surface using biocompatible materials, including poloxamer 407, epigallocatechin gallate, and octanoic acid. These materials demonstrate high biocompatibility and thermal stability after autoclaving. The developed plate, named antibacterial immunonegative surface, releases antibacterial agents and prevents adhesion between human tissue and metal surfaces. Antibacterial immunonegative surface plates exhibit low cell toxicity, robust antibacterial effects against pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa, high resistance to biofilm formation on the implant surface and surrounding tissues, and minimal immune reaction in a rabbit femoral fracture model. This innovation holds promise for addressing periprosthetic infections and improving the performance of orthopedic implants.

Resin Acid Copper Salt, an Interesting Chemical Pesticide, Controls Rice Bacterial Leaf Blight by Regulating Bacterial Biofilm, Motility, and Extracellular Enzymes

Bacterial virulence plays an important role in infection. Antibacterial virulence factors are effective for preventing crop bacterial diseases. Resin acid copper salt as an effective inhibitor exhibited excellent anti-Xanthomonas oryzae pv. oryzae (Xoo) activity with an EC50 of 50.0 μg mL-1. Resin acid copper salt (RACS) can reduce extracellular polysaccharides' (EPS's) biosynthesis by down-regulating gumB relative expression. RACS can also effectively inhibit the bio-mass of Xoo biofilm. It can reduce the activity of Xoo extracellular amylase at a concentration of 100 μg mL-1. Meanwhile, the results of virtual computing suggested that RACS is an enzyme inhibitor. RACS displayed good curative activity with a control effect of 38.5%. Furthermore, the result of the phytotoxicity assessment revealed that RACS exhibited slight toxicity compared with the control at a concentration of 200 μg mL-1. The curative effect was increased to 45.0% using an additional antimicrobial agent like orange peel essential oil. RACS markedly inhibited bacterial pathogenicity at a concentration of 100 μg mL-1 in vivo.

Smart zwitterionic coatings with precise pH-responsive antibacterial functions for bone implants to combat bacterial infections

Hydrophilic antifouling coatings based on zwitterionic polymers have been widely applied for the surface modification of bone implants to combat biofilm formation and reduce the likelihood of implant-related infections. However, their long-term effectiveness is significantly limited by the lack of effective and precise antibacterial activity. Here, a pH-responsive smart zwitterionic antibacterial coating (PSB/GS coating) was designed and robustly fabricated onto titanium-base bone implants by using a facile two-step method. First, dopamine (DA) and a poly(sulfobetaine methacrylate-co-dopamine methacrylamide) (PSBDA) copolymer were deposited on implants via mussel-inspired surface chemistry, resulting in a hydrophilic base coating with abundant catechol residues. Next, an amino-rich antibiotic, gentamicin sulfate (GS), was covalently linked to the coating through the formation of acid-sensitive Schiff base bonds between the amine groups of GS and the catechol residues present in both the zwitterionic polymer and the DA component. During the initial implantation period, the hydrophilic zwitterionic polymers demonstrated the desired anti-fouling properties that could effectively reduce protein and bacterial adhesion by over 90%. With time, the bacterial proliferation led to a decrease in the microenvironment pH value, resulting in the hydrolysis of the acid-sensitive Schiff base bonds, thereby releasing GS on demand and effectively enhancing the anti-biofilm properties of coatings. Benefiting from this synergistic antifouling and smart antibacterial activities, the PSB/GS coating exerted an excellent anti-infective activity in both in vivo preoperative and postoperative infection rat models. This proposed facile yet effective coating strategy is expected to provide a promising solution to combat bone implant-related infections.

Postoperative Long-Term Monitoring of Mechanical Characteristics in Reconstructed Soft Tissues Using Biocompatible, Immune-Tolerant, and Wireless Electronic Sutures

Accurate postoperative assessment of varying mechanical properties is crucial for customizing patient-specific treatments and optimizing rehabilitation strategies following Achilles tendon (AT) rupture and reconstruction surgery. This study introduces a wireless, chip-less, and immune-tolerant in vivo strain-sensing suture designed to continuously monitor mechanical stiffness variations in the reconstructed AT throughout the healing process. This innovative sensing suture integrates a standard medical suturing thread with a wireless fiber strain-sensing system, which incorporates a fiber strain sensor and a double-layered inductive coil for wireless readout. The winding design of Au nanoparticle-based fiber electrodes and a hollow core contribute to the fiber strain sensor's high sensitivity (factor of 6.2 and 15.1 pF for revised sensitivity), negligible hysteresis, and durability over 10,000 stretching cycles. To ensure biocompatibility and immune tolerance during extended in vivo periods, an antibiofouling lubricant layer was applied to the sensing suture. Using this sensing system, we successfully monitored the strain responses of the reconstructed AT in an in vivo porcine model. This facilitated the postoperative assessment of mechanical stiffness variations through a well-established analytical model during the healing period.

N-Halaminated spermidine-containing polymeric coating enables titanium to achieve dual functions of antibacterial and osseointegration

Titanium (Ti) and its alloys have been widely employed in the treatment of orthopedics and other hard tissue diseases. However, Ti-based implants are bioinert and suffer from bacterial infections and poor osseointegration in clinical applications. Herein, we successfully modified Ti with a porous N-halaminated spermidine-containing polymeric coating (Ti-SPD-Cl) through alkali-heat treatment, surface grafting and chlorination, and it has both excellent antibacterial and osteogenic abilities to significantly enhance osseointegration. The as-obtained Ti-SPD-Cl contains abundant N-Cl groups and demonstrates effective antibacterial ability against S. aureus and E. coli. Meanwhile, due to the presence of the spermidine component and construction of a porous hydrophilic surface, Ti-SPD-Cl is also beneficial for maintaining cell membrane homeostasis and promoting cell adhesion, exhibiting good biocompatibility and osteogenic ability. The rat osteomyelitis model demonstrates that Ti-SPD-Cl can effectively suppress bacterial infection and enhance bone-implant integration. Thus, Ti-SPD-Cl shows promising clinical applicability in the prevention of orthopedic implant infections and poor osseointegration.

Three-Dimensional-Printed Spherical Hollow Structural Scaffolds for Guiding Critical-Sized Bone Regeneration

The treatment of bone tissue defects continues to be a complex medical issue. Recently, three-dimensional (3D)-printed scaffold technology for bone tissue engineering (BTE) has emerged as an important therapeutic approach for bone defect repair. Despite the potential of BTE scaffolds to contribute to long-term bone reconstruction, there are certain challenges associated with it including the impediment of bone growth within the scaffolds and vascular infiltration. These difficulties can be resolved by using scaffold structural modification strategies that can effectively guide bone regeneration. This study involved the preparation of biphasic calcium phosphate spherical hollow structural scaffolds (SHSS) with varying pore sizes using 3D printing (photopolymerized via digital light processing). The chemical compositions, microscopic morphologies, mechanical properties, biocompatibilities, osteogenic properties, and impact on repairing critical-sized bone defects of SHSS were assessed through characterization analyses, in vitro cytological assays, and in vivo biological experiments. The results revealed the biomimetic properties of SHSS and their favorable biocompatibility. The scaffolds stimulated cell adhesion, proliferation, differentiation, and migration and facilitated the expression of osteogenic genes and proteins, including Col-1, OCN, and OPN. Furthermore, they could effectively repair a critical-sized bone defect in a rabbit femoral condyle by establishing an osteogenic platform and guiding bone regeneration in the defect region. This innovative strategy presents a novel therapeutic approach for assessing critical-sized bone defects.

Ginger extract loaded Fe2O3/MgO-doped hydroxyapatite: Evaluation of biological properties for bone-tissue engineering

Since antiquity, the medicinal properties of naturally sourced biomolecules such as ginger (Zingiber officinale) extract are documented in the traditional Indian and Chinese medical systems. However, limited work is performed to assess the potential of ginger extracts for bone-tissue engineering. Our work demonstrates the direct incorporation of ginger extract on iron oxide-magnesium oxide (Fe2O3 and MgO) co-doped hydroxyapatite (HA) for enhancement in the biological properties. The addition of Fe2O3 and MgO co-doping system and ginger extract with HA increases the osteoblast viability up to ~ 1.4 times at day 11. The presence of ginger extract leads to up to ~ 9 times MG-63 cell viability reduction. The co-doping does not adversely affect the release of ginger extract from the graft surface in the biological medium at pH 7.4 for up to 28 days. Assessment of antibacterial efficacy according to the modified ISO 22196: 2011 standard method indicates that the combined effects of Fe2O3, MgO, and ginger extract lead to ~ 82 % more bacterial cell reduction, compared to the control HA against S. aureus. These ginger extract-loaded artificial bone grafts with enhanced biological properties may be utilized as a localized site-specific delivery vehicle for various bone tissue engineering applications.

Injective Programmable Proanthocyanidin-Coordinated Zinc-Based Composite Hydrogel for Infected Bone Repair

Effectively integrating infection control and osteogenesis to promote infected bone repair is challenging. Herein, injective programmable proanthocyanidin (PC)-coordinated zinc-based composite hydrogels (ipPZCHs) are developed by compositing antimicrobial and antioxidant PC-coordinated zinc oxide (ZnO) microspheres with thioether-grafted sodium alginate (TSA), followed by calcium chloride (CaCl2 ) crosslinking. Responsive to the high endogenous reactive oxygen species (ROS) microenvironment in infected bone defects, the hydrophilicity of TSA can be significantly improved, to trigger the disintegration of ipPZCHs and the fast release of PC-coordinated ZnOs. This together with the easily dissociable PC-Zn2+ coordination induced fast release of antimicrobial zinc (Zn2+ ) with/without silver (Ag+ ) ions from PC-coordinated ZnOs (for Zn2+ , > 100 times that of pure ZnO) guarantees the strong antimicrobial activity of ipPZCHs. The exogenous ROS generated by ZnO and silver nanoparticles during the antimicrobial process further speeds up the disintegration of ipPZCHs, augmenting the antimicrobial efficacy. At the same time, ROS-responsive degradation/disintegration of ipPZCHs vacates space for bone ingrowth. The concurrently released strong antioxidant PC scavenges excess ROS thus enhances the immunomodulatory (in promoting the anti-inflammatory phenotype (M2) polarization of macrophages) and osteoinductive properties of Zn2+ , thus the infected bone repair is effectively promoted via the aforementioned programmable and self-adaptive processes.

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.

Nanomaterials for Anti-Infection in Orthopedic Implants: A Review

Postoperative implant infection is a severe complication in orthopedic surgery, often leading to implant failure. Current treatment strategies mainly rely on systemic antibiotic therapies, despite contributing to increasing bacterial resistance. In recent years, nanomaterials have gained attention for their potential in anti-infection methods. They exhibit more substantial bactericidal effects and lower drug resistance than conventional antimicrobial agents. Nanomaterials also possess multiple bactericidal mechanisms, such as physico-mechanical interactions. Additionally, they can serve as carriers for localized antimicrobial delivery. This review explores recent applications of nanomaterials with different morphologies in post-orthopedic surgery infections and categorizes their bactericidal mechanisms.

Construction of antibacterial bone implants and their application in bone regeneration

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

Perfluoropolyether-incorporated polyurethane with enhanced antibacterial and anti-adhesive activities for combating catheter-induced infection

To avoid the undesired bacterial attachment on polyurethane-based biomedical devices, we designed a class of novel perfluoropolyether-incorporated polyurethanes (PFPU) containing different contents of perfluoropolyether (PFPE) segments. After blending with Ag nanoparticles (AgNPs), a series of bifunctional PFPU/AgNPs composites with bactericidal and anti-adhesion abilities were obtained and correspondingly made into PFPU/AgNPs films (PFPU/Ag-F) using a simple solvent-casting method. Due to its highest hydrophobicity and suitable mechanical properties, PFPU8/Ag-F containing 8 mol% of PFPE content was chosen as the optimized one for the next antibacterial assessment. The PFPU8/Ag-F can effectively deactivate over 99.9% of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) cells at 106 CFU mL-1 within 30 min. Furthermore, the PFPU8/AgNPs composite was used as painting material to form a protective coating for the commercial polyurethane (PU) catheter. The as-prepared PFPU8/Ag coating exhibits high resistance to bacterial adhesion in a continuous-flow artificial urine model in an 8 day exposure. Therefore, it can be expected that the proposed PFPE-containing films and coatings can effectively prevent bacterial colonization and biofilm formation on catheters or other implants, thereby reducing the risk of postoperative catheter-induced infection.

Heparin-network-mediated long-lasting coatings on intravascular catheters for adaptive antithrombosis and antibacterial infection

Bacteria-associated infections and thrombosis, particularly catheter-related bloodstream infections and catheter-related thrombosis, are life-threatening complications. Herein, we utilize a concise assembly of heparin sodium with organosilicon quaternary ammonium surfactant to fabricate a multifunctional coating complex. In contrast to conventional one-time coatings, the complex attaches to medical devices with arbitrary shapes and compositions through a facile dipping process and further forms robust coatings to treat catheter-related bloodstream infections and thrombosis simultaneously. Through their robustness and adaptively dissociation, coatings not only exhibit good stability under extreme conditions but also significantly reduce thrombus adhesion by 60%, and shows broad-spectrum antibacterial activity ( > 97%) in vitro and in vivo. Furthermore, an ex vivo rabbit model verifies that the coated catheter has the potential to prevent catheter-related bacteremia during implantation. This substrate-independent and portable long-lasting multifunctional coating can be employed to meet the increasing clinical demands for combating catheter-related bloodstream infections and thrombosis.

Biomimetic Apatite/Natural Polymer Composite Granules as Multifunctional Dental Tissue Regenerative Material

This study presents a comprehensive evaluation of novel composite biomaterials designed for dental applications, aiming to potentially address the prevalent challenge of dental and periodontal tissue loss. The composites consisted of biomimetic hydroxyapatite (mHA) enriched with Mg2+, CO32-, and Zn2+ ions, type I collagen, alginate, and, additionally, chitosan and sericin. The granules were loaded with ibuprofen sodium salt. The investigation encompassed a morphology characterization, a porosity analysis, a chemical structure assessment, and an examination of the swelling behavior, drug release kinetics (ibuprofen), and release profiles of zinc and magnesium ions. The granules exhibited irregular surfaces with an enhanced homogeneity in the chitosan-coated granules and well-developed mesoporous structures. The FT-IR spectra confirmed the presence of ibuprofen sodium, despite overlapping bands for the polymers. The granules demonstrated a high water-absorption capacity, with delayed swelling observed in the chitosan-coated granules. Ibuprofen displayed burst-release profiles, especially in the G1 and G3 samples. In the case of the chitosan-coated granules (G2 and G4), lower amounts of ibuprofen were released. In turn, there was a significant difference in the released amount of magnesium and zinc ions from the granules, which was most likely caused by their different location in the hydroxyapatite crystals. The cytotoxicity assays confirmed the non-cytotoxic behavior of the biomaterial. These findings suggest the potential applicability of these biomaterials in dental scenarios, emphasizing their multifunctional and biocompatible nature.

Guided Bone Regeneration Using Barrier Membrane in Dental Applications

Guided bone regeneration (GBR) is a widely used technique in preclinical and clinical studies due to its predictability. Its main purpose is to prevent the migration of soft tissue into the osseous wound space, while allowing osseous cells to migrate to the site. GBR is classified into two main categories: resorbable and non-resorbable membranes. Resorbable membranes do not require a second surgery but tend to have a short resorption period. Conversely, non-resorbable membranes maintain their mechanical strength and prevent collapse. However, they require removal and are susceptible to membrane exposure. GBR is often used with bone substitute graft materials to fill the defect space and protect the bone graft. The membrane can also undergo various modifications, such as surface modification and biological factor loading, to improve barrier functions and bone regeneration. In addition, bone regeneration is largely related to osteoimmunology, a new field that focuses on the interactions between bone and the immune system. Understanding these interactions can help in developing new treatments for bone diseases and injuries. Overall, GBR has the potential to be a powerful tool in promoting bone regeneration. Further research in this area could lead to advancements in the field of bone healing. This review will highlight resorbable and non-resorbable membranes with cellular responses during bone regeneration, provide insights into immunological response during bone remodeling, and discuss antibacterial features.

Dynamic surface adapts to multiple service stages by orchestrating responsive polymers and functional peptides

Control over the implant surface functions is highly desirable to enhance tissue healing outcomes but has remained unexplored to adapt to the different service stages. In the present study, we develop a smart titanium surface by orchestrating thermoresponsive polymer and antimicrobial peptide to enable dynamic adaptation to the implantation stage, normal physiological stage and bacterial infection stage. The optimized surface inhibited bacterial adhesion and biofilm formation during surgical implantation, while promoted osteogenesis in the physiological stage. The further temperature increase driven by bacterial infection induced polymer chain collapse to expose antimicrobial peptides by rupturing bacterial membranes, as well as protect the adhered cells from the hostile environment of infection and abnormal temperature. The engineered surface could inhibit infection and promote tissue healing in rabbit subcutaneous and bone defect infection models. This strategy enables the possibility to create a versatile surface platform to balance bacteria/cell-biomaterial interactions at different service stages of implants that has not been achieved before.

Long-term stability of aerophilic metallic surfaces underwater

Aerophilic surfaces immersed underwater trap films of air known as plastrons. Plastrons have typically been considered impractical for underwater engineering applications due to their metastable performance. Here, we describe aerophilic titanium alloy (Ti) surfaces with extended plastron lifetimes that are conserved for months underwater. Long-term stability is achieved by the formation of highly rough hierarchically structured surfaces via electrochemical anodization combined with a low-surface-energy coating produced by a fluorinated surfactant. Aerophilic Ti surfaces drastically reduce blood adhesion and, when submerged in water, prevent adhesion of bacteria and marine organisms such as barnacles and mussels. Overall, we demonstrate a general strategy to achieve the long-term stability of plastrons on aerophilic surfaces for previously unattainable underwater applications.

Modification of Low-Energy Surfaces Using Bicyclic Peptides Discovered by Phage Display

Solid-binding peptides are a simple and versatile tool for the non-covalent modification of solid material surfaces, and a variety of peptides have been developed by reference to natural proteins or de novo design. Here, for the first time, we report the discovery of a bicyclic peptide targeting the heterogeneous material polypropylene by combining phage display technology and next-generation sequencing. We find that the enrichment properties of bicyclic peptides capable of binding to polypropylene are distinct from linear peptides, as reflected in amino acid abundance and a trend toward negative net charges and high hydrophobicity. The selected bicyclic peptide has a higher binding affinity for polypropylene compared with a previously reported linear peptide, enabling the hydrophilic and adhesive properties of the polypropylene to be more effectively enhanced. Our work paves the way for the exploration and utilization of conformational-restricted cyclic peptides as a new family of functionally evolvable agents for material surface modification.

Dopamine-Mediated Biopolymer Multilayer Coatings for Modulating Cell Behavior, Lubrication, and Drug Release

Biopolymer coatings on implants mediate the interactions between the synthetic material and its biological environment. Owing to its ease of preparation and the possibility to incorporate other bioactive molecules, layer-by-layer deposition is a method commonly used in the construction of biopolymer multilayers. However, this method typically requires at least two types of oppositely charged biopolymers, thus limiting the range of macromolecular options by excluding uncharged biopolymers. Here, we present a layer-by-layer approach that employs mussel-inspired polydopamine as the adhesive intermediate layer to build biopolymer multilayer coatings without requiring any additional chemical modifications. We select three biopolymers with different charge states─anionic alginate, neutral dextran, and cationic polylysine─and successfully assemble them into mono-, double-, or triple-layers. Our results demonstrate that both the layer number and the polymer type modulate the coating properties. Overall, increasing the number of layers in the coatings leads to reduced cell attachment, lower friction, and higher drug loading capacity but does not alter the surface potential. Moreover, varying the biopolymer type affects the surface potential, macrophage differentiation, lubrication performance, and drug release behavior. This proof-of-concept study offers a straightforward and universal coating method, which may broaden the use of multilayer coatings in biomedical applications.

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.

A smart coating with integrated physical antimicrobial and strain-mapping functionalities for orthopedic implants

The prevalence of orthopedic implants is increasing with an aging population. These patients are vulnerable to risks from periprosthetic infections and instrument failures. Here, we present a dual-functional smart polymer foil coating compatible with commercial orthopedic implants to address both septic and aseptic failures. Its outer surface features optimum bioinspired mechano-bactericidal nanostructures, capable of killing a wide spectrum of attached pathogens through a physical process to reduce the risk of bacterial infection, without directly releasing any chemicals or harming mammalian cells. On its inner surface in contact with the implant, an array of strain gauges with multiplexing transistors, built on single-crystalline silicon nanomembranes, is incorporated to map the strain experienced by the implant with high sensitivity and spatial resolution, providing information about bone-implant biomechanics for early diagnosis to minimize the probability of catastrophic instrument failures. Their multimodal functionalities, performance, biocompatibility, and stability are authenticated in sheep posterolateral fusion model and rodent implant infection model.

Enhancement of antibacterial properties and biocompatibility of Ti6Al4V by graphene oxide/strontium nanocomposite electrodepositing

Ti₆Al₄V is a widely used orthopedic implant material in clinics. Due to its poor antibacterial properties, surface modification is required to prevent peri-implantation infection. However, chemical linkers used for surface modification have generally been reported to have detrimental effects on cell growth. In this work, by optimizing parameters related to electrodeposition, a composite structural coating with graphene oxide (GO) compact films in the inner layer and 35 nm diameter strontium (Sr) nanoparticles in the outer layer was constructed on the surface of Ti₆Al₄V without using substance harmful to bone marrow mesenchymal stem cells (BMSCs) growth. The antibacterial properties of Ti₆Al₄V are enhanced by the controlled release of Sr ions and incomplete masking of the GO surface, showing excellent antibacterial activity against Staphylococcus aureus in bacterial culture assays. The biomimetic GO/Sr coating has a reduced roughness of the implant surface and a water contact angle of 44.1°, improving the adhesion, proliferation and differentiation of BMSCs. Observations of synovial tissue and fluid in the joint in an implantation model of rabbit knee also point to the superior anti-infective properties of the novel GO/Sr coating. In summary, the novel GO/Sr nanocomposite coating on the surface of Ti₆Al₄V effectively prevents surface colonization of Staphylococcus aureus and eliminates local infections in vitro and in vivo.

Host Immune Regulation in Implant-Associated Infection (IAI): What Does the Current Evidence Provide Us to Prevent or Treat IAI?

The number of orthopedic implants for bone fixation and joint arthroplasty has been steadily increasing over the past few years. However, implant-associated infection (IAI), a major complication in orthopedic surgery, impacts the quality of life and causes a substantial economic burden on patients and societies. While research and study on IAI have received increasing attention in recent years, the failure rate of IAI has still not decreased significantly. This is related to microbial biofilms and their inherent antibiotic resistance, as well as the various mechanisms by which bacteria evade host immunity, resulting in difficulties in diagnosing and treating IAIs. Hence, a better understanding of the complex interactions between biofilms, implants, and host immunity is necessary to develop new strategies for preventing and controlling these infections. This review first discusses the challenges in diagnosing and treating IAI, followed by an extensive review of the direct effects of orthopedic implants, host immune function, pathogenic bacteria, and biofilms. Finally, several promising preventive or therapeutic alternatives are presented, with the hope of mitigating or eliminating the threat of antibiotic resistance and refractory biofilms in IAI.

Enzymatic bionanocatalysts for combating peri-implant biofilm infections by specific heat-amplified chemodynamic therapy and innate immunomodulation

Bacterial biofilm-associated infection is a life-threatening emergency contributing from drug resistance and immune escape. Herein, a novel non-antibiotic strategy based on the synergy of bionanocatalysts-driven heat-amplified chemodynamic therapy (CDT) and innate immunomodulation is proposed for specific biofilm elimination by the smart design of a biofilm microenvironment (BME)-responsive double-layered metal-organic framework (MOF) bionanocatalysts (MACG) composed of MIL-100 and CuBTC. Once reaching the acidic BME, the acidity-triggered degradation of CuBTC allows the sequential release of glucose oxidase (GOx) and an activable photothermal agent, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). GOx converts glucose into H₂O₂ and gluconic acid, which can further acidify the BME to accelerate the CuBTC degradation and GOx/ABTS release. The in vitro and in vivo results show that horseradish peroxidase (HRP)-mimicking MIL-100 in the presence of self-supplied H₂O₂ can catalyze the oxidation of ABTS into oxABTS to yield a photothermal effect that breaks the biofilm structure via eDNA damage. Simultaneously, the Cu ion released from the degraded CuBTC can deplete glutathione and catalyze the splitting of H₂O₂ into •OH, which can effectively penetrate the heat-induced loose biofilms and kill sessile bacteria (up to 98.64%), such as E. coli and MRSA. Particularly, MACG-stimulated M1-macrophage polarization suppresses the biofilm regeneration by secreting pro-inflammatory cytokines (e.g., IL-6, TNF-α, etc.) and forming a continuous pro-inflammatory microenvironment in peri-implant biofilm infection animals for at least 14 days. Such BME-responsive strategy has the promise to precisely eliminate refractory peri-implant biofilm infections with extremely few adverse effects.

Oxygen-vacancy-rich molybdenum carbide MXene nanonetworks for ultrasound-triggered and capturing-enhanced sonocatalytic bacteria eradication

Incurable bacterial infection and intractable multidrug resistance remain critical challenges in public health. A prevalent approach against bacterial infection is phototherapy including photothermal and photodynamic therapy, which is unfortunately limited by low penetration depth of light accompanied with inevitable hyperthermia and phototoxicity damaging healthy tissues. Thus, eco-friendly strategy with biocompatibility and high antimicrobial efficacy against bacteria is urgently desired. Herein, we propose and develop an oxygen-vacancy-rich MoO_xin situ on fluorine-free Mo₂C MXene with unique neural-network-like structure, namely MoO_x@Mo₂C nanonetworks, in which their desirable antibacterial effectiveness originates from bacteria-capturing ability and robust reactive oxygen species (ROS) generation under precise ultrasound (US) irradiation. The high-performance, broad-spectrum microbicidal activity of MoO_x@Mo₂C nanonetworks without damaging normal tissues is validated based on systematic in vitro and in vivo assessments. Additionally, RNA sequencing analysis illuminates that the underlying bactericidal mechanism is attributed to the chaotic homeostasis and disruptive peptide metabolisms on bacteria instigated by MoO_x@Mo₂C nanonetworks under US stimulation. Considering antibacterial efficiency and a high degree of biosafety, we envision that the MoO_x@Mo₂C nanonetworks can serve as a distinct antimicrobial nanosystem to fight against diverse pathogenic bacteria, especially eradicating multidrug-resistant bacteria-induced deep tissue infection.

Alkaline "Nanoswords" Coordinate Ferroptosis-like Bacterial Death for Antibiosis and Osseointegration

Ferroptosis is an iron-dependent cell death and is associated with cancer therapy. Can it play a role in resistance of postoperative infection of implants, especially with an extracellular supplement of Fe ions in a non-cytotoxic dose? To answer this, "nanoswords" of Fe-doped titanite are fabricated on a Ti implant surface to resist bacterial invasion by a synergistic action of ferroptosis-like bacteria killing, proton disturbance, and physical puncture. The related antibiosis mechanism is explored by atomic force microscopy and genome sequencing. The nanoswords induce an increased local pH value, which not only weakens the proton motive force, reducing adenosine triphosphate synthesis of Staphylococcus aureus, but also decreases the membrane modulus, making the nanoswords distort and even puncture a bacterial membrane easily. Simultaneously, more Fe ions are taken by bacteria due to increased bacterial membrane permeability, resulting in ferroptosis-like death of bacteria, and this is demonstrated by intracellular iron enrichment, lipid peroxidation, and glutathione depletion. Interestingly, a microenvironment constructed by these nanoswords improves osteoblast behavior in vitro and bone regeneration in vivo. Overall, the nanoswords can induce ferroptosis-like bacterial death without cytotoxicity and have great promise in applications with clinical implants for outstanding antibiosis and biointegration performance.

A polypeptide coating for preventing biofilm on implants by inhibiting antibiotic resistance genes

Aging population has been boosting the need for orthopedic implants. However, biofilm has been a major obstacle for orthopedic implants due to its insensitivity to antibiotics and tendency to drive antimicrobial resistance. Herein, an antibacterial polypeptide coating with excellent in vivo adhesive capacity was prepared to prevent implants from forming biofilms and inducing acquired antibiotic resistance. A peptide-based copolymer, poly[phenylalanine₁₀-stat-lysine₁₂]-block-3,4-dihydroxy-l-phenylalanine [Poly(Phe₁₀-stat-Lys₁₂)-DOPA] was modularly designed, where poly(Phe₁₀-stat-Lys₁₂) is antibacterial polypeptide with high antibacterial activity, and DOPA provides strong adhesion in both wet and dry microenvironments. Meanwhile, compared to traditional "graft-onto" methods, this antibacterial coating can be facilely achieved by immersing Titanium substrates into antibacterial polypeptide solution for 5 min at room temperature. The poly(Phe₁₀-stat-Lys₁₂)-DOPA polymer showed good antibacterial activity with minimum inhibitory concentrations against S. aureus and E. coli of 32 and 400 μg/mL, respectively. Compared to obvious antimicrobial resistance of S. aureus after continuous treatment with vancomycin, this antibacterial coating doesn't drive antimicrobial resistance upon long-term utilization. Transcriptome sequencing and qPCR tests further confirmed that the antibacterial coating was able to inhibit the expression of multiple peptide resistance factor (mprF) and lipoteichoic acid modification D-alanylation genes (dltB and dltC) that can increase the net positive charge of bacterial cell wall to induce the resistance to cationic antimicrobial peptides. In vivo experiments confirmed that this poly(Phe₁₀-stat-Lys₁₂)-DOPA coating can both effectively prevent biofilm formation through surface contact sterilization and avoid local and systemic infections. Overall, we proposed a facile method for preparing antibacterial orthopedic implants with longer indwelling time and without inducing antimicrobial resistance by coating a polypeptide-based polymer on the implants.

Infection-responsive long-term antibacterial bone plates for open fracture therapy

The infections in open fracture induce high morbidity worldwide. Thus, developing efficient anti-infective orthopedic devices is of great significance. In this work, we designed a kind of infection-responsive long-term antibacterial bone plates. Through a facile and flexible volatilization method, a multi-aldehyde polysaccharide derivative, oxidized sodium alginate, was crosslinked with multi-amino compounds, gentamycin and gelatin, to fabricate a uniform coating on Ti bone plates via Schiff base reaction, which was followed by a secondary crosslinking process by glutaraldehyde. The double-crosslinked coating was stable under normal condition, and could responsively release gentamycin by the triggering of the acidic microenvironment caused by bacterial metabolism, owning to the pH-responsiveness of imine structure. The thickness of the coating was ranging from 22.0 μm to 63.6 μm. The coated bone plates (Ti-GOGs) showed infection-triggered antibacterial properties (>99%) and high biocompatibility. After being soaked for five months, it still possessed efficient antibacterial ability, showing its sustainable antibacterial performance. The in vivo anti-infection ability was demonstrated by an animal model of infection after fracture fixation (IAFF). At the early stage of IAFF, Ti-GOGs could inhibit the bacterial infection (>99%). Subsequently, Ti-GOGs could promote recovery of fracture of IAFF. This work provides a convenient and universal strategy for fabrication of various antibacterial orthopedic devices, which is promising to prevent and treat IAFF.

Enhanced Bactericidal Effect of Calcinated Mg-Fe Layered Double Hydroxide Films Driven by the Fenton Reaction

Osteogenic and antibacterial abilities are the permanent pursuit of titanium (Ti)-based orthopedic implants. However, it is difficult to strike the right balance between these two properties. It has been proved that an appropriate alkaline microenvironment formed by Ti modified by magnesium-aluminum layered double hydroxides (Mg-Al LDHs) could achieve the selective killing of bacteria and promote osteogenesis. However, the existence of Al induces biosafety concerns. In this study, iron (Fe), an essential trace element in the human body, was used to substitute Al, and a calcinated Mg-Fe LDH film was constructed on Ti. The results showed that a proper local alkaline environment created by the constructed film could enhance the antibacterial and osteogenic properties of the material. In addition, the introduction of Fe promoted the Fenton reaction and could produce reactive oxygen species in the infection environment, which might further strengthen the in vivo bactericidal effect.

Strategies to Mitigate and Treat Orthopaedic Device-Associated Infections

Orthopaedic device implants play a crucial role in restoring functionality to patients suffering from debilitating musculoskeletal diseases or to those who have experienced traumatic injury. However, the surgical implantation of these devices carries a risk of infection, which represents a significant burden for patients and healthcare providers. This review delineates the pathogenesis of orthopaedic implant infections and the challenges that arise due to biofilm formation and the implications for treatment. It focuses on research advancements in the development of next-generation orthopaedic medical devices to mitigate against implant-related infections. Key considerations impacting the development of devices, which must often perform multiple biological and mechanical roles, are delineated. We review technologies designed to exert spatial and temporal control over antimicrobial presentation and the use of antimicrobial surfaces with intrinsic antibacterial activity. A range of measures to control bio-interfacial interactions including approaches that modify implant surface chemistry or topography to reduce the capacity of bacteria to colonise the surface, form biofilms and cause infections at the device interface and surrounding tissues are also reviewed.

Progress in partially degradable titanium-magnesium composites used as biomedical implants

Titanium-magnesium composites have gained increasing attention as a partially degradable biomaterial recently. The titanium-magnesium composite combines the bioactivity of magnesium and the good mechanical properties of titanium. Here, we discuss the limitations of conventional mechanically alloyed titanium-magnesium alloys for bioimplants, in addition we summarize three suitable methods for the preparation of titanium-magnesium composites for bioimplants by melt: infiltration casting, powder metallurgy and hot rotary swaging, with a description of the advantages and disadvantages of all three methods. The titanium-magnesium composites were comprehensively evaluated in terms of mechanical properties and degradation behavior. The feasibility of titanium-magnesium composites as bio-implants was reviewed. In addition, the possible future development of titanium-magnesium composites was discussed. Thus, this review aims to build a conceptual and practical toolkit for the design of titanium-magnesium composites capable of local biodegradation.

Contamination and carryover free handling of complex fluids using lubricant-infused pipette tips

Cross-contamination of biological samples during handling and preparation, is a major issue in laboratory setups, leading to false-positives or false-negatives. Sample carryover residue in pipette tips contributes greatly to this issue. Most pipette tips on the market are manufactured with hydrophobic polymers that are able to repel high surface tension liquids, yet they lack in performance when low surface tension liquids and viscous fluids are involved. Moreover, hydrophobicity of pipette tips can result in hydrophobic adsorption of biomolecules, causing inaccuracies and loss in precision during pipetting. Here we propose the use of lubricant-infused surface (LIS) technology to achieve omniphobic properties in pipette tips. Using a versatile and simple design, the inner lumen of commercially available pipette tips was coated with a fluorosilane (FS) layer using chemical vapor deposition (CVD). The presence of FS groups on the tips is confirmed by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) tests. After lubrication of the tips through a fluorinated lubricant, the omniphobicity and repellent behaviour of the tips drastically enhanced which are revealed via static and hysteresis contact angle measurements. The repellency of the lubricant-infused pipette tips against physical adsorption is investigated through pipetting a food coloring dye as well as human blood samples and are compared to the untreated tips. The results show significantly less amount carryover residue when the lubricant-infused tips are utilized compared to commercially available ones. We also demonstrate the lubricant-infused tips reduce bacteria contamination of the inner lumen by 3 to 6-log (over 99%, depending on the tip size) after pipetting up and down the bacteria solution.

Lubricant skin on diverse biomaterials with complex shapes via polydopamine-mediated surface functionalization for biomedical applications

Implantable biomedical devices require an anti-biofouling, mechanically robust, low friction surface for a prolonged lifespan and improved performance. However, there exist no methods that could provide uniform and effective coatings for medical devices with complex shapes and materials to prevent immune-related side effects and thrombosis when they encounter biological tissues. Here, we report a lubricant skin (L-skin), a coating method based on the application of thin layers of bio-adhesive and lubricant-swellable perfluoropolymer that impart anti-biofouling, frictionless, robust, and heat-mediated self-healing properties. We demonstrate biocompatible, mechanically robust, and sterilization-safe L-skin in applications of bioprinting, microfluidics, catheter, and long and narrow medical tubing. We envision that diverse applications of L-skin improve device longevity, as well as anti-biofouling attributes in biomedical devices with complex shapes and material compositions.

Graphene oxide/gallium nanoderivative as a multifunctional modulator of osteoblastogenesis and osteoclastogenesis for the synergistic therapy of implant-related bone infection

Currently, implant-associated bacterial infections account for most hospital-acquired infections in patients suffering from bone fractures or defects. Poor osseointegration and aggravated osteolysis remain great challenges for the success of implants in infectious scenarios. Consequently, developing an effective surface modification strategy for implants is urgently needed. Here, a novel nanoplatform (GO/Ga) consisting of graphene oxide (GO) and gallium nanoparticles (GaNPs) was reported, followed by investigations of its in vitro antibacterial activity and potential bacterium inactivation mechanisms, cytocompatibility and regulatory actions on osteoblastogenesis and osteoclastogenesis. In addition, the possible molecular mechanisms underlying the regulatory effects of GO/Ga nanocomposites on osteoblast differentiation and osteoclast formation were clarified. Moreover, an in vivo infectious microenvironment was established in a rat model of implant-related femoral osteomyelitis to determine the therapeutic efficacy and biosafety of GO/Ga nanocomposites. Our results indicate that GO/Ga nanocomposites with excellent antibacterial potency have evident osteogenic potential and inhibitory effects on osteoclast differentiation by modulating the BMP/Smad, MAPK and NF-κB signaling pathways. The in vivo experiments revealed that the administration of GO/Ga nanocomposites significantly inhibited bone infections, reduced osteolysis, promoted osseointegration located in implant-bone interfaces, and resulted in satisfactory biocompatibility. In summary, this synergistic therapeutic system could accelerate the bone healing process in implant-associated infections and can significantly guide the future surface modification of implants used in bacteria-infected environments.

Multimodal Potentials of Gold Nanoparticles for Bone Tissue Engineering and Regenerative Medicine: Avenues and Prospects

Osseous tissue repair has advanced due to the introduction of tissue engineering. The key elements required while engineering new tissues involve scaffolds, cells, and bioactive cues. The macrostructural to the nanostructural framework of such complex tissue has engrossed the intervention of nanotechnology for efficient neo-bone formation. Gold nanoparticles (GNPs) have recently gained interest in bone tissue regeneration due to their multimodal functionality. They are proven to modulate the properties of scaffolds and the osteogenic cells significantly. GNPs also influence different metabolic functions within the body, which directly or indirectly govern the mechanism of bone regeneration. Therefore, this review highlights nanoparticle-mediated osteogenic development, focusing on different aspects of GNPs ranging from scaffold modulation to cellular stimulation. The toxic aspects of gold nanoparticles studied so far are critically explicated, while further insight into the advancements and prospects of these nanoparticles in bone regeneration is also highlighted.

Cellular studies and sustained drug delivery via nanostructures fabricated on 3D printed porous Neovius lattices of Ti6Al4V ELI

Site-specific drug delivery has the potential to reduce drug dosage by 3 to 5-folds. Given the propensity of drugs used in the treatment of tuberculosis and cancers, the increased drug dosages via oral ingestion for several months to a few years of medication is often detrimental to the health of patients. In this study, the sustained delivery of drugs with multiscale structured novel Neovius lattices was achieved. 3D Neovius Open Cell Lattices (NOCL) with porosities of 40, 45, and 50 % were fabricated layer-by-layer on the laser bed fusion process. Micron-sized Ti6Al4V Eli powder was used for 3D printing. The Young's modulus achieved from the novel Neovius lattices were in the range of 1.2 to 1.6 GPa, which is comparable to human cortical bone and helps to improve implant failure due to the stress shielding effect. To provide sustained drug delivery, nanotubes (NTs) were fabricated on NOCLs via high-voltage anodisation. The osteogenic agent icariin was loaded onto the NOCL-NT samples and their release profiles were studied for 7 days. A significantly steady and slow release rate of 0.05% per hour of the drug was achieved using NOCL-NT. In addition, the initial burst release of NOCL-NT was 4 fold lower than that of the open-cell lattices without nanotubes. Cellular studies using MG63 human osteoblast-like cells were performed to determine their biocompatibility and osteogenesis which were analysed using Calcein AM staining and Alamar Blue after 1, 5, and 7 days. 3D printed NOCL samples with NTs and with Icariin loaded NTs demonstrated a significant increase in cell proliferation as compared to as printed NOCL samples.

Advancing bone tissue engineering one layer at a time: a layer-by-layer assembly approach to 3D bone scaffold materials

The layer-by-layer (LbL) assembly technique has shown excellent potential in tissue engineering applications. The technique is mainly based on electrostatic attraction and involves the sequential adsorption of oppositely charged electrolyte complexes onto a substrate, resulting in uniform single layers that can be rapidly deposited to form nanolayer films. LbL has attracted significant attention as a coating technique due to it being a convenient and affordable fabrication method capable of achieving a wide range of biomaterial coatings while keeping the main biofunctionality of the substrate materials. One promising application is the use of nanolayer films fabricated by LbL assembly in the development of 3-dimensional (3D) bone scaffolds for bone repair and regeneration. Due to their versatility, nanoscale films offer an exciting opportunity for tailoring surface and bulk property modification of implants for osseous defect therapies. This review article discusses the state of the art of the LbL assembly technique, and the properties and functions of LbL-assembled films for engineered bone scaffold application, combination of multilayers for multifunctional coatings and recent advancements in the application of LbL assembly in bone tissue engineering. The recent decade has seen tremendous advances in the promising developments of LbL film systems and their impact on cell interaction and tissue repair. A deep understanding of the cell behaviour and biomaterial interaction for the further development of new generations of LbL films for tissue engineering are the most important targets for biomaterial research in the field. While there is still much to learn about the biological and physicochemical interactions at the interface of nano-surface coated scaffolds and biological systems, we provide a conceptual review to further progress in the LbL approach to 3D bone scaffold materials and inform the future of LbL development in bone tissue engineering.

Bioinspired ultra-low fouling coatings on medical devices to prevent device-associated infections and thrombosis

Addressing thrombosis and biofouling of indwelling medical devices within healthcare institutions is an ongoing problem. In this work, two types of ultra-low fouling surfaces (i.e., superhydrophobic and lubricant-infused slippery surfaces) were fabricated to enhance the biocompatibility of commercial medical grade silicone rubber (SR) tubes that are widely used in clinical care. The superhydrophobic (SH) coatings on the tubing substrates were successfully created by dip-coating in superhydrophobic paints consisting of polydimethylsiloxane (PDMS), perfluorosilane-coated hydrophobic zinc oxide (ZnO) and copper (Cu) nanoparticles (NPs) in tetrahydrofuran (THF). The SH surfaces were converted to lubricant-infused slippery (LIS) surfaces through the infusion of silicone oil. The anti-biofouling properties of the coatings were investigated by adsorption of platelets, whole blood coagulation, and biofilm formation in vitro. The results revealed that the LIS tubes possess superior resistance to clot formation and platelet adhesion than uncoated and SH tubes. In addition, bacterial adhesion was investigated over 7 days in a drip-flow bioreactor, where the SH-ZnO-Cu tube and its slippery counterpart significantly reduced bacterial adhesion and biofilm formation of Escherichia coli relative to control tubes (>5 log10 and >3 log10 reduction, respectively). The coatings also demonstrated good compatibility with fibroblast cells. Therefore, the proposed coatings may find potential applications in high-efficiency on-demand prevention of biofilm and thrombosis formation on medical devices to improve their biocompatibility and reduce the risk of complications from medical devices.

In vitro response of THP-1 derived macrophages to antimicrobially effective PHMB-coated Ti6Al4V alloy implant material with and without contamination with S. epidermidis and P. aeruginosa

AIM

Periprosthetic joint infections are a devastating complication after arthroplasty, leading to rejection of the prosthesis. The prevention of septic loosening may be possible by an antimicrobial coating of the implant surface. Poly (hexamethylene) biguanide hydrochloride [PHMB] seems to be a suitable antiseptic agent for this purpose since previous studies revealed a low cytotoxicity and a long-lasting microbicidal effect of Ti6Al4V alloy coated with PHMB. To preclude an excessive activation of the immune system, possible inflammatory effects on macrophages upon contact with PHMB-coated surfaces alone and after killing of S. epidermidis and P. aeruginosa are analyzed.

METHODS

THP-1 monocytes were differentiated to M0 macrophages by phorbol 12-myristate 13-acetate and seeded onto Ti6Al4V surfaces coated with various amounts of PHMB. Next to microscopic immunofluorescence analysis of labeled macrophages after adhesion on the coated surface, measurement of intracellular reactive oxygen species and analysis of cytokine secretion at different time points without and with previous bacterial contamination were conducted.

RESULTS

No influence on morphology of macrophages and only slight increases in iROS generation were detected. The cytokine secretion pattern depends on the surface treatment procedure and the amount of adsorbed PHMB. The PHMB coating resulted in a high reduction of viable bacteria, resulting in no significant differences in cytokine secretion as reaction to coated surfaces with and without bacterial burden.

CONCLUSION

Ti6Al4V specimens after alkaline treatment followed by coating with 5-7 μg PHMB and specimens treated with H2O2 before PHMB-coating (4 μg) had the smallest influence on the macrophage phienotype and thus are considered as the surface with the best cytocompatibility to macrophages tested in the present study.