Biocompatible mechano-bactericidal nanopatterned surfaces with salt-responsive bacterial release

Design and Fabrication of Bioactive and Antibacterial LIPSS Surfaces on Titanium Alloy by Femtosecond Laser

A titanium alloy is widely used in implants for its excellent mechanical properties and corrosion resistance. However, the bonding strength between a titanium alloy and bone tissue is low, and the bacterial adhesion is easily triggered on the implant surface, which may cause the failure of implants. Therefore, surface modification is necessary to improve the biological activity and antibacterial properties. In this work, four different types of laser-induced periodic surface structure (LIPSS) surfaces are designed and fabricated on the TiNi alloy by a femtosecond laser according to the size of MC3T3-E1 mouse embryonic osteoblasts. The in vitro osteogenic activity of the LIPSS surface is investigated. It is found that the LIPSS helps improve the in vitro osteogenic activity, and bonelike apatite tends to deposit and distribute on the LIPSS. The biological activity and antibacterial activity of the LIPSS surface are evaluated through cell culture experiments and Escherichia coli culture experiments. It is demonstrated that the horizontal LIPSS sample with a width of 30 μm has the highest cell proliferation rate (142.5% after 1 day, 132.3% after 3 days) and a good antibacterial rate (50.2%). These results provide guidance for the application of the LIPSS in biocompatibility and antibacterial aspects.

Development of endolysin-integrated pH-responsive antiadhesive and antibacterial coatings with nanorods for the prevention of cross-contamination in fresh produce

Cross-contamination is a major food safety risk during the harvesting and processing of fresh produce, leading to significant losses in global human well-being and the economy. The surface of food contact areas is a high-risk zone for cross-contamination. Therefore, developing an effective antimicrobial coating for food-contact surfaces is essential. This study developed a smart antimicrobial coating that self-regulated in response to environmental conditions, via grafting the stimuli-responsive polymer polyacrylic acid (PAA) and the phage-derived endolysin Lysin81 onto ZnO nanocolumns. During the initial stage of bacterial adhesion, the surface of the nanocolumns exhibited significant mechanical bactericidal activity, while the super hydrophilic PAA layer effectively inhibited bacterial adhesion. At a later stage, when numerous live and dead bacteria adhered to the surface of the nanocolumns, the PAA chains disintegrated, exposing the underlying layer of endolysin that lysed the compromised bacteria. In addition, as the environmental pH increases, the attached dead bacteria can be released once the PAA chains regain their hydrophilicity. This research aimed to apply the antibacterial coating to stainless steel surfaces used in food processing, potentially enhancing surface hygiene and preventing cross-contamination of fresh produce.

Comprehensive Overview of Interface Strategies in Implant Osseointegration

With the improvement of implant design and the expansion of application scenarios, orthopedic implants have become a common surgical option for treating fractures and end‐stage osteoarthritis. Their common goal is rapidly forming and long‐term stable osseointegration. However, this fixation effect is limited by implant surface characteristics and peri‐implant bone tissue activity. Therefore, this review summarizes the strategies of interface engineering (osteogenic peptides, growth factors, and metal ions) and treatment methods (porous nanotubes, hydrogel embedding, and other load‐release systems) through research on its biological mechanism, paving the way to achieve the adaptation of both and coordination between different strategies. With the transition of the osseointegration stage, interface engineering strategies have demonstrated varying therapeutic effects. Especially, the activity of osteoblasts runs almost through the entire process of osseointegration, and their physiological activities play a dominant role in bone formation. Furthermore, diseases impacting bone metabolism exacerbate the difficulty of achieving osseointegration. This review aims to assist future research on osseointegration engineering strategies to improve implant‐bone fixation, promote fracture healing, and enhance post‐implantation recovery.

Surprisingly fast self-healing coatings with anti-fog and antimicrobial activities via host-guest interaction

Dual functional coatings with anti-fog and antimicrobial performances greatly enhance the safety and reliability of medical detection devices, but are prone to mechanical damage, resulting in reduced performance and a shorter service lifespan. Herein, a semi-interpenetrating polymer network (SIPN) coating, featuring hydrophobic-hydrophilic balanced copolymers as bulk chains and host-guest inclusion compounds (HGICs) as cross-linkers, is reported, which demonstrates particularly effective anti-fog and antibacterial performances, along with a surprisingly fast self-healing capability under various scenarios. This HGIC-based coating displayed remarkable anti-fog capability over a wide temperature range from -20 ℃ to 85 ℃ and exhibited reliable antibacterial activities (≥98 %) against both gram-positive and gram-negative bacteria. Also, this coating showed extremely high self-healing ability (≥92 % recovery rate) within just 20 s, significantly outperforming traditional self-healing systems. These findings support the development of functional coatings that can highly maintain rapid self-healing performance while also providing anti-fog and antibacterial properties in medical detection devices.

Nanocomposite hyaluronic acid adhesive hydrogel with controllable drug release for bone regeneration

Hyaluronic acid (HA) hydrogels have arisen as candidate materials to simulate the extracellular matrix and restore the functions of both cartilage and hard bones. However, integration of bone tissue adhesion and long-term osteogenic properties in one hydrogel is often ignored. Herein, a strategy to construct nanocomposite hydrogel with host tissue adhesive properties, enhanced mechanical strength, improved stability and osteogenic effects was developed. Simvastatin (SIM) was firstly incorporated into zeolitic imidazolate framework-8 (ZIF-8) and surface decoration with hydroxyapatite was realized to obtain SIM loaded and hydroxyapatite modified ZIF-8 particles (SP). As the inorganic strengthening component, SP could further cross-link the mixture of dopamine-hyaluronic acid (dHA) and tannic (TA) via coordination interaction to fabricate the hybrid adhesive hydrogel (dHA/TA/SP). Sufficient phenolic groups endowed dHA/TA/SP with excellent tissue adhesion and antibacterial properties, while incorporation of SP significantly improved the mechanical strength and stability of hydrogel. Further, due to the multiple protective effects of ZIF-8 and hydrogel, SIM was sustainably released from dHA/TA/SP. Together with the active Zn2+ and Ca2+, the expressions of ALP, OCN and RUNX2 were upregulated, and the mineralization was also promoted. With significant osteogenic effect in vitro and in vivo, this nanocomposite adhesive hydrogel holds great potential for bone defects repair.

Bioinspired Hybrid Nanostructured PEEK Implant with Enhanced Antibacterial and Anti-inflammatory Synergy

Implant-associated infections and excessive immune responses are two major postsurgical issues for successful implantation. However, conventional strategies including antibiotic treatment and inflammatory regulation are always compromised due to the comodification of various biochemical agents and instances of functional interference. It is imperative to provide implant surfaces with satisfactory antibacterial and anti-inflammatory properties. Here, a dual-effect nanostructured polyetheretherketone (PEEK) surface (NP@PDA/Zn) with bionic mechano-bactericidal nanopillars and immobilized immunomodulatory Zn2+ is designed. The constructed hybrid nanopillars display remarkable antibacterial performance against Gram-negative and Gram-positive strains through the synergy of physical and chemical bactericidal effects imposed by nanopillars and Zn2+. Meanwhile, the immunoregulatory property is evaluated through the investigation of macrophage polarization both in vitro and in vivo, and the results reveal that NP@PDA/Zn could downregulate the expression of M1-related cytokines and decrease the M1 macrophage recruitment to lower the inflammatory response. Notably, the surface exhibited exceptional biocompatibility with discerning biocidal activity between bacterial and mammalian cells and antioxidant performance that effectively scavenges ROS, minimizing potential cytotoxicity. Taken together, NP@PDA/Zn presents a convenient and promising strategy of combining synergistic bactericidal activity and inflammatory regulation without any mutual interference, which can support the development of multifunctional implant-associated materials.

Bioinspired Nanotopography for Combinatory Osseointegration and Antibacterial Therapy

The ongoing global health has highlighted the critical issue of secondary infections, particularly antibiotic-resistant bacterial infections, which have been significant contributors to mortality rates. Orthopedic implants, while essential for trauma and orthopedic surgeries, are particularly susceptible to these infections, leading to severe complications and economic burdens. The traditional use of antibiotics in treating these infections poses further challenges including the risk of developing antibiotic-resistant bacteria. This study introduces a novel approach to combat this issue by developing nanostructured surfaces for orthopedic implants using target ion-induced plasma sputtering. Inspired by the natural design of dragonfly wings, these surfaces aim to prevent bacterial adhesion while promoting preosteoblast activity, offering a dual-function solution to the problems of bacterial infection and implant integration without relying on antibiotics. The in vitro results demonstrate the effectiveness of these bioinspired surfaces in eradicating bacteria and supporting cell proliferation and differentiation, presenting a promising alternative for the development of biomedical implants.

Reusable mechano-bactericidal surface with echinoid-shaped hierarchical micro/nano-structure

Biofilms formed owing to the attachment of bacteria to surfaces have caused various problems in industries such as marine transportation/logistics and medicine. In response, many studies have been conducted on bactericidal surfaces, and nanostructured surfaces mimicking cicada and dragonfly wings are emerging as candidates for mechano-bactericidal surfaces. In specific circumstances involving mechano-bactericidal activity, certain nanostructured surfaces could exhibit their bactericidal effects by directly deforming the membranes of bacteria that adhere to these nanostructures. Additionally, in most cases, debris of bacterial cells may accumulate on these nanostructured surfaces. Such accumulation poses a significant challenge: it diminishes the mechano-bactericidal effectiveness of the surface, as it hinders the direct interaction between the nanostructures and any new bacteria that attach subsequently. In specific circumstances involving mechano-bactericidal activity, certain nanostructured surfaces could exhibit their bactericidal effects by directly deforming the membranes of bacteria that adhere to these nanostructures. Additionally, in most cases, debris of bacterial cells may accumulate on these nanostructured surfaces. Such accumulation poses a significant challenge: it diminishes the mechano-bactericidal effectiveness of the surface, as it hinders the direct interaction between the nanostructures and any new bacteria that attach subsequently.In other words, there is a need for strategies to remove the accumulated bacterial debris in order to sustain the mechano-bactericidal effect of the nanostructured surface. In this study, hierarchical micro/nano-structured surface (echinoid-shaped nanotextures were formed on Al micro-particle's surfaces) was fabricated using a simple pressure-less sintering method, and effective bactericidal efficiency was shown against E. coli (97 ± 3.81%) and S. aureus (80 ± 9.34%). In addition, thermal cleaning at 500 °C effectively eliminated accumulated dead bacterial debris while maintaining the intact Al2O3 nanostructure, resulting in significant mechano-bactericidal activity (E. coli: 89 ± 6.86%, S. aureus: 75 ± 8.31%). As a result, thermal cleaning maintains the intact nanostructure and allows the continuance of the mechano-bactericidal effect. This effect was consistently maintained even after five repetitive use (E. coli: 80 ± 16.26%, S. aureus: 76 ± 12.67%).

Light-Based Anti-Biofilm and Antibacterial Strategies

Biofilm formation and antimicrobial resistance pose significant challenges not only in clinical settings (i.e., implant-associated infections, endocarditis, and urinary tract infections) but also in industrial settings and in the environment, where the spreading of antibiotic-resistant bacteria is on the rise. Indeed, developing effective strategies to prevent biofilm formation and treat infections will be one of the major global challenges in the next few years. As traditional pharmacological treatments are becoming inadequate to curb this problem, a constant commitment to the exploration of novel therapeutic strategies is necessary. Light-triggered therapies have emerged as promising alternatives to traditional approaches due to their non-invasive nature, precise spatial and temporal control, and potential multifunctional properties. Here, we provide a comprehensive overview of the different biofilm formation stages and the molecular mechanism of biofilm disruption, with a major focus on the quorum sensing machinery. Moreover, we highlight the principal guidelines for the development of light-responsive materials and photosensitive compounds. The synergistic effects of combining light-triggered therapies with conventional treatments are also discussed. Through elegant molecular and material design solutions, remarkable results have been achieved in the fight against biofilm formation and antibacterial resistance. However, further research and development in this field are essential to optimize therapeutic strategies and translate them into clinical and industrial applications, ultimately addressing the global challenges posed by biofilm and antimicrobial resistance.

Mechano-Bactericidal Surfaces: Mechanisms, Nanofabrication, and Prospects for Food Applications

Mechano-bactericidal (MB) nanopatterns have the ability to inactivate bacterial cells by rupturing cellular envelopes. Such biocide-free, physicomechanical mechanisms may confer lasting biofilm mitigation capability to various materials encountered in food processing, packaging, and food preparation environments. In this review, we first discuss recent progress on elucidating MB mechanisms, unraveling property-activity relationships, and developing cost-effective and scalable nanofabrication technologies. Next, we evaluate the potential challenges that MB surfaces may face in food-related applications and provide our perspective on the critical research needs and opportunities to facilitate their adoption in the food industry.

Regulable Polyelectrolyte-Surfactant Complex for Antibacterial Biomedical Catheter Coating via a Readily Scalable Route

Constructing multifunctional surfaces is one of the practical approaches to address catheter-related multiple complications but is generally time-consuming and substrate-dependent. Herein, a novel anti-adhesion, antibacterial, low friction, and robustness coating on medical catheters are developed via a universal and readily scalable method based on a regulable polyelectrolyte surfactant complex. The complex is rapidly assembled in one step by electrostatic and hydrophobic interactions between organosilicon quaternary ammonium surfactant (N⁺ _Si ) and adjustable polyelectrolyte with cross-linkable, anti-adhesive, and anionic groups. The alcohol-soluble feature of the complex is conducive to the rapid formation of coatings on any medical device with arbitrary shapes via dip coating. Different from the conventional polyelectrolyte-surfactant complex coating, the regulated complex coating with nonleaching mode could be stable in harsh conditions (high concentration salt solution, organic reagents, etc.) because of the cross-linked structure while improving the biocompatibility and reducing the adhesion of various bacteria, proteins, and blood cells. The coated catheter exhibits good antibacterial infection in vitro and in vivo, owing to the synergistic effect of N⁺ _Si and zwitterionic groups. Therefore, the rationally designed complex supplies a facile coating approach for the potential development in combating multiple complications of the medical catheter.

Nanomechanical probing of bacterial adhesion to biodegradable Zn alloys

Bacterial infections on implants cause an inflammatory response and even implant failure. Bacterial adhesion is an initial and critical step during implant infection. The prevention of bacterial adhesion to implant materials has attracted much attention, especially for biodegradable metals. A deep understanding of the mechanisms of bacterial adhesion to biodegradable metals is urgently needed. In this work, a bacterial probe based on atomic force spectroscopy was employed to determine the bacterial adhesion to Zn alloy, which depended on surface charge, roughness, and wettability. Negative surface charges of Zn, Zn-0.5Li, and 316L generated electrostatic repulsion force towards bacteria. The surface roughness of Zn-0.5Li was significantly increased by localized corrosion. Bacterial adhesion forces on Zn, Zn-0.5Li, and 316L were 325.2 pN, 519.1 pN, and 727.7 pN, respectively. The density of attached bacteria (early-stage bacterial adhesion) on these samples exhibited a positive correlation with the bacterial adhesion force. The bacterial adhesion force and adhesion work provide a quantitative determination of the interactions between bacteria and biodegradable alloys. These results provide a deeper understanding of early bacterial adhesion on Zn alloys, which can further guide the antibacterial surface design of biodegradable materials for clinical application.

Recent advances in responsive antibacterial materials: design and application scenarios

Bacterial infection is one of the leading causes of death globally, although modern medicine has made considerable strides in the past century. As traditional antibiotics are suffering from the emergence of drug resistance, new antibacterial strategies are of great interest. Responsive materials are appealing alternatives that have shown great potential in combating resistant bacteria and avoiding the side effects of traditional antibiotics. In this review, the responsive antibacterial materials are introduced in terms of stimulus signals including intrinsic (pH, enzyme, ROS, etc.) and extrinsic (light, temperature, magnetic fields, etc.) stimuli. Their biomedical applications in therapeutics and medical devices are then discussed. Finally, the author's perspective of the challenge and the future of such a system is provided.

Slippery liquid-infused porous surface (SLIPS) with super-repellent and contact-killing antimicrobial performances

Slippery liquid-filled porous surfaces (SLIPS) have attracted extensive research attention for their unique repellent properties, but such surfaces typically lack essential bactericidal activity and cannot defend against the spread of bacteria once bacterial contamination occurs. Herein, a slippery liquid-infused porous surface (SLIPS), endowed with both super-repellent and contact-killing antimicrobial performances is reported. Firstly, polystyrene (PS) based porous structures are developed via a facile microphase separation technique with poly(ethylene glycol) (PEG) as the sacrifice template. The porous surface was then covalently modified by 3-(trimethoxysilyl)propyl dimethyl undecyl ammonium chloride (QAC-Silane) to get the contact-killing antimicrobial performances. After lubricant (silicone oil) is introduced to the porous structure, the SLIPS surface demonstrates remarkably high super-repellence against both Gram-positive and negative bacteria, and also maintains essential contact-killing antimicrobial activities from the fixed QAC-11 groups, once the infused lubricant was depleted. Also, this surface demonstrates a reduced coefficient of friction (COF) of ∼56% as compared to that of the control flat surface. Moreover, this SLIPS surface can be easily realized on various substrates, such as silica glass, polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE) and silicone catheter tube. Owing to its simple, low-cost and fast fabrication approach, this kind of surface may find unique biomedical applications where an effective antibacterial performance and lubricity are highly needed.

Biomimetic Bacteriophage-Like Particles Formed from Probiotic Extracts and NO Donors for Eradicating Multidrug-Resistant Staphylococcus aureus

Effectively clearing multidrug-resistant bacteria through nonantibiotic treatments is crucial for the recovery of infected tissues in favorable biological environments. Herein, a thermally responsive donor of cell-messenger nitric oxide (NO) is combined with extracts of food-grade Lactobacillus casei to form biomimetic phage-like microparticles with a tailspike structure. These particles can invade bacterial membranes and release NO to disrupt nitrogen and respiratory metabolisms, which initiates the programmed death of multidrug-resistant Staphylococcus aureus (MRSA) for inducing lysis, like the bacterial virus. Experiments suggest that these microparticles can also weaken bacterial toxicity and provide favorable conditions for cell proliferation because of the continuously released NO. By encapsulating these microparticles into graphene-oxide-doped polymers, a dual-mode antibacterial hydrogel (DMAH) can be constructed. In vivo results reveal that the DMAH achieves a long-time sterilization of MRSA with 99.84 ± 0.13% antibacterial rate in the dark because of the phage-like performance of the biomimetic microparticles. In its other antibacterial mode, DMAH subjected to 20 min of near-infrared irradiation release NO, which, together with the photothermal effect, synergistically damages bacterial cell membranes to achieve very fast disinfection (97.13 ± 0.41% bactericidal rate). This multifunctional hydrogel can also significantly accelerate wound healing due to the phage-like particles.

Bio-Inspired Self-Adaptive Nanocomposite Array: From Non-antibiotic Antibacterial Actions to Cell Proliferation

Pathogenic bacterial infection and poor native tissue integration are two major issues encountered by biomaterial implants and devices, which are extremely hard to overcome within a single surface, especially for those without involvement of antibiotics. Herein, a self-adaptive surface that can transform from non-antibiotic antibacterial actions to promotion of cell proliferation is developed by in situ assembly of bacteriostatic 3,3'-diaminodipropylamine (DADP)-doped zeolitic imidazolate framework-8 (ZIF-8) on bio-inspired nanopillars. Initially, the nanocomposite surface shows impressive antibacterial effects, even under severe bacterial infection, due to the combination of mechano-bactericidal activity from a nanopillar structure and bacteriostatic activity contributed by pH-responsive release of DADP. After the complete degradation of the ZIF-8 layer, the refurbished nanopillars not only can still physically rupture bacterial membrane but also facilitate mammalian cell proliferation, due to the obvious difference in cell size. More strikingly, the nanocomposite surface totally avoids the usage of antibiotics, eradicating the potential risk of antimicrobial resistance, and the surface exhibited excellent histocompatibility and lower inflammatory response properties as revealed by in vivo tests. This type of self-adaptive surface may provide a promising alternative for addressing the intractable implant-associated requirements, where antibiotic-free antibacterial activity and native tissue integration are both highly needed.

Antibacterial Designs for Implantable Medical Devices: Evolutions and Challenges

The uses of implantable medical devices are safer and more common since sterilization methods and techniques were established a century ago; however, device-associated infections (DAIs) are still frequent and becoming a leading complication as the number of medical device implantations keeps increasing. This urges the world to develop instructive prevention and treatment strategies for DAIs, boosting the studies on the design of antibacterial surfaces. Every year, studies associated with DAIs yield thousands of publications, which here are categorized into four groups, i.e., antibacterial surfaces with long-term efficacy, cell-selective capability, tailored responsiveness, and immune-instructive actions. These innovations are promising in advancing the solution to DAIs; whereas most of these are normally quite preliminary “proof of concept” studies lacking exact clinical scopes. To help identify the flaws of our current antibacterial designs, clinical features of DAIs are highlighted. These include unpredictable onset, site-specific incidence, and possibly involving multiple and resistant pathogenic strains. The key point we delivered is antibacterial designs should meet the specific requirements of the primary functions defined by the “intended use” of an implantable medical device. This review intends to help comprehend the complex relationship between the device, pathogens, and the host, and figure out future directions for improving the quality of antibacterial designs and promoting clinical translations.