Initiated Chemical Vapor Deposition of Graded Polymer Coatings Enabling Antibacterial, Antifouling, and Biocompatible Surfaces

Dual Antibacterial Properties of Copper-Coated Nanotextured Stainless Steel

Bacterial adhesion to stainless steel, an alloy commonly used in shared settings, numerous medical devices, and food and beverage sectors, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, Cu-coated nanotextured stainless steel (nSS) fabrication have been demonstrated using electrochemical technique and its potential as an antibiotic-free biocidal surface against Gram-positive and negative bacteria. As nanotexture and Cu combine for dual methods of killing, this material should not contribute to drug-resistant bacteria as antibiotic use does. This approach involves applying a Cu coating on nanotextured stainless steel, resulting in an antibacterial activity within 30 min. Comprehensive characterization of the surface revealing that the Cu coating consists of metallic Cu and oxidized states (Cu2+ and Cu+), has been performed by this study. Cu-coated nSS induces a remarkable reduction of 97% in Gram-negative Escherichia coli and 99% Gram-positive Staphylococcus epidermidis bacteria. This material has potential to be used to create effective, scalable, and sustainable solutions to prevent bacterial infections caused by surface contamination without contributing to antibiotic resistance.

Ultrathin hierarchical hydrogel-carbon nanocomposite for highly stretchable fast-response water-proof wearable humidity sensors

Wearable humidity sensors play an important role in human health monitoring. However, challenges persist in realizing high performance wearable humidity sensors with fast response and good stretchability and durability. Here we report wearable humidity sensors employing an ultrathin micro-nano hierarchical hydrogel-carbon nanocomposite. The nanocomposite is synthesized on polydimethylsiloxane (PDMS) films via a facile two-step solvent-free approach, which creates a hierarchical architecture consisting of periodic microscale wrinkles and vapor-deposited nanoporous hydrogel-candle-soot nanocoating. The hierarchical surface topography results in a significantly enlarged specific surface area (>107 times that of planar hydrogel), which along with the ultrathin hydrogel endow the sensor with high sensitivity and a fast response/recovery (13/0.48 s) over a wide humidity range (11-96%). Owing to the wrinkle structure and interpenetrating network between the hydrogel and PDMS, the sensor is stable and durable against repeated 180° bending, 100% strain, and even scratching. Furthermore, encapsulation of the sensor imparts excellent resistance to water, sweat, and bacteria without influencing its performance. The sensor is then successfully used to monitor different human respiratory behaviors and skin humidity in real time. The reported method is convenient and cost-effective, which could bring exciting new opportunities in the fabrication of next-generation wearable humidity sensors.

Self-Cross-Linkable Maleic Anhydride Terpolymer Coating with Inherent High Antimicrobial Activity and Low Cytotoxicity

Developing coating materials with low cytotoxicity and high antimicrobial activity has been recognized as an effective way to prevent medical device-associated infections. In this study, a maleic anhydride terpolymer (PPTM) is synthesized and covalently attached to silicone rubber (SR) surface. The formed coating can be further cross-linked (SPM) through the self-condensation of pendent siloxane groups of terpolymer. No crack or delamination of SPM was observed after 500 cycles of bending and 7 day immersion in deionized water. The sliding friction force of a catheter was reduced by 50% after coating with SPM. The SPM coating without adding any extra antibacterial reagents can kill 99.99% of Staphylococcus aureus and Escherichia coli and also significantly reduce bacterial coverage, while the coating displayed no antimicrobial activity when maleic anhydride groups of SPM were aminated or hydrolyzed. The results of the repeated disinfection tests showed that the SR coated with SPM could maintain 87.3% bactericidal activity within 5 cycles. Furthermore, the SPM coating only imparted slight toxic effect (>85% viability) on L929 cells after 36 h of coculture, which is superior to the coating of aminated SPM conjugated with the antimicrobial peptide E6. The terpolymer containing maleic anhydride units have great potential as a flexible and durable coating against implant infections.

Colloidal antibiotic mimics: selective capture and killing of microorganisms by shape-anisotropic colloids

The development of targeted and efficient antimicrobials for the selective killing of pathogenic bacteria is of great importance, yet remains challenging. Here, we propose a targeted approach to selectively capture and kill microorganisms with colloidal antibiotic mimics that are readily prepared by common chemical syntheses. The mimics are shape-anisotropic colloids, which can selectively capture shape-matching microorganisms due to lock-key depletion attractions. Furthermore, after being modified with gold nanoparticles (AuNPs) and irradiated with near-infrared light, the colloidal mimics can kill the selectively captured microorganisms due to the localized photothermal effect of the AuNPs. The work demonstrates the important ability of anisotropic colloids to selectively capture and precisely kill microorganisms, which holds considerable promise for safe and adaptive antibacterial therapies without the risk of antibiotic resistance.

Pruney Finger-Inspired Switchable Surface with Water-Actuated Dynamic Textures

Switchable surfaces play an important role in the development of functional materials. However, the construction of dynamic surface textures remains challenging due to the complicated structural design and surface patterning. Herein, a pruney finger-inspired switchable surface (PFISS) is developed by constructing water-sensitive surface textures on a polydimethylsiloxane substrate by taking advantage of the hygroscopicity of the inorganic salt filler and the 3D printing technology. Like human fingertips, the PFISS shows high water sensitivity with obvious surface variation in wet and dry states, which is actuated by water absorption-desorption of the hydrotropic inorganic salt filler. Besides, when the fluorescent dye is optionally added into the matrix of the surface texture, water-responsive fluorescent emitting is observed, providing a feasible surface-tracing strategy. The PFISS shows effective regulation of the surface friction and performs a good antislip effect. The reported synthetic strategy for the PFISS offers a facile way for building a wide range of switchable surfaces.

Development of Crosslinker-Free Polysaccharide-Lysozyme Microspheres for Treatment Enteric Infection

Antibiotic abuse in the conventional treatment of microbial infections, such as inflammatory bowel disease, induces cumulative toxicity and antimicrobial resistance which requires the development of new antibiotics or novel strategies for infection control. Crosslinker-free polysaccharide-lysozyme microspheres were constructed via an electrostatic layer-by-layer self-assembly technique by adjusting the assembly behaviors of carboxymethyl starch (CMS) on lysozyme and subsequently outer cationic chitosan (CS) deposition. The relative enzymatic activity and in vitro release profile of lysozyme under simulated gastric and intestinal fluids were investigated. The highest loading efficiency of the optimized CS/CMS-lysozyme micro-gels reached 84.9% by tailoring CMS/CS content. The mild particle preparation procedure retained relative activity of 107.4% compared with free lysozyme, and successfully enhanced the antibacterial activity against E. coli due to the superposition effect of CS and lysozyme. Additionally, the particle system showed no toxicity to human cells. In vitro digestibility testified that almost 70% was recorded in the simulated intestinal fluid within 6 h. Results demonstrated that the cross-linker-free CS/CMS-lysozyme microspheres could be a promising antibacterial additive for enteric infection treatment due to its highest effective dose (573.08 μg/mL) and fast release at the intestinal tract.

Antibacterial and Antiviral Coating on Surfaces through Dopamine-Assisted Codeposition of an Antifouling Polymer and In Situ Formed Nanosilver

Bacteria and viruses can adhere onto diverse surfaces and be transmitted in multiple ways. A bifunctional coating that integrates both antibacterial and antiviral activities is a promising approach to mitigate bacterial and viral infections arising from a contaminated surface. However, current coating approaches encounter a slow reaction, limited activity against diverse bacteria or viruses, short-term activity, difficulty in scaling-up, and poor adaptation to diverse material surfaces. Here, we report a new one-step strategy for the development of a polydopamine-based nonfouling antibacterial and antiviral coating by the codeposition of various components. The in situ formed nanosilver in the presence of polydopamine was incorporated into the coating and served as both antibacterial and antiviral agents. In addition, the coassembly of polydopamine and a nonfouling hydrophilic polymer was constructed to prevent the adhesion of bacteria and viruses on the coating. The coating was prepared on model surfaces and thoroughly characterized using various surface analytical techniques. The coating exhibited strong antifouling properties with a reduction of nonspecific protein adsorption up to 90%. The coating was tested against both Gram-positive and Gram-negative bacteria and showed long-term antibacterial effectiveness, which correlated with the composition of the coating. The antiviral activity of the coating was evaluated against human coronavirus 229E. A possible mechanism of action of the coating was proposed. We anticipate that the optimized coating will have applications in the development of infection prevention devices and surfaces.

Advanced Surface Modification for 3D-Printed Titanium Alloy Implant Interface Functionalization

With the development of three-dimensional (3D) printed technology, 3D printed alloy implants, especially titanium alloy, play a critical role in biomedical fields such as orthopedics and dentistry. However, untreated titanium alloy implants always possess a bioinert surface that prevents the interface osseointegration, which is necessary to perform surface modification to enhance its biological functions. In this article, we discuss the principles and processes of chemical, physical, and biological surface modification technologies on 3D printed titanium alloy implants in detail. Furthermore, the challenges on antibacterial, osteogenesis, and mechanical properties of 3D-printed titanium alloy implants by surface modification are summarized. Future research studies, including the combination of multiple modification technologies or the coordination of the structure and composition of the composite coating are also present. This review provides leading-edge functionalization strategies of the 3D printed titanium alloy implants.

Surfaces with Antifouling-Antimicrobial Dual Function via Immobilization of Lysozyme on Zwitterionic Polymer Thin Films

Due to the emergence of wide-spread infectious diseases, there is a heightened need for antimicrobial and/or antifouling coatings that can be used to prevent infection and transmission in a variety...

Surface Engineering Strategies to Enhance the In Situ Performance of Medical Devices Including Atomic Scale Engineering

Decades of intense scientific research investigations clearly suggest that only a subset of a large number of metals, ceramics, polymers, composites, and nanomaterials are suitable as biomaterials for a growing number of biomedical devices and biomedical uses. However, biomaterials are prone to microbial infection due to Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis), hepatitis, tuberculosis, human immunodeficiency virus (HIV), and many more. Hence, a range of surface engineering strategies are devised in order to achieve desired biocompatibility and antimicrobial performance in situ. Surface engineering strategies are a group of techniques that alter or modify the surface properties of the material in order to obtain a product with desired functionalities. There are two categories of surface engineering methods: conventional surface engineering methods (such as coating, bioactive coating, plasma spray coating, hydrothermal, lithography, shot peening, and electrophoretic deposition) and emerging surface engineering methods (laser treatment, robot laser treatment, electrospinning, electrospray, additive manufacturing, and radio frequency magnetron sputtering technique). Atomic-scale engineering, such as chemical vapor deposition, atomic layer etching, plasma immersion ion deposition, and atomic layer deposition, is a subsection of emerging technology that has demonstrated improved control and flexibility at finer length scales than compared to the conventional methods. With the advancements in technologies and the demand for even better control of biomaterial surfaces, research efforts in recent years are aimed at the atomic scale and molecular scale while incorporating functional agents in order to elicit optimal in situ performance. The functional agents include synthetic materials (monolithic ZnO, quaternary ammonium salts, silver nano-clusters, titanium dioxide, and graphene) and natural materials (chitosan, totarol, botanical extracts, and nisin). This review highlights the various strategies of surface engineering of biomaterial including their functional mechanism, applications, and shortcomings. Additionally, this review article emphasizes atomic scale engineering of biomaterials for fabricating antimicrobial biomaterials and explores their challenges.

Dual-Functional Surfaces Based on an Antifouling Polymer and a Natural Antibiofilm Molecule: Prevention of Biofilm Formation without Using Biocides

Pathogenic biofilms formed on the surfaces of implantable medical devices and materials pose an urgent global healthcare problem. Although conventional antibacterial surfaces based on bacteria-repelling or bacteria-killing strategies can delay biofilm formation to some extent, they usually fail in long-term applications, and it remains challenging to eradicate recalcitrant biofilms once they are established and mature. From the viewpoint of microbiology, a promising strategy may be to target the middle stage of biofilm formation including the main biological processes involved in biofilm development. In this work, a dual-functional antibiofilm surface is developed based on copolymer brushes of 2-hydroxyethyl methacrylate (HEMA) and 3-(acrylamido)phenylboronic acid (APBA), with quercetin (Qe, a natural antibiofilm molecule) incorporated via acid-responsive boronate ester bonds. Due to the antifouling properties of the hydrophilic poly(HEMA) component, the resulting surface is able to suppress bacterial adhesion and aggregation in the early stages of contact. A few bacteria are eventually able to break through the protection of the anti-adhesion layer leading to bacterial colonization. In response to the resulting decrease in the pH of the microenvironment, the surface could then release Qe to interfere with the microbiological processes related to biofilm formation. Compared to bactericidal and anti-adhesive surfaces, this dual-functional surface showed significantly improved antibiofilm performance to prevent biofilm formation involving both Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus for up to 3 days. In addition, both the copolymer and Qe are negligibly cytotoxic, thereby avoiding possible harmful effects on adjacent normal cells and the risk of bacterial resistance. This dual-functional design approach addresses the different stages of biofilm formation, and (in accordance with the growth process of the biofilm) allows sequential activation of the functions without compromising the viability of adjacent normal cells. A simple and reliable solution may thus be provided to the problems associated with biofilms on surfaces in various biomedical applications.

One-step vapor deposition of fluorinated polycationic coating to fabricate antifouling and anti-infective textile against drug-resistant bacteria and viruses

The ongoing pandemic caused by the novel coronavirus has turned out to be one of the biggest threats to the world, and the increase of drug-resistant bacterial strains also threatens the human health. Hence, there is an urgent need to develop novel anti-infective materials with broad-spectrum anti-pathogenic activity. In the present study, a fluorinated polycationic coating was synthesized on a hydrophilic and negatively charged polyester textile via one-step initiated chemical vapor deposition of poly(dimethyl amino methyl styrene-co-1H,1H,2H,2H-perfluorodecyl acrylate) (P(DMAMS-co-PFDA), PDP). The surface characterization results of SEM, FTIR, and EDX demonstrated the successful synthesis of PDP coating. Contact angle analysis revealed that PDP coating endowed the polyester textile with the hydrophobicity against the attachment of different aqueous foulants such as blood, coffee, and milk, as well as the oleophobicity against paraffin oil. Zeta potential analysis demonstrated that the PDP coating enabled a transformation of negative charge to positive charge on the surface of polyester textile. The PDP coating exhibited excellent contact-killing activity against both gram-negative Escherichia coli and gram-positive methicillin-resistant Staphylococcus aureus, with the killing efficiency of approximate 99.9%. In addition, the antiviral capacity of PDP was determined by a green fluorescence protein (GFP) expression-based method using lentivirus-EGFP as a virus model. The PDP coating inactivated the negatively charged lentivirus-EGFP effectively. Moreover, the coating showed good biocompatibility toward mouse NIH 3T3 fibroblast cells. All the above properties demonstrated that PDP would be a promising anti-pathogenic polymeric coating with wide applications in medicine, hygiene, hospital, etc., to control the bacterial and viral transmission and infection.

Design of nanoengineered antibacterial polymers for biomedical applications

Pathogenic bacteria have become global threats to public health. Since the advent of antibiotics about 100 years ago, their use has been embraced with great enthusiasm because of their effective treatment of bacterial infections. However, the evolution of pathogenic bacteria with resistance to conventional antibiotics has resulted in an urgent need for the development of a new generation of antibiotics. The use of antimicrobial polymers offers the promise of enhancing the efficacy of antimicrobial agents. Of the various antibacterial polymers that effectively eradicate pathogenic bacteria, those that are nanoengineered have garnered significant research interest in their design and biomedical applications. Because of their high surface area and high reactivity, these polymers show greater antibacterial activity than conventional antibacterial agents, by inhibiting the growth or destroying the cell membrane of pathogenic bacteria. This review summarizes several strategies for designing nanoengineered antibacterial polymers, explores the factors that affect their antibacterial properties, and examines key features of their design. It then comments briefly on the future prospects for nanoengineered antibacterial polymers. This review thus provides a feasible guide to developing nanoengineered antibacterial polymers by presenting both broad and in-depth bench research, and it offers suggestions for their potential in biomedical applications.

Robust and Antiswelling Hollow Hydrogel Tube with Antibacterial and Antithrombotic Ability for Emergency Vascular Replacement

Infection and thrombosis are the two major complications in almost any indwelling intravascular catheters, leading to adverse consequences. Here, we report a robust and antiswelling hollow hydrogel tube that is prepared by copolymerizing a hydrogen-bonding (H-bonding) monomer and a zinc methacrylate (ZMA) monomer in the absence of any chemical cross-linker. The strong H-bonding interactions from the side chain of N-acryloylsemicarbazide (NASC) endow the hydrogel with high mechanical strength and swelling stability. Introduction of ZMA affords a superhydrophilic surface, and the release of a zinc ion (Zn²⁺) from the hydrogel can kill nearly 100% both of Staphylococcus aureus and Escherichia coli, indicating its excellent antibacterial ability. Importantly, the P(NASC-co-ZMA) hydrogel exhibits better antithrombosis ability due to the resistant adhesion of fibrinogen protein and platelets, as well binding calcium ions (Ca²⁺) from the blood. The hydrogel tube is used to connect the ex vivo arteriovenous shunt circuit or implanted into the left carotid artery in the rabbit model, showing a better patency rate. All of these results suggest that this hydrogel tube may mitigate infection and thrombosis complications, thus holding potential as an artificial blood vessel for emergency vascular replacement.

Solvent-Free Fabrication of Self-Regenerating Antibacterial Surfaces Resisting Biofilm Formation

Biofilm formation on indwelling medical devices is a major cause of hospital-acquired infections. Monofunctional antibacterial surfaces have been developed to resist the formation of biofilms by killing bacteria on contact, but the adsorption of killed bacterial cells and debris gradually undermines the function of these surfaces. Here, we report a facile approach to produce an antibacterial surface that can regenerate its function after contamination. The self-regenerating surface was achieved by sequential deposition of alternating antibacterial and biodegradable layers of coating using a solvent-free initiated chemical vapor deposition method. As the top antibacterial layer gradually loses its killing ability due to the accumulation of debris, the underlying biodegradable layer degrades, shedding off the top surface layers and exposing another fresh antibacterial surface. Urinary catheters coated with monofunctional and self-regenerating antibacterial coatings both showed more than 99% bacterial killing ability at the initial antibacterial test, but the monofunctional surface lost its killing ability after continued exposure to concentrated bacterial solution, whereas the self-regenerating surfaces regained strong bacterial killing ability after prolonged exposure. Employing poly(methacrylic anhydride) and its copolymers with varied composition as the degrading layer, the degradation kinetics can be well-tailored and the self-regeneration duration spanned from minutes to days. The designed self-regenerating antibacterial surfaces could provide an effective approach to resist biofilm formation and extend the service life of indwelling medical devices.

Initiated Chemical Vapor Deposition (iCVD) Functionalized Polylactic Acid-Marine Algae Composite Patch for Bone Tissue Engineering

The current study aimed to describe the fabrication of a composite patch by incorporating marine algae powders (MAPs) into poly-lactic acid (PLA) for bone tissue engineering. The prepared composite patch was functionalized with the co-polymer, poly (2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) (p(HEMA-co-EGDMA)) via initiated chemical vapor deposition (iCVD) to improve its wettability and overall biocompatibility. The iCVD functionalized MAP–PLA composite patch showed superior cell interaction of human osteoblasts. Following the surface functionalization by p(HEMA-co-EGDMA) via the iCVD technique, a highly hydrophilic patch was achieved without tailoring any morphological and structural properties. Moreover, the iCVD modified composite patch exhibited ideal cell adhesion for human osteoblasts, thus making the proposed patch suitable for potential biomedical applications including bone tissue engineering, especially in the fields of dentistry and orthopedy.

A mussel-bioinspired multi-functional hyperbranched polymeric coating with integrated antibacterial and antifouling activities for implant interface modification

On the basis of a function integrating strategy, a mussel-inspired hyperbranched polymeric coating with antibacterial and antifouling properties was ingeniously designed and synthesized for the interface modification of implants.

Self-Adaptive Antibacterial Coating for Universal Polymeric Substrates Based on a Micrometer-Scale Hierarchical Polymer Brush System

Surface-tethered hierarchical polymer brushes find wide applications in the development of antibacterial surfaces due to the well-defined spatial distribution and the separate but complementary properties of different blocks. Existing methods to achieve such polymer brushes mainly focused on inorganic material substrates, precluding their practical applications on common medical devices. In this work, a hierarchical polymer brush system is proposed and facilely constructed on polymeric substrates via light living graft polymerization. The polymer brush system with micrometer-scale thickness exhibits a unique hierarchical architecture consisting of a poly(hydroxyethyl methacrylate) (PHEMA) outer layer and an anionic inner layer loading with cationic antimicrobial peptide (AMP) via electrostatic attraction. The surface of this system inhibits the initial adhesion of bacteria by the PHEMA hydration outer layer under neutral pH conditions; when bacteria adhere and proliferate on this surface, the bacterially induced acidification triggers the cleavage of labile amide bonds within the inner layer to expose the positively charged amines and vigorously release melittin (MLT), allowing the surface to timely kill the adhering bacteria. The hierarchical surface employs multiple antibacterial mechanisms to combat bacterial infection and shows high sensitiveness and responsiveness to pathogens. A new paradigm is supplied by this modular hierarchical polymer brushes system for the progress of intelligent surfaces on universal polymer substrates, showing great potential to a promising strategy for preventing infection related to medical devices.