Hierarchical Surface Inspired by Geminized Cationic Amphiphilic Polymer Brushes for Super-Antibacterial and Self-Cleaning Properties

Theoretical investigation on the conformation of polymer brushes in mixtures of binary solvents

Polymer brushes are extensively used in various applications, such as antifouling coatings and biomedical sensors. Mixed solvents entail versatile regulations on the conformation of polymer brushes. The understanding of the conformation of polymer brushes in mixtures of two solvents, however, is far from mature. In this work, we develop a self-consistent field (SCF) theory and an Alexander-de Gennes (A-dG) theory to examine the chain conformation of polymer brushes in mixtures of two miscible solvents. We systematically investigate how the Flory-Huggins interaction parameters among the three components, the composition of the mixed solvent, the grafting density, and the chain length, influence the brush height and the density profiles of various species. Our calculations exhibit many non-trivial phenomena, such as the collapse of brushes in mixtures of two good solvents and the worsening of solvent quality when adding a good solvent to a poor solvent. The physical mechanisms of these intriguing phenomena are rationalized via the interplay among the chain conformation entropy, the mixing entropy of the two solvents, and the competition in the interactions among the three species. Quantitative comparison between the SCF and the A-dG theories demonstrates that the latter theory can qualitatively capture the variation trends of the brush height and the average concentrations of different species, while the former theory can provide more detailed descriptions on the density profiles of various species in the brush. Our results here not only exhibit the richness and complexity of polymer brushes in mixed solvents but also provide valuable principles for the rational design of stimuli-responsive brushes.

Tuning Surface Functions by Hydrophilic/Hydrophobic Polymer Brushes

Polymer brushes, an optimal method for surface modification, have garnered significant interest due to their potential in surface wettability and functions regulation. This review summarizes the recent advancements in functional polymer brush surfaces based on surface wettability regulation. First, the fundamental structure and fabrication methods of polymer brushes, emphasizing the two primary strategies, "grafting-to" and "grafting-from", were introduced, and special attention was accorded to the method of subsurface-initiated atom transfer radical polymerization (SSI-ATRP) for the construction of mechanically robust polymer brushes. Subsequently, we delved into the attributes of the stimuli-responsive polymer brush surface, which can effectuate reversible surface wettability transitions in response to external stimuli. Then, this review also offered an in-depth exploration of the potential applications of polymer brushes based on their surface wettability, including lubrication, drag reduction, antifouling, antifogging, anti-icing, oil-water separation, actuation, and emulsion stability. Lastly, the challenges of polymer brush surfaces encountered in practical applications, including mechanical strength, biocompatibility, recyclability, and preparation efficiency, were addressed, and significant achievements in current research were summarized and insights into future directions were offered. This review intends to provide researchers with a comprehensive understanding of the potential applications of polymer brushes based on surface wettability regulation, and with the development of the polymer brush preparation technology, it will be anticipated that they will assume increasingly pivotal roles in various fields.

A fucoidan-loaded hydrogel coating for enhancing corrosion resistance, hemocompatibility and endothelial cell growth of magnesium alloy for cardiovascular stents

Although magnesium alloy has received tremendous attention in biodegradable cardiovascular stents, the poor in vivo corrosion resistance and limited endothelialization are still the bottlenecks for its application in cardiovascular stents. Fabrication of the multifunctional bioactive coating with excellent anti-corrosion on the surface is beneficial for rapid re-endothelialization and the normal physiological function recovery of blood vessels. In the present study, a bioactive hydrogel coating was established on the surface of magnesium alloy by copolymerization of sulfobetaine methacrylate (SBMA) and acrylamide (AM) via ultraviolet (UV) polymerization, followed by the immobilization of fucoidan (Fu). The results showed that the as-prepared multifunctional hydrogel coating could enhance the corrosion resistance and the surface wettability of the magnesium alloy surface, endowing it with the ability of selective albumin adsorption; meanwhile, it could augment biocompatibility. The following introduction of fucoidan on the surface could further improve the hemocompatibility characterized by reducing protein adsorption, minimizing hemolysis, and preventing platelet aggregation and activation. Additionally, the immobilized fucoidan promoted endothelial cell (EC) growth, as well as up-regulated the expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO) in endothelial cells (ECs). Consequently, this research paves a novel approach to developing a versatile bioactive coating for magnesium alloy surfaces and lays a foundation in cardiovascular biomaterials.

Antifouling nanoplatform for controlled attachment ofE. coli

Biofouling is the most common cause of bacterial contamination in implanted materials/devices resulting in severe inflammation, implant mobilization, and eventual failure. Since bacterial attachment represents the initial step toward biofouling, developing synthetic surfaces that prevent bacterial adhesion is of keen interest in biomaterials research. In this study, we develop antifouling nanoplatforms that effectively impede bacterial adhesion and the consequent biofilm formation. We synthesize the antifouling nanoplatform by introducing silicon (Si)/silica nanoassemblies to the surface through ultrafast ionization of Si substrates. We assess the effectiveness of these nanoplatforms in inhibitingEscherichia coli(E. coli) adhesion. The findings reveal a significant reduction in bacterial attachment on the nanoplatform compared to untreated silicon, with bacteria forming smaller colonies. By manipulating physicochemical characteristics such as nanoassembly size/concentration and nanovoid size, we further control bacterial attachment. These findings suggest the potential of our synthesized nanoplatform in developing biomedical implants/devices with improved antifouling properties.

Polyelectrolyte-Surfactant Complex Nanofibrous Membranes for Antibacterial Applications

Polyelectrolyte-surfactant complexes (PESCs) have garnered significant attention due to their extensive range of biological and industrial applications. Most present applications are predominantly used in liquid or emulsion states, which limits their efficacy in solid material-based applications. Herein, pre-hydrolyzed polyacrylonitrile (HPAN) and quaternary ammonium salts (QAS) are employed to produce PESC electrospun membranes via electrospinning. The formation process of PESCs in a solution is observed. The results show that the degree of PAN hydrolysis and the varying alkyl chain lengths of surfactants affect the rate of PESC formation. Moreover, PESCs/PCL hybrid electrospun membranes are fabricated, and their antibacterial activities against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) are investigated. The resulting electrospun membranes exhibit high bactericidal efficacy, which enables them to serve as candidates for future biomedical and filtration applications.

Dendritic systems for bacterial outer membrane disruption as a method of overcoming bacterial multidrug resistance

The alarming rise of multi-drug resistant microorganisms has increased the need for new approaches through the development of innovative agents that are capable of attaching to the outer layers of bacteria and causing permanent damage by penetrating the bacterial outer membrane. The permeability (disruption) of the outer membrane of Gram-negative bacteria is now considered to be one of the main ways to overcome multidrug resistance in bacteria. Natural and synthetic permeabilizers such as AMPs and dendritic systems seem promising. However, due to their advantages in terms of biocompatibility, antimicrobial capacity, and wide possibilities for modification and synthesis, highly branched polymers and dendritic systems have gained much more interest in recent years. Various forms of arrangement, and structure of the skeleton, give dendritic systems versatile applications, especially the possibility of attaching other ligands to their surface. This review will focus on the mechanisms used by different types of dendritic polymers, and their complexes with macromolecules to enhance their antimicrobial effect, and to permeabilize the bacterial outer membrane. In addition, future challenges and potential prospects are illustrated in the hope of accelerating the advancement of nanomedicine in the fight against resistant pathogens.

Super Antibacterial Capacity and Cell Envelope-Disruptive Mechanism of Ultrasonically Grafted N-Halamine PBAT/PBF Films against Escherichia coli

Antibacterial materials are urgently needed to combat bacterial contamination, growth, or attachment on contact surfaces, as bacterial infections remain a public health crisis worldwide. Here, a novel ultrasound-assisted method is utilized for the first time to fabricate oxidative chlorine-loaded AH@PBAT/PBF-Cl films with more superior grafting efficiency and rechargeable antibacterial effect than those from conventional techniques. The films remarkably inactivate 99.9999% Escherichia coli and Staphylococcus aureus cells, inducing noticeable cell deformations and mechanical instability. The specific antibacterial mechanism against E. coli used as a model organism is unveiled using several cell envelope structural and functional analyses combined with proteomics, peptidoglycomics, and fluorescence probe techniques. Film treatment partially neutralizes the bacterial surface charge, induces oxidative stress and cytoskeleton deformity, alters membrane properties, and disrupts the expression of key proteins involved in the synthesis and transport of the lipopolysaccharide and peptidoglycan, indicating the cell envelope as the primary target. The films specifically target lipopolysaccharides, resulting in structural impairment of the polysaccharide and lipid A components, and inhibit peptidoglycan precursor synthesis. Together, these lead to metabolic disorders, membrane dysfunction, structural collapse, and eventual death. Given the films' antibacterial effects via the disruption of key cell envelope components, they can potentially combat a wide range of bacteria. These findings lay a theoretical basis for developing efficient antibacterial materials for food safety or biomedical applications.

Smart Copolymer Surface Derived from Geminized Cationic Amphiphilic Polymers for Reversibly Switchable Bactericidal and Self-Cleaning Abilities

Bacterial adhesion and colonization on material surfaces pose a serious problem for healthcare-associated devices. Cationic amphiphilic polymer brushes are usually used as surface coatings in antibacterial materials to endow an interface with excellent bactericidal efficiency, but they are easily contaminated, which puts a great limitation on their application. Herein, novel antibacterial copolymer brush surfaces containing geminized cationic amphiphilic polymers (pAGC₈) and thermoresponsive poly(N-isopropylacrylamide) polymers (pNIPAm) have been synthesized. Surface functionalization of polymer brushes was investigated by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy, and water contact angle measurements. A proportion of AGC₈ and NIPAm units in copolymer brushes has been adjusted to obtain a high-efficiency bactericidal surface with minimal interference to its self-cleaning property. The killing and releasing efficiency of the optimized surface simultaneously reached up to above 80% for both Staphylococcus aureus and Escherichia coli bacteria, and the bactericidal and self-cleaning abilities are still excellent even after three kill-release cycles. Such a novel copolymer brush system provides innovative guidance for the development of high-efficiency antibacterial materials in biomedical application.

Simultaneous deposition of tannic acid derivative and covalent conjugation of poly(2-methyl-2-oxazoline) for the construction of antifouling coatings

Bacterial adhesion and subsequent colonization play an important role in the failure of biomedical implants and devices. Thus, development of a simple surface modification strategy to combat bacterial adhesion is highly desirable. In this work, "one-pot" fabrication of antifouling coatings based on simultaneous surface adhesion of trihydroxyphenyl and dihydroxyphenyl moieties of tannic acid (TA) derivative and covalent conjugation of hydrophilic poly(2-methyl-2-oxazoline) (PMOXA) was demonstrated. Surface co-depositions of TA/PMOXA hybrids of different TA derivative to PMOXA weight ratios and different molecular weights of PMOXA were conducted. The surface hydrophilicity and deposition universality on various substrates were investigated. The anti-bacterial and anti-platelet adhesion, as well as anti-biofilm formation abilities, of the TA/PMOXA-based coating were also studied. In vitro hemolysis and cytotoxicity, and in vivo biocompatibility of the TA/PMOXA-based coating were further evaluated. All the results indicate that the TA/PMOXA-based coating could be employed as an antifouling additive on biomedical implants and devices.

Antibacterial coatings on orthopedic implants

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

Shear-Stable Polymer Brush Surfaces

Research on polymer brushes (PBs) has aroused great interest due to their wide range of applications in lubrication, antifogging, antifouling, self-cleaning, antiadhesion, antibacterial effects, and so forth. However, the weak mechanical strength, especially the low bond strength between the PBs and the substrate surface, is a long-standing challenge for its practical applications, which is directly related to the service life of the PB surface. Fortunately, the imperfection of the PB surface was gradually solved by researchers by combining the action of the chemical and physical anchoring strength, and many shear-stable PB surfaces were developed. In this Perspective, we present recent developments in the studies of shear-stable PBs. Conventional strategies that altered the structure of PB chain methods, including increasing grafted density, cross-linking of PBs, cyclic PBs, and so forth, are introduced briefly. The systematic subsurface grafting of the polymer brush (SSPB) strategy was introduced emphatically. The SSPB method grafted PB into the subsurface with considerable depth and gave a robust and reusable PB layer, which provided an approach for tackling the shear-resistance issue. Besides, the robust hydrophobic poly(dimethylsiloxane) (PDMS) brush surface that lubricated itself in air was also introduced. Finally, we provide a synopsis and discuss the outlook of the shear-stable PB surface.

Antibacterial features of material surface: strong enough to serve as antibiotics?

Bacteria are small but need big efforts to control. The use of antibiotics not only produces superbugs that are increasingly difficult to inactivate, but also raises environmental concerns with the growing consumption. It is now believed that the antibacterial task can count on some physiochemical features of material surfaces, which can be anti-adhesive or bactericidal without releasing toxicants. It is necessary to evaluate to what extent can we rely on the surface design since the actual application scenarios will need the antibacterial performance to be sharp, robust, environmentally friendly, and long-lasting. Herein, we review the recent laboratory advances that have been classified based on the specific surface features, including hydrophobicity, charge potential, micromorphology, stiffness and viscosity, and photoactivity, and the antibacterial mechanisms of each feature are included to provide a basic rationale for future design. The significance of anti-biofilms is also introduced, given the big role of biofilms in bacteria-caused damage. A perspective on the potential wide application of antibacterial surface features as a substitute or supplement to antibiotics is then discussed. Surface design is no doubt a solution worthy to explore, and future success will be a result of further progress in multiple directions, including mechanism study and material preparation.

Polymers showing intrinsic antimicrobial activity

Pathogenic microorganisms are considered to a major threat to human health, impinging on multiple sectors including hospitals, dentistry, food storage and packaging, and water contamination. Due to the increasing levels of antimicrobial resistance shown by pathogens, often caused by long-term abuse or overuse of traditional antimicrobial drugs, new approaches and solutions are necessary. In this area, antimicrobial polymers are a viable solution to combat a variety of pathogens in a number of contexts. Indeed, polymers with intrinsic antimicrobial activities have long been an intriguing research area, in part, due to their widespread natural abundance in materials such as chitin, chitosan, carrageen, pectin, and the fact that they can be tethered to surfaces without losing their antimicrobial activities. In addition, since the discovery of the strong antimicrobial activity of some synthetic polymers, much work has focused on revealing the most effective structural elements that give rise to optimal antimicrobial properties. This has often been synthesis targeted, with the generation of either new polymers or the modification of natural antimicrobial polymers with the addition of antimicrobial enhancing modalities such as quaternary ammonium or guanidinium groups. In this review, the growing number of polymers showing intrinsic antimicrobial properties from the past decade are highlighted in terms of synthesis; often based on post-synthesis modification and their utilization. This includes as surface coatings, for example on medical devices, such as intravascular catheters, orthopaedic implants and contact lenses, or directly as antibacterial agents (specifically as eye drops). Surface functionalisation with inherently antimicrobial polymers is highlighted and has been achieved via various techniques, including surface-bound initiators allowing RAFT or ATRP surface-based polymerization, or via physical immobilization such as by layer-by-layer techniques. This article also covers the mechanistic modes of action of intrinsic antimicrobial polymers against bacteria, viruses, or fungi.

Temperature-triggered fluorocopolymer aggregate coating switching from antibacterial to antifouling and superhydrophobic hemostasis

The multifunction antibacterial hemostatic materials can reduce blood loss, infection and wound complications, which probably decrease morbidity and health care costs. However, the contradictory relationship between antibacterial ability and biocompatibility, and the unnecessary blood loss restricts the practical application of hydrophilic cationic antibacterial hemostatic materials. Herein, a multifunctional temperature-triggered antibacterial hemostatic fluorocopolymer aggregate coating was developed. After self-assembly and quaternization process, the quaternized poly(N,N-dimethylaminoethylmethacrylate)-b-poly(1H,1H,2H,2H-heptadecafluorodecyl acrylate) block copolymers (PDMA-b-PFOEMA) aggregate coating consisting of fluoropolymer and quaternary ammonium salt were built. The synergistic effect on fluorinated block with low surface energy and quaternary ammonium salt block with bactericide activity severs the way of initial bacterial attachment and proliferation, while the migration of fluorinated block greatly promotes the biocompatibility and anti-adhesion performance in response to the switch from room temperature to physiological temperature. Furthermore, the fluorocopolymer aggregate coating with hydrophobic properties possessed the property of rapid coagulation, low blood loss, minor secondary bleeding and least bacteria infiltration. The multifunctional temperature-triggered fluorocopolymer aggregate coating with antifouling, antibacterial and hemostatic properties may have a great potential in the biomedical application.

Enabling Antibacterial and Antifouling Coating via Grafting of a Nitric Oxide-Releasing Ionic Liquid on Silicone Rubber

Infections caused by bacteria and biofilms on the surfaces of biomedical devices and implants pose serious threats to public health. Herein, a nitric oxide (NO) gas-releasing quaternary ammonium-type ionic liquid (IL)-based coating on polydimethylsiloxane (PDMS), PDIL-NO, with effective and long-acting antibacterial and antifouling properties was prepared. N-(2-((2, 3-Dimethylbut-3-enoyl)oxy)ethyl)-N, N-dimethyloctan-1-aminium bromide (IL-Br), and 2-methyl-2-propenoic acid 2-(2-methoxyethoxy) ethyl ester were covalently grafted onto the surfaces of PDMS by a thiol-ene click chemical reaction, followed by incorporation of l-proline anions (Pro^-) through anion exchange with Br^- to adsorb NO gas. The prepared PDIL-NO showed a prolonged NO-releasing time (>1440 min) and a relatively high concentration (88 μM). Additionally, PDIL-NO possessed good and long-term antimicrobial activity, and could effectively reduce the adsorption of bovine serum albumin and adhesion of bacteria, as well as inhibit wound infection and reduce inflammation in vivo due to the synergetic effect of IL and the released NO. This study may provide a new approach to combat bacterial infections associated with biomedical devices and implants.

Host Defense Peptide-Mimicking Polymers and Polymeric-Brush-Tethered Host Defense Peptides: Recent Developments, Limitations, and Potential Success

Amphiphilic antimicrobial polymers have attracted considerable interest as structural mimics of host defense peptides (HDPs) that provide a broad spectrum of activity and do not induce bacterial-drug resistance. Likewise, surface engineered polymeric-brush-tethered HDP is considered a promising coating strategy that prevents infections and endows implantable materials and medical devices with antifouling and antibacterial properties. While each strategy takes a different approach, both aim to circumvent limitations of HDPs, enhance physicochemical properties, therapeutic performance, and enable solutions to unmet therapeutic needs. In this review, we discuss the recent advances in each approach, spotlight the fundamental principles, describe current developments with examples, discuss benefits and limitations, and highlight potential success. The review intends to summarize our knowledge in this research area and stimulate further work on antimicrobial polymers and functionalized polymeric biomaterials as strategies to fight infectious diseases.

Recent breakthroughs of antibacterial and antiviral protective polymeric materials during COVID-19 pandemic and after pandemic: Coating, packaging, and textile applications

The global epidemic owing to COVID-19 has generated awareness to ensuring best practices for avoiding the microorganism spread. Indeed, because of the increase in infections caused by bacteria and viruses such as SARS-CoV-2, the global demand for antimicrobial materials is growing. New technologies by using polymeric systems are of great interest. Virus transmission by contaminated surfaces leads to the spread of infectious diseases, so antimicrobial coatings are significant in this regard. Moreover, antimicrobial food packaging is beneficial to prevent the spread of microorganisms during food processing and transportation. Furthermore, antimicrobial textiles show an effective role. We aim to provide a review of prepared antimicrobial polymeric materials for use in coating, food packaging, and textile during the COVID-19 pandemic and after pandemic.

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.