Engineering and Application Perspectives on Designing an Antimicrobial Surface

Guardians of Future Food Safety: Innovative Applications and Advancements in Anti-biofouling Materials

Biofilm formation is a widespread natural phenomenon that poses a substantial threat to food microbiological safety, with direct implications for consumer health. To combat this challenge effectively, one promising strategy involves the development of functional anti-biofouling layers on food-contact surfaces to deter microbial adhesion. Herein, we explore the methodologies for fabricating both hydrophilic and hydrophobic anti-biofouling materials, along with a detailed examination of their inherent antiadhesive mechanisms. Furthermore, we provide concise insights into exemplary applications of anti-biofouling materials within the context of the food industry. This comprehensive analysis not only advances our understanding of biofilm prevention but also sets the stage for innovative developments in anti-biofouling materials and their future applications in food science. These advancements hold the potential to significantly enhance food microbiological safety, ensuring that consumers can confidently enjoy food products of the highest standards in terms of hygiene and quality.

Electrically polarized nanoscale surfaces generate reactive oxygenated and chlorinated species for deactivation of microorganisms

Because of the decreasing supply of new antibiotics, recent outbreaks of infectious diseases, and the emergence of antibiotic-resistant microorganisms, it is imperative to develop new effective strategies for deactivating a broad spectrum of microorganisms and viruses. We have implemented electrically polarized nanoscale metallic (ENM) coatings that deactivate a wide range of microorganisms including Gram-negative and Gram-positive bacteria with greater than 6-log reduction in less than 10 minutes of treatment. The electrically polarized devices were also effective in deactivating lentivirus and Candida albicans. The key to the high deactivation effectiveness of ENM devices is electrochemical production of micromolar cuprous ions, which mediated reduction of oxygen to hydrogen peroxide. Formation of highly damaging species, hydroxyl radicals and hypochlorous acid, from hydrogen peroxide contributed to antimicrobial properties of the ENM devices. The electric polarization of nanoscale coatings represents an unconventional tool for deactivating a broad spectrum of microorganisms through in situ production of reactive oxygenated and chlorinated species.

Wrinkled TiNAgNW Nanocomposites for High-Performance Flexible Electrodes on TEMPO-Oxidized Nanocellulose

In this study, we present a novel method for fabricating semi-transparent electrodes by combining silver nanowires (AgNW) with titanium nitride (TiN) layers, resulting in conductive nanocomposite coatings with exceptional electromechanical properties. These nanocomposites were deposited on cellulose nanopaper (CNP) using a plasma-enhanced pulsed laser deposition (PE-PLD) technique at low temperatures (below 200 °C). Repetitive bending tests demonstrate that incorporating AgNW into TiN coatings significantly enhances the microstructure, increasing the electrode's electromechanical robustness by up to four orders of magnitude compared to commercial PET/ITO substrates. Furthermore, the optical and electrical conductivities can be optimized by adjusting the AgNW network density and TiN synthesis temperature. Our results also indicate that the nanocomposite electrodes exhibit improved stability in air and superior adhesion compared to bare AgNW coatings.

Durable Antimicrobial Microstructure Surface (DAMS) Enabled by 3D-Printing and ZnO Nanoflowers

A. Numerous studies have been trying to create nanomaterials based antimicrobial surfaces to combat the growing bacterial infection problems. Mechanical durability has become one of the major challenges to applying those surfaces in real life. In this study, we demonstrate the Durable Antimicrobial Microstructures Surface (DAMS) consisting of DLP 3D printed microstructures and zinc oxide (ZnO) nanoflowers. The microstructures serve as a protection armor for the nanoflowers during abrasion. The antimicrobial ability was tested by immersing in 2E8 CFU/mL Escherichia coli ( E. coli ) suspension and then evaluated using electron microscopy. Compared to the bare control, our results show that the DAMS reduces bacterial coverage by more than 90% after 12 hrs of incubation and approximately 50% after 48 hrs of incubation before abrasion. Importantly, bacterial coverage is reduced by approximately 50% after 2 min of abrasion with a tribometer, and DAMS remains effective even after 6 min of abrasion. These findings highlight the potential of DAMS as an affordable, scalable, and durable antimicrobial surface for various biomedical applications.

Zwitterionic Hydrogel Coating with Antisediment Properties for Marine Antifouling Applications

Biofouling is a serious issue affecting the marine industry because the attached micro- and macrocontaminants can increase fuel consumption and damage ship hulls. A hydrophilic hydrogel-based coating is considered a promising antifouling material because it is environmentally friendly and the dense hydration layer can protect the substrate from microbial attachment. However, sediment adsorption can be an issue for hydrogel-based coatings. Their natural soft and porous structures can trap sediment from the marine environment and weaken the antifouling capability. There is still little research on the antisediment properties of hydrogels, and none of them deal with this problem. Here, we report on optimizing zwitterionic hydrogel-based coatings to improve their antisediment properties and achieve comparable performance to commercial biocidal coatings, which are the gold standard in the antifouling coating area. After 1 week of sediment contamination and 2 weeks of diatom coculturing, this optimized zwitterionic hydrogel coating maintained its antifouling properties with a few diatoms on the surface. Its large-scale samples also achieved antifouling performance similar to that of biocidal coatings in the Atlantic Ocean for 1.5 months. More importantly, our research provides a universal strategy to improve the antisediment properties of soft hydrogel-based coatings. For the first time, we report that the introduction of interfacial electrostatic interactions enhanced the antisediment properties of hydrogels.

Targeting biofilm infections in humans using small scale robotics

The eradication of drug-resistant microbial biofilms remains an unresolved global health challenge. Small-scale robotics are providing innovative therapeutic and diagnostic approaches with high precision and efficacy. These approaches are rapidly moving from proof-of-concept studies to translational biomedical applications using ex vivo, animal, and clinical models. Here, we discuss the fundamental and translational aspects of how microrobots target the infection sites to disrupt the structural and functional traits of biofilms and their antimicrobial resistance mechanisms. We emphasize current approaches of mechanochemical disruption and on-site drug delivery that are supported by in vivo models and preclinical testing, while also highlighting diagnostics potential. We also discuss clinical translation challenges and provide perspectives for development of microrobotics approaches to combat biofilm infections and biofouling in humans.

Flexible and Biocompatible Antifouling Polyurethane Surfaces Incorporating Tethered Antimicrobial Peptides through Click Reactions

Efficient, simple antibacterial materials to combat implant-associated infections are much in demand. Herein, the development of polyurethanes, both cross-linked thermoset and flexible and versatile thermoplastic, suitable for "click on demand" attachment of antibacterial compounds enabled via incorporation of an alkyne-containing diol monomer in the polymer backbone, is described. By employing different polyolic polytetrahydrofurans, isocyanates, and chain extenders, a robust and flexible material comparable to commercial thermoplastic polyurethane is prepared. A series of short synthetic antimicrobial peptides are designed, synthesized, and covalently attached in a single coupling step to generate a homogenous coating. The lead material is shown to be biocompatible and does not display any toxicity against either mouse fibroblasts or reconstructed human epidermis according to ISO and OECD guidelines. The repelling performance of the peptide-coated materials is illustrated against colonization and biofilm formation by Staphylococcus aureus and Staphylococcus epidermidis on coated plastic films and finally, on coated commercial central venous catheters employing LIVE/DEAD staining, confocal laser scanning microscopy, and bacterial counts. This study presents the successful development of a versatile and scalable polyurethane with the potential for use in the medical field to reduce the impact of bacterial biofilms.

Silver Coordination Polymers Driven by Adamantoid Blocks for Advanced Antiviral and Antibacterial Biomaterials

The development of sustainable biomaterials and surfaces to prevent the accumulation and proliferation of viruses and bacteria is highly demanded in healthcare areas. This study describes the assembly and full characterization of two new bioactive silver(I) coordination polymers (CPs) formulated as [Ag(aca)(μ-PTA)]n·5nH2O (1) and [Ag2(μ-ada)(μ3-PTA)2]n·4nH2O (2). These products were generated by exploiting a heteroleptic approach based on the use of two different adamantoid building blocks, namely 1,3,5-triaza-7-phosphaadamantane (PTA) and 1-adamantanecarboxylic (Haca) or 1,3-adamantanedicarboxylic (H2ada) acids, resulting in the assembly of 1D (1) and 3D (2). Antiviral, antibacterial, and antifungal properties of the obtained compounds were investigated in detail, followed by their incorporation as bioactive dopants (1 wt %) into hybrid biopolymers based on acid-hydrolyzed starch polymer (AHSP). The resulting materials, formulated as 1@AHSP and 2@AHSP, also featured (i) an exceptional antiviral activity against herpes simplex virus type 1 and human adenovirus (HAd-5) and (ii) a remarkable antibacterial activity against Gram-negative bacteria. Docking experiments, interaction with human serum albumin, mass spectrometry, and antioxidation studies provided insights into the mechanism of antimicrobial action. By reporting these new silver CPs driven by adamantoid building blocks and the derived starch-based materials, this study endows a facile approach to access biopolymers and interfaces capable of preventing and reducing the proliferation of a broad spectrum of different microorganisms, including bacteria, fungi, and viruses.

Zwitterionic polymers-armored amyloid-like protein surface combats thrombosis and biofouling

Proteins, cells and bacteria adhering to the surface of medical devices can lead to thrombosis and infection, resulting in significant clinical mortality. Here, we report a zwitterionic polymers-armored amyloid-like protein surface engineering strategy we called as "armored-tank" strategy for dual functionalization of medical devices. The "armored-tank" strategy is realized by decoration of partially conformational transformed LZM (PCTL) assembly through oxidant-mediated process, followed by armoring with super-hydrophilic poly-2-methacryloyloxyethyl phosphorylcholine (pMPC). The outer armor of the "armored-tank" shows potent and durable zone defense against fibrinogen, platelet and bacteria adhesion, leading to long-term antithrombogenic properties over 14 days in vivo without anticoagulation. Additionally, the "fired" PCTL from "armored-tank" actively and effectively kills both Gram-positive and Gram-negative bacterial over 30 days as a supplement to the lacking bactericidal functions of passive outer armor. Overall, this "armored-tank" surface engineering strategy serves as a promising solution for preventing biofouling and thrombotic occlusion of medical devices.

Antibacterial mechanism of lignin and lignin-based antimicrobial materials in different fields

The control of microbial infection transmission often relies on the utilization of synthetic and metal-based antimicrobial agents. However, their non-biodegradability and inadequate disposal practices lead to significant environmental contamination. To address this concern, the quest for natural alternatives has gained paramount importance. Lignin, a widely available renewable aromatic compound, emerges as a promising candidate owing to its inherent phenolic moiety, which lends itself well to acting as a natural antimicrobial agent either independently or in combination with other agents. This article provides a comprehensive account of the structure and primary classes of lignin. Additionally, it elucidates the antimicrobial mechanism of lignin, the factors influencing its efficacy, and the methods employed for its detection. Moreover, it describes the progress made in developing the antimicrobial capacity of lignin in different areas. In conclusion, this paper not only outlines the current state of research on the antimicrobial function of lignin, but also identifies challenges and future possibilities for enhancing its antimicrobial properties. This work holds great significance in the ongoing endeavor to contribute to high-impact research on natural alternatives for controlling infections and fostering environmentally conscious practices.

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

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

Using SMART Magnetic Fluids and Gels for Prevention and Destruction of Bacterial Biofilms

Biofouling is a major problem in all natural and artificial settings where solid surfaces meet liquids in the presence of living microorganisms. Microbes attach to the surface and form a multidimensional slime that protects them from unfavorable environments. These structures, known as biofilms, are detrimental and very hard to remove. Here, we used SMART magnetic fluids [ferrofluids (FFs), magnetorheological fluids (MRFs), and ferrogels (FGs) containing iron oxide nano/microparticles] and magnetic fields to remove bacterial biofilms from culture tubes, glass slides, multiwell plates, flow cells, and catheters. We compared the ability of different SMART fluids to remove biofilms and found that commercially available, as well as homemade, FFs, MRFs, and FGs can successfully remove biofilm more efficiently than traditional mechanical methods, especially from textured surfaces. In tested conditions, SMARTFs reduced bacterial biofilms by five orders of magnitude. The ability to remove biofilm increased with the amount of magnetic particles; therefore, MRFs, FG, and homemade FFs with high amounts of iron oxide were the most efficient. We showed also that SMART fluid deposition can protect a surface from bacterial attachment and biofilm formation. Possible applications of these technologies are discussed.

Demonstrating the In Vitro and In Situ Antimicrobial Activity of Oxide Mineral Microspheres: An Innovative Technology to Be Incorporated into Porous and Nonporous Materials

The antimicrobial activity of surfaces treated with zinc and/or magnesium mineral oxide microspheres is a patented technology that has been demonstrated in vitro against bacteria and viruses. This study aims to evaluate the efficiency and sustainability of the technology in vitro, under simulation-of-use conditions, and in situ. The tests were undertaken in vitro according to the ISO 22196:2011, ISO 20473:2013, and NF S90-700:2019 standards with adapted parameters. Simulation-of-use tests evaluated the robustness of the activity under worst-case scenarios. The in situ tests were conducted on high-touch surfaces. The in vitro results show efficient antimicrobial activity against referenced strains with a log reduction of >2. The sustainability of this effect was time-dependent and detected at lower temperatures (20 ± 2.5 °C) and humidity (46%) conditions for variable inoculum concentrations and contact times. The simulation of use proved the microsphere's efficiency under harsh mechanical and chemical tests. The in situ studies showed a higher than 90% reduction in CFU/25 cm² per treated surface versus the untreated surfaces, reaching a targeted value of <50 CFU/cm². Mineral oxide microspheres can be incorporated into unlimited surface types, including medical devices, to efficiently and sustainably prevent microbial contamination.

Repurposing Anthelmintics: Rafoxanide- and Copper-Functionalized SBA-15 Carriers against Methicillin-Resistant Staphylococcus aureus

The development of materials that can more efficiently administer antimicrobial agents in a controlled manner is urgently needed due to the rise in microbial resistance to traditional antibiotics. While new classes of antibiotics are developed and put into widespread usage, existing, inexpensive compounds can be repurposed to fight bacterial infections. Here, we present the synthesis of amine-functionalized SBA-15 mesoporous silica nanomaterials with physisorbed rafoxanide (RFX), a commonly used salicylanilide anthelmintic, and anchored Cu(II) ions that exhibit enhanced antimicrobial efficacy against the pathogenic bacterium Staphylococcus aureus. The synthesized nanomaterials are structurally characterized by a combination of physicochemical, thermal, and optical methods. Additionally, release studies are carried out in vitro to determine the effects of pH and the synthetic sequence used to produce the materials on Cu(II) ion release. Our results indicate that SBA-15 mesoporous silica nanocarriers loaded with Cu(II) and RFX exhibit 10 times as much bactericidal action against wild-type S. aureus as the nanocarrier loaded with only RFX. Furthermore, the synthetic sequence used to produce the nanomaterials could significantly affect (enhance) their bactericidal efficacy.

Crosslinkable fluorophenoxy-substituted poly[bis(octafluoropentoxy) phosphazene] biomaterials with improved antimicrobial effect and hemocompatibility

Biomaterial-associated microbial infection is one of the most frequent and severe complications associated with the use of biomaterials in medical devices. In previous studies, we developed new fluorinated polyphosphazenes, poly[bis(octafluoropentoxy) phosphazene] (OFP) and crosslinkable OFP (X-OFP), and demonstrated the inhibition of bacterial adhesion and biofilm formation, thereby controlling microbial infection. In this study, two additional fluorinated polyphosphazenes (PPs, defined as LS02 and LS03) with fluorophenoxy-substituted side groups, 4-fluorophenoxy and 4-(trifluoromethyl)phenoxy, respectively, based on X-OFP general structure, were synthesized and applied as coatings on stainless steel. The linkage of fluorophenoxy groups to the P-N backbone of PPs was found to increase the surface stiffness and significantly reduced Staphylococcus bacterial adhesion and inhibited biofilm formation. It also significantly reduced microbial infection compared to OFP, our prior X-OFPs or poly[bis(trifluoroethoxy) phosphazene] (TFE). The biofilm experiments show that the newly synthesized PPs LS02 and LS03 are biofilm free up to 28 days. Plasma coagulation and platelet adhesion/activation experiments also demonstrated that new PPs containing fluorophenoxy side groups are hemocompatible. The development of new crosslinkable fluorinated PPs containing fluorophenoxy-substituted side groups provides a new generation of polyphosphazene materials for medical devices with improved resistance to microbial infections and thrombosis formation.

Evaluation of Activity of Zinc Oxide Nanoparticles on Human Rotavirus and Multi-Drug Resistant Acinetobacter Baumannii

BACKGROUND

Rotaviruses are the cause of acute gastroenteritis and severe diarrheal diseases in children worldwide. Children under the age of five are more susceptible to rotavirus infections. Due to such as the lack of effective drugs and supportive therapy only, the development of new antiviral agents against rotaviruses is required. Multi-drug-resistant Acinetobacter baumannii is also one of the most challenging Gram-negative bacteria to control and treat due to its antibiotic resistance, particularly in intensive care units.

OBJECTIVE

This study aimed to investigate the activity of zinc oxide nanoparticles against human rotavirus and multi-drug resistant Acinetobacter baumannii.

METHODS

The standard 50% tissue culture infectious dose method and the real-time polymerase chain reaction assay were used to investigate the effects of zinc oxide nanoparticles on rotaviruses. The well diffusion and the minimum inhibitory concentration method were used to assess the antibacterial activity of zinc oxide nanoparticles against Acinetobacter baumannii.

RESULTS

300 μg/ml of zinc oxide nanoparticles demonstrated the highest anti-rotavirus effects, resulting in a 3.16 logarithmic decrease in virus infectious titer, and a four-unit increase in the cycle threshold value of the real-time polymerase chain reaction assay compared to the untreated control (P value <0.001 and P value = 0.005, respectively). The diameter of the inhibition zone of zinc oxide nanoparticles solution against Acinetobacter baumannii was 17 mm. The minimum inhibitory concentration results of the zinc oxide nanoparticles solution against Acinetobacter baumannii was 1.56 mg/ml.

CONCLUSION

Our findings showed that zinc oxide nanoparticles could be considered a promising antimicrobial compound.

Surface antimicrobial functionalization with polymers: fabrication, mechanisms and applications

Undesirable adhesion of microbes such as bacteria, fungi and viruses onto surfaces affects many industries such as marine, food, textile, and healthcare. In particular in healthcare and food packaging, the effects of unwanted microbial contamination can be life-threatening. With the current global COVID-19 pandemic, interest in the development of surfaces with superior anti-viral and anti-bacterial activities has multiplied. Polymers carrying anti-microbial properties are extensively used to functionalize material surfaces to inactivate infection-causing and biocide-resistant microbes including COVID-19. This review aims to introduce the fabrication of polymer-based antimicrobial surfaces through physical and chemical modifications, followed by the discussion of the inactivation mechanisms of conventional biocidal agents and new-generation antimicrobial macromolecules in polymer-modified antimicrobial surfaces. The advanced applications of polymer-based antimicrobial surfaces on personal protective equipment against COVID-19, food packaging materials, biomedical devices, marine vessels and textiles are also summarized to express the research trend in academia and industry.

Surface Texturing and Combinatorial Approaches to Improve Biocompatibility of Implanted Biomaterials

Biomaterial associated microbial infection and blood thrombosis are two of the barriers that inhibit the successful use of implantable medical devices in modern healthcare. Modification of surface topography is a promising approach to combat microbial infection and thrombosis without altering bulk material properties necessary for device function and without contributing to bacterial antibiotic resistance. Similarly, the use of other antimicrobial techniques such as grafting poly(ethylene glycol) (PEG) and nitric oxide (NO) release also improve the biocompatibility of biomaterials. In this review, we discuss the development of surface texturing techniques utilizing ordered submicron-size pillars for controlling bacterial adhesion and biofilm formation, and we present combinatorial approaches utilizing surface texturing in combination with poly(ethylene glycol) (PEG) grafting and NO release to improve the biocompatibility of biomaterials. The manuscript also discusses efforts towards understanding the molecular mechanisms of bacterial adhesion responses to the surface texturing and NO releasing biomaterials, focusing on experimental aspects of the approach.

Highly Permeable Polylactic Acid Membrane Grafted with Quaternary Ammonium Salt for Effective and Durable Water Disinfection

Given the increasing usage of drinking water purifiers, highly permeable membranes with strong antimicrobial functions are desperately desirable for effective and durable water disinfection. Hereby, we prepared such antimicrobial membranes by chemical grafting of quaternary ammonium salt (QAS) molecules, 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride (TPMMC), onto air plasma pretreated biodegradable polylactic acid (PLA) substrates. The high chemical grafting density promoted very strong and positive zeta potential charge of the resulted PLA-QAS membrane, contributing to effective and broad-spectrum antimicrobial efficiencies (>99.99%) against different microbes, including fungi and conventional and drug-resistant bacteria. The solid grafting of QAS molecules produced a durable antimicrobial performance of the PLA-QAS membrane. In addition, the pleated filter (0.45 m²) of PLA-QAS membrane showed outstanding bacteria rejection properties (>99.99%) and excellent washing durability (up to 20 m³ water) even at very high water filtration rates (up to 4 L/min). The disinfection mechanism was clarified that negatively charged bacteria could be rapidly adsorbed to positively charged PLA-QAS spinnings, followed by devastating cell membrane damage to bacterial debris, leaving a clean environment without significant biofilm and biofouling formation.

Hydrophobic Biodegradable Hyperbranched Copolymers with Excellent Marine Diatom Resistance

As the utilization of degradable polymer coatings increased, the accompanying trade-off between good degradability and high-efficiency antidiatom adhesion due to their hydrophobic nature remains unresolved. The study presents a new hydrophobic surface-fragmenting coating consisting of degradable hyperbranched polymers (hereafter denoted as h-LLA_x) synthesized by reversible complexation-mediated copolymerization with isobornyl acrylate (IBOA) and divinyl-functional oligomeric poly(l-lactide) (OLLA-V₂), both derived from biomass, that exhibited superior resistance (∼0 cell mm^-2) to marine diatom Navicula incerta (N. incerta) attachment with higher OLLA content. The combined impact of the microscale hollow semisphere micelles that self-assembled degradable hyperbranched copolymers and hydrolysis-driven self-renewable surfaces following immersion in seawater may account for the remarkable resistance of h-LLA_x coatings against N. incerta. Detailed investigations were conducted across multiple perspectives, from hydrolytic degradation to broad-spectrum antibacterial attachment to ecotoxicity assessment. The excellent features of high resistance to marine diatoms and bacterial attachment, degradability, and environmental friendliness make the as-prepared h-LLA_x coatings widely sought after for antifouling coating applications.

Three lines of defense: A multifunctional coating with anti-adhesion, bacteria-killing and anti-quorum sensing properties for preventing biofilm formation of Pseudomonas aeruginosa

Surfaces of synthetic materials are highly susceptible to pathogenic bacteria colonization and further biofilm formation, leading to device failure in both biomedical and industrial applications. Complete elimination of the mature biofilms formed on the surfaces, however, remains a great challenge due to the complexity of chemical composition and physical structure. Therefore, prevention of biofilm formation becomes a preferred strategy for solving the biofilm-associated problems. Herein, a multifunctional coating showing three lines of defense to prevent biofilm formation of Pseudomonas aeruginosa is fabricated by a simple and versatile method. This coating is composed of multilayers of quaternized chitosan with bactericidal property and acylase with anti-quorum sensing property and a topmost layer of hyaluronic acid with anti-adhesion property. The substrate deposited with this coating could suppress initial adhesion of a majority of bacteria, and then kill the attached bacteria and interfere with their quorum sensing systems related to biofilm formation. The results of short-term antibacterial experiments show that our coating reduced 98 ± 2% of attached live bacteria. In long-term antibiofilm experiments, this "three lines of defense" design endows the coating with enhanced antibiofilm property against the biofilm formation for at least 3 days by reducing 98 ± 1% of bacterial proliferation and 71 ± 2% of biomass production. Benefiting from the natural building blocks with good biocompatibility and the versatile and environmentally friendly preparation method, this coating shows negligible cytotoxicity and broad applicability, providing great potential for a variety of biomedical applications. STATEMENT OF SIGNIFICANCE: Pathogenic biofilms formed on the surfaces of medical devices and materials pose an urgent problem, and it remains challenging to treat and eradicate the established biofilms. Herein, we developed an antibiofilm coating showing three lines of defense to prevent biofilm formation, which could be deposited on diverse substrates via a simple and versatile method. This coating was based on three natural materials with anti-adhesive, bactericidal, and anti-quorum sensing properties and showed different function in a self-adaptive way to target the sequential stages of biofilm formation by preventing initial bacterial adhesion, killing attached bacteria and interfering with their quorum sensing system to inhibit bacterial proliferation and biofilm maturation. This coating with improved antibiofilm performance might provide a simple and reliable solution to the problems associated with biofilm on surfaces.

Functionalized Self-Assembled Monolayers: Versatile Strategies to Combat Bacterial Biofilm Formation

Bacterial infections due to biofilms account for up to 80% of bacterial infections in humans. With the increased use of antibiotic treatments, indwelling medical devices, disinfectants, and longer hospital stays, antibiotic resistant infections are sharply increasing. Annual deaths are predicted to outpace cancer and diabetes combined by 2050. In the past two decades, both chemical and physical strategies have arisen to combat biofilm formation on surfaces. One such promising chemical strategy is the formation of a self-assembled monolayer (SAM), due to its small layer thickness, strong covalent bonds, typically facile synthesis, and versatility. With the goal of combating biofilm formation, the SAM could be used to tether an antibacterial agent such as a small-molecule antibiotic, nanoparticle, peptide, or polymer to the surface, and limit the agent’s release into its environment. This review focuses on the use of SAMs to inhibit biofilm formation, both on their own and by covalent grafting of a biocidal agent, with the potential to be used in indwelling medical devices. We conclude with our perspectives on ongoing challenges and future directions for this field.

Developing Novel Biointerfaces: Using Chlorhexidine Surface Attachment as a Method for Creating Anti-Fungal Surfaces

There is an increasing focus in healthcare environments on combatting antimicrobial resistant infections. While bacterial infections are well reported, infections caused by fungi receive less attention, yet have a broad impact on society and can be deadly. Fungi are eukaryotes with considerable shared biology with humans, therefore limited technologies exist to combat fungal infections and hospital infrastructure is rarely designed for reducing microbial load. In this study, a novel antimicrobial surface (AMS) that is modified with the broad-spectrum biocide chlorhexidine is reported. The surfaces are shown to kill the opportunistic fungal pathogens Candida albicans and Cryptococcus neoformans very rapidly (<15 min) and are significantly more effective than current technologies available on the commercial market, such as silver and copper.

One-step surface modification strategy with composition-tunable microgels: From bactericidal surface to cell-friendly surface

As modifiers for biomaterial surfaces, soft colloidal particles not only have good film-forming properties, but can also contribute to the function of the biomaterial via their chemical and biological properties. This general approach has proven effective for surface modification, but little is known about methods to control the properties of the colloidal particles to regulate film formation and biological function. In this work, we prepared poly (N-isopropylacrylamide) microgels (ZQP) containing both a zwitterionic component (Z) to provide anti-fouling functionality, and a quaternary ammonium salt (Q) to give bactericidal functionality. Fine-tuning of the Z and Q contents allowed the preparation of microgels over a range of particle size, size distribution, charge, and film-forming capability. The films showed anti-adhesion and contact-killing properties versus Escherichia coli (E. Coli), depending on the chemical composition. They also showed excellent cytocompatibility relative to L929 cells. A variety of microgel-coated substrates (silicon wafer, PDMS, PU, PVC) showed long-term anti-bacterial activity and resistance to chemical and mechanical treatments. It is concluded that this approach allows the preparation of effective bactericidal, cytocompatible surfaces. The properties can be fine-tuned by regulation of the microgel composition, and the method is applicable universally, i.e., independent of substrate.

Hyperbranched Polyesters Based on Indole- and Lignin-Derived Monomeric Aromatic Aldehydes as Effective Nonionic Antimicrobial Coatings with Excellent Biocompatibility

This research aims to investigate nonionic hyperbranched polyesters (HBPs) derived from indole and lignin resources as new nontoxic antimicrobial coatings. Three nonionic HBPs with zero to two methoxy ether substituents on each benzene ring in the polymer backbones were synthesized by melt-polycondensation of three corresponding AB2 monomers. The molecular structures and thermal properties of the obtained HBPs were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry analyses. These HBPs were conveniently spin-coated on a silicon substrate, which exhibited significant antibacterial effect against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis). The presence of methoxy substituents enhanced the antimicrobial effect, and the resulting polymers showed negligible leakage in water. Finally, the polymers with the methoxy functionality exhibited excellent biocompatibility according to the results of hemolysis and MTT assay, which may facilitate their biomedical applications.

Nanostructured Surfaces with Multimodal Antimicrobial Action

Self-disinfecting surfaces are a current pressing need for public health and safety in view of the current COVID-19 pandemic, where the keenly felt worldwide repercussions have highlighted the importance of infection control, frequent disinfection, and proper hygiene. Because of its potential impact upon real-world translation into downstream applications, there has been much research interest in multiple disciplines such as materials science, chemistry, biology, and engineering. Various antimicrobial technologies have been developed and currently applied on surfaces in public spaces, such as elevator buttons and escalator handrails. These technologies are mainly based on conventional methods of grafting quaternary ammonium salts (QACs) such as benzalkonium chloride or the immobilization of metal species of silver or copper. However, neither the long-term efficacy nor the fast-killing properties have been proven, and the future repercussions from extended use, such as environmental hazards and the induction of MDR development, is unknown. Nanostructured surfaces with excellent antimicrobial activities have been claimed to be the next generation of self-disinfecting surfaces with various promising applications and passive antimicrobial mechanisms, without the potential repercussions of active ingredient overuse. In this Account, we briefly introduce the concept of mechanobactericidal action realized by these nanostructured surfaces first discovered on cicada wings. The elimination of microbes on the surface was actualized by the physical rupture of the microbe cell wall by nanoprotusions, without any involvement of chemical species. By mimicking the physical features of naturally occurring biocidal surfaces, the fabrication of nanostructures on various substrates such as titania, silicon, and polymers has been well described. Observations of the dependence of their antimicrobial efficacy on physical characteristics such as height, density, and rigidity have also been documented. However, the complex fabrication of such nanostructures remains the main drawback preventing its widespread application. We outline our efforts in fabricating a series of zinc-based nanostructured materials with facile and generally applicable wet chemistry methods, including nanodaggered zeolitic imidazolate frameworks (ZIF-L) and ZnO nanoneedles. In our investigations, we discovered that there were additional modes of action that contributed to the excellent biocidal activities of our materials. The impact of surface chemistry and charge was partially responsible for the selectivity and efficacy of ZIF-L-coated surfaces, where the positively charged surfaces were able to attract and adhere negatively charged bacteria to the surface. The combination of semiconductor ZnO nanoneedles on electron-donating substrates allowed for the generation of reactive oxygen species (ROS), realizing the remote killing of bacteria unadhered to the nanostructured surface. Additionally, we demonstrate several real-life applications of the synthesized materials, underscoring the importance of materials development suited for scale-up and eventual translation to potential applications and commercial end products.

Physically Switchable Antimicrobial Surfaces and Coatings: General Concept and Recent Achievements

Bacterial environmental colonization and subsequent biofilm formation on surfaces represents a significant and alarming problem in various fields, ranging from contamination of medical devices up to safe food packaging. Therefore, the development of surfaces resistant to bacterial colonization is a challenging and actively solved task. In this field, the current promising direction is the design and creation of nanostructured smart surfaces with on-demand activated amicrobial protection. Various surface activation methods have been described recently. In this review article, we focused on the "physical" activation of nanostructured surfaces. In the first part of the review, we briefly describe the basic principles and common approaches of external stimulus application and surface activation, including the temperature-, light-, electric- or magnetic-field-based surface triggering, as well as mechanically induced surface antimicrobial protection. In the latter part, the recent achievements in the field of smart antimicrobial surfaces with physical activation are discussed, with special attention on multiresponsive or multifunctional physically activated coatings. In particular, we mainly discussed the multistimuli surface triggering, which ensures a better degree of surface properties control, as well as simultaneous utilization of several strategies for surface protection, based on a principally different mechanism of antimicrobial action. We also mentioned several recent trends, including the development of the to-detect and to-kill hybrid approach, which ensures the surface activation in a right place at a right time.

Adhesive Antimicrobial Peptides Containing 3,4-Dihydroxy-L-Phenylalanine Residues for Direct One-Step Surface Coating

Bacterial colonization and transmission via surfaces increase the risk of infection. In this study, we design and employ novel adhesive antimicrobial peptides to prevent bacterial contamination of surfaces. Repeats of 3,4-dihydroxy-L-phenylalanine (DOPA) were added to the C-terminus of NKC, a potent synthetic antimicrobial peptide, and the adhesiveness and antibacterial properties of the resulting peptides are evaluated. The peptide is successfully immobilized on polystyrene, titanium, and polydimethylsiloxane surfaces within 10 min in a one-step coating process with no prior surface functionalization. The antibacterial effectiveness of the NKC-DOPA₅-coated polystyrene, titanium, and polydimethylsiloxane surfaces is confirmed by complete inhibition of the growth of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus within 2 h. The stability of the peptide coated on the substrate surface is maintained for 84 days, as confirmed by its bactericidal activity. Additionally, the NKC-DOPA₅-coated polystyrene, titanium, and polydimethylsiloxane surfaces show no cytotoxicity toward the human keratinocyte cell line HaCaT. The antimicrobial properties of the peptide-coated surfaces are confirmed in a subcutaneous implantation animal model. The adhesive antimicrobial peptide developed in this study exhibits potential as an antimicrobial surface-coating agent for efficiently killing a broad spectrum of bacteria on contact.

Universal Antifouling and Photothermal Antibacterial Surfaces Based on Multifunctional Metal-Phenolic Networks for Prevention of Biofilm Formation

Biofilms formed from the pathogenic bacteria that attach to the surfaces of biomedical devices and implantable materials result in various persistent and chronic bacterial infections, posing serious threats to human health. Compared to the elimination of matured biofilms, prevention of the formation of biofilms is expected to be a more effective way for the treatment of biofilm-associated infections. Herein, we develop a facile method for endowing diverse substrates with long-term antibiofilm property by deposition of a hybrid film composed of tannic acid/Cu ion (TA/Cu) complex and poly(ethylene glycol) (PEG). In this system, the TA/Cu complex acts as a multifunctional building block with three different roles: (i) as a versatile "glue" with universal adherent property for substrate modification, (ii) as a photothermal biocidal agent for bacterial elimination under irradiation of near-infrared (NIR) laser, and (iii) as a potent linker for immobilization of PEG with inherent antifouling property to inhibit adhesion and accumulation of bacteria. The resulted hybrid film shows negligible cytotoxicity and good histocompatibility and could prevent biofilm formation for at least 15 days in vitro and suppress bacterial infection in vivo, showing great potential for practical applications to solve the biofilm-associated problems of biomedical materials and devices.

Evaluation of the ZnO Nanopillar Surface for Disinfection Applications

Much attention has been devoted to the synthesis and antimicrobial studies of nanopatterned surfaces. However, factors contributing to their potential and eventual application, such as large-scale synthesis, material durability, and biocompatibility, are often neglected in such studies. In this paper, the ZnO nanopillar surface is found to be amenable to synthesis in large forms and stable upon exposure to highly accelerated lifetime tests (HALT) without any detrimental effect on its antimicrobial activity. Additionally, the material is effective against clinically isolated pathogens and biocompatible in vivo. These findings illustrate the broad applicability of ZnO nanopillar surfaces in the common equipment used in health-care and consumer industries.

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.

Engineered Bioactive Polymeric Surfaces by Radiation Induced Graft Copolymerization: Strategies and Applications

The interest in developing antimicrobial surfaces is currently surging with the rise in global infectious disease events. Radiation-induced graft copolymerization (RIGC) is a powerful technique enabling permanent tunable and desired surface modifications imparting antimicrobial properties to polymer substrates to prevent disease transmission and provide safer biomaterials and healthcare products. This review aims to provide a broader perspective of the progress taking place in strategies for designing various antimicrobial polymeric surfaces using RIGC methods and their applications in medical devices, healthcare, textile, tissue engineering and food packing. Particularly, the use of UV, plasma, electron beam (EB) and γ-rays for biocides covalent immobilization to various polymers surfaces including nonwoven fabrics, films, nanofibers, nanocomposites, catheters, sutures, wound dressing patches and contact lenses is reviewed. The different strategies to enhance the grafted antimicrobial properties are discussed with an emphasis on the emerging approach of in-situ formation of metal nanoparticles (NPs) in radiation grafted substrates. The current applications of the polymers with antimicrobial surfaces are discussed together with their future research directions. It is expected that this review would attract attention of researchers and scientists to realize the merits of RIGC in developing timely, necessary antimicrobial materials to mitigate the fast-growing microbial activities and promote hygienic lifestyles.

Chemical design principles of next-generation antiviral surface coatings

The ongoing coronavirus disease 2019 (COVID-19) pandemic has accelerated efforts to develop high-performance antiviral surface coatings while highlighting the need to build a strong mechanistic understanding of the chemical design principles that underpin antiviral surface coatings. Herein, we critically summarize the latest efforts to develop antiviral surface coatings that exhibit virus-inactivating functions through disrupting lipid envelopes or protein capsids. Particular attention is focused on how cutting-edge advances in material science are being applied to engineer antiviral surface coatings with tailored molecular-level properties to inhibit membrane-enveloped and non-enveloped viruses. Key topics covered include surfaces functionalized with organic and inorganic compounds and nanoparticles to inhibit viruses, and self-cleaning surfaces that incorporate photocatalysts and triplet photosensitizers. Application examples to stop COVID-19 are also introduced and demonstrate how the integration of chemical design principles and advanced material fabrication strategies are leading to next-generation surface coatings that can help thwart viral pandemics and other infectious disease threats.

Silver Nanodot Decorated Dendritic Copper Foam As a Hydrophobic and Mechano-Chemo Bactericidal Surface

The present work investigates the time-dependent antibacterial activity of the silver nanodot decorated dendritic copper foam nanostructures against Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) bacteria. An advanced antibacterial and antifouling surface is fabricated utilizing the collective antibacterial properties of silver nanodots, chitosan, and dendritic copper foam nanostructures. The porous network of the Ag nanodot decorated Cu foam is made up of nanodendrites, which reduce the wettability of the surface. Hence, the surface exhibits hydrophobic nature and inhibits the growth of bacterial flora along with the elimination of dead bacterial cells. The fabricated surface exhibits a water contact angle (WCA) of 158.7 ± 0.17°. Specifically, we tested the fabricated material against both the Gram-positive and Gram-negative bacterial models. The antibacterial activity of the fabricated surface is evident from the growth inhibition percentage of bacterial strains of Escherichia coli (72.30 ± 0.60%) and Bacillus subtilis (48.30 ± 1.71%). The micrographs obtained from scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) of the treated cells show the damaged cellular structures of the bacteria, which is strong evidence of successful antibacterial action. The antibacterial effect can be attributed to the synergistic mechano-chemo mode of action involving mechanical disruption of the bacterial cell wall by the nanoprotrusions present on the Cu dendrites along with the chemical interaction of the Ag nanodots with vital intracellular components.

Antimicrobial Efficacy and Spectrum of Phosphorous-Fluorine Co-Doped TiO2 Nanoparticles on the Foodborne Pathogenic Bacteria Campylobacter jejuni, Salmonella Typhimurium, Enterohaemorrhagic E. coli, Yersinia enterocolitica, Shewanella putrefaciens, Listeria monocytogenes and Staphylococcus aureus

Contamination of meats and meat products with foodborne pathogenic bacteria raises serious safety issues in the food industry. The antibacterial activities of phosphorous-fluorine co-doped TiO2 nanoparticles (PF-TiO2) were investigated against seven foodborne pathogenic bacteria: Campylobacter jejuni, Salmonella Typhimurium, Enterohaemorrhagic E. coli, Yersinia enterocolitica, Shewanella putrefaciens, Listeria monocytogenes and Staphylococcus aureus. PF-TiO2 NPs were synthesized hydrothermally at 250 °C for 1, 3, 6 or 12 h, and then tested at three different concentrations (500 μg/mL, 100 μg/mL, 20 μg/mL) for the inactivation of foodborne bacteria under UVA irradiation, daylight exposure or dark conditions. The antibacterial efficacies were compared after 30 min of exposure to light. Distinct differences in the antibacterial activities of the PF-TiO2 NPs, and the susceptibilities of tested foodborne pathogenic bacterium species were found. PF-TiO2/3 h and PF-TiO2/6 h showed the highest antibacterial activity by decreasing the living bacterial cell number from ~106 by ~5 log (L. monocytogenes), ~4 log (EHEC), ~3 log (Y. enterolcolitca, S. putrefaciens) and ~2.5 log (S. aureus), along with complete eradication of C. jejuni and S. Typhimurium. Efficacy of PF-TiO2/1 h and PF-TiO2/12 h NPs was lower, typically causing a ~2-4 log decrease in colony forming units depending on the tested bacterium while the effect of PF-TiO2/0 h was comparable to P25 TiO2, a commercial TiO2 with high photocatalytic activity. Our results show that PF-co-doping of TiO2 NPs enhanced the antibacterial action against foodborne pathogenic bacteria and are potential candidates for use in the food industry as active surface components, potentially contributing to the production of meats that are safe for consumption.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

Future antiviral polymers by plasma processing

Coronavirus disease 2019 (COVID-19) is largely threatening global public health, social stability, and economy. Efforts of the scientific community are turning to this global crisis and should present future preventative measures. With recent trends in polymer science that use plasma to activate and enhance the functionalities of polymer surfaces by surface etching, surface grafting, coating and activation combined with recent advances in understanding polymer-virus interactions at the nanoscale, it is promising to employ advanced plasma processing for smart antiviral applications. This trend article highlights the innovative and emerging directions and approaches in plasma-based surface engineering to create antiviral polymers. After introducing the unique features of plasma processing of polymers, novel plasma strategies that can be applied to engineer polymers with antiviral properties are presented and critically evaluated. The challenges and future perspectives of exploiting the unique plasma-specific effects to engineer smart polymers with virus-capture, virus-detection, virus-repelling, and/or virus-inactivation functionalities for biomedical applications are analysed and discussed.

Photoactive antimicrobial coating based on a PEDOT-fullerene C60 polymeric dyad

A photostable and photodynamic antimicrobial surface was successfully obtained and applied to photoinactivate microorganisms. This approach was based on the synthesis of a fullerene C60 derivative (EDOT-C60) where fullerene C60 is covalently linked to 3,4-ethylenedioxythiophene (EDOT) through a 1,3-dipolar cycloaddition reaction. This dual-functional monomer bears an EDOT center connected via an alkyl chain to a fullerene C60 moiety. In this structure, EDOT acts as an electropolymerizable unit that allows the film formation over conducting substrates, while fullerene C60 performs the photodynamic antimicrobial activity. Electrochemical polymerization of EDOT was used to obtain stable and photodynamic polymeric films (PEDOT-C60) in a controllable procedure. Cyclic voltammetry and UV-visible spectroscopy studies showed that the fullerene C60 units were not altered during the electropolymerization process, obtaining surfaces with high fullerene content. Photobleaching measurements demonstrated that the electropolymerized films were highly photostable. Moreover, photodynamic properties of PEDOT-C60 were compared with fullerene C60 and showed that electrodeposited films were able to generate reactive oxygen species (ROS) through the two photomechanisms, producing singlet molecular oxygen (type II) and superoxide radical anion (type I). All studies demonstrated that fullerene C60 moieties covalently attached to the polymeric matrix mainly conserve the photodynamic characteristics. Hence, photodynamic action sensitized by PEDOT-C60 was assessed in vitro against Staphylococcus aureus. The photosensitized inactivation by the electropolymerized films on bacteria suspensions produced >99.9% reduction in S. aureus survival. Fluorescence microscopy experiments with S. aureus adhered to the PEDOT-C60 surface showed a complete microbe annihilation. Also, the eradication of biofilms formed on PEDOT-C60 surfaces resulted in a photokilling >99.9% after visible light irradiation. Our results demonstrated that these antimicrobial photodynamic polymeric films are a promising and versatile platform to photoinactivate microorganisms and to obtain photostable self-sterilizing surfaces.

Charge transfer channels of silver @ cuprous oxide heterostructure core-shell nanoparticles strengthen high photocatalytic antibacterial activity

Marine biological fouling has always been a hot research topic. In this study, silver @ cuprous oxide (Ag@Cu₂O) core-shell nanoparticles were synthesized via in-situ synthesis method and developed an outstanding antibacterial activity. The bacteriostasis efficiency of Ag@Cu₂O reached to 99% and 98% against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. The minimum inhibitory concentration of Ag@Cu₂O decreased from 113.6 μg/mL to 56.8 μg/mL compared with Cu₂O. Ag@Cu₂O had better antibacterial activity than Cu₂O with lower content of Cu₂O and was more environment friendly. The heterostructure formed at the interface between Ag and Cu₂O promoted the separation and diffusion of photogenerated electron-hole pairs through the charge transfer channel and promoted the generation of reactive oxygen species. The outstanding antibacterial activity of Ag@Cu₂O was strongly depended on the generation of the reactive oxygen species. Density functional theory and finite element method calculations demonstrated that the structure of core-shell improved photocatalytic efficiency. Additionally, synergetic effect of released Ag⁺ and Cu²⁺ also enhanced the bacteriostasis rate and the long-term antifouling performance in 60 days. Hence, the synthesized core-shell Ag@Cu₂O can be applied as novel antifoulants in the marine field.

An intrinsically bioactive hydrogel with on-demand drug release behaviors for diabetic wound healing

Prolonged, intense inflammation and excessive oxidative stress hinder diabetic wounds from healing normally, leading to disorders downstream including the postponement of re-epithelialization and extracellular matrix (ECM) formation. Herein, we report a hyaluronic acid (HA) and chitosan based hydrogel (OHA-CMC) with inherent antibacterial and hemostatic activities fabricated via Schiff base reaction. By encapsulating nanotechnologically-modified curcumin (CNP) and epidermal growth factor (EGF) into the hydrogel, OHA-CMC/CNP/EGF exhibited extraordinary antioxidant, anti-inflammatory, and migration-promoting effects in vitro. Meanwhile, OHA-CMC/CNP/EGF presented on-demand drug release in synchrony with the phases of the wound healing process. Specifically, curcumin was rapidly and constantly released to alleviate inflammation and oxidative stress in the early phase of wound healing, while a more gradual and sustained release of EGF supported late proliferation and ECM remodeling. In a diabetic full-thickness skin defect model, OHA-CMC/CNP/EGF dramatically improved wound healing with ideal re-epithelialization, granulation tissue formation, and skin appendage regeneration, highlighting the enormous therapeutic potential this biomaterial holds as a diabetic wound dressing.

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OHA-CMC hydrogel showed excellent inherent antibacterial and hemostatic activities.

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OHA-CMC co-delivered curcumin and EGF with on-demand drug release that met the repair requirements of each healing stage.

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OHA-CMC/CNP/EGF showed potent antioxidant and anti-inflammation activities, and was capable of promoting cell migration.

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OHA-CMC/CNP/EGF significantly accelerated diabetic wound healing.

Biomimetic surface coatings for marine antifouling: Natural antifoulants, synthetic polymers and surface microtopography

Marine biofouling is a ubiquitous problem that accompanies human marine activities and marine industries. It exerts detrimental impacts on the economy, environment, ecology, and safety. Traditionally, mainstream approaches utilize metal ions to prevent biological contamination, but this also leads to environmental pollution and damage to the ecosystem. Efficient and environmentally friendly coatings are urgently needed to prevent marine devices from biofouling. Since nature is always the best teacher for humans, it offers us delightful thoughts on the research and development of high-efficiency, broad-spectrum and eco-friendly antifouling coatings. In this work, we focus on the research frontier of marine antifouling coatings from a bionic perspective. Enlightened by three distinctive dimensions of bionics: chemical molecule bionic, physiological mechanism bionic, and physical structure bionic, the research status of three main bioinspired strategies, which are natural antifoulants, bioinspired polymeric antifouling coatings, and biomimetic surface microtopographies, respectively, are demonstrated. The antifouling mechanisms are further interpreted based on biomimetic comprehension. The main fabrication methods and antifouling performances of these coatings are presented along with their advantages and drawbacks. Finally, the challenges are summarized, and future research prospects are proposed. It is believed that biomimetic antifouling strategies will contribute to the development of nontoxic antifouling techniques with exceptional repellency and stability.