Antimicrobial Coatings Research Articles

ZnO nanolayer on polypropylene fabrics: a highly effective antimicrobial coating against pathogenic bioaerosols

Abstract Antimicrobial coatings offer a promising solution for enhancing the efficacy of materials used to fabricate protective equipment for healthcare personnel. Given the rapid spread of respiratory diseases caused by pathogenic bioaerosols, our study delves into probing the antimicrobial properties of a sputtered ZnO nanolayer deposited onto polypropylene fabrics earmarked for the production of respiratory protective gear such as facemasks. A comprehensive methodology was developed to assess the immediate antimicrobial effect of the zinc oxide nanolayer against bioaerosols laden with four DNA or RNA viral surrogates and eight aerobic and anaerobic bacterial species. Additionally, its antimicrobial efficacy was measured over time across contact durations ranging from 0.5 to 24 h. The ZnO nanolayer exhibited an immediate reduction in infectivity of approximately 40% for RNA viruses, whereas only an 11% reduction was noted for the DNA virus. Remarkably, the infectivity of RNA viruses was totally eradicated after 12 h of contact with the ZnO nanolayer. In the case of anaerobic bacteria-laden bioaerosols, inhibition ratios ranged from 58% to 97% across various anaerobic strains, while aerobic bacteria aerosols demonstrated inhibition ranging from 26% to 74%. Notably, after 24 h of direct contact between bacteria and ZnO nanolayer, a substantial viability inhibition of most strains (80%–90%) was achieved. These findings underscore the potential of ZnO nanolayer for diverse biomedical purposes, encompassing personal protective equipment and other applications such as air purification systems.

Enhanced surface antimicrobial, biocompatible and mechanical properties of 3D printed titanium alloys by electrophoretic deposition of chitosan/ZnO

In this study, to address the susceptibility of 3D-printed titanium implants to bacterial infection, we propose to form a chitosan/ZnO composite coating by electrophoretic deposition to enhance its antimicrobial, biocompatible, and mechanical properties. The surface morphology of the composite coating is relatively flat, showing good hydrophilicity and coating adhesion, and the corrosion current density is significantly lower than that of the untreated titanium alloy. According to the results of the study, the composite coatings containing more than 0.1g of ZnO (Z2, Z3, Z4 groups) showed excellent antibacterial effects against Staphylococcus aureus and Escherichia coli, with antibacterial rates of more than 95%, and the medium-concentration ZnO coatings (Z2 group) showed good cellular activity, with cell viability rates of more than 80%. In contrast, the high-concentration ZnO coatings (Z3, Z4 groups) showed a certain degree of cytotoxicity. The inherent film-forming property of the composite coating enabled the cells to adhere well to the coating surface. It was found through SBF body fluid immersion that Zn²⁺ can increase the rate of hydroxyapatite precipitation and enhance bioactivity. These results emphasize the importance of precise control of the ZnO content in the improved antimicrobial and biocompatible chitosan-ZnO composite coatings to ensure excellent antimicrobial properties and necessary biocompatibility.

Transformation of agro industrial waste from peanut hulls as an innovative source for sustainable cellulosic dyeing and antimicrobial finish

Transformation of agro industrial waste from peanut hulls as an innovative source for sustainable cellulosic dyeing and antimicrobial finish

Antimicrobial Coatings Based on a Photoreactive (Meth)acrylate Syrup and Ferulic Acid-The Effectiveness against Staphylococcus epidermidis.

A novel photopolymerizable (meth)acrylate oligomer syrup modified with ferulic acid (FA) was verified as an antimicrobial coating binder against a biofilm of Staphylococcus epidermidis. A solution-free UV-LED-initiated photopolymerization process of aliphatic (meth)acrylates and styrene was performed to prepare the oligomer syrup. The influence of ferulic acid on the UV crosslinking process of the varnish coatings (kinetic studies using photo-DSC) as well as their chemical structure (FTIR) and mechanical (adhesion, hardness), optical (gloss, DOI parameter), and antibacterial properties against S. epidermidis were investigated. The photo-DSC results revealed that FA has a positive effect on reducing the early occurrence of slowing processes and has a favorable effect on the monomer conversion increment. It turned out, unexpectedly, that the more FA in the coating, the greater its adhesion to a glass substrate and hardness. The coating containing 0.9 wt. part of FA exhibited excellent antimicrobial properties against S. epidermidis, i.e., the bacterial number after 24 h was only 1.98 log CFU/mL. All the coatings showed relatively high hardness, gloss (>80 G.U.), and DOI parameter values (30-50 a.u.).

Layer-by-layer self-assembly coatings on strontium titanate nanotubes with antimicrobial and anti-inflammatory properties to prevent implant-related infections

One way to effectively address endophyte infection and loosening is the creation of multifunctional coatings that combine anti-inflammatory, antibacterial, and vascularized osteogenesis. This study started with the preparation of strontium-doped titanium dioxide nanotubes (STN) on the titanium surface. Next, tannic acid (TA), gentamicin sulfate (GS), and pluronic F127 (PF127) were successfully loaded into the STN via layer-by-layer self-assembly, resulting in the STN@TA-GS/PF composite coatings. The findings demonstrated the excellent hydrophilicity and bioactivity of the STN@TA-GS/PF coating. STN@TA-GS/PF inhibited E. coli and S. aureus in vitro to a degree of roughly 80.95 % and 92.45 %, respectively. Cellular investigations revealed that on the STN@TA-GS/PF surface, the immune-system-related RAW264.7, the vasculogenic HUVEC, and the osteogenic MC3T3-E1 showed good adhesion and proliferation activities. STN@TA-GS/PF may influence RAW264.7 polarization toward the M2-type and encourage MC3T3-E1 differentiation toward osteogenesis at the molecular level. Meanwhile, the STN@TA-GS/PF coating achieved effective removal of ROS within HUVEC and significantly promoted angiogenesis. In both infected and non-infected bone defect models, the STN@TA-GS/PF material demonstrated strong anti-inflammatory, antibacterial, and vascularization-promoting osteogenesis properties. In addition, STN@TA-GS/PF had good hemocompatibility and biosafety. The three-step process used in this study to modify the titanium surface for several purposes gave rise to a novel concept for the clinical design of antimicrobial coatings with immunomodulatory properties.

Antimicrobial finish of bioscoured cotton fabric using immobilized cutinase

Antimicrobial finish of bioscoured cotton fabric using immobilized cutinase

Copper I-II-containing composites and coatings with high and broad-spectrum antimicrobial activity

Recently, antimicrobial surface coatings have emerged as an effective strategy to mitigate microbial contamination and disease transmission. The application of cuprous (I) oxide (Cu2O) and copper (II) pyrithione (CPT) in antimicrobial surfaces faces several challenges such as deep color, weak stability, limited functionality, and poor dispersion in coatings. These challenges complicate the design of novel copper-based antimicrobial agents. In this study, high-purity CPT was synthesized innovatively using Cu2O as a copper source, differing from traditional methods. Following this approach, diatomaceous earth/cuprous oxide/copper pyrithione (DME/Cu2O/CPT) composites with enhanced antimicrobial activity and a lighter color than Cu2O and CPT were prepared by adjusting the SPT dosage. Notably, in DME/Cu2O/CPT composites, Cu2O existed as nanoscale fragments adhering to the surfaces of CPT. Furthermore, coatings made from composites and latex paint exhibited a lighter color difference, higher stability, and exceptional antimicrobial activity against pathogens such as S. aureus, E. coli, P. aeruginosa, C. albicans, and human enterovirus 71. The DME/Cu2O/CPT composites displayed high, stable, and broad-spectrum antimicrobial efficacy, attributing to the synergistic enhancement effects of released Cu+ and Cu2+. Consequently, this study introduced a simple and scalable method for preparing DME/Cu2O/CPT composites, serving as a coating additive with broad-spectrum antimicrobial activity and long-term stability for various solid surfaces.

Chitosan-puerarin composite hydrogel with magnetic enhanced photothermal properties as sustained antimicrobial coatings for beef preservation

The bactericidal properties of traditional food coatings mostly depend on the amount of fungicides present, which reduces the sustainability of food packaging. Herein, we proposed a magnetic field to precisely modulate the near-infrared (NIR) absorption activity to enhance antimicrobial coatings sustainability. Inspired by the typical grinding procedure, the assembly of CP/Fe3O4@TA nanofiber hydrogel was proposed as the coating, applying mechanical force and encouraging the collision of effective molecules of puerarin (PUE), chitosan (CS), and Fe3O4@TA NFs. This hydrogel design offers precise control over the physical and chemical properties, including appearance, viscoelasticity, and rheology. Particularly, significant changes in photothermal performance were observed as a result of magnetic regulation of NIR absorption activity. As a result, the CP/Fe3O4@TA coatings achieve effective bacteria killing performance under NIR irradiation, magnetocaloric effect, boric acid adsorption, and aggregation interference. Finally, the hydrogel coating was applied to the beef surface and serves as an effective barrier against the growth of pathogenic bacteria, thereby preserving the freshness and tenderness of the beef. The finding from this work is expected to open up a new way in active nano hydrogel coating for food preservation.

Alternating current electrophoretic deposition of maleic anhydride modified chitosan on Ti implants to combat biofilm formation

Chitosan, a cationic biopolymer, holds promise for diverse applications, including dental implant surface modification, due to its biocompatibility, non-toxicity, and antimicrobial properties. However, its limited water solubility at neutral pH complicates its use in alternating current electrophoretic deposition (AC-EPD). This study explores the novel use of water-soluble maleic anhydride modified chitosan (MA-CS) in AC-EPD to create antimicrobial coatings on titanium substrates. We optimize AC-EPD parameters for uniform MA-CS coatings and compare AC-EPD with conventional dipping. AC-EPD MA-CS coatings exhibit enhanced surface topography and amphiphilic, isotropic behavior, while other MA-CS-treated samples display anisotropic, monopolar behavior. We assess AC-EPD MA-CS-coated metallic substrates' biofunctionality, focusing on protein adsorption and antimicrobial properties. These coatings effectively adsorb proteins through diverse interactions with bovine serum albumin. To combat peri-implant diseases, we evaluate antimicrobial activity against oral bacterial communities, showing that AC-EPD successfully concentrates water-soluble MA-CS on titanium without compromising its biological performance. In summary, this study highlights AC-EPD as a versatile, efficient method for depositing polysaccharides in biomedical applications. It offers the potential for enhancing dental implant surface antimicrobial properties, addressing peri-implant diseases, and promoting overall dental health.

Versatile Fabrication of Biocompatible Antimicrobial Materials Enabled by Cationic Peptide Bundles.

Antimicrobial peptides (AMPs) are expected to be an alternative promising solution to the global public health problem of antibiotic resistance due to their unique antimicrobial mechanism. However, extensive efforts are still needed to improve the shortcomings of traditional AMPs, such as rapid proteolysis, hemolysis, slow response, toxicity, etc., by exploring AMP-based new antimicrobial strategies. Here, we develop cationic peptide bundles into novel antimicrobial architectures that can rapidly kill multiple types of bacteria including drug-resistant bacteria. Remarkably, cationic peptide bundles can be used as polymerization units to cross-link with other polymers through simple two-component polymerization to produce diverse antimicrobial materials. For the proof of concept, three materials were fabricated and investigated, including an antimicrobial hydrogel that can significantly accelerate the healing of infected wounds, a multifunctional antimicrobial bioadhesive that shows promise in antimicrobial coatings for medical devices, and a photo-cross-linked antimicrobial gelatin hydrogel with broad application potential. The integration of antimicrobial units into the materials' backbone endows their biocompatibility. Cationic peptide bundles not only represent a new antimicrobial strategy but also provide a versatile and promising processing method to create diversified, multifunctional, and biocompatible antimicrobial materials.

Fabrication of smart nanogel based on carrageenan and green coffee extract as a long-term antifouling agent to improve biofilm prevention in food production

This study investigates the extract of the bioactive compounds from green coffee extract (GCE) and the loading of two different concentrations of GCE (1% and 2%) onto carrageenan nanogels (CAR NGs) to compare their antibacterial and antibiofilm effects with unloaded nanogels (NGs). The bioactive compounds of GCE were characterized using GC–MS analysis. The GCE1 and GCE2 were successfully deposited onto the surface of CAR NGs. The antibacterial and antibiofilm potential of prepared NGs were conducted against some foodborne pathogens (E. coli O157, Salmonella enterica, Staphylococcus aureus, and Listeria monocytogenes). The results of GC–MS analysis indicated that there were identified 16 bioactive compounds in GCE, including caffeine (36.27%), Dodemorph (9.04%), and D-Glycero-d-ido-heptose (2.44%), contributing to its antimicrobial properties. The antibacterial coatings demonstrated a notable antimicrobial effect, showing zone of inhibition (ZOI) diameters of up to 37 mm for GCE2 loaded CAR NGs. The minimum inhibitory concentration (MIC) values for GCE2 loaded CAR NGs were 80 ppm for E. coli O157, and 120 ppm for S. enterica, S. aureus, and L. monocytogenes, achieving complete bacterial inactivation within 10–15 min of exposure. Both GCE1 and GCE2 loaded CAR NGs significantly reduced biofilm cell densities on stainless steel (SS) materials for E. coli O157, S. enterica, S. aureus, and L. monocytogenes, with reductions ranging from 60% to 95%. Specifically, biofilm densities were reduced by up to 95% for E. coli O157, 89% for S. enterica, 85% for S. aureus, and 80% for L. monocytogenes. Results of the toxicity evaluation indicated that the NGs were non-toxic and biocompatible, with predicted EC50 values proved their biocompatibility and safety. These results recommended that GCE loaded CAR NGs are promising as natural antimicrobial agents for enhancing food safety and extending shelf life. Further, the study concluded that incorporating GCE into CAR NGs is an effective strategy for developing sustainable antimicrobial coatings for the food industry and manufacturing.

Development and evaluation of antimicrobial PVC-grafted polymer for enhanced paint applications.

Demand for antimicrobial paints is increasing globally due to the rising need to control microbial growth and reduce infection risks in various environments. This increased demand underscores the crucial role of advanced antimicrobial coatings in promoting health and safety. In this context, an innovative poly(vinyl chloride) (PVC) grafted polymer with 1-(2-aminoethyl piperazine) (AEP) was prepared and studied in detail. In this study, the prepared polymer was characterized using FTIR and NMR spectroscopy to examine the polymer's chemical structure and employed TGA and DSC for thermal stability analysis. The antimicrobial activity of the grafted polymer was evaluated through the agar diffusion method and showed a significant inhibition zone of 21.6 mm for S. aureus, 16.3 mm for E. coli, 18.3 mm for M. smegmatis, and 20.3 mm for C. albicans at a lowest concentration of 12.5 μg mL-1. To assess surface characteristics, the PVC-g-AEP polymer was mixed with commercial paint and applied to a glass surface. SEM and AFM analysis showed a 5-times increase in porosity while maintaining visual aesthetics. Additionally, the paint displayed excellent stability against water, retaining around 90% of its antimicrobial activity even after 15 washes. This advanced polymer not only exhibits superior antimicrobial properties but also improves paint durability, setting a new benchmark for high-performance antimicrobial coatings and significantly advancing protective paint technology.

Instant Disinfecting Face Masks Utilizing Electroporation Powered by Respiration‐Driven Triboelectric Nanogenerators

AbstractWearing face masks is an effective non‐pharmaceutical strategy to inhibit the transmission of airborne diseases. Nonetheless, most commercial face masks lack disinfecting capabilities, posing risks of secondary transmission, while those with antimicrobial coatings are incapable of instant pathogen inactivation. Herein, a proof‐of‐concept instant disinfecting face mask is demonstrated consisting of a Cu(OH)2‐nanowire electroporation filter powered by a respiration‐driven triboelectric nanogenerator (R‐TENG). The R‐TENG comprises electrospun polyvinyl alcohol (PVA) and polyvinylidene fluoride (PVDF) membranes. A dome‐shaped PVA membrane is specifically designed to maximize the effective contact area. Coupling the novel dome‐shape design with maximized β‐phase crystallites of PVDF, the enhanced R‐TENG generates an open‐circuit voltage of 120 V under the normal breathing rate of an adult, resulting in an amplified electric field of 19 MV m−1 at the nanowire tips of the electroporation filter. Under this high localized electric field, effective inactivation of bacteria (>99.9%) is achieved via a synergy of electroporation and physical penetration. Conversely, when the R‐TENG is disconnected, only partial inactivation (90%–99%) via physical penetration is realized. For the first time, it shows that R‐TENG powered electroporation is a viable solution to achieve instant, effective disinfection, paving the way for next‐generation face masks.

Biocide-encapsulated core–shell polymer microspheres: A novel approach for preparing long-lasting antimicrobial coatings

Antimicrobial coatings play a crucial role in combating pathogenic microorganisms. However, developing long-lasting antimicrobial coatings presents substantial challenges. In this study, we developed a robust method for fabricating durable antimicrobial coatings using crosslinked, biocide-encapsulated core–shell polymer microspheres. These microspheres were prepared by emulsion polymerization, facilitating simultaneous synthesis and biocide loading. Designed with a hydrophilic shell and a hydrophobic core, the microspheres predominantly stored the hydrophobic biocides within the core, thus reducing the biocide concentration at the shell. This design, which is governed by Fickian diffusion, substantially slowed the rate of biocide migration from the shell to the external environment, thereby enhancing the coating's antimicrobial longevity. The synthetic process for these biocide-encapsulated microspheres was optimized to encapsulate biocides with a Log P range of 1–3, achieving an encapsulation efficiency exceeding 85 % for all tested biocides. Specifically, microspheres containing N-butyl-1,2-benzisothiazolin-3-one (BBIT) were used to develop an antimicrobial coating. The coating can be applied to various substrates, including glass, metal, wood, ceramics, and plastics. It exhibits excellent hardness, adhesion, mechanical strength, and solvent resistance on these surfaces. Antimicrobial tests and release analyses demonstrated that the coating maintains high biological activity for at least 10 months, effectively inhibiting bacterial and fungal growth. The release behavior of the coating adhered to the Peppas–Sahlin model, with diffusion as the predominant mechanism. The model predicted an antimicrobial retention rate of over 66 % after 1 year, confirming its sustained antimicrobial effectiveness.

Construction of biomass-based flame-retardant, antimicrobial and hydrophobic wood coatings with POSS organic-inorganic nanoparticles

The present study utilizes chitosan (CS) and phytic acid (PA) as natural polyelectrolytes, while incorporating Polyhedral Oligomeric Silsesquioxane (POSS), an organic–inorganic hybrid Si-O-Si cage structure, to create a flame retardant, antimicrobial, and hydrophobic coating for wood materials using the layer-by-layer self-assembly method. The POSS flame retardant bisDOPO-NH2-POSS was synthesized by combining 9,10-dihydro-9-oxa-10-phosphaphenathrene (DOPO) with octaminopropyl silsesquioxane (OA-POSS). Subsequently, AgNPs were incorporated into the cage structure of bisDOPO-NH2-POSS through in-situ reduction to fabricate Ag@bisDOPO-NH2-POSS for enhanced antimicrobial efficacy. The CS/PA coating was deposited using the LBL method, which resulted in the formation of a dense char layer during combustion due to both the presence of an inorganic Si-O-Si physical barrier and the synergistic effect of P-N-Si. As a result, self-extinguishing behavior was observed during vertical burning tests, and there was an increase in the limiting oxygen index value to 30.9%. Moreover, by incorporating chitosan, Ag@bisDOPO-NH2-POSS exhibited inhibitory effects against mold such as Aspergillus niger and Lasiodiplodia. The heat release rate (HRR) was reduced by 42.3%, while the total heat release (THR) decreased by 44.4%. The modified wood demonstrates exceptional water repellency, characterized by a static contact angle exceeding 90°. Additionally, the multifunctional coating shows remarkable resilience as it withstands 100 abrasion cycles without compromising its hydrophobic properties. This study presents a sustainable approach to developing a bio-based coating for wood materials that is flame retardant, hydrophobic, and antimicrobial, thereby expanding the potential applications of wood in construction and furniture.

Photothermal Antibacterial and Osteoinductive Polypyrrole@Cu Implants for Biological Tissue Replacement.

The treatment of bone defects caused by disease or accidents through the use of implants presents significant clinical challenges. After clinical implantation, these materials attract and accumulate bacteria and hinder the integration of the implant with bone tissue due to the lack of osteoinductive properties, both of which can cause postoperative infection and even lead to the eventual failure of the operation. This work successfully prepared a novel biomaterial coating with multiple antibacterial mechanisms for potent and durable and osteoinductive biological tissue replacement by pulsed PED (electrochemical deposition). By effectively regulating PPy (polypyrrole), the uniform composite coating achieved sound physiological stability. Furthermore, the photothermal analysis showcased exceptional potent photothermal antibacterial activity. The antibacterial assessments revealed a bacterial eradication rate of 100% for the PPy@Cu/PD composite coating following a 24 h incubation. Upon the introduction of NIR (near-infrared) irradiation, the combined effects of multiple antibacterial mechanisms led to bacterial reduction rates of 99% for E. coli and 98% for S. aureus after a 6 h incubation. Additionally, the successful promotion of osteoblast proliferation was confirmed through the application of the osteoinductive drug PD (pamidronate disodium) on the composite coating's surface. Therefore, the antimicrobial Ti-based coatings with osteoinductive properties and potent and durable antibacterial properties could serve as ideal bone implants.

Green synthesis of Fe[sbnd]Ni[sbnd]Sn trimetallic oxides from Moringa oleifera for photocatalytic degradation of Reactive Red 6B dye

The nanocomposite FeNiSn trimetallic oxides were synthesized using an aqueous Moringa Oleifera leaf extract. The prepared nanocomposite was analyzed using SEM, FTIR, XRD, N2 adsorption-desorption, Zeta potential, and UV–vis analysis. A common Azo dye named Reactive Red 6B (RR-6B), widely applied in the dyeing industry and causing environmental pollution, was selected to examine the photodegradation of FeNiSn trimetallic oxides nanocomposite under sunlight irradiation, and it was shown that this dye could be successfully degraded by prepared nanocomposite. Effects of parameters such as inorganic salt concentration, H2O2 concentration, contact time, pH, and impact of different concentrations of catalyst and dye were examined to find out degradation conditions. This prepared nanocomposite was applied for the photodegradation of RR-6B dye, and 95 % degradation efficiency was obtained at pH 4, 10 mg of catalyst concentration, 10 ppm of dye concentration, and contact time of 2 h. Degradation kinetics were carried out using Langmuir-Hinshelwood and first-order reaction models. These results showed a facile technique for forming nanocomposite to efficiently degrade organic contaminants from wastewater, which directly impacts industrial wastewater treatment. The antibacterial activity was performed using the Time assay kill method for Gram-positive S. aureus and Gram-negative E. coli bacteria. The results of antibacterial activity showed an inhibition effect on bacterial growth by trimetallic oxides NPs, suggesting their potential use in antimicrobial coatings and materials. These findings underscore the practical applications of our research, demonstrating its relevance and potential impact in real-world scenarios.

Benefits of Core-Shell Particles over Single-Metal Coatings: Mechanical and Chemical Exposure and Antimicrobial Efficacy.

One of the greatest challenges worldwide is containing the spread of problematic microorganisms. A promising approach is the use of antimicrobial coatings (AMCs). The antimicrobial potential of certain metals, including copper and zinc, has already been verified. In this study, polyethylene terephthalate and aluminum (PET-Al) foils were coated with copper, zinc, and a combination of these two metals, known as core-shell particles, respectively. The resistance of the three different types of coatings to mechanical and chemical exposure was evaluated in various ways. Further, the bacteria Staphylococcus aureus and the bacteriophage ϕ6 were used to assess the antimicrobial efficacy of the coatings. The best efficacy was achieved with the pure copper coating, which was not convincing in the abrasion tests. The result was a considerable loss of copper particles on the surfaces and reduced effectiveness against the microorganisms. The core-shell particles demonstrated better adhesion to the surfaces after abrasion tests and against most chemical agents. In addition, the antimicrobial efficiency remained more stable after the washability treatment. Thus, the core-shell particles had several benefits over the pure copper and zinc coatings. In addition, the best core-shell loading for durability and efficacy was determined in this study.

Cationic homopolypeptides: A versatile tool to design multifunctional antimicrobial nanocoatings

Postoperative infections are the most common complications faced by surgeons after implant surgery. To address this issue, an emerging and promising approach is to develop antimicrobial coatings using antibiotic substitutes. We investigated the use of polycationic homopolypeptides in a layer-by-layer coating combined with hyaluronic acid (HA) to produce an effective antimicrobial shield. The three peptide-based polycations used to make the coatings, poly(l-arginine) (PAR), poly(l-lysine), and poly(l-ornithine), provided an efficient antibacterial barrier by a contact-killing mechanism against Gram-positive, Gram-negative, and antibiotic-resistant bacteria. Moreover, this activity was higher for homopolypeptides containing 30 amino-acid residues per polycation chain, emphasizing the impact of the polycation chain length and its mobility in the coatings to deploy its contact-killing antimicrobial properties. However, the PAR-containing coating emerged as the best candidate among the three selected polycations, as it promoted cell adhesion and epithelial monolayer formation. It also stimulated nitric oxide production in endothelial cells, thereby facilitating angiogenesis and subsequent tissue regeneration. More interestingly, bacteria did not develop a resistance to PAR and (PAR/HA) also inhibited the proliferation of eukaryotic pathogens, such as yeasts. Furthermore, in vivo investigations on a (PAR/HA)-coated hernia mesh implanted on a rabbit model confirmed that the coating had antibacterial properties without causing chronic inflammation. These impressive synergistic activities highlight the strong potential of PAR/HA coatings as a key tool in combating bacteria, including those resistant to conventional antibiotics and associated to medical devices.

Photodynamic coatings kill bacteria on near-patient surfaces in intensive care units with low light intensities

Surfaces in close proximity to patients within hospitals may cause healthcare-associated infections. These surfaces are repositories for pathogens facilitating their transmission among staff and patients. Regular cleaning and disinfection of these surfaces provides only a temporary elimination of pathogens with inevitable recontamination. Antimicrobial coatings (AMCs) of such surfaces may additionally reduce the risk of pathogen transmissions. To evaluate the efficacy of a standard and a novel photodynamic AMC, even at very low light intensities, in a field study conducted in two ICUs at our university hospital. The microbial burden was determined on three coatings: standard photodynamic AMC (A), a novel photodynamic AMC (B), and an inactive AMC as control (C). The control coating C was identical to standard coating A, but it contained no photosensitizer. During a three-month period, 699 samples were collected from identical surfaces using eSwab and were analysed (cfu/cm2). Mean values of all surfaces covered with control coating (C) showed a microbial burden of 5.5 ± 14.8cfu/cm2. Photodynamic AMC showed significantly lower mean value of 1.6 ± 4.6cfu/cm2 (coating A; P < 0.001) and 2.7 ± 9.6 (coating B; P < 0.001). When considering a benchmark of 2.5cfu/cm2, the relative risk for higher microbial counts was reduced by 52% (coating A) or 40% (coating B), respectively. Both photodynamic AMCs offer a substantial, permanent risk reduction of microbial counts on near-patient surfaces in ICUs with low light intensities.