Polymeric Coatings with Antimicrobial Activity: A Short Review

Guanidine Derivatives Leverage the Antibacterial Performance of Bio-Based Polyamide PA56 Fibres

Bacterial damage has significantly impacted humanity, prompting the control of harmful microorganisms and infectious diseases. In this study, antibacterial bio-based PA56 fibres were prepared with high-speed spinning using ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA) as the compatibiliser and polypentamethylene guanidine sulphate (PPGS) as the antibacterial agent. The effects of PPGS content on the properties of PA56 draw-textured yarns (DTYs) were investigated. The compatibility between PPGS and PA greatly improved with EMA incorporation. Compared with PA56 fibres, the elongation at break of the sample containing 2.0 wt% EMA and PPGS increased by 25.93%. The inhibition rates of the fibres with 1.0 wt% PPGS against Escherichia coli and Staphylococcus aureus reached over 99.99%. Samples were easily coloured with dyes, exhibiting good colour fastness, regardless of the EMA content. However, the antibacterial performances of dyed DTYs decreased to varying degrees. the inhibition rates of samples of 0.5wt% addition of PPGS against E. coli were reduced from 99.99% to 28.50% and 25.36% after dyeing with Acid Blue 80 and Dispersible Blue 2BLN, respectively. The EMA-modified fibres exhibited the best antibacterial activity after dyeing with neutral gray 2BL. These findings are expected to promote the wider use of biobased PA56 in practical applications that require antibacterial performance and to guide the dyeing process of antimicrobial fibres.

Quorum sensing inhibiting dihydropyrrol-2-ones embedded polymer/graphene oxide nanocomposite waterborne antimicrobial coatings

With increasing antibiotic resistance and hospital acquired microbial infections, there has been a growing interest to explore alternate antimicrobial approaches. This is particularly challenging when aiming to protect surfaces over a large area to avoid contact mediated infection transmission. Quorum sensing (QS) inhibition has emerged as an alternate antimicrobial approach overcoming evolutionary stress driven resistance observed in antibiotic treatment. However, specific surface orientation requirements and limited work on delivery of small molecule QS inhibiting compounds have limited their widespread applicability certainly when it comes to coating large surfaces. Here, we report antimicrobial nanocomposite coatings overcoming the dependence on molecular orientation of QS inhibiting dihydropyrrol-2-ones (DHP) analogues and release small molecule analogues. In a systematic study, we developed poly(styrene-stat-n-butyl acrylate)/graphene oxide (GO)/DHP analogue nanocomposite antimicrobial coatings that can be easily applied to surfaces of any length scale and studied their efficacy against Staphylococcus aureus. The polymer nanocomposite was designed to undergo coating formation at ambient temperature. The antimicrobial coatings exhibited DHP dose dependent antimicrobial response both in the supernatant growth media with a ∼7-log10 reduction in cell growth and virtually a complete inhibition in cell adhesion on the surface in the best coating compared to controls. When compared, DHP-Br coatings outperformed other DHP analogues (-F and -Ph) both in limiting the cell growth in the media and cellular adhesion on the coating surface. This is the first example of nanocomposite coatings comprising QS inhibiting compounds, and their exceptional performance is expected to pave the way for further research in the field.

Complementary supramolecular drug associates in perfecting the multidrug therapy against multidrug resistant bacteria

The inappropriate and inconsistent use of antibiotics in combating multidrug-resistant bacteria exacerbates their drug resistance through a few distinct pathways. Firstly, these bacteria can accumulate multiple genes, each conferring resistance to a specific drug, within a single cell. This accumulation usually takes place on resistance plasmids (R). Secondly, multidrug resistance can arise from the heightened expression of genes encoding multidrug efflux pumps, which expel a broad spectrum of drugs from the bacterial cells. Additionally, bacteria can also eliminate or destroy antibiotic molecules by modifying enzymes or cell walls and removing porins. A significant limitation of traditional multidrug therapy lies in its inability to guarantee the simultaneous delivery of various drug molecules to a specific bacterial cell, thereby fostering incremental drug resistance in either of these paths. Consequently, this approach prolongs the treatment duration. Rather than using a biologically unimportant coformer in forming cocrystals, another drug molecule can be selected either for protecting another drug molecule or, can be selected for its complementary activities to kill a bacteria cell synergistically. The development of a multidrug cocrystal not only improves tabletability and plasticity but also enables the simultaneous delivery of multiple drugs to a specific bacterial cell, philosophically perfecting multidrug therapy. By adhering to the fundamental tenets of multidrug therapy, the synergistic effects of these drug molecules can effectively eradicate bacteria, even before they have the chance to develop resistance. This approach has the potential to shorten treatment periods, reduce costs, and mitigate drug resistance. Herein, four hypotheses are presented to create complementary drug cocrystals capable of simultaneously reaching bacterial cells, effectively destroying them before multidrug resistance can develop. The ongoing surge in the development of novel drugs provides another opportunity in the fight against bacteria that are constantly gaining resistance to existing treatments. This endeavour holds the potential to combat a wide array of multidrug-resistant bacteria.

Nano-enabled antimicrobial thin films: design and mechanism of action

Antimicrobial thin films are types of protective coatings that are applied to surfaces such as medical devices, food packaging materials, water-resistant coatings, and other systems. These films prevent and reduce the spread of microbial organisms, including bacteria, fungi, and viruses. Antimicrobial thin films can be prepared from a variety of nanostructured materials including metal nanoparticles, metal oxides, plant materials, enzymes, bacteriocins and polymers. Their antimicrobial mechanism varies mostly based on the types of active agents from which the film is made of. Antimicrobial thin films are becoming increasingly popular microbial treatment methods due to their advantages such as enhanced stability, reduced toxicity levels, extended effectiveness over time and broad spectrum antimicrobial action without side effects on human health or the environment. This popularity and enhanced performance is mainly due to the extended possibility of film designs. Thin films offer convenient formulation methods which makes them suitable for commercial practices aiming at high turnover rates along with residential applications requiring frequent application cycles. This review focuses on recent developments in the possible processing methods and design approaches for assembling the various types of antimicrobial materials into nanostructured thin film-based delivery systems, along with mechanisms of action against microbes.

Ag2O-Containing Biocidal Interpolyelectrolyte Complexes on Glass Surfaces-Adhesive Properties of the Coatings

Biocidal coatings are of great interest to the healthcare system. In this work, the biocidal activity of coatings based on a complex biocide containing polymer and inorganic active antibacterial components was studied. Silver oxide was distributed in a matrix of a positively charged interpolyelectrolyte complex (IPEC) of polydiallyldimethylammonium chloride (PDADMAC) and sodium polystyrene sulfonate (PSS) using ultrasonic dispersion, forming nanoparticles with an average size of 5-6 nm. The formed nanoparticles in the matrix are not subject to agglomeration and changes in morphology during storage. It was found that the inclusion of silver oxide in a positively charged IPEC allows a more than 4-fold increase in the effectiveness of the complex biocide against E. coli K12 in comparison with the biocidal effect of PDADMAC and IPEC. Polycation, IPEC, and the IPEC/Ag2O ternary complex form coatings on the glass surface due to electrostatic adsorption. Adhesive and cohesive forces in the resulting coatings were studied with micron-scale coatings using dynamometry. It was found that the stability of the coating is determined primarily by adhesive interactions. At the macro level, it is not possible to reliably identify the role of IPEC formation in adhesion. On the other hand, use of the optical tweezers method makes it possible to analyze macromolecules at the submicron scale and to evaluate the multiple increase in adhesive forces when forming a coating from IPEC compared to coatings from PDADMAC. Thus, the application of ternary IPEC/Ag2O complexes makes it possible to obtain coatings with increased antibacterial action and improved adhesive characteristics.

Transient Coatings from Nanoparticles Achieving Broad-Spectrum and High Antimicrobial Performance

Cationic and hydrophilic coatings based on casting and drying water dispersions of two different nanoparticles (NPs) onto glass are here described and evaluated for antimicrobial activity. Discoid cationic bilayer fragments (BF) surrounded by carboxy-methylcellulose (CMC) and poly (diallyl dimethyl ammonium) chloride (PDDA) NPs and spherical gramicidin D (Gr) NPs dispersed in water solution were cast onto glass coverslips and dried, forming a coating quantitatively evaluated against Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. From plating and colony forming units (CFU) counting, all strains interacting for 1 h with the coatings lost viability from 10⁵ to 10⁶, to zero CFU, at two sets of Gr and PDDA doses: 4.6 and 25 μg, respectively, or, 0.94 and 5 μg, respectively. Combinations produced broad spectrum, antimicrobial coatings; PDDA electrostatically attached to the microbes damaging cell walls, allowing Gr NPs interaction with the cell membrane. This concerted action promoted optimal activity at low Gr and PDDA doses. Further washing and drying of the deposited dried coatings showed that they were washed out so that antimicrobial activity was no longer present on the glass surface. Significant applications in biomedical materials can be foreseen for these transient coatings.

Implantable biomedical materials for treatment of bone infection

The treatment of bone infections has always been difficult. The emergence of drug-resistant bacteria has led to a steady decline in the effectiveness of antibiotics. It is also especially important to fight bacterial infections while repairing bone defects and cleaning up dead bacteria to prevent biofilm formation. The development of biomedical materials has provided us with a research direction to address this issue. We aimed to review the current literature, and have summarized multifunctional antimicrobial materials that have long-lasting antimicrobial capabilities that promote angiogenesis, bone production, or "killing and releasing." This review provides a comprehensive summary of the use of biomedical materials in the treatment of bone infections and a reference thereof, as well as encouragement to perform further research in this field.

Fluoroplast Doped by Ag2O Nanoparticles as New Repairing Non-Cytotoxic Antibacterial Coating for Meat Industry

Foodborne infections are an important global health problem due to their high prevalence and potential for severe complications. Bacterial contamination of meat during processing at the enterprise can be a source of foodborne infections. Polymeric coatings with antibacterial properties can be applied to prevent bacterial contamination. A composite coating based on fluoroplast and Ag₂O NPs can serve as such a coating. In present study, we, for the first time, created a composite coating based on fluoroplast and Ag₂O NPs. Using laser ablation in water, we obtained spherical Ag₂O NPs with an average size of 45 nm and a ζ-potential of -32 mV. The resulting Ag₂O NPs at concentrations of 0.001-0.1% were transferred into acetone and mixed with a fluoroplast-based varnish. The developed coating made it possible to completely eliminate damage to a Teflon cutting board. The fluoroplast/Ag₂O NP coating was free of defects and inhomogeneities at the nano level. The fluoroplast/Ag₂O NP composite increased the production of ROS (H₂O₂, OH radical), 8-oxogualnine in DNA in vitro, and long-lived active forms of proteins. The effect depended on the mass fraction of the added Ag₂O NPs. The 0.01-0.1% fluoroplast/NP Ag₂O coating exhibited excellent bacteriostatic and bactericidal properties against both Gram-positive and Gram-negative bacteria but did not affect the viability of eukaryotic cells. The developed PTFE/NP Ag₂O 0.01-0.1% coating can be used to protect cutting boards from bacterial contamination in the meat processing industry.

In Situ Surface-Directed Assembly of 2D Metal Nanoplatelets for Drug-Free Treatment of Antibiotic-Resistant Bacteria

The development of antibiotic resistance among bacterial strains is a major global public health concern. To address this, drug-free antibacterial approaches are needed. Copper surfaces have long been known for their antibacterial properties. In this work, a one-step surface modification technique is used to assemble 2D copper chloride nanoplatelets directly onto copper surfaces such as copper tape, transmission electron microscopy (TEM) grids, electrodes, and granules. The nanoplatelets are formed using copper ions from the copper surfaces, enabling their direct assembly onto these surfaces in a one-step process that does not require separate nanoparticle synthesis. The synthesis of the nanoplatelets is confirmed with TEM, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Antibacterial properties of the Cu nanoplatelets are demonstrated in multidrug-resistant (MDR) Escherichia coli, MDR Acinetobacter baumannii, MDR Staphylococcus aureus, E. coli, and Streptococcus mutans. Nanoplatelets lead to a marked improvement in antibacterial properties compared to the copper surfaces alone, affecting bacterial cell morphology, preventing bacterial cell division, reducing their viability, damaging bacterial DNA, and altering protein expression. This work presents a robust method to directly assemble copper nanoplatelets onto any copper surface to imbue it with improved antibacterial properties.

Polyaniline-coated nanoparticles of zinc oxide and copper oxide as antifungal agents against Aspergillus parasiticus

Aspergillus parasiticus (A. parasiticus) is known for producing aflatoxins and is a major threat to the food industry. Green synthesis of nanoparticles (NPs) is a cost-effective and environment-friendly approach. A variety of NPs have been explored as antifungal agents; however, their antifungal characteristics need to be further enhanced to compete with traditional fungicides. The present work describes the green synthesis of ZnO and CuO NPs by precipitation method using aqueous leaf extract of Manilkara zapota and their surface modification through polyaniline (PANI). Still, there is no published study on the application of PANI-coated particles as antifungal agents against A. parasiticus and hence was the focus of this work. The polymer-coated NPs were synthesized, characterized, and investigated for their antifungal properties against A. parasiticus. Textural and structural characterization of PANI-coated and non-coated ZnO and CuO NPs were confirmed through FT-IR, SEM, and XRD techniques. The PANI-coated NPs presented higher fungal growth inhibition (%) as compared to the non-coated ones. The maximum inhibition of 77 ± 2% (n = 3) was shown by PANI/ZnO NPs at a concentration of 12 mmol L^-1 and 72 h of incubation. The non-coated NPs presented a lower inhibition rate with respect to their coated NPs, thus justifying the role of polymeric coating in improving antifungal efficiency.

Self-Organized Nanoparticles of Random and Block Copolymers of Sodium 2-(Acrylamido)-2-methyl-1-propanesulfonate and Sodium 11-(Acrylamido)undecanoate as Safe and Effective Zika Virus Inhibitors

A series of anionic homopolymers, poly(sodium 2-(acrylamido)-2-methyl-1-propanesulfonate) (PAMPS) and amphiphilic copolymers of AMPS and sodium 11-(acrylamido)undecanoate (AaU), both block (PAMPS75-b-PAaUn), and random (P(AMPSm-co-AaUn)), were synthesized and their antiviral activity against Zika virus (ZIKV) was evaluated. Interestingly, while the homopolymers showed limited antiviral activity, the copolymers are very efficient antivirals. This observation was explained considering that under the conditions relevant to the biological experiments (pH 7.4 PBS buffer) the macromolecules of these copolymers exist as negatively charged (zeta potential about -25 mV) nanoparticles (4-12 nm) due to their self-organization. They inhibit the ZIKV replication cycle by binding to the cell surface and thereby blocking virus attachment to host cells. Considering good solubility in aqueous media, low toxicity, and high selectivity index (SI) of the PAMPS-b-PAaU copolymers, they can be considered promising agents against ZIKV infections.

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.

Improving the Antimicrobial and Mechanical Properties of Epoxy Resins via Nanomodification: An Overview

The main purpose of this work is to provide a comprehensive overview on the preparation of multifunctional epoxies, with improved antimicrobial activity and enhanced mechanical properties through nanomodification. In the first section, we focus on the approaches to achieve antimicrobial activity, as well as on the methods used to evaluate their efficacy against bacteria and fungi. Relevant application examples are also discussed, with particular reference to antifouling and anticorrosion coatings for marine environments, dental applications, antimicrobial fibers and fabrics, and others. Subsequently, we discuss the mechanical behaviors of nanomodified epoxies with improved antimicrobial properties, analyzing the typical damage mechanisms leading to the significant toughening effect of nanomodification. Some examples of mechanical properties of nanomodified polymers are provided. Eventually, the possibility of achieving, at the same time, antimicrobial and mechanical improvement capabilities by nanomodification with nanoclay is discussed, with reference to both nanomodified epoxies and glass/epoxy composite laminates. According to the literature, a nanomodified epoxy can successfully exhibit antibacterial properties, while increasing its fracture toughness, even though its tensile strength may decrease. As for laminates-obtaining antibacterial properties is not followed by improved interlaminar properties.

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.

Facile Synthesis of Bio-Antimicrobials with "Smart" Triiodides

Multi-drug resistant pathogens are a rising danger for the future of mankind. Iodine (I₂) is a centuries-old microbicide, but leads to skin discoloration, irritation, and uncontrolled iodine release. Plants rich in phytochemicals have a long history in basic health care. Aloe Vera Barbadensis Miller (AV) and Salvia officinalis L. (Sage) are effectively utilized against different ailments. Previously, we investigated the antimicrobial activities of smart triiodides and iodinated AV hybrids. In this work, we combined iodine with Sage extracts and pure AV gel with polyvinylpyrrolidone (PVP) as an encapsulating and stabilizing agent. Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), Surface-Enhanced Raman Spectroscopy (SERS), microstructural analysis by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-Ray-Diffraction (XRD) analysis verified the composition of AV-PVP-Sage-I₂. Antimicrobial properties were investigated by disc diffusion method against 10 reference microbial strains in comparison to gentamicin and nystatin. We impregnated surgical sutures with our biohybrid and tested their inhibitory effects. AV-PVP-Sage-I₂ showed excellent to intermediate antimicrobial activity in discs and sutures. The iodine within the polymeric biomaterial AV-PVP-Sage-I₂ and the synergistic action of the two plant extracts enhanced the microbial inhibition. Our compound has potential for use as an antifungal agent, disinfectant and coating material on sutures to prevent surgical site infections.