Antimicrobial Thin Films Research Articles

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.

Gracilaria salicornia as potential substratum for green synthesis of Cerium Oxide Nanoparticles coupled hydrogel: An effective antimicrobial thin film

Sodium alginate based (SA) hydrogel supplemented Cerium Oxide nanoparticles (CeO2NPs) was produced to fabricate an antimicrobial thin film using an aqueous extract of G. salicornia (Gs). The Gs-CeO2NPs were characterized via SEM, FT-IR, EDX, XRD and DLS, the particle size was 200 nm, agreed with XRD. Gs-SA powder was extracted and incorporated with CeO2NPs. The Gs-SA and its composite thin film (Gs-CeO2NPs-SATF) were characterized including viscosity, FT-IR, TGA, and SEM. The adhesion of Gs-SA coating around Gs-CeO2NPs confirmed via FTIR. The antimicrobial properties of Gs-CeO2NPs and CeO2NPs-SATF were proved in MICs for E. coli and Candida albicans at 62.5 and 250.0 μg/mL. The biofilm inhibition efficiency of CeO2NPs-SATF was 74.67 ± 0.98% and 65.45 ± 0.40% for E. coli and Candida albicans. The CeO2NPs-SATF was polydisperse in nature and film structure gets fluctuated with NPs concentration. Increased NPs into SATF enhances pore size of gel and corroborated with viscous behaviour. The cytotoxicity of Gs-CeO2NP-SA in Artemia salina at higher concentration 100 μg/mL provides less lethal effect into the adult. The antioxidant activity of Gs-CeO2NP-SA in DPPH assay was noticed at 0.6 mg ml−1 with radical scavenging activity at 65.85 ± 0.81%. Thus the Gs-CeO2NP-SATF would be suitable in antimicrobial applications.

Antimicrobial and Aging Properties of Ag-, Ag/Cu-, and Ag Cluster-Doped Amorphous Carbon Coatings Produced by Magnetron Sputtering for Space Applications.

Inside a spacecraft, the temperature and humidity, suitable for the human crew onboard, also creates an ideal breeding environment for the proliferation of bacteria and fungi; this can present a hazard to human health and create issues for the safe running of equipment. To address this issue, wear-resistant antimicrobial thin films prepared by magnetron sputtering were developed, with the aim to coat key internal components within spacecrafts. Silver and copper are among the most studied active bactericidal materials, thus this work investigated the antibacterial properties of amorphous carbon coatings, doped with either silver, silver and copper, or with silver clusters. The longevity of these antimicrobial coatings, which is heavily influenced by metal diffusion within the coating, was also investigated. With a conventional approach, amorphous carbon coatings were prepared by cosputtering, to generate coatings that contained a range of silver and copper concentrations. In addition, coatings containing silver clusters were prepared using a separate cluster source to better control the metal particle size distribution in the amorphous carbon matrix. The particle size distributions were characterized by grazing-incidence small-angle X-ray scattering (GISAXS). Antibacterial tests were performed under both terrestrial gravity and microgravity conditions, to simulate the condition in space. Results show that although silver-doped coatings possess extremely high levels of antimicrobial activity, silver cluster-doped coatings are equally effective, while being more long-lived, despite containing a lower absolute silver concentration.

Carvacrol loaded halloysite coatings for antimicrobial food packaging applications

Abstract Antimicrobial thin film coatings that can be utilized in food packaging provide an effective approach to enhance food quality and safety. Here, the coating of polyethylene films with an antimicrobial thin film through a Layer-by-Layer (LbL) assembly is demonstrated. Halloysite nanotubes (HNTs) which are tubular clay nanoparticles were utilized for the encapsulation and sustained release of carvacrol, the active component of essential thyme oil. Antimicrobial thin film coatings of 225 nm thickness were prepared by the deposition of ten bilayers of chitosan (CHI) and carvacrol loaded HNTs onto the polyethylene surface by spray LbL. Coated films reduced the viability of a food pathogen, Aeromonas hydrophila by 85% and the aerobic count on chicken meat surfaces by 48%. Furthermore, coated film surfaces demonstrated lower bacterial attachment compared to control polyethylene films indicating their antibiofilm character. Composed of natural and safe components, antimicrobial coatings developed in this study provide a novel and effective approach to obtain antimicrobial food packaging materials that can greatly contribute to food safety.

Nano silica-carbon-silver ternary hybrid induced antimicrobial composite films for food packaging application

Abstract In this work, Ag assisted biobased silica-carbon nanoparticles (SCAg-NPs) were incorporated into a viscous biopolymer solution to fabricate antimicrobial thin films using 3D printing technique. The Ag NPs were prepared in situ from AgNO3 through one-step ball milling in the presence of silica-carbon hybrid obtained from pyrolysis of rice husk. The nanostructure of the SCAg-NPs was determined by XRD and TEM. These as-synthesized particles were also characterized by XPS analysis. The printed films were characterized by XRD, FE-SEM, Raman microanalysis, TGA, DSC and tensile testing to investigate the influence of nanoparticles on the thermal and mechanical properties on the films. Antimicrobial testing was carried out on the films to assess the inhibitory effect of SCAg NPs on Salmonella Enteritidis inoculum. XRD, XPS and Raman microanalysis confirmed the incorporation of Ag particles into SCNPs, while FE-SEM size measurement of the SCAg NPs ranged between 10–100 nm in diameter. Thermal analysis revealed that the inclusion of SCAg NPs led to improvement in the thermal stability of the fabricated nanocomposites films. Tensile test was carried out to determine the influence of SCAg NPs on mechanical properties of the films and found moderate increase in the strength of the polymer film.

Fabrication and characterization of novel antimicrobial thin film nano‐composite membranes based on copper nanoparticles

AbstractBACKGROUNDCopper nanoparticles (CuNPs) are studied for the design of advanced nanocomposite membranes owing to their highly antimicrobial properties, specific catalytic and chemical activities, abundancy and low cost. In this work, thin film nanocomposite membranes (TFN) containing CuNPs in the polyamide (PA) layer were designed via a facile interfacial polymerization method. The nanoparticles were incorporated into an aqueous solution containing piperazine monomers which is poured on the top surface of the polyethersulfone ultrafiltration membrane followed by adding trimesoyl chloride to form a polymerized PA film.RESULTSThe results show that the surface morphological structure investigated by scanning electron microscopy and atomic force microscopy images is subject to visible changes of surface morphology, with a rougher net‐like structure while analysis of the chemical structure using attenuated total reflection–Fourier transform infrared spectroscopy confirms that the introduction of CuNPs did not impede the structure of the PA layer.The effect of addition of inorganic functionalized nanomaterials on the overall membrane performance was significant. The water flux was greatly increased (twice the original water permeability), while maintaining high retention of Na2SO4, demonstrating good performance in the range of nanofiltration (NF). Furthermore, the TFN membranes exhibited a specific antibacterial effect, reducing the number of living bacteria (Escherichia coli) by 94.0%.CONCLUSIONInorganic functionalization using CuNPs in the aqueous phase strongly enhanced membrane performance and provided the membrane surface with antimicrobial properties. This study suggests a new approach to TFN membrane research for the design of NF membranes for water treatment. © 2018 Society of Chemical Industry

Antimicrobial and anti-biofilm properties of polypropylene meshes coated with metal-containing DLC thin films.

A promising strategy to reduce nosocomial infections related to prosthetic meshes is the prevention of microbial colonization. To this aim, prosthetic meshes coated with antimicrobial thin films are proposed. Commercial polypropylene meshes were coated with metal-containing diamond-like carbon (Me-DLC) thin films by the magnetron sputtering technique. Several dissimilar metals (silver, cobalt, indium, tungsten, tin, aluminum, chromium, zinc, manganese, tantalum, and titanium) were tested and compositional analyses of each Me-DLC were performed by Rutherford backscattering spectrometry. Antimicrobial activities of the films against five microbial species (Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis) were also investigated by a modified Kirby-Bauer test. Results showed that films containing silver and cobalt have inhibited the growth of all microbial species. Tungsten-DLC, tin-DLC, aluminum-DLC, zinc-DLC, manganese-DLC, and tantalum-DLC inhibited the growth of some strains, while chromium- and titanium-DLC weakly inhibited the growth of only one tested strain. In-DLC film showed no antimicrobial activity. The effects of tungsten-DLC and cobalt-DLC on Pseudomonas aeruginosa biofilm formation were also assessed. Tungsten-DLC was able to significantly reduce biofilm formation. Overall, the experimental results in the present study have shown new approaches to coating polymeric biomaterials aiming antimicrobial effect.

Antimicrobial thin films based on ayurvedic plants extracts embedded in a bioactive glass matrix

Ayurvedic medicine is one of the oldest medical systems. It is an example of a coherent traditional system which has a time-tested and precise algorithm for medicinal plant selection, based on several ethnopharmacophore descriptors which knowledge endows the user to adequately choose the optimal plant for the treatment of certain pathology.This work aims for linking traditional knowledge with biomedical science by using traditional ayurvedic plants extracts with antimicrobial effect in form of thin films for implant protection. We report on the transfer of novel composites from bioactive glass mixed with antimicrobial plants extracts and polymer by matrix-assisted pulsed laser evaporation into uniform thin layers onto stainless steel implant-like surfaces. The comprehensive characterization of the deposited films was performed by complementary analyses: Fourier transformed infrared spectroscopy, glow discharge optical emission spectroscopy, scanning electron microscopy, atomic force microscopy, electrochemical impedance spectroscopy, UV–VIS absorption spectroscopy and antimicrobial tests. The results emphasize upon the multifunctionality of these coatings which allow to halt the leakage of metal and metal oxides into the biological fluids and eventually to inner organs (by polymer use), to speed up the osseointegration (due to the bioactive glass use), to exert antimicrobial effects (by ayurvedic plants extracts use) and to decrease the implant price (by cheaper stainless steel use).

Intrinsic Hydrophobic Antibacterial Thin Film from Renewable Resources: Application in the Development of Anti-Biofilm Urinary Catheters

The use of renewable resources to develop functional materials is increasing in order to meet the sustainability challenges. In an era of inexorable evolution of antimicrobial resistance, there is a substantial increase in demand for the development of efficient antimicrobial thin film coating from renewable resources for public bacterial threats, food, biomedical, and industrial applications. In the present investigation, we have used cardanol, a phenolic compound having unsaturated hydrophobic tail isolated from cashew fruits, and linseed oil, a vegetable oil and an important biobased building block, which are cheap and easy to regenerate. This study reports the synthesis of cardanol based metal complexes having unsaturated hydrophobic unit and acrylated epoxidized linseed oil (AELO) prepared via epoxidation of double bonds followed by acrylation. The double bond present in the metal complexes and AELO is prone to form assembled thin film under atmospheric conditions, without the need of any initiators....

Zeolitic Imidazolate Framework/Graphene Oxide Hybrid Nanosheets Functionalized Thin Film Nanocomposite Membrane for Enhanced Antimicrobial Performance.

Inspired by the rational design concept, a novel antimicrobial agent zeolitic imidazolate framework-8 (ZIF-8)/graphene oxide (GO) was synthesized and utilized as a novel and efficient bactericidal agent to fabricate antimicrobial thin film nanocomposite (TFN) membranes via interfacial polymerization. The resultant hybrid nanosheets not only integrates the merits of both ZIF-8 and GO but also yields a uniform dispersion of ZIF-8 onto GO nanosheets simultaneously, thus effectively eliminating the agglomeration of ZIF-8 in the active layer of membranes. A ZIF-8/GO thin film nanocomposite (TFN-ZG) membrane with typical water permeability (40.63 L m(-2) h(-1) MPa(-1)) allows for efficient bivalent salt removal (rejections of Na2SO4 and MgSO4 were 100% and 77%, respectively). Furthermore, the synthesized ZIF-8/GO nanocomposites were verified to have an optimal antimicrobial activity (MIC,128 μg/mL) in comparison with ZIF-8 and GO separately, which sufficiently endowed the TFN-ZG membrane with excellent antimicrobial activity (84.3% for TFN-ZG3). Besides, the antimicrobial mechanisms of ZIF-8/GO hybrid nanosheets and TFN-ZG membranes were proposed. ZIF-8/GO functionalized membrane with high antimicrobial activity and salt retention denoted its great potential in water desalination, and we suggest that ZIF-8 based crystal may offer a new pathway for the synthesis of a multifunctional bactericide.

Large-area chemical vapor deposition-grown monolayer graphene-wrapped silver nanowires for broad-spectrum and robust antimicrobial coating

New types of antimicrobial systems are urgently needed owing to the emergence of pathogenic microbial strains that gain resistance to antibiotics commonly used in daily life and medical care. In this study, we developed for the first time a broad-spectrum and robust antimicrobial thin film coating based on large-area chemical vapor deposition (CVD)-grown graphene-wrapped silver nanowires (AgNWs). The antimicrobial graphene/AgNW hybrid coating can be applied on commercial flexible transparent ethylene vinyl acetate/ polyethylene terephthalate (EVA/PET) plastic films by a full roll-to-roll process. The graphene/AgNW hybrid coating showed broad-spectrum antimicrobial activity against Gram-negative (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus), and fungi (Candida albicans). This effect was attributed to a weaker microbial attachment to the ultra-smooth graphene film and the sterilization capacity of Ag+, which is sustainably released from the AgNWs and presumably enhanced by the electrochemical corrosion of AgNWs. Moreover, the robust antimicrobial activity of the graphene/AgNW coating was reinforced by AgNW encapsulation by graphene. Furthermore, the antimicrobial efficiency could be enhanced to ~100% by water electrolysis by using the conductive graphene/AgNW coating as a cathode. We developed a transparent and flexible antimicrobial cover made of graphene/AgNW/EVA/PET and an antimicrobial denture coated by graphene/ AgNW, to show the potential applications of the antimicrobial materials.

Functionalized Antimicrobial Thin Films Based on Antibiotic Imbedded in Polymer Matrix for Implants Coating

In this study we investigated the possibility to use in implantology of a new composite made from antibiotic imbedded in polymer matrix with goal to merge the mechanical advantages of the metallic substrate with the excellent corrosion protection of the polymer and antimicrobial effect of the antibiotics. Furthermore the addition of small quantity of bioactive glass allows the antibiotic release and hastens the osteointegration. The biological properties of the coatings were tested including the microbial viability using Gram - and Gram + bacterial strains with known antibiotic susceptibility behavior. The proposed system could be used for development of new antimicrobial materials or strategies for fighting medical biofilm pathogens often implicated in the occurrence of chronic infections.

Surface modification of thin film composite forward osmosis membrane by silver-decorated graphene-oxide nanosheets

Antimicrobial thin film composite forward osmosis membrane is developed using silver-decorated graphene-oxide nanosheets coating.

Modified hyperbranched epoxy/clay nanocomposites: A study on thermal, antimicrobial and biodegradation properties

Abstract In the present study vegetable oil-based, highly branched polyester modified hyperbranched epoxy nanocomposites were prepared with organically modified montmorillonite clay at different wt.% of clay loadings. X-ray diffraction patterns and transmission electron microscopy revealed the partially exfoliated structure of the nanocomposites. Cured nanocomposites exhibited improved properties such as gloss (80 – 95°), scratch hardness (3 – 5 kg), impact strength (60 – 100 cm), tensile strength (8 – 13 MPa), adhesive strength (0.9 – 1.4 × 1010 N m−1), flexibility (< 5 – 3 mm), chemical resistance etc. compared to the pristine system. The nanocomposites exhibited enhanced thermosatbility and antimicrobial activity against different bacterial, fungal and algal strains. The nanocomposites were also found to be biodegradable. The study showed that the nanocomposites have potential to be used as biodegradable antimicrobial thin film materials.

Visible light photocatalysts—N-doped TiO2 by sol–gel, enhanced with surface bound silver nanoparticle islands

Antimicrobial thin film photocatalysts consisting of N-doped titania have been prepared by sol–gel methods and further enhanced using silver nanoparticles formed in situ on the surface of the films. The films have been characterised using XRD, SEM, XPS, UV-Visible spectroscopy and functionally tested using measurements for the photoinduced superhydrophilicity, stearic acid destruction and anti-microbial measurements using both E. coli and an epidemic strain of MRSA, EMRSA-16. The N-doped TiO2 films were seen to have interstitially doped nitrogen with the N 1s peak appearing at 400.0 eV in the XPS and as such showed good photocatalytic activity under white light. The photoactivity was then further enhanced by silver nanoparticle formations on the surface. The highly active photocatalytic films were seen to be effective agents against both bacteria and stearic acid using a white light source that is commonly found in UK hospitals.

Plasma deposited metal Schiff-base compounds as antimicrobials

This paper details the synthesis, characterisation including crystal structure, and testing for antimicrobial efficacy of two compounds: a zinc centred bis(N-allylsalicylideneiminato)-zinc (ZSB) and its known copper analogue, bis(N-allylsalicylideneiminato)-copper (CSB). Differences in antimicrobial efficacy of the two compounds were observed, suggesting possible mechanisms for antimicrobial activity. The ZSB system was plasma deposited under various pulse conditions onto non-woven fabric, and the antimicrobial efficacy of the resultant film measured for Staphylococcus aureus and Pseudomonas aeruginosa. These results suggest the potential utility of this compound as an effective antimicrobial thin film, and confirm the critical role the ligands play in effecting antimicrobial activity.

Deposition of antibacterial of poly(1,3-bis-(p-carboxyphenoxy propane)-co-(sebacic anhydride)) 20:80/gentamicin sulfate composite coatings by MAPLE

We report on thin film deposition of poly(1,3-bis-(p-carboxyphenoxy propane)-co-sebacic anhydride)) 20:80 thin films containing several gentamicin concentrations by matrix assisted pulsed laser evaporation (MAPLE). A pulsed KrF* excimer laser was used to deposit the polymer–drug composite thin films. Release of gentamicin from these MAPLE-deposited polymer conjugate structures was assessed. Fourier transform infrared spectroscopy was used to demonstrate that the functional groups of the MAPLE-transferred materials were not changed by the deposition process nor were new functional groups formed. Scanning electron microscopy confirmed that MAPLE may be used to fabricate thin films of good morphological quality. The activity of gentamicin-doped films against Escherichia coli and Staphylococcus aureus bacteria was demonstrated using disk diffusion and antibacterial drop test. Our studies indicate that deposition of polymer–drug composite thin films prepared by MAPLE is a suitable technique for performing controlled drug delivery. Antimicrobial thin film coatings have several medical applications, including use for indwelling catheters and implanted medical devices.

Surface Modification of Titanium Using Nanothin Films of Copper for Biofouling Control

Biofouling is one of the major impediment in the use of titanium, which is otherwise excellent material with respect to corrosion resistance and mechanical properties, for seawater-cooled condensers of power plants. The routine chlorination treatment and sponge ball cleaning may not be successful to keep the titanium condenser tube clean over a period extending to years. This brings into focus the relevance of surface modification of titanium to improve the antimicrobial properties, which can effectively supplement the present treatment programmes. In this study antimicrobial thin film of copper (Cu) is developed on titanium surfaces, as copper is known to be very toxic to microorganisms and effectively kills most of the microbes by blocking the respiratory enzyme system. The preparation of nanocrystalline thin films of copper on titanium surfaces was done by pulsed DC magnetron-sputtering technique. Then this thin film was characterized using Glancing Incidence X-ray Diffraction (GIXRD) and Atomic Force Microscopy (AFM). Antimicrobial properties of these specimens were evaluated by exposure studies in seawater. Results showed two order decrease in the bacterial density on copper coated surface and epifluorescence micrographs depicted very few fluorescing cells and no biofilm formation clearly demonstrating the superior antibacterial capability of this nanocrystalline copper thin film.