Antimicrobial activity of novel nanostructured Cu-SiO2 coatings prepared by chemical vapour deposition against hospital related pathogens.

There is increasing recognition that the healthcare environment acts as an important reservoir for transmission of healthcare acquired infections (HCAI). One method of reducing environmental contamination would be use of antimicrobial materials. The antimicrobial activity of thin silica-copper films prepared by chemical vapour deposition was evaluated against standard strains of bacteria used for disinfectant testing and bacteria of current interest in HCAI. The structure of the coatings was determined using Scanning Electron Microscopy and their hardness and adhesion to the substrate determined. Antimicrobial activity was tested using a method based on BS ISO 22196:2007. The coatings had a pale green-brown colour and had a similar hardness to steel. SEM showed nano-structured aggregates of Cu within a silica matrix. A log10 reduction in viability of >5 could be obtained within 4 h for the disinfectant test strains and within 6 h for producing Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia. Activity against the other hospital isolates was slower but still gave log10 reduction factors of >5 for extended spectrum ß-lactamase producing Escherichia coli and >3 for vancomycin resistant Enterococcus faecium, methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa within 24 h. The results demonstrate the importance of testing antimicrobial materials destined for healthcare use against isolates of current interest in hospitals as well as standard test strains. The coatings used here can also be applied to substrates such as metals and ceramics and have potential applications where reduction of microbial environmental contamination is desirable.

Durability of silver nanoparticulate films within a silica matrix by flame assisted chemical vapour deposition for biocidal applications.

Healthcare acquired infection (HCAI) rates have come under increasing scrutiny in recent years and been a major priority for health professionals in the UK and elsewhere. Of particular concern is the rise of so called 'superbugs', or those resistant to conventional antibiotics, such as Escherichia coli, Clostridium difficile and methicillin resistant Staphylococcus aureus (MRSA). The reasons for this rise are many and complex, but one important factor is bacterial survival rates on wards and other hospital areas. In this respect, nanostructured biocidal surfaces offer a potentially powerful weapon in the fight against HCAI. In addition to providing a toxic environment to a range of infectious disease-causing bacteria (while remaining harmless to human health), any potential bioactive coated surface is required to be durable enough to withstand regular hospital cleaning methods without a reduction in biocidal activity over time and be economically viable to mass produce. The flame assisted chemical vapour deposition (FACVD) of silver and silver/silica films offer a means of producing such surfaces. In this work, we report investigations into a wide range of experimental factors and parameters affecting film durability, including burner head design and relative water vapour content in the flame environment. The produced films were assessed in terms of durability (by scratch testing) and relative silver content using glow discharge optical emission spectroscopy (GDOES).

Photocatalytic disinfection using titanium dioxide: spectrum and mechanism of antimicrobial activity.

The photocatalytic properties of titanium dioxide are well known and have many applications including the removal of organic contaminants and production of self-cleaning glass. There is an increasing interest in the application of the photocatalytic properties of TiO(2) for disinfection of surfaces, air and water. Reviews of the applications of photocatalysis in disinfection (Gamage and Zhang 2010; Chong et al., Wat Res 44(10):2997-3027, 2010) and of modelling of TiO(2) action have recently been published (Dalrymple et al. , Appl Catal B 98(1-2):27-38, 2010). In this review, we give an overview of the effects of photoactivated TiO(2) on microorganisms. The activity has been shown to be capable of killing a wide range of Gram-negative and Gram-positive bacteria, filamentous and unicellular fungi, algae, protozoa, mammalian viruses and bacteriophage. Resting stages, particularly bacterial endospores, fungal spores and protozoan cysts, are generally more resistant than the vegetative forms, possibly due to the increased cell wall thickness. The killing mechanism involves degradation of the cell wall and cytoplasmic membrane due to the production of reactive oxygen species such as hydroxyl radicals and hydrogen peroxide. This initially leads to leakage of cellular contents then cell lysis and may be followed by complete mineralisation of the organism. Killing is most efficient when there is close contact between the organisms and the TiO(2) catalyst. The killing activity is enhanced by the presence of other antimicrobial agents such as Cu and Ag.