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Smart surfaces to tackle infection and antimicrobial resistance

30/03/2021 12:04:34
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ImagesClick Image for 300dpi jpg fileSmart surfaces to tackle infection and antimicrobial resistanceSmart surfaces to tackle infection and antimicrobial resistance

Simon Mercer from Signo-Nanocare evaluates antimicrobial nano-coatings in relation to the ten ideal performance criteria put forward by Imperial College London (ICL) Institute of Molecular Science & Engineering briefing paper ‘Smart surfaces to tackle infection and antimicrobial resistance.

During March 2020, Imperial College London (ICL) Institute of Molecular Science and Engineering published a briefing paper titled ‘Smart surfaces to tackle infection and antimicrobial resistance.’ That looked specifically at how the number of hospital acquired infections (HAI) could be reduced through the use of ‘smart surfaces’.

Existing research work has already established that contamination on surfaces and on medical devices contribute to the transmission of healthcare-associated infections (HCAI). Evidence has come from several sources including studies modelling transmission routes, microbiologic studies, observational epidemiologic studies, intervention studies and outbreak reports.

As highlighted by the ICL team, a 2016 Public Health England survey of over 48,000 patient records found that 6.6% of the patients had an acquired HCAI while they were in hospital, posing a significant risk to health, causing extended stays in hospital, increasing costs and the potential spread of antimicrobial resistance (AMR).

Microorganisms attach to and grow on surfaces forming a biofilm. Tese support microbes’ survival and replication whilst also protecting them from biocidal cleaners attack. Biofilms have also been shown to play an important role in several infection pathways, contributing to AMR.

Antimicrobial resistance is a broad term that encompasses resistance to drugs to treat infections caused by microbes and therefore includes antibiotic resistance. It was identified as early as 1945 when Sir Alexander Fleming warned of the overuse of the newly discovered antibiotics, and as we now know, it’s now considered as one of the biggest threats to global health by the World health Organisation (WHO).

The ICL team define a smart surface as an ‘antimicrobial surface that could disrupt the microbial habit by reducing microbial attachment and/or killing attached microbes’ thereby reducing the formation and persistence of microbial biofilms on surfaces and in turn reducing the transmission of infection between hand-surface-hand contact.

The ICL team took a multi-disciplined approach to the problem of finding the ideal smart surface for use in medical settings. Their Ideal antimicrobial surface would reduce bacterial attachment and biofilm formation, disrupting the four-stage process of microbial breeding and transfer of AMR -related genetic material between other microbial organisms.

They looked at three ways that an antimicrobial surface can be achieved:-

Firstly, surface topography where the physical properties of the surface are altered to reduce the ability of microbes to adhere to the surface or making the surface easier to clean. The example looked at was the Cicada insects’ wings, which have evolved to exhibit antimicrobial properties. The surface of their wings are constructed with layers of nano-spikes that puncture the cell walls of bacteria landing upon them, therefore not just preventing biofilm formation, but instantly killing the microbe itself.

Secondly, the in-built and slow release of antimicrobial agents, e.g., a surface that can be engineered with antimicrobial agents that are released over time. Both Copper and Silver alloys have shown the ability to kill bacteria on contact.

The third route evaluated self-cleaning and self -polishing surfaces; these typically rely on a liquid wash to remove the outer layer of the contamination. Photocatalytic surfaces are an example of a such surfaces, in which a chemical reaction between titanium dioxide, water and UV produce a hydroxyl free radical which can kill microbes by attacking the cell membrane.

Over the last twenty years the benefits of nano-coatings have been taken up by many industries to give substrates and surfaces enhanced stain resistance, easy-clean and dirt removal performance. In recent years there have been developments which have enabled the creation of permanent bonded antimicrobial surface coating. These have undergone independent laboratory testing and have been proven effective against an extensive range of bacteria and viruses, combined with weathering and abrasion resistance.

Having evaluated the problem of surface contamination and transmission of microbes within the healthcare setting the ICL team concluded with a list of ten ideal properties of an antimicrobial surface and they were:-

‘Skin Safe. The surface must be able to remain safe for regular contact with skin of patients, staff and visitors, and in particular sensitive or broken skin’. Antimicrobial Nano-coatings are inert have been found to gain a rating of ‘excellent’ in relation to dermatological contact.

‘Healthcare Economics. The use of antimicrobial surfaces will bring additional costs, which must represent ‘good value healthcare’ by demonstrating associated cost saving in other related budgets.’ By using an antimicrobial nano-coating significant cost savings can be made against labour and material costs involved with repeated ‘moment in time’ cleaning; along with those associated with reductions in healthcare acquired infections, extended hospital stays and additional associated treatment.

‘Simple application technology. Ideally the additional antimicrobial properties could be added at the point of manufacture or applied as a liquid to existing surfaces in situ.’ The application of antimicrobial nano-coatings can take place as a final stage of the manufacturing process. Surfaces already in situ can be coated quickly as easily as part of a ‘deep clean’ programme or incorporated into regular cleaning routines.

‘Long term. That the surface would retain its antimicrobial activity for months/years without the need for reapplication’. Longevity of the antimicrobial nano-coating activity has been independently certified for 1, 3 and 10 years - ISO testing has been used to verify its weatherproofing and surface resilience.

‘Rapid antimicrobial activity. For effective healthcare applications, the antimicrobial activity must occur within seconds or minutes of surface contact from the contaminant (rather than hours)’. Functionality is instantaneous. The speed of full kill will depend on the deposits of Colony Forming Units (CFU’s) in any particular deposit.

‘Prevention of biofilm formation. To have the ability to prevent the formation or to disrupt those that have formed.’ Due to the two-part application process of antimicrobial nano-coatings, if there are microbes already bound to the surface (or present as a biofilm) they will be removed during the first part of the application process. Once cured the coating will kill any microbes that subsequently land on the surface; they are destroyed before being able to bind to the surface and create a biofilm.

‘Compatibility with current cleaning and disinfection products. Any chemicals used for regular cleaning and disinfection should not interfere with the antimicrobial activity.’ Normal cleaning routines are required to remove dust, dirt and debris from the treated surface, however only non- abrasive/residual cleaners with a pH of between 4-9 should be used on the treated surface.

‘Retention of activity with low level soiling. Hospital surfaces often gather dust, dirt and organic matter debris between cleans, through which time the surfaces should remain active.’ The activity level of the antimicrobial nano-coating is not affected by low level soiling – as has been demonstrated using in-situ Adenosine Triphosphate (ATP testing).

‘Does not promote clinically-significant microbial resistance or reduced -susceptibility. There is a theoretical risk that continuous sub-lethal exposure of microbes could occur on the surface, which could lead to resistance or reduced susceptibility to the antimicrobial surfaces.’ The method of kill utilised is non-mutagenic, because the microbe is physically killed due to the outer cell wall being punctured. This contrasts significantly with the chemical kill of traditional disinfectants

‘Sporicidal activity. C.Difficile spores present a particular challenge to antimicrobial surfaces. There is concern that introducing a surface that is not effective against c. difficile spores could provide it with a selective advantage.’ Antimicrobial nano-coatings have been shown to be effective against C.Difficile.

Over the ten points put forward by the ICL team, antimicrobial nano-coatings comprehensively meet all ten, along with proven activity against some of the most concerning HAI, MRSA, C.Difficile, Staphylococcus and Streptococcus. Recently through independent testing they have been shown to be effective against SARS CoV-2 and Influenza A.

Liquid Guard®antimicrobial nano-coating is available from Signo-Nanocare UK Ltd.

About Signo-Nanocare UK

Signo-Nanocare UK specialise in the development and manufacture of nanoscale easy-clean and stain-resistant smart coatings. Our product range consists of nano coatings that provide protection for a diverse range of surfaces from cloth to concrete.

Since the year 2000, our multi-national Nano-Care group of companies, from state-of-the-art product development and laboratory testing facilities, has evolved its leading technical knowledge and expertise in the manufacturing of SiO2-based high-performance coatings. Based in Shropshire, we distribute throughout the UK and overseas.

Editor Contact

DMA Europa Ltd. : Brittany Kennan
Tel: +44 (0)1562 751436 Fax: +44 (0)1562 748315

Company Contact

Signo-Nanocare UK Ltd : Helen Holman
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