Imperial College London (ICL) Institute of Molecular Science and Engineering published a very timely briefing paper titled ‘Smart surfaces to tackle infection and antimicrobial resistance.’
Back in March 2020, when it began to dawn on us just how much SARS CoV-2 was going to affect the way we went about our daily lives, the Imperial College London (ICL) Institute of Molecular Science and Engineering published a very timely briefing paper titled ‘Smart surfaces to tackle infection and antimicrobial resistance.’
This paper highlights the role that contaminated surfaces play in the transmission of healthcare-associated infection (HCAI) and the spread of antimicrobial resistance (AMR) – both critical issues to the health sector that have only been exacerbated by the Covid pandemic.
In brief, the solution would be ‘surfaces that could disrupt the microbial habit by reducing microbial attachment and /or killing attached microbes.’ The areas of application for this type of surface within the medical industry would include ‘the clinical environment to have touch surfaces with antimicrobial properties (e.g. coated bed rails)’.
The team at Imperial College London looked at several different ways that smart surfaces can be created. They focused on the construction of the Cicadas insect’s wings, as they have evolved to have amicrobial properties. Their wings have developed nanoscale spikes on the surface, these then rupture the cell wall of microbes that meet the surface of the wing.
Unfortunately, there is no great story of biomimicry here, just coincidence; Liquid Guard® is an antimicrobial nano coating that has been developed through nanoscale engineering to form nanoscale spikes on treated surfaces. These spikes act in the same way as the ones on the Cicada’s wings; they rupture the microbe’s outer wall causing instant death, preventing replication and mutation.
In the briefing paper, the ICL team listed the ideal properties of an antimicrobial surface – and here is how Liquid Guard lines up against their ideal:-
|Surface property||Liquid Guard attributes|
|Safe – The surface must remain safe for regular contact with patients, staff and visitors with particular consideration of likely contact with sensitive areas and broken skin.||Independently Dermatologically tested – rating of ‘excellent’|
|Healthcare Economics. The introduction of antimicrobial surfaces will engender associated additional costs, which must represent good value healthcare.||Liquid Guard application will, by any measure, create a significant cost saving against the labour and material costs involved in repeated “moment in time” extraordinary cleaning schedules on high touch points|
|Simple application technology. Ideally, the antimicrobial properties of the surface would be put in place during manufacture or applied as a liquid agent in situ.||Can be applied at manufacture or in situ ; mechanically with mist spraying or through simple spray and wipe application.|
|Long term. The surface should remain antimicrobial for months or years, without the need for re-application.
|Antimicrobial activity certified at 1,3 and 10 years
Weatherproof: 2000 hours according to ISO 11507 (corresponds to circa 3-4 years)
Meets ISO 11998 for resilience as follows.
Glass. ceramic > 40,000 cycles
Noble metals > 20,000 cycles
Plastics > 5,000 cycles
|Rapid antimicrobial activity. For effective healthcare applications, surfaces with an antimicrobial activity that occurs in seconds or minutes (rather than hours) are needed||Antimicrobial action is instant on contact with the coating. Speed of full kill will depend on the deposit of CFU’s (Colony Forming Units)|
|Prevention of biofilm formation. The ability to prevent the formation of biofilms, or disrupt biofilms that have been formed, is a property of some oxidizing disinfectants. This property may be shared by a surface that exerts antimicrobial activity through oxidation. Modification of the physical structure of a surface may also inhibit biofilm formation.||If bacteria are already bound to a surface (or present as biofilm) they will be removed during the application of Liquid Guard. However, since Liquid Guard will kill bacteria which subsequently land on the surface , they will be destroyed before being able to bind to the surface/form a biofilm.|
|Compatibility with current cleaning and disinfection products. Any chemicals used for regular cleaning and disinfection should not interfere with the antimicrobial activity of the surface, either in the short or long-term.
|Normal cleaning routines are required to remove dust, dirt and debris from the surface.
Only non-abrasive and non-residual cleaners with a pH of between 4-9 should be used on the treated surface.
|Retention of activity with low-level soiling. Surfaces in hospitals often retain and accumulate organic matter.||Activity continues with low level soiling – as is demonstrated through use of in-situ ATP testing|
|Does not promote clinically-significant resistance or reduced-susceptibility. There is a theoretical risk that continuous sub-lethal exposure of microbes could occur on the surface, and that this may lead to the development of resistance or reduced susceptibility to an antimicrobial surface. However, there is currently no specific evidence for resistance as a result of the implementation of antimicrobial surfaces in hospitals.||It 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 a selective advantage to C. difficile, potentially leading to increased levels of infection by this microbe||Liquid Guard is independently tested effective against C.Difficile|
With UK Covid deaths significantly over 100,000 at the time of writing and with at least two new Covid variants having been identified as ‘significantly’ more transmissible, there has never been a greater need for smart surfaces that can kill microbes on contact.
Research from the Commonwealth Scientific and Industrial Research Organisation (CSIRO Australia’s national research agency) has recently undertaken a study to establish the ‘Transmission of SARS CoV-2 via surfaces’.
The investigation looked at six different surface types that they felt represented commonly touched, everyday surfaces. It looked at the survival of infectious SARS CoV-2 suspended in artificial mucous at three different temperatures (20oC, 30oC, 40oC).
They found that at a room temperature of 20oC, they were able to recover infectious material at 28 days from smooth nonporous surfaces such as stainless steel, glass and paper/polymer bank notes. These results demonstrate how infectious this virus can be at normal room temperature. UNISON recommend that a comfortable working temperature is between 16-24oC. This is the temperature range that the majority of indoor spaces (public and private) are kept within in the UK; therefore any virus that comes into contact with surfaces is likely to remain infectious accordingly – with a potential to transfer to anyone, and consequently any other surface until its removed by cleaning.
Liquid Guard’s effectiveness against SARS CoV-2 has been proven during independent laboratory testing, and, coupled with its ability to meet ten out of ten of the ICL IMSE team’s ‘ideal properties of an antimicrobial surface’ it has a serious part to play in the reducing the transmission of many HCAI’s as well as Covid 19.