Interest in antimicrobial technologies for self-cleaning or self-disinfecting surfaces has surged during the COVID-19 pandemic, even as the realization has grown that the primary transmission mode for SARS-CoV-2 is through aerosols. Now, a team of UBC researchers has developed a polysiloxane coating for textiles that works through a combination of passive and active mechanisms to inactivate or decrease infectivity of pathogens, including SARS-CoV-2.
The work, led by doctoral student Taylor Wright at the University of British Columbia with a team of five others, including senior author and UBC chemistry professor Michael Wolf, was a pandemic pivot from their previous work on antimicrobial polymers. “We’ve been largely working within the solid-state and thin films. So the research really began on textiles during the pandemic when things like face masks were becoming more and more common,” says Wright.
It’s work that contributes to addressing a significant knowledge gap. A recent review paper in Nature led by Paulina Rakowska of the National Biofilms Innovation Centre at the University of Southampton in Southampton, Hampshire, UK, noted that antimicrobial properties of materials are widely studied but antiviral properties much less so.
The coating Wright and colleagues developed is outlined in the January 3 issue of the journal ACS Applied Materials and Interfaces and produced in a two-step process. The team had previously developed a method for turning liquid polymers into crosslinked solids, using various colours of light, particularly UV. This new project found a way to apply this solid layer to fabric, explains Wright. They tested the effectiveness of the polymer coating on cotton and polyester.
Step one in their antimicrobial and antiviral textile production involves a soaking procedure to get the liquid onto the fabric as a wet coating. The second step acts to cure the material using UV light. “UV light reacts with the photocatalyst, generating singlet oxygen and crosslinking the material, turning the initially liquid silicone into an elastic solid that’s right on the surface,” Wright explains.
The solution is a polysiloxone polymer with an attached dye – the light absorber – that generates the singlet oxygen, explains Wolf. The antimicrobial polymer was prepared by condensing aminopropylmethylsiloxane-dimethylsiloxane copolymer (PNH2-7) with Rose Bengal lactone, both assessed as non-toxic and safe for human use.
In previous work, the team looked at contact killing of Esheria coli and Methicillin-resistant Staphylococcus aureus (MRSA), whereby bacteria landing on the surface of their material were split open by amine functionalities. The added functionality in this new process, explains Wright, is the photoactive component. “When it’s exposed to light, it generates the singlet oxygen and can sterilize and kill a much wider variety of things,” says Wright. Tested against E. coli and MRSA, they demonstrated that light activation made the material more effective than with passive contact only.
Moving on to test viruses, they weren’t able to hinder COVID with just the passive step, but when exposed to UV light, they found it inactivated the virus quite rapidly, resulting in an up to 90% decrease in infectious virus compared to that for untreated fabric and fabric not exposed to light. The singlet oxygen is like an antimicrobial hammer, explains Wright.
Chemical engineer Babak Adeli, Senior Director of Research and Development at ACUVA Technologies in Burnaby, BC, who co-authored a review on Ultraviolet Disinfection Systems against COVID-19 in 2020, but was not involved in the current study, says, “The results are promising, although 90% reduction in microbiology language is not significant.” Nevertheless, he notes the importance of having achieved such an inactivation rate under visible light, “which is considerable and opens up many applications,” he says.
Wolf acknowledges that further testing of their product is needed. He hopes the simplicity of the process and its scalability will allow for broader applications. Expanded uses could include gowns, curtains and dividers in a clinical setting as potential measures to avoid hospital-acquired infections. Other applications could include face masks and exercise clothing to prevent microbially-created odours, says Wolf. There are opportunities to apply this to anything that can be soaked in solution, says Wright, even woods, fibres, rubbers and foams.