Infectious diseases can be transmitted through surfaces - surfaces such as doorknobs, toys, light switches, and other often-touched objects. Now, research has shown that a thin cellulose film can reduce or even prevent contaminated surfaces from becoming a route of transmission for various virual and bacterial infections. The new coating was found to inactivate the SARS-CoV-2 virus within minutes, inhibit the growth of bacteria, including E.Coli, and mitigate contact transfer of pathogens.
The coating, developed by scientific teams from the University of Birmingham, Cambridge University, and FiberLean Technologies, consists of a thin film of cellulose fibre that is invisible to the naked eye and is abrasion-resistant under dry conditions, making it suitable for use on high traffic objects such as door handles and handrails.
While conventional chemical disinfectants and antiviral surface designs target either the structural proteins or nucleic acids, the researchers, led by Professor Zhenyu Jason Zhang, from Birmingham’s School of Chemical Engineering, focussed on drying out the respiratory droplets that contain the viruses by the capillary force introduced by the porous structure.
The COVID-19 virus is known to remain active for several days on surfaces such as plastic and stainless steel, but for only a few hours on newspaper. The team, which has expertise in surface chemistry and formulation engineering, investigated the structure and performance of a coating made from micro-fibrillated cellulose (MFC) provided by FiberLean Technologies, the leading global producer of MFC for the paper and packaging industry.
The researchers found that the porous nature of the film plays a significant role: it accelerates the evaporation rate of liquid droplets, and introduces an imbalanced osmotic pressure across bacteria membrane.
In tests using droplets containing the virus left on the coating for 5 minutes, a three-fold reduction of infectivity occurred; after 10 minutes, the infectivity fell to zero. By contrast, when droplets containing SARS-CoV-2 were left on a glass surface, their initial infectivity was still maintained after 10 minutes. The antimicrobial tests were repeated with droplets containing bacteria (E.Coli and S.epidermidis), and here again, the researchers saw substantial reductions in infectivity at 1 hour and 24 hours.
The experiments were repeated with aerosolised artificial saliva, and here the analysis suggested that the cellulose thin film is also effective in suppressing the contact transfer of respiratory aerosols.
