Chennai: Researchers at ACS Applied Materials and Interfaces have developed a special type of cotton face mask that kills up to 99.9999 percent of bacteria and viruses within 60 minutes of daylight exposure.
The statutory regulation to wear protective masks has been an effective strategy in fighting SARS-CoV-2 infections. Wearing face masks covering the mouth and nose is mandatory in most countries.
During the Covid-19 pandemic, many people have become accustomed to wearing cotton face masks in public places. However, viruses and bacteria that stick to the mask could be transferred elsewhere when the wearer removes or touches it.
Also, face masks made of various cloth materials can filter nanoscale aerosol particles, such as those released by a cough or sneezeāpotentially helping to reduce the spread of diseases, including Covid-19. But live bacteria and viruses on the surface of the mask could still be contagious.
Peixin Tang, Gang Sun, Nitin Nitin and colleagues wanted to develop a new cotton fabric that would release reactive oxygen species (ROS) when exposed to daylight, killing microbes attached to the fabric’s surfaces while being washable, reusable and safe for the wearer. Then, a person could disinfect their cloth mask during their lunch hour outside in the sun, or by spending a longer period of time under office or building lights, which are much less intense than sunlight.
The team found that a fabric made with a dye called rose Bengal as the photosensitiser killed 99.9999 per cent of bacteria added to the fabric within 60 minutes of daylight exposure and inactivated 99.9999 percent of T7 bacteriophage, a virus thought to be more resistant to ROS than some coronaviruses within 30 minutes.
Further testing showed that the material could be hand washed at least 10 times and constantly exposed to daylight for at least seven days without losing its antimicrobial activity. The fabric shows promise for making reusable, antibacterial/ antiviral cloth face masks and protective suits, the researchers say.
The team made their antimicrobial fabrics by attaching positively charged chains of 2-diethylaminoethyl chloride (DEAE-Cl) to ordinary cotton. Then, the researchers dyed the modified cotton in a solution of a negatively charged photosensitiser (a compound that releases ROS upon exposure to light), which is attached to the DEAE chains by strong electrostatic interactions.