Less spread of diseases through a special coating?
Bacterial infections are often transmitted through everyday objects. A special light-activated antimicrobial coating on telephone screens and keyboards could, according to a recent study, counteract the spread of diseases.
The University College London investigation found that a special light-activated antimicrobial coating could prevent the spread of diseases via telephone screens, keyboards or even catheters and breathing tubes. The results of the study were published in the English language journal "Nature Communications".
How are therapy-associated infections triggered?
Telephone screens, keyboards and the inside of catheters and breathing tubes represent a main source of so-called therapy-associated infections (HCAIs). The best-known therapy-associated infections are caused by Clostridioides difficile (C. difficile), methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) causes. These often occur during inpatient medical or surgical treatment or when visiting a healthcare facility and pose a serious health threat.
New coating needs weaker light
The current study shows that a light-activated antimicrobial coating successfully kills bacteria even at low intensity and ambient light (300 lux). Previously, similar coatings required intense light (3,000 lux), such as that found in operating theaters, to activate their killing properties.
What role does gold play in coating?
The new bactericidal coating consists of tiny clusters of chemically modified gold, which are embedded in a polymer with crystal violet (a dye with antibacterial and antifungal properties). Dyes such as crystal violet are promising candidates for killing bacteria and sterilizing surfaces, as they are often used to disinfect wounds, the researchers report.
What happens when the dye is exposed to light?
When exposed to bright light, such dyes produce reactive oxygen species, which in turn kill bacteria by damaging their protective membranes and DNA. This is reinforced when they are paired with metals such as silver, gold and zinc oxide, the researchers report.
Coating could be used in a variety of ways
The researchers were surprised to see how effectively the coating kills both S. aureus and E. coli in ambient light, making it promising for use in a variety of healthcare environments. The bactericidal coating was made using a scalable method and it was examined how well the coating kills S. aureus and E. coli under different lighting conditions.
Bacterial growth examined
The sample surfaces were treated with either the bactericidal coating or a control coating before they were contaminated with 100,000 colony forming units (CFU) per ml of S. coli. The growth of the bacteria was then examined under various light conditions between 200 and 429 lux.
How much was the growth of the bacteria reduced?
The researchers found that a control coating of crystal violet in a polymer alone did not kill either of the two types of bacteria in ambient light. Under the same light conditions, however, the bactericidal coating reduced the growth of S. aureus (by 3.3 log after six hours) and of E. coli (by 2.8 log after 24 hours).
Why is E. coli more resistant?
E. coli was more resistant to the bactericidal coating than S. aureus because it took longer to significantly reduce the number of viable bacteria on the surface. This is probably due to the fact that E. coli has a cell wall with a double membrane structure, while S. aureus only has a single membrane barrier, the researchers speculate.
Hydrogen peroxide chemically attacks cell membranes
The team unexpectedly discovered that the coating kills bacteria by producing hydrogen peroxide. It works by chemically attacking the cell membrane, so it takes longer to fight bacteria with more protective layers. The gold clusters in the coating are the key to generating hydrogen peroxide through the action of light and moisture. Since the clusters contain only 25 gold atoms, very little of this precious metal is required compared to similar coatings, which makes the coating attractive for wider use. (as)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
- Gi Byoung Hwang, He Huang, Gaowei Wu, Juhun Shin, Andreas Kafizas et al .: Photobactericidal activity activated by thiolated gold nanoclusters at low flux levels of white light, in Nature Communications (published March 5, 2020), Nature Communications