Copper to combat microorganisms
Benefits of textiles with antiviral and antibacterial effect now proven
BÖNNIGHEIM (dh/msz/ri) As part of an AiF research project (AiF-No. N 17407 N1), scientists at the Hohenstein Institute in Bönnigheim have for the first time developed a textile treatment with both antiviral and antibacterial functionality. This technology should lead to the development of products to help break the chain of infection in kindergartens, children's daycare centres and hospitals.
The majority of infectious respiratory illnesses are caused by viruses. For example, the respiratory syncytial virus, a pathogen belonging to the family of paramyxoviruses, causes infections of the upper respiratory tract in the form of coughs, colds, acute bronchitis or even pneumonia, especially in young children. This means that the rate of infection in childcare centres and kindergartens regularly rises at the start of winter. Diarrhoea caused by the norovirus or rotavirus, on the other hand, as well as bacterial illnesses of the respiratory tract and gut, are "in season" all year round.
To avoid infection by droplets or smearing, it is essential to maintain high hygiene standards with regard to hands, textiles and surfaces.
The key to avoiding or limiting cases of illness in childcare facilities is regular and thorough hand-washing, by both the children themselves and their carers.
However, pathogens can also be transmitted and distributed via textiles. Admittedly, viruses do not have their own metabolism and so can only survive for a limited period outside the host body, and, unlike bacteria, cannot reproduce there. However, studies have proved convincingly that textiles which are in regular contact with hands can contribute to the spread of viruses (Sauver et al., 1998). Scientists believe that, in addition to people's hands, their clothing and household and hospital textiles in the form of bed linen, towels, tea-towels etc. also represent an important potential transmission route for viruses (see Figure 1).
The third main transmission route for viruses is via surfaces of all kinds, which can also be contaminated with viruses and bacteria from people's hands or exhaled breath. That is why another important element in preventing infection is the cleaning of surfaces. This is the issue that has been addressed by the Hohenstein scientists in their current research project.
The trial therefore used cleaning cloths in which an antiviral and antibacterial effect were combined for the first time in a single functional textile treatment. "Ultimately we are interested in whether the risk of infection, i.e. the transmission of microorganisms from person to person, can be reduced in future by using biofunctional textiles," said Prof. Dirk Höfer, Head of the Department of Hygiene, Environment & Medicine at the Hohenstein Institute.
To achieve this objective, first of all various organic and inorganic copper compounds in colloidal (suspended) form or as nanoparticles and copper complexes, were applied in a sol-gel process. The effectiveness of the textile microfibre substrates was optimised by using various different application techniques such as Foulard or spraying processes. The textiles' ability to render the test viruses inactive was significant, lasted over 15 wash cycles and was also resistant to rubbing.
A second, alternative antiviral treatment for microfibre cloths was achieved by finishing them with copper pigments in a high-temperature exhaust process. In a similar process to dyeing using dispersion dyes, the dispersed copper pigments were applied to the fibres in a slightly acidic milieu. In a second step, they were fixed using a polymer bonding agent in the cold-pad-batch process (CPB) to protect the copper particles from mechanical abrasion. These copper treatments also had good results, although the originally light-coloured woven fabric developed a slightly greenish colour (see Figure 2). All the samples passed the laboratory tests for skin compatibility.
The practical tests for effectiveness were carried out on different surfaces such as glass, stainless steel and wood, which had been contaminated with viruses and were then wiped with the specially treated cleaning cloths (see Figure 3). The test virus used was the bacterial virus MS2, an apathogenic surrogate virus which, because of its structure and environmental stability, is similar to clinically relevant viruses such as Norovirus, the polio virus, Hepatitis A or enteroviruses. The treated microfibre cloths absorbed 91% of the viruses that had been applied. At the same time, the concentration of the virus in the cloth was reduced by about 90%. Tests were also carried out to measure effectiveness against bacteria and fungi in accordance with official standards (DIN EN ISO 20743 and EN 14119). The trial was designed in this way so that the treatments could be made as effective as possible.
The research project shows that antiviral cleaning cloths do have a measurable hygienic effect and could help reduce the rate of transmission of microorganisms, including pathogens, in childcare centres and kindergartens. The new functionality could also be of interest in the domestic environment, in hospitals, old people's and care homes or in communal catering facilities (e.g. canteens), as well as for protective clothing used by firefighters, disaster relief workers and the armed forces.