Are Lewis acids the antimicrobial solution for textiles?

A new research project at the Hohenstein Group aims to look at the antimicrobial effects of Lewis acids, once applied on textile surfaces. The research may contribute to the measures for cutting the spread of multi-resistant bacteria in medical facilities

Investigation of antimicrobial activity. Image copyright of Hohenstein Group

Many areas of everyday and professional life require antimicrobial protection. Antimicrobial textile surfaces are currently achieved using silver- or ammonium-containing compounds. However, there are questions surroundin possible adverse ecological and toxicological effects around the use of such compounds. In addition, these compounds are generally expensive.

Lewis acids exhibit an acidic surface effect and have already been shown to have an antimicrobial effect. These compounds can already be found in applications such as the cleaning agents for hospital floors. However, they have not yet been applied to textile surfaces.

In presence of moisture, Lewis acids (such as metal oxides, e.g. zinc oxide) generate low pH-values on their surfaces, resulting in antimicrobial effects comparable to the natural protective acid mantle of human skin.

Lewis acids have proved useful against different pathogens such as fungi, bacteria and even viruses. Furthermore, they have been found to be very effective and stable, even on exposure to human sweat and proteins.

From a cost point of view, estimations suggest that the use of Lewis acids in antimicrobial textile coatings may result in cost-reductions of up to 90%.

With the current project the Hohenstein Group, researchers will cooperate closely with manufacturers of products for the textile industry, e.g., those producing knitted and woven fabrics or textile auxiliaries as well as textile finishers.

Part of the work includes the determination of suitable metal oxides featuring very low aqueous solubility that can be applied to textile surfaces. By combining different substances, it is hoped that synergistic effects might be generated. Systems based on a binder matrix and a Lewis acid will be selected, as this concept is already known in the field of surface functionalisation.

The project includes the development of an innovative finish based on suitable Lewis acids with different binder matrices.

To provide relevant results for a broad audience, different textiles will be finished and characterised. Correlating the amount of Lewis acid applied to the textile surface with the amount finally released will serve as a basis for a cost/benefit analysis. Biocompatibility testing will be performed to ensure that any harmful effect on the skin originating from the treated textiles can be ruled out.

Based on the project results, optimised compositions for antimicrobial textile finishes and the corresponding process parameters will be provided to the textile industry.

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