Antifungal Activity of Polyoxometalate-Ionic Liquids on Historical Brick.

Katarzyna Rajkowska,Isabel Franco-Castillo,Anna Otlewska,Anna Koziróg,Scott G Mitchell,Małgorzata Piotrowska,Elena Atrián-Blasco

doi:10.3390/molecules25235663

Abstract

Moulds inhabiting mineral-based materials may cause their biodeterioration, contributing to inestimable losses, especially in the case of cultural heritage objects and architectures. Fungi in mouldy buildings may also pose a threat to human health and constitute the main etiological factor in building related illnesses. In this context, research into novel compounds with antifungal activity is of high importance. The aim of this study was to evaluate the antifungal activity of polyoxometalate-ionic liquids (POM-ILs) and their use in the eradication of moulds from historical brick. In the disc diffusion assay, all the tested POM-ILs inhibited growth of a mixed culture of moulds including Engyodontium album, Cladosporium cladosporioides, Alternaria alternata and Aspergillus fumigatus. These were isolated from the surfaces of historical brick barracks at the Auschwitz II-Birkenau State Museum in Oświęcim, Poland. POM-IL coatings on historical brick samples, under model conditions, showed that two compounds demonstrated very high antifungal activity, completely limiting mould growth and development. The antifungal activity of the POM-ILs appeared to stem from their toxic effects on conidia, as evidenced by environmental scanning transmission electron microscopy observations. The results herein indicated that POM-ILs are promising disinfectant materials for use not only on historical objects, but probably also on other mineral-based materials.

Highlights

The susceptibility of brick, concrete, mortar, stone and other mineral-based building materials to colonisation by various organisms is defined as bioreceptivity
The highest activity was found for [THepA]+ and [THexA]+ (Figure 1). These results indicate that diffusion-based antifungal activity of polyoxometalate-ionic liquids (POM-Ionic liquids (ILs)) resulted mostly from activity of the cation species, which is consistent with previous findings of Kubo et al [26], who explained that the antibacterial activity of these compounds arises primarily from the cationic action
POM-ILs as part of thisto project showed high antifungal activitybuilding against materials

Summary

Introduction

The susceptibility of brick, concrete, mortar, stone and other mineral-based building materials to colonisation by various organisms is defined as bioreceptivity. This concept was introduced by Guillette [1] and included chemical and physical parameters such as mineralogical composition, water availability, temperature, pH, surface porosity and roughness influence on biological succession [2,3]. From a biological point of view, mineral-based building materials represent an extreme microniche for microbial growth due to large variations in environmental parameters and higher desiccation conditions in vertical and subvertical surfaces [3]. Bacteria and fungi inhabit pits, cracks and fissures on the surface of mineral-based materials, and they often may interact with substrate causing their deterioration [4].

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