In Vitro Evaluation of MgB2 Powders as Novel Tools to Fight Fungal Biodeterioration of Heritage Buildings and Objects

Irina Gheorghe,Ionela Avram,Viorica Maria Corbu,Mihai Alexandru Grigoroscuta,Mariana Carmen Chifiriuc,Ion Blăjan,Adina Daniela Datcu,Venus Mateescu,Marcela Popa,Lia Mara Diţu,Octavia Emilia Zetu,Violeta Corina Cristea,Irina Balotescu,Dan Batalu,G Aldica ,Coralia Bleoţu ,Ionuţ Pecete ,Daniela Victoria Zaharia ,Nıcoleta Ianovici ,Andreea Ştefania Dumbravă ,P Badica ,Veronica Lazăr ,M Burdusel ,Luminiţa Măruţescu

doi:10.3389/fmats.2020.601059

Abstract

The 17th–19th century wooden and stone churches are an iconic symbol for the Romanian national heritage, raising urgent needs for the development of efficient and ecofriendly restoration and preservation solutions. Nanotechnology has a great but largely unexplored potential in this field, providing new tools and methods to achieve higher consolidation and protection efficiency, mainly due to the ability of nanoparticles to inhibit the growth and metabolic activity of different biodeteriorating agents, including fungi. The purpose of the present study was to report for the first time on the efficiency of MgB2materials, mainly prized for their practical superconducting properties, against a large collection of filamentous fungal strains recently isolated from biodeteriorated wooden and stone heritage objects. Four types of MgB2powders, with a crystallite size of 42–113 nm, were tested by qualitative (on 149 strains) and quantitative (on 87 strains) assays. The cytotoxicity was evaluated by the microscopic analysis of SiHa cells morphology and Hep2 cell cycle analysis and the ecotoxicity by theAlliumtest. The tested filamentous fungal strains belonged to 11 different genera, and those isolated from mural paintings and wooden objects exhibited the best capacity to colonize the inert substratum. All MgB2powders exhibited similar and relatively low minimal inhibitory concentrations (MIC) values against theAspergillusandPenicilliumisolates, which were predominated among isolates. From the tested powders, PVZ and CERAC proved to be more efficient against the strains isolated from stone and wood materials, while LTS was active against the fungal strains colonizing the mural paintings and museum objects. The cytotoxicity results indicated that the tested powders are toxic for the human cells at concentrations higher than 50 µg/ml, but, however, the very short lifetime of these NPs prevents their accumulation in the natural environment and, thus, the occurrence of toxic effects. The tested powders proved to be ecofriendly at the active antifungal concentrations, as suggested by the phytotoxicity test results. Taken together, our results suggest the potential of the MgB2materials for the development of environmentally safe antifungal substances, which can be used in the control of the material cultural heritage biodeterioration process.

Highlights

Romania hosts the territory of a valuable heritage of a few hundreds of churches, classified according to their national or local importance as monuments of category A or B, respectively (Angelescu, 1957; Nicu and Stoleriu, 2019)
In order to evaluate the antifungal activity of MgB2 NPs, different filamentous fungal strains belonging to 11 different genera with a large species richness of species (Alternaria, two species of Arthrinium, at least 11 species of Aspergillus, at least two species of Cladosporium, Byssochlamys, and Curvularia, two species of Fusarium and Mucor, at least 14 species of Penicillium, and two species of Rhizopus and Purpureocillium) were selected, and the tested strains belonged predominantly to Penicillium and Aspergillus species
The initial qualitative screening was performed on a larger number of strains, and the most susceptible ones were further tested by the quantitative assay, in order to establish the minimum inhibitory concentration (MIC) values of the tested NPs

Summary

Introduction

Romania hosts the territory of a valuable heritage of a few hundreds of churches, classified according to their national or local importance as monuments of category A or B, respectively (Angelescu, 1957; Nicu and Stoleriu, 2019). The 17th–19th century wooden and stone churches are an iconic symbol for the Romanian national heritage, representing important places for the spiritual and for secular individual and collective events of the founding communities (Bratu, 1982; Sasaran et al, 2020). Many of the Romanian heritage churches of national importance (category A) are in different stages of degradation, being, over time, subjected to extremely different conservation, protection, restoration, and capitalization procedures (Georgescu et al, 2017). Despite the major ecological role in the biogeochemical cycles, microorganisms could have deleterious effects when colonizing the wood and stones parts of historic buildings and monuments, as well as cultural heritage objects made of natural materials (e.g., paper, wood, and textiles). In order to develop effective strategies to prevent biodeterioration and allow restoration and conservation of heritage monuments, one must know the type and metabolic activity of microorganisms which are involved in the biodeterioration in different geographical regions, with different climate (Negi and Sarethy, 2019)

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