Inhibition of bacterial growth on marble stone of 18th century by treatment of nanoencapsulated essential oils

Controlling of cultural heritage biodeterioration is a serious problem in the world. Chemical biocides, used to kill
unwanted microorganism, can represent a risk for human health and environment, and interfere with the restoration
material. Natural biocides could represent a valid alternative to conventional ones. In this study we
report the use of nanocapsules suspensions (NCs) loaded with Origanum vulgare and Thymus capitatus essential
oils (EOs) to contrast the development of bacterial growth of two microrganisms (Escherichia coli and Kokuria
rhizophila) on the marble stone from 18th century church altar. No structural change was observed on the stone
after treatment with the aqueous suspension containing nanoparticles as evidenced by SEM-EDX analysis. The
nanostructurate systems (EO-NCs) were able to inhibit the bacterial grow on the stone pretreated with bacterial
inoculum as showed by agar discs contact test. Nanocapsules, based on biodegradable and biocompatible
polymer (poly(?-caprolactone)), loaded with thyme EO are more efficient than nanocapsules loaded with oregano
EO. The obtained results evidenced the potential of these natural biocides in the treatment of biodeteriorated
cultural heritage.