Preserving Heritage Spaces by a Tea Tree Oil-Loaded Silica Microparticles System for Air Purification

Airborne fungi and bacteria pose a severe challenge for conservators, as they can settle on artistic surfaces, leading to chemical, physical and aesthetic degradation of artworks. A new air-cleaning system has been developed to reduce indoor airborne microorganisms by leveraging the antimicrobial potential of Tea Tree (Melaleuca alternifolia) Essential Oil (TTEO) encapsulated within the pores of MCM-41 mesoporous silica microparticles (MCM-TTEO), thereby extending its antimicrobial activity and enhancing its efficacy. Experimental data showed a progressive release of TTEO from the MCM-TTEO system during the 5 weeks monitoring. The release rate was quite linear in the first week, reaching about 16.2%, before plateauing at approximately 30% in the next weeks. A comparison of the performances of the MCM-TTEO system with those of the non-encapsulated (‘free’) TTEO was performed using a comprehensive air quality monitoring approach, which tracked temperature, relative humidity, microbial loads and particulate matter. Results demonstrate that the MCM-TTEO system maintained higher biocidal activity over the 5-week study period than the free EO. Furthermore, the biocidal efficacy increased when the MCM-TTEO system was used in direct contact with microorganisms. These promising findings highlight the potential for exploring different combinations of the two components in both passive and active configurations, including the development of air filtration systems.