MARE, CDRSP, CI-IPO, i3S, FEUP, LIFE, ARNET

Cultural heritage refers to the legacies passed down from our ancestors, safeguarding a nation's history and identity. Artefacts and historically significant objects, such as Roman limestone mosaics, are vulnerable to microbial colonisation under favourable environmental conditions. Various microbial groups, including bacteria, contribute to biodeterioration, leading to both physicochemical and aesthetic damage to stone artefacts. Preserving these cultural treasures is important not only to keep history alive but also for their cultural and economic significance. Traditional methods to prevent microbial colonisation often use toxic substances, have short-term effectiveness, and may damage artefacts, sometimes due to incompatibility with the material. In recent years, silver nanoparticles (AgNPs) have emerged as a promising alternative for protecting heritage objects from microbial contamination. Nanomaterials such as AgNPs are valued for their unique physicochemical and biological properties. These characteristics make AgNPs highly versatile, with applications spanning various industries including the preservation of cultural heritage, a rapidly growing field with significant cultural and economic implications. AgNPs can be synthesised through physicochemical or biological methods, with biosynthesis emerging as a sustainable, cost-effective, and environmentally friendly alternative. This approach enables the production of AgNPs with the desired characteristics according to their specific application. However, the application of biosynthesised AgNPs in this context still remains underexplored. This study, in collaboration with the Conímbriga National Museum, investigated the antibacterial and antibiofilm properties of AgNPs biosynthesised using cell-free filtrates (CFFs) from marine endophytic fungi associated with seaweed. These AgNPs targeted environmental bacterial species isolated from limestone tesserae of mosaics test pieces exposed in different locations within the ruins of the Roman city of Conímbriga. After AgNPs characterisation, antibacterial effects were tested at concentrations of 6.25 μg/mL and 25 μg/mL, with antibiofilm activity assessed at the lower concentration. The results demonstrated that marine fungal CFFs facilitate an eco-friendly synthesis of AgNPs with significant antibacterial and antibiofilm properties against environmental bacteria that can colonise cultural artefacts. These findings highlight the potential of biosynthesised AgNPs in heritage preservation. Future research should focus on optimising concentrations, refining application methods, and ensuring long-term safety to enhance their practical implementation in cultural conservation.