L-Lysine-Based Dendritic Coatings with Antimicrobial and Hydrophobic Properties for Preventive Conservation of Natural Stone

Natural stone used in cultural heritage is highly susceptible to deterioration driven by environmental, chemical, and biological factors, with microbial biodeterioration and water playing a critical role in physicochemical and aesthetic degradation. Therefore, this study aimed to develop innovative organic coatings with antimicrobial and hydrophobic properties based on dendritic polymers derived from L-lysine functionalized with different fatty acids. Dendrons of generations G0 and G1 were synthesized via amidation and hydrolysis reactions, followed by structural characterization using NMR, FTIR and mass spectrometry, and their antimicrobial activity was evaluated against microorganisms associated with biodeterioration, alongside assessments of hydrophobic performance, aesthetic compatibility and durability on natural stone substrates. The results showed that antimicrobial activity and hydrophobic performance depended on the dendritic architecture, fatty acid chain length, and stone substrate. Most formulations also exhibited acceptable colorimetric compatibility after accelerated ageing. Overall, these findings highlight the potential of the developed coatings as a promising, sustainable, and effective strategy for protecting natural stone against the deleterious effects of water, contributing to the mitigation of biodeterioration and the conservation of cultural heritage assets.