Exploring versatile applications of cyclodextrins in heritage science

The need of eco-compatible, safe and long-lasting materials and methods for the protection and conservation of Cultural Heritage is now increasingly mandatory. In the daily practice of Restores, commercial products, as corrosion inhibitors for metal artworks and anti-microbials for stone surfaces, suffer from their toxicity and environmentally unfriendly nature. Their leaching process could induce dispersion of chemicals in the surroundings and reduce the protective action, demanding for further maintenance actions. In the last decade, our research group was involved in the design, synthesis and validation of innovative products and/or formulations for conservation and restoration.[1-3] To reduce the toxicity of the commercial products and to increase the durability of the protective treatment, smart nanostructured coatings were designed by using nanocarriers for a sustained release of the active agents. Due to their inclusion ability, β-Cyclodextrin (β-CD) and its derivatives can be fruitfully used for molecule entrapment and for improvement of bioavailability. These smart stimuli-responsive cyclodextrin-based coatings can assure the absence of direct contact of the product with the Restorer and its controlled and gradual release on the surface. In this work, examples of β-CD applications for the sustainable conservation of copper-based artworks and the preservation of stone materials against biodeterioration are reported. The β-CD inclusion complexes and the corresponding coatings were analyzed by UV-VIS spectroscopy, Xray Photoelectron Spectroscopy (XPS) and electrochemical techniques for the determination of the surface chemical analysis, the kinetics of release of the active agent and the corrosion inhibitor performance. A chloride solution was used to simulate the corrosive environment of a marine context harmful for Cu-based alloys, and an acidic solution was used to mimic the typical pollution of an urban atmosphere. The coatings were tested on the metallic/stone surfaces before and after the corrosive or biological attack to evaluate their efficacy as corrosion inhibitors and antimicrobials.