New Biocide Based on Tributyltin(IV) Ferulate-Loaded Halloysite Nanotubes for Preserving Historical Paper Artworks

Combining biologically active compounds with nanocarriers is an emerging and promising strategy for enhancing the activities of molecules while reducing their levels of toxicity. Green nanomaterials have recently gained momentum in developing protocols for treating and preserving artifacts. In this study, we designed a functional biohybrid material by incorporating tributyltin(IV) ferulate (TBT-F) into halloysite nanotubes (HNTs), generating a new formulation called HNT/TBT-F. The primary objective was to develop a formulation with robust antimicrobial properties and reinforcing features for treating paper with artistic and historical value. To characterize HNT/TBT-F, assess the HNT's loading capacity, and investigate the TBT-F release kinetics from the nanotubes, various analytical techniques, including UV-Vis and infrared spectroscopies, thermogravimetry, and microscopy analysis, were employed. Furthermore, we evaluated the antimicrobial potential of TBT-F and HNT/TBT-F against Kocuria rhizophila, a bacterial strain known for its opportunistic behavior and a cause of artifact biodeterioration. HNT/TBT-F exhibited a significantly stronger bactericidal effect than TBT-F alone against K. rhizophila cells growing planktonically or those forming a biofilm. This enhanced performance could relate to the confinement of TBT-F within the nanotubes, which likely improved its physical-chemical stability and increased the local concentration of TBT-F upon contact with the bacterial cells. Additionally, we evaluated the mechanical properties of a paper treated with HNT/TBT-F, assessing any potential alterations in its color. The findings of this study highlight the favorable attributes of the HNT/TBT-F formulation and its potential for developing protocols aimed at consolidating and preserving culturally significant paper objects.