New multi-functional encapsulation systems based on HP-β-cyclodextrin, chitosan and essential oils for conservation of organic-media cultural heritage

• A multi-functional ready-to-use antifungal formulation is created. • The formula is based on hydroxy-propyl-β-cyclodextrin, chitosan and essential oils. • Micro-encapsulation by spray drying provides a long-lasting antifungal action. • A de-acidifying effect on the treated substrate is also observed. • No color changes occur on treated artificially aged paper mocks-up. In this study, a new multi-functional encapsulation system was formulated by using, for the first time, spray drying technique for application in cultural heritage conservation. A bio-based and safe ready to use formulation allowing homogeneous application of the anti-fungal and de-acidifying substance in an aqueous medium, without using surfactants or solvents that may interfere with the artistic substrates, was obtained. The chemical profile of lavender and rosemary essential oils (EOs) were obtained by GC-MS. These EOs were encapsulated in HP-β-cyclodextrin and chitosan by spray drying. Thermogravimetric and differential scanning calorimetry analyses (TGA, DSC) of encapsulated samples were performed, whereas structural and morphological analyses were carried out by X-ray Diffraction (XRD) and scanning electron microscopy (SEM), respectively. Encapsulated materials showed good performance in terms of Encapsulation Efficiency and Yield, with 95% and 54% for encapsulated lavender (LEEO), and 86% and 76% for encapsulated rosemary (REEO), respectively. Antifungal activity of raw and encapsulated EOs was studied towards Alternaria alternata in poisoned culture media and on paper mocks-up. The studied materials also showed improved thermal stability and enhanced antifungal properties of EOs. The paper models treated with LEEO and REEO and subjected to artificial aging showed total colorimetric variation ΔE < 3 and a surface pH of 6.5. This research demonstrated the potential of using antifungal encapsulated EOs for the conservation of artistic organic-media objects in cultural heritage. These materials can perform a dual action by preserving the artworks from biological damage as well as acting as a de-acidifying treatment for the support.