Biostability enhancement of oil core — polysaccharide multilayer shell via photoinitiator free thiol-ene ‘click’ reaction

We report on the preparation of nanocapsules completely made of natural biomaterials. A lipophilic core (soybean oil and egg lecithin as surfactant) is coated with a polysaccharides-based multilayer shell (glycol chitosan and heparin) covalently cross-linked. Polysaccharides, opportunely modified with thiol and olefin moieties, are covalently cross-linked, exploiting the light initiated thiol-ene reaction, known as click reaction. [Display omitted] •Glycol chitosan and heparin were modified at significantly high degrees of modification.•An oil core—polysaccharide multilayer has been fabricated.•Biostability has been enhanced through a photoinitiator free thiol-ene ‘click’ reaction.•The final product results to be stable and completely biocompatible. Layer-by-layer of polyelectrolytes has emerged as one of the easiest and most controlled techniques to deposit ultrathin polymer layers mainly driven by electrostatic interactions. However, this kind of interaction results to be weak and easily breakable in physiological environment. Here we report on the preparation of nanocapsules completely made of natural biomaterials: a lipophilic core (soybean oil and egg lecithin as surfactant) as nanometric template and a polysaccharide-based multilayer shell (glycol chitosan and heparin) covalently cross-linked. We first modified glycol chitosan with a thiol moiety and heparin with an alkene moiety, respectively, and then we built a polymer multilayer film with a covalent cross-linkage among layers, exploiting the light initiated thiol-ene reaction, known as click chemistry. We showed the possibility to perform the covalent cross-linkage without any photoinitiator or metal catalyst, thus avoiding cytotoxic effects and further purification steps. The so realized nanocapsules resulted to be stable and completely biocompatible and, therefore, of interest for the biotechnology fields, mainly for drug delivery.