Design of Polycation-Functionalized Resveratrol Nanocrystals for Intranasal Administration

Background/Objectives: Nanocrystals (NCs) are a relatively underexplored yet adaptable platform with broad potential for various applications. Currently, the surface modification of NCs leads to the development of versatile platforms capable of enhancing targeted delivery potential and supporting the advancement of precision medicine. With this in mind, this study focused on the design and surface functionalization of a resveratrol (RSV) NC selected for its antioxidant and neuroprotective effects. Methods: The design of the RSV NC was assessed by the Quality by Design approach. With the aim of intranasal administration, we assessed the RSV NC functionalization with a cationic poly (amino acid) belonging to the class of cell-penetrating peptides. Both naked and surface-modified RSV nanosuspensions were characterized in terms of mucoadhesion, behavior in artificial cerebrospinal fluid, crystallinity, solubility, and storage stability. The scavenging activity (%) of neat RSV and its nanosized forms was measured using the DPPH assay. Results: RSV NCs were successfully designed, producing truncated cubic crystals (~240 nm) with an ~80% drug content. Functionalization was efficiently achieved with poly-l-arginine hydrochloride as revealed by DSC and FTIR and resulted in a positively charged nanosuspension. Nanonization technology improved drug solubility in water and did not affect RSV scavenging activity. Technological characterization demonstrated that both nanosuspensions present suitable properties for intranasal administration in terms of particle size, mucoadhesive tendency, and stability in artificial cerebrospinal fluid. An MTT assay revealed the safety of all treatments in human microglia (HMC3) cells. Conclusions: RSV NCs' functionalization enhanced their brain delivery potential, establishing a promising platform to improve therapeutic outcomes in neurodegenerative diseases.