Covalent functionalization of polymeric nanoparticles prepared from nano-emulsion templates for gene silencing and antioxidant delivery at neuronal level

Poly(lactic- co -glycolic acid) (PLGA)-based polymeric nanoparticles (PLGA NPs) have proven to be effective as potential drug delivery systems. The presence of carboxylate groups on their surface facilitates the development of multifunctional NPs enhancing therapeutic efficacy through synergetic effects. Our study describes the preparation of PLGA NPs using oil-in-water polymeric nano-emulsions, generated via a phase inversion composition low-energy emulsification method. Rosmarinic acid (RA), a phytochemical with neuroprotective effects, and an antisense oligonucleotide (ASO) were selected respectively as a phytochemical to be entrapped and as a ligand to decorate the surface of PLGA nanoparticles respectively, aiming to enhance ASO delivery to neuronal cells . Physicochemical characterization confirmed that RA and ASO incorporation preserved colloidal stability, with no adverse effect on particle size, surface charge, or morphology . In vitro-controlled release experiments showed a cumulative RA release of ca. 12% over 24 h governed by a semi-Fickian diffusion mechanism after adjusting to different equation models. Importantly, RA entrapment displayed measurable radical scavenging capacity, leading to a EC 50 of 76 ± 0.9 μg·mL −1 . Cell culture experiments confirmed biocompatibility in both a non-cancer cell line (HEK293) and neuroblastoma cell model (SH-SY5Y). Uptake studies revealed efficient internalization of PLGA NPs by SH-SY5Y cells and primary murine neurons, promoting gene silencing of luciferase expression (53.7 ± 7.9%). Together, these results show a modular PLGA nanoplatform that enables the simultaneous incorporation of an antioxidant payload and a covalently grafted antisense oligonucleotide, allowing independent assessment of redox modulation and gene silencing in neuronal models.