Controlled and sustained release of a corticosteroid drug from block copolymers synthetized by ATRP

During last decades, implantable drug delivery systems (DDS) have been developed to optimize therapeutic properties of drugs and ensure their release in a specific site. Acrylic polymers have obtained growing interest in biomedical applications for their biocompatibility and chemical properties that make them extremely versatile. In this work, we focused on the realization of polymeric systems for controlled and sustained release of betamethasone 17,21-dipropionate (BDP), a corticosteroid drug, in the treatment of the posterior eye diseases (PED). The investigated DDS were made of opportunely designed methacrylic block copolymers. Different series of methylmethacrylate/2-hydroxyethylmethacrylate (MMA/HEMA) block copolymers, with various monomeric compositions (20-60 mol% HEMA), were synthetized by Atom Transfer Radical Polymerization to find the best hydrophilic/hydrophobic ratio, able to ensure optimal kinetic release. Copolymers were characterized by nuclear magnectic resonance, size exclusion chromatography, and differential scanning calorimetry. Monitoring of drug release from films loaded with BDP was carried out by HPLC analysis. In particular, PMMA-b-PHEMA with 47 mol% of HEMA showed the best release profile to achieve the therapeutic reference dose, used in the treatment of PED (1-3 μg/day), up to four months. Additionally, intraocular inserts with different shapes were prepared using silicon molds made by means of a 3D printer.