Design of a photo-responsive polymeric injectable nanosystem for the sustained delivery of macromolecules

Abstract

Delivery of macromolecules has proven to be challenging due to molecular weight, instability and triggering of immune response. The demand for biodegradable sustained release carriers with minimally invasive and less frequent administration properties for such therapeutics has increased over the years. Stimuli responsive polymers have gained significant interest in drug discovery for their flexibility, site specificity and potential for remotely controlled drug release, especially for irregular targets such as intraocular sites which possess a complex anatomy. The purpose of achieving sustained minimally invasive and site-specific delivery of macromolecules led to the investigation of stimuli responsive materials for this study. This research explored a biodegradable prolamin, zein, modified with 4,4’- dihydroxyazobenzene (DHAB) to synthesize photo-responsive azoprolamin (AZP) nanospheres incorporated in a hyaluronic acid (HA) hydrogel to formulate a novel injectable photo-responsive nanosystem (HA-NSP) for prolonged release of a model monoclonal antibody, Immunoglobulin G (IgG), as a potential approach for the treatment of chorioretinal diseases such as age related macular degeneration (AMD) and diabetic retinopathy. Photo responsive AZP nanospheres incorporating IgG were prepared via coacervation technique, characterised for physicochemical properties via infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Size and morphology were studied via scanning electron microscopy (SEM) and dynamic light scattering (DLS). Further characterisation for photo-responsiveness of AZP nanospheres was studied using UV spectroscopy. Optimised nanospheres were dispersed in HA gel to form HA-NSP which was characterised for rheological properties and injectability through texture analyser and rheometer as well as cytotoxicity effect on HRPE cell lines. Spherical nanoparticles were obtained with particle size <200nm and demonstrating photo responsiveness to UV=365nm by decreasing particle diameter to 94nm which was confirmed by DLS. Encapsulation efficiency of the optimised nanospheres was 85% and IgG was released over 32 days up to 60%. Injectability of HA-NSP was confirmed with maximum force 10N required and shear-thinning behaviour observed in rheology studies. In vitro cell cytotoxicity effect of both NSPs and HA-NSP showed non-cytotoxicity where the relative cell viability was ≥80%. Cell death was further explored through apoptotic and necrotic pathways and necrosis from HA-NSP treatment was <1% after 48 hours of incubation. A biocompatible, biodegradable injectable photo-responsive nanosystem for sustained release of macromolecular IgG was successfully prepared.