Electro-responsive macroporous polypyrrole scaffolds for triggered dexamethasone delivery.

Corticosteroids such as dexamethasone are first line ophthalmic treatment for non-infectious posterior uveitis. Corticosteroids are often administered via intravitreal injection to treat this condition with frequent injections associated with poor treatment adherence and complications such as endophthalmitis. Current ocular implants provide sustained corticosteroid release at predetermined rates and lack the ability for dose individualisation. This study describes the successful fabrication of electrically responsive macroporous polypyrrole (PPy) thin films, and their subsequent application to triggered dexamethasone release. Colloidal crystal films composed of 370nm polymethylmethacrylate colloids were first deposited on ITO coated glass substrates, and subsequently used as sacrificial templates for the fabrication of high surface area, 3-dimensionally ordered macroporous PPy inverse opal (PPy IO) thin films. SEM, UV-Vis reflectance and cyclic voltammetry measurements established that the redox state of the PPy IO films could be controlled via electrical stimulation, which in turn influences both porosity and optical properties of the films. Incorporation of the anti-inflammatory corticosteroid, dexamethasone phosphate (DexP), in the PPy IO films during their fabrication resulted in an effective delivery platform for triggered DexP release. A sustained release profile was observed for the PPy IO-DexP films, bursts of release could be triggered by electrical stimulation. The amount of DexP released from the PPy IO-DexP films was significantly higher than that released from the conventional non-porous PPy-DexP films of comparable mass. Results suggest that electrically responsive PPy IO structures are highly suitable for on-demand drug delivery applications. This technology may enable physicians to fine-tune the required dose according to disease state and patients' needs to enhance the safety and efficacy of corticosteroid treatment.