Development of gellan gum containing formulations for transdermal drug delivery: Component evaluation and controlled drug release using temperature responsive nanogels.

Enhancing skin permeation is important for development of new transdermal drug delivery formulations. This is particularly relevant for non-steroidal anti-inflammatory drugs (NSAIDs). To address this, semisolid gel and solid hydrogel film formulations containing gellan gum as a gelling agent were developed and the effects of penetration enhancers (dimethyl sulfoxide, isopropyl alcohol and propylene glycol) on transport of the NSAID diclofenac sodium was quantified. A transwell diffusion system was used to accelerate formulation development. After 4h, diclofenac flux from a superior formulation of the semisolid gel or the solid hydrogel film was 130±11μg/cm(2)h and 108±7μg/cm(2)h, respectively, and significantly greater than that measured for a currently available diclofenac sodium topical gel (30±4μg/cm(2)h, p<0.05) or solution formulation (44±6μg/cm(2)h, p<0.05) under identical conditions. Over 24h diclofenac transport from the solid hydrogel film was greater than that measured for any new or commercial diclofenac formulation. Entrapment of temperature-responsive nanogels within the solid hydrogel film provides temperature-activated prolonged release of diclofenac. Diclofenac transport was minimal at 22°C, when diclofenac is entrapped within temperature-responsive nanogels incorporated into the solid hydrogel film, but increased 6-fold when the temperature was increased to skin surface temperature of 32°C. These results demonstrate the feasibility of the semisolid gel and solid hydrogel film formulations that can include thermo-responsive nanogels for development of transdermal drug formulations with adjustable drug transport kinetics.