pH-sensitive Eudragit® L 100 nanoparticles promote cutaneous penetration and drug release on the skin

Nanoparticles (NPs) are promising carriers for dermal and transdermal drug delivery. However, the underlying dynamics of drug release from the NPs, especially, how the physiological changes of diseased skin influence the drug release, remain poorly understood. We utilized electron paramagnetic resonance (EPR) and confocal laser scanning microscopy (CLSM) to comprehensively investigate the penetration behavior of a spin-labeled dexamethasone (DxPCA)-loaded pH-sensitive Eudragit® L 100 NP on intact and barrier-disrupted skins. The EPR investigation showed that a rapid in vitro DxPCA release from the NPs was triggered above pH 5.9. It also demonstrated that the NPs considerably improved the cutaneous penetration of the model drug in comparison to a commercial cream. Besides, as compared to the intact skin, a faster drug release and a higher drug penetration into the viable skin layers were obtained with barrier-disrupted skin. In accordance, CLSM studies confirmed that the NPs enhanced the penetration of the lipophilic model drug Nile red (NR) across the skin, whose penetration depth into glabrous skin was 160 μm. Moreover, a significant transfollicular penetration of NR from the NPs was observed. In conclusion, the pH-sensitive Eudragit® L 100 NPs improved the cutaneous penetration and controlled the release of a lipophilic drug, especially on barrier-disrupted skin. This may allow targeted drug delivery to lesional skin, avoiding side effects.