Smart core-shell microneedles for psoriasis therapy: In situ self-assembly of calcium ion-coordinated dexamethasone hydrogel

Psoriasis is a prevalent relapsing dermatological condition that often necessitates lifelong treatment. The distinctive thickening of the stratum corneum presents a challenge to drug penetration. The employment of microneedles has been demonstrated to enhance the transdermal drug delivery efficacy by creating multiple microchannels in the skin. Nevertheless, polymeric microneedles often encounter difficulties in meeting the requirements for sustained drug release. It is imperative to acknowledge that sustained-release hydrogel microneedles are invariably fabricated under harsh crosslinking conditions. In addressing these challenges, a core-shell microneedles (CSMNs) system was customized at a facile, accessible process, enabling the in situ formation of supramolecular microhydrogels within the skin. This concept was realized by leveraging the interaction between the therapeutic drug dexamethasone sodium phosphate (DexP) and calcium chloride (CaCl 2 ), combined with the differential biphasic release technology (DexP HMNs). Upon insertion into the skin, the core of the microneedles rapidly released CaCl 2 , which diffused to the shell and formed a hydrogel with DexP, creating multiple reservoirs for the sustained release of DexP. In vitro transdermal permeation experiments demonstrated that DexP HMNs greatly prolonged the skin retention time of DexP. In the context of psoriasis treatment, DexP HMNs were demonstrated to be more effective than DexP CSMNs in inhibiting keratinocyte proliferation and significantly reducing the levels of inflammatory factors and immune cell infiltration at the lesion site. This study provides a new direction for the development of intelligent microneedle drug delivery systems for sustained drug release and enhanced management of chronic skin diseases.