Co-delivery of targeted hypoallergens and resiquimod powders using silk fibroin microneedles for effective allergen-specific immunotherapy.

The cutaneous route exploits the immunocompetence of the skin, making it a favourable route for allergen-specific immunotherapy (AIT), but there must be a balance between minimal skin disruption and precise allergen delivery. Thus, we propose the use of powder-laden microneedles (pMNs) for the sustained epidermal delivery of powdery hypoallergens and immunomodulators. In this study, targeted hypoallergenic derivatives, namely, mannan-ovalbumin (mOVA) conjugates, were synthesized in a single-step process. For minimally invasive self-administration into the skin, pMNs were constructed using highly biocompatible silk fibroin (SF) with a cavity in the basal portion of each needle, which was filled with lyophilized mOVA and resiquimod powders (mOVA/R848 pMN). The resulting mOVA/R848 pMN arrays were thoroughly examined for their physical morphology, mechanical property, accumulation ability, and immune profile. The deposition of powdery mOVA and R848 improved uptake by skin dendritic cells (DCs) and stimulated the immune system more than 10 d after application. On the basis of these features, mOVA/R848 pMN arrays increased the induction of protective immune mechanisms to suppress Th2 immunity, including the Treg/Th1 bias, as well as the production of anti-inflammatory cytokines and neutralizing antibodies in an asthmatic mouse model. Compared with traditional subcutaneous immunotherapy (SCIT), a total dose of only 75 μg of OVA over three treatments was sufficient to restore immune balance and alleviate allergic symptoms during allergen exposure, highlighting the dose-sparing and frequency-sparing potential of mOVA/R848 pMN. Optimal mOVA/R848 pMN arrays represent a new therapeutic strategy for allergy treatment with convenient administration and satisfactory outcomes.