Engineered vesicles facilitate the programmed transdermal-intestinal delivery of cinnabar for insomnia mitigation by modulating serotonin-Htr1d-cAMP

Insomnia is a prevalent sleep disorder and it affects brain development, with pediatric populations being particularly vulnerable. Cinnabar, a mineral drug composed of HgS, has demonstrated efficacy in alleviating insomnia through suppressing the overactivity of glutamate receptors (NMDA/AMPA), etc. However, oral administration of cinnabar poses risks, including binding with hemoglobin and accumulation in tissues and organs, resulting in neurotoxicity. To overcome these limitations, we developed a novel transdermal and intestinal targeting programmed nanoplatform for cinnabar delivery (TAT/CSK-cinnabar vesicle, TCCV), of which, cinnabar was encapsulated within a lipid vesicle, which was then co-engineered with cell-penetrating peptide TAT and the intestinal-targeting CSK ligand. Accordingly, TCCV showed exceptional sequential penetration through the stratum corneum (SC) and intestinal barriers, and also actively targeted intestinal goblet cells with a 15-fold increase in efficiency compared to non-engineered vesicles. Furthermore, TCCV forms a reservoir releasing cinnabar at the intestinal site with controlled manner, significantly reducing fluctuations in cinnabar concentration in blood and organs, thereby reducing toxicity. In current anti-insomnia studies, TCCV exhibited predominantly enhanced therapeutic efficiency compared to the oral control group, with drug efficiency increased by 1.5 to 2.5-fold. With the analysis of RNA sequencing and 16S rRNA, the regulation of the serotonin (5-HT) production in gut microbes and activating the Htr1d-cAMP pathway of cerebral cortex through the "brain-gut axis" by TCCV is identified as the novel mechanism for the insomnia mitigation effect of cinnabar. This study offers a novel non-invasive transdermal and targeted nanoplatform that significantly improves the efficacy and biosafety of cinnabar delivery and highlights a new gut-brain axis-mediated mechanism in insomnia mitigation.