Quercetin Nanocrystal Gel: A Novel Topical Therapeutic Strategy for Androgenetic Alopecia

<b>Purpose</b>: Androgenetic alopecia (AGA) is a common, chronic, non-cicatricial dermatological condition characterized by progressive miniaturization of hair follicles. Although AGA is a benign disorder, it has a considerable impact on patients' quality of life and psychological health. The current treatment options often demonstrate limited efficacy and are frequently associated with undesirable side effects. This study aimed to co-mill two natural compounds, quercetin (QT) and glycyrrhizic acid (GL), to develop follicle-targeted nanocrystals (NCs), thereby enhancing local accumulation, improving the pathological follicular microenvironment associated with AGA, and promoting hair regrowth. <b>Methods</b>: QT nanocrystals (QT-NCs) were fabricated using a top-down wet media milling technique with GL as a bioactive stabilizer. The resulting QT-NCs were characterized regarding their particle size, crystallinity, morphology, and stability. The skin permeation properties of the QT-NCs were further evaluated in vitro, and their therapeutic efficacy was assessed in a dihydrotestosterone (DHT)-induced AGA mouse model. <b>Results</b>: The QT-NCs exhibited an irregular structure with a particle size ranging from 200 to 300 nm, demonstrating uniform dimensions and excellent storage stability. In vitro permeation studies revealed a 2.27-fold increase in cumulative penetration and a 2.47-fold enhancement in skin retention compared to raw QT. In the DHT-induced AGA mouse model, QT-NCs significantly reduced local DHT levels while concurrently modulating the follicular microenvironment, resulting in markedly improved therapeutic outcomes. Notably, when co-administered, QT and GL demonstrated synergistic pharmacological effects, suggesting potential combinatory benefits. <b>Conclusions</b>: This study presents the first demonstration of QT-NCs for AGA treatment, establishing a novel therapeutic strategy with substantial potential for clinical translation.