Percutaneous extraction using sponge spicules for disease diagnosis and therapeutic drug monitoring

Diagnostic and therapeutic drug monitoring are necessary means of precision medicine. Our previous study demonstrated that the sponge Haliclona sp. spicules (SHS) can be employed as a new class of microneedles, capable of forming a substantial number of microchannels within the skin. In this study, dermal interstitial fluid (ISF) was obtained via percutaneous extraction using sponge Haliclona sp. spicules (SHS) to explore the correlation between the concentration of target compounds in the extract and their content in the skin or blood. Methodologically, we compared SHS with dermaroller, ultrasound, and reverse iontophoresis for interstitial fluid (ISF) extraction efficacy in vitro, while optimizing extraction parameters (dosage of SHS, extraction solvent, extraction time) via orthogonal experimental design. Target compounds spanning diverse physicochemical properties (fluorescein sodium, rhodamine B, salicylic acid, FD 1 k, urea, glucose) were evaluated. We also detected the concentration of target compounds and their levels in the blood in vivo. Key results showed that robust linear correlations were observed between the detected concentration of target compounds through SHS and their levels in various skin layers, as well as in the blood. Additionally, we developed a mathematical model predicting extraction efficiency log k_p = 2.9711 + 0.00235MV - 0.059526 log P + 6.7506 log MW^-0.6. These findings provide a new non-invasive percutaneous sampling strategy.