Fabrication of sponge-forming microneedle patch for rapidly sampling interstitial fluid for analysis.

Microneedle (MN) patch has been used for collecting dermal interstitial fluid (ISF) containing biomarkers from patients with safety, pain-free and easy-to-use manner. However, long sampling time for biomarkers analysis still poses a significant challenge. Here, we describe a new sponge-forming MN patch consisting of polyvinyl formal (PVF) for rapidly extracting ISF from skin. Owing to the supreme water affinity of PVF, this MN patch can extract 1.6 mg ISF in 1 min without the assistance of extra devices, which remarkably facilitates timely analysis. The MN patch had preserved structural integrity in the swelling hydrated state without leaving residues in skin after usage, and the treated skin recovered within 8 h. More importantly, the extracted ISF can be efficiently recovered from the MN patch by simple centrifugation for the subsequent offline analysis of biomarkers such as glucose and cholesterol. Our results reveal that the new sponge-forming MN patch holds considerable promise for minimally invasive sampling ISF for biomarkers detection in real-life situations.