Dermal interstitial fluid (ISF) contains comparable analytes and demonstrates analogous response to systemic levels quantified from blood, urine, saliva, and plasma. Dermal ISF can be similarly analyzed, making it a target for medical diagnostic tests and consumer health monitors. Sampling of dermal ISF is challenging. Dermal ISF is maintained at a negative pressure, requiring the use of mechanical or chemical extraction techniques. Sampling ISF using a microneedle (MN) patch enables a noninvasive, painless alternative to common finger-stick blood draw. Methacrylated hyaluronic acid (MeHA) is a common material for the development of drug-delivery microneedles, due to its biocompatibility, which is essential for prevention of adverse reaction when the patch is applied to the skin. Moreover, control over the degree of methacrylation and molecular weight provides for tunable mechanical strength and swelling characteristics. This enables the engineering of MN patches which maintain its structure even after fluid absorption. MeHA MN patches extract only small volumes of ISF (1-2 μL), so increasing the volume and the rate of extraction is necessary for accurate quantification and monitoring of ISF biomarkers. Utilizing an osmotic hydrogel pump and evaporation pads, the volume of extracted ISF can be increased a great deal. The former takes advantage of a chemical gradient to pull fluid whereas the latter uses the evaporation of the fluid that wicks a paper to increase the extraction rate. We will present the production and characterization of MeHA MN patches for the extraction of ISF and electrochemical sensor integration with the patch and pump.

Microneedle sensing system for minimally invasive extraction and analysis of dermal interstitial fluid

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ACS Fall 2022

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