Poster W3 - Sweat Biomarker Detection using Hydrophilic Skin-interfaced Semi-cured Microfluidic Systems

Introduction:

Introduction: Human sweat biomarker detection has emerged as a promising avenue in biomedical engineering, offering a non-invasive and accessible means to monitor physiological and pathological conditions. This study investigates the application of liquid chromatography-mass spectrometry (LC-MS) for the identification and quantification of biomarkers present in sweat. The methodology involves the collection of sweat samples through a conformable, wearable biosensor-integrated system with a new semi-bonding technique to create a strong bond decreasing the capillary force needed. The advantages of LC-MS in this context include its high sensitivity, specificity, and ability to detect a wide range of molecular species with a focus on its potential applications in disease diagnosis and health monitoring.

Materials and

Methods: Materials and

Methods: Polyethylene Glycol (PEG) block copolymer (0, 0.5, 1.0, and 3.0 wt.%) is added to PDMS (10:1). PDMS-PEG films (1 mm) were created using a Film Applicator and cured at 75 ℃ overnight. 1.5 wt% PDMS-PEG microfluidic devices are constructed using a fully cured channel layer placed on a semi-cured layer at 75 °C in increments of 10 min. Sweat is collected over time with sweat-inducing activities​ and analyzed in the LCMS Thermo Scientific Q Exactive HF-X Hybrid Quadrupole-Orbitrap Mass Spectrometer (2018). In LC, the sample is carried through a stationary phase by a liquid mobile phase. The mass analyzer separates ions based on their mass-to-charge ratio (m/z), producing a mass spectrum that represents the distribution of ions in the sample.

Results, Conclusions, and Discussions: Results and

Discussion: When PEG wt% increased, the contact angles decreased indicating hydrophilicity. 1.5% PDMS PEG microfluidic device showed the strongest bond when semi-cured at 15 minutes at 75 °C. The device is placed on the subject skin on the forearm, lower back, and upper arm. Activities such as running and sauna were methods to induce sweat effectively. Sweat was collected using the sweat patch successfully multiple times accumulating ~0.1 mL of sweat. LCMS analysis found 1800+ unique metabolites in our sweat samples. The LCMS method is effective for human sweat metabolome profiling with high coverage.

Conclusions: This approach allows for the comprehensive profiling of sweat biomarkers, including small molecules, peptides, and proteins. We have detected many metabolites that have never been associated with human sweat, indicating that the human sweat metabolome is much more complex than previously thought.

Acknowledgements (Optional): Acknowledgments: This material is based on research sponsored by Air Force Research Laboratory under the agreement number FA8650-18-2-5402. This research is also supported by National Science Foundation (ECCS #1920979, ECCS #2020486, CBET #2238173) and the Small Scale Systems Integration and Packaging(S3IP) Center of Excellence