BME PhD Preliminary Exam Announcement for Khalid Khalaf (J. Linnes and T. Kinzer-Ursem, Co-Advisors) Everyone is invited to attend the public presentation beginning at 12:30PM. Title: The Development of a Cortisol Electrochemical Sensor for Depression Treatment Personalization Date: November 18, 2025 Time: 12:30PM Location: MJIS 2001 Committee: Dr. Jacqueline Linnes (Chair), Dr. Tamara Kinzer-Ursem (Co-Chair), Dr. Susan Conroy (Member), Dr. Rahim Rahimi (Member) Abstract: Major depressive disorder (MDD) affects more than 25 million adults in the United States. Treatment selection commonly relies on trial and error, reflecting limited availability of objective physiological markers. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, indicated by altered cortisol secretion patterns, has been documented in several depressive subtypes and may normalize with effective therapy. Cortisol therefore represents a potential biomarker for treatment response. Conventional assays for cortisol measurement, such as venipuncture and saliva collection, provide only discrete time points and require laboratory analysis, which constrains temporal resolution and clinical utility. These methods are not suited for continuous monitoring of neuroendocrine dynamics. This project develops a minimally invasive hydrogel microneedle platform incorporating a methylene blue-labeled electrochemical aptamer sensor designed to enable future continuous measurement of cortisol in interstitial fluid (ISF). The present work will establish the analytical feasibility of reagent-free cortisol detection and evaluate ISF as a reliable sampling medium, laying the groundwork for subsequent clinical validation during transcranial magnetic stimulation therapy. Future continuous monitoring systems could support correlation of real-time cortisol changes with clinical outcomes, enabling development of data-driven models of neuroendocrine response. The resulting measurements may provide a basis for individualized assessment of treatment effects and facilitate objective evaluation of therapeutic interventions targeting HPA axis regulation in depressive disorders. -- Bmeroundtable-list mailing list Bmeroundtable-list@ecn.purdue.edu https://engineering.purdue.edu/ECN/mailman/listinfo/bmeroundtable-list