Continuous Steroid Monitoring in Interstitial Fluid With Wearable and Nanoparticle-enhanced Biosensors for Improved Management of Adrenal Disorders

To trace steroid dynamics in a routine setting, the choice of body fluid is critical, as it dictates the ease and frequency of collection that is tolerated by individuals. While the gold standard is based on blood assay, several body fluids can be accessed minimally invasive, including urine, sweat, breath, saliva and interstitial fluid. More promising for steroid monitoring is interstitial fluid, as it closely mirrors the composition of blood plasma due to continuous mass transfer. In fact, this has been demonstrated just last year using a subcutaneously implanted micro-dialysis catheter that collected interstitial fluid with an infusion pump. Worn around the waist, samples were collected for 24 hours in 214 volunteers and analysed offline by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). That way, cortisol was accurately traced and followed a similar dynamic in tissue (i.e., interstitial fluid) compared to blood plasma. On this basis, disease-related differences were detected, for example, elevated cortisol concentrations in a patient suffering from Cushing syndrome. Yet, extended investigations of the aldosterone and cortisol dynamics in interstitial fluid under different clinical scenarios of hormone excess and deficiency, and validation against serum measurements are required to establish this method for diagnostic and treatment purposes.

This project has the overarching goals of (1) establishing dynamic interstitial aldosterone and cortisol monitoring as reliable diagnostic tool for cortisol and aldosterone excess or deficiency, and (2) develop a wearable molecular sensing device to detect them accurately. In the work package 1 (Characterization of interstitial cortisol and aldosterone concentrations): The diagnostic utility of cortisol and aldosterone measurement in the interstitial fluid will be assessed by comparative quantification to serum concentration by LC-MS/MS. Therefore, interstitial fluid and blood will be collected in healthy individuals and patients during the morning (when cortisol and aldosterone reach the highest levels) and during dynamic tests to investigate adrenal diseases, such as ACTH (cosyntropin) stimulation test (which evaluates the peak cortisol response following an exogenous stimulus) and saline infusion test (which evaluates aldosterone suppression following volume and sodium overload). Since continuous interstitial fluid is not yet possible, commercially available hollow microneedle devices will be used for single timepoint extraction.

Main hypothesis 1: Cortisol and aldosterone concentrations in interstitial fluid reflect sufficiently well blood serum concentrations to reliably indicate normal steroid secretion and the onset of cortisol and aldosterone disorders.

In this first step, the investigators will perform a pairwise comparison of cortisol and aldosterone concentrations in interstitial fluid with serum measurements. This study will be submitted to the responsible Ethics Committees of USP. The written informed consent will be signed by all participants. The investigators will evaluate 150 individuals, including healthy controls and patients with adrenal hyper- and hypofunction referred for evaluation in the outpatient clinic of the Adrenal Unit, Division of Endocrinology, USP. Clinical and hormone evaluation of the enrolled patients with adrenal disorders will follow the standard guidelines of the Endocrine and European Society of Endocrinology. All healthy controls (without a previous diagnosis of adrenal disease) will have an appointment to fill out a questionnaire of medical history and to collect blood tests.

Individuals (males and females) older than 18 years will be eligible for inclusion. Patients covering a broad spectrum of adrenal diseases will be recruited: cortisol and aldosterone deficiency (primary adrenal insufficiency), cortisol excess (Cushing syndrome) and aldosterone excess (primary aldosteronism). A single timepoint of each participant will be evaluated in the morning following overnight fasting and without morning medication. This baseline evaluation will allow to sample material with normal, low (adrenal insufficiency) and high (Cushing's syndrome and primary aldosteronism, respectively) adrenal steroid content. In addition, ACTH (intravenous 250 µg cosyntropin) stimulation test will be performed in healthy controls and patients under investigation of adrenal insufficiency and primary aldosteronism to correlate interstitial aldosterone and cortisol levels with the peak of serum cortisol and aldosterone after 1h of ACTH stimulus. The saline infusion test (intravenous 2 liter of 0.9% saline over 4h) will be performed in the patients under investigation for primary aldosteronism. These dynamic tests will be performed in a dynamic test room in the outpatient clinic, which counts with a team of endocrinologist, nurse, and technicians trainned for endocrine dynamic evaluation. Exclusion criteria will be as follows: use of estrogen-containing oral contraceptive medication within the past 6 weeks; pregnancy or lactation; use of oral, inhaled, parenteral, or topical glucocorticoids within the past 30 days. Basal sample collection and dynamic tests will be performed at fasting between 8 am to 10 am.