Real-time monitoring of sweat of Cystic Fibrosis patients

Abstract

This research provide a proof of principle to use a sweat sensor system for real-time monitoring of medicine effectiveness in Cystic Fibrosis (CF) patients. CF is an autosomal recessive genetic disorder affecting mostly the respiratory, digestive and perspiration system. Patients with CF have dysfunctional chloride channels in their cells, due to mutations in both copies of the gene for the CFTR protein. The CFTR proteins are necessary for the production of mucus, a malfunction of the CFTR protein will result in tough mucus. In CF, a lack of functional CFTR prevents normal sodium and chloride absorption in sweat and leads to excessive salt loss. Due to increased sodium and chloride concentration in sweat from CF patients, sweat makes a good clinical body fluid to indicate the medicines' effectiveness. By measuring the chloride or sodium concentration before treatment with the medicine and after treatment, an indication of the medicines’ effectiveness can be obtained. In this study, a potentiometric screen-printed sweat sensor has been developed to monitor the medicine effectiveness in CF patients. The sensor consists of a reference electrode and ion-selective electrodes for measurements of chloride and sodium concentrations. Multiple prototypes of the sensor have been developed and evaluated on their performance. Furthermore, a read-out circuit with low leakage/bias currents and 8 channels is designed to increase the read-out accuracy and speed. Since the sweat volume during rest appeared to be too low for real-time measurements, a sweat collector was implemented with the sensor to increase the sweat sample volume during real-time measurements. Furthermore, a pilocarpine sweat stimulator has been designed and tested to artificially increase the sweat rate.
The developed system proofed to be a functional concept for real-time patient monitoring. In future research, the chemical structure of the membranes is the most important topic to be improved. Improvements in this field could extend the life-time of the sensor and would minimise the sensitivity differences between the sensors. Finally, the sweat sensor, collector and stimulator have to be integrated and minimised in one design to make a wearable device out of it.