A Fluorescent Micro-Optofluidic Sensor for In-Line Ion Selective Electrolyte Monitoring

In-line electrolyte monitoring during hemodialysis treatment is an important step towards personalized treatment, for optimization of clinical blood pressure management and minimization of cardiovascular complications and bone-mineral disease. But how to achieve such in-line measurement? We propose a real-time electrolyte measurement system based on a molecular fluorescence "on-off" switching mechanism. We have fabricated a disposable polymeric micro-optofluidic device in polydimethylsiloxane (PDMS) with integrated optical fibers to enable in-line electrolyte monitoring. The sensing principle is based on photoinduced electron transfer (PET) that ionselectively quenches the fluorescence of a molecular optical probe. The PET molecules are covalently immobilized onto the PDMS microchannel walls. As a proof-of-concept, we determine sodium concentration in a flowing medium. A clear relation between fluorescence intensity and sodium concentration is observed. The PET principle can also be applied to many other ion types.