Biosample Concentration Using Microscale Forward Osmosis with Electrochemical Monitoring

We report the design and operation of an integrated microfluidics system that uses cellulose ester dialysis membranes coupled with disposable carbon and copper electrodes for monitoring and concentration of microliter scale biofluid samples. Dialysis membranes are typically used for buffer exchange, but in this work, membranes with 100-500 Da MWCO were evaluated for feasibility in concentrating small volume samples. This is an alternative to the use of centrifugation, ultrafiltration, and evaporative methods, where quantitative inline monitoring of sample concentration is challenging. The impact of draw solution used, osmotic concentration gradient, pH, and temperature were studied for the optimized concentration of bodily fluids. A system using sucrose in the draw solution generated the best results, with water removal rates of 0.023 mL min^-1. PBS, urine, and saliva samples were concentrated up to 20-fold (PBS), 15-fold (urine), and 5-fold (saliva) in less than 3 h. The osmotic system further showed a 5-fold increase in the electrochemical signal for detecting pyocyanin, a biomarker for early diagnostics of the Pseudomonas aeruginosa pathogen in urine and saliva samples. Overall, the osmotic system can be easily integrated with point of care diagnostic systems for low cost improvement in signal amplification and limit of detection.