AVS 62nd International Symposium & Exhibition
    Biomaterial Interfaces Monday Sessions
       Session BI+AS-MoA

Paper BI+AS-MoA6
Paper-based Device for Home Phenylalanine Monitoring from a Sample of Whole Blood

Monday, October 19, 2015, 4:00 pm, Room 211D

Session: Characterization of Biological and Biomaterials Surfaces (2)
Presenter: Elain Fu, Oregon State University
Authors: R. Robinson, Oregon State University
E. Fu, Oregon State University
Correspondent: Click to Email
Paper microfluidics is a rapidly growing subfield of microfluidics that makes use of paper-like porous materials to create devices for use in low-resource settings. Advantages of the use of porous materials include capillary flow, removing the need for equipment for pumping fluids, and lower material costs compared to traditional microfluidics-based devices composed of silicon or glass. In the current presentation, we describe the development of a paper-based device for home therapy monitoring. For persons with phenylketonuria (PKU), maintaining a restricted level of phenylalanine (Phe) in the body is a continuing challenge. Given the large inter-person variation in Phe metabolism, maintaining nutritional therapy can be a lengthy and difficult process that would be aided by the ability to perform real-time monitoring of Phe levels. Adherence to diet therapy is an even greater challenge for young children, adolescents, and women during pregnancy, and for these groups in particular, rapid feedback could be critical in tailoring a diet to be optimal for each individual. Current tests for Phe require a high-resource laboratory environment and are not suitable for the rapid detection of Phe levels and feedback to the patient that is needed for effective monitoring of PKU therapy. Our solution is a semi-quantitative, paper-based device that is rapid, easy to use, and low cost for patient home use. Device operation is based on simple user steps. The user applies whole blood (40 mL) to a plasma separation membrane, which filters out the cellular components of the blood and releases plasma to two downstream glass fiber pads. There, Phe in the sample and NAD+, catalyzed by the enzyme phenylalanine dehydrogenase, react to form Phe-pyruvate, NADH, and NH3. At 6 min, the user folds the card closed and fluid is transferred to a final glass fiber detection pad, in which NADH, nitroblue tetrazolium, and methoxy phenazine methosulfate react to form NAD+ and a purple-colored product. The device is read at ~7.5 min. Visibly distinct signal intensities are generated from whole blood samples containing 0 (normal), 3.75 (slightly elevated), and >7.5 mg/dL (substantially elevated) spiked-in Phe. Thus, this test may allow users to distinguish between normal versus elevated levels of blood Phe on a rapid timescale that could inform their diet therapy. The assay exhibited reasonable reproducibility with coefficients of variation between 11 and 24%. A focus of the presentation will be on the controled patterning and drying of biochemical reagents in porous materials for later rehydration on the device, which is key to the robust operation of the device.