A highly integrated lab-on-a-disc immunoturbidimetric assay from whole blood with on-chip calibration

Human immune dysfunction will cause a variety of immune system diseases, so the detection of immune-related indicators (immunoglobulin and complement) has been increasingly attractive. However, for most commercial biochemical analysers, sample pre-treatment and analysis are tedious, nonportable because processes are separated and professional operations are needed. Therefore, the applications in Point-of-Care testing (POCT) are limited. In this paper, we present a highly integrated immunoturbidimetric assay for immune globulin identification from whole blood sample, based on the centrifugal microfluidic or lab-on-a-disc (LOAD) platform with an embedded self-calibrated absorbance detection system. When compared with traditional methods, our platform is low-cost, portable because of the reduction of manual steps and testing time. At the step of blood pre-treatment, the chip provides the platform for on-chip sedimentation of blood cells and onsite extraction of purified plasma by a novel capillary siphon valve during spinning. The chip is integrated with an on-chip calibration unit to obtain more accurate standard curves and reduce the effect of chip fluctuation. Then, better measurement accuracy will be received. As an application, we conducted Immunoglobulin A (IgA) identification in human whole blood based on our LOAD system. To increase the throughput, we further design a parallel multisample chip with only two critical calibration points. Our LOAD system was demonstrated to have good accuracy (CV: 4.23%), good sensitivity (limit of detection: 0.206 gL(-1)) and high repeatability. The experimental results are in good agreement with those measured by conventional method. Clearly, our LOAD system provides a solution for immunological detection on rotating disc.