UC Riverside

The affordable, rapid, sensitive, specific biosensors are critical to prompt disease diagnosis, especially in developing areas with low resources. However, traditional technologies to detect disease biomarkers such as colorimetric lateral flow assays and polymerase chain reaction tests, suffer from low sensing performance, high operation complexity, high cost, and long assay time. Therefore, it is imperative to develop an affordable biosensing platform with high sensing performances and high user-friendliness to meet the ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverable to end-users) for diagnostic tools in resource-limited areas. Hence, this research developed the paper-based microfluidic chemiresistive biosensors employing single-walled carbon nanotubes (SWCNTs) and specific bioreceptors for the detection of important biomarkers in various biological samples. By synthesizing the pyrene carboxylic acid (PCA) modified SWCNTs and characterizing PCA/SWCNTs, we successfully fabricate the chemiresistors via facile methods of vacuum filtration and inkjet printing. Both fabrication methods enabled the control of PCA/SWNTs networks density on paper substrate. We optimized the biosensing performance by optimizing the sensitivity, assay time, and balanced material cost. With the final goal of developing the fully assembled devices for biomarker detections, we have also worked on the wax printing-patterned paper-based microfluidics with proper sealing materials to manipulate the microflows of samples and buffers for the controlled sample delivery during the test. We have investigated the paper-based microflows in both vertical and lateral directions and integrated with the chemiresistive biosensor arrays to achieve the fully assembled devices for the rapid and easy electrical measurements. Using the PCA/SWCNTs, specific bioreceptors, and paper-based microfluidics, the developed biosensors were able to detect important biomarkers of human serum albumin, human immunoglobin G, and micro RNAs, in various biological matrices with great sensitivity and specificity. This work shows the great potential of paper-based microfluidics chemiresistive biosensor in future applications such as medical diagnosis, environmental hazard monitoring and food safety.