This work reports a novel optical microfluidic biosensor with highly sensitive organic photodetectors (OPDs) for absorbance-based detection of salivary protein biomarkers at the point of care. The compact and miniaturized biosensor has comprised OPDs made of polythiophene-C70 bulk heterojunction for the photoactive layer; whilst a calcium-free cathode interfacial layer, made of linear polyethylenimine, was incorporated to the photodetectors to enhance the low cost. The OPDs realized onto a glass chip were aligned to antibody-functionalized chambers of a poly(methyl methacrylate) microfluidic chip, in where immunogold-silver assays were conducted. The biosensor has detected IL-8, IL-1β and MMP-8 protein in spiked saliva with high detection specificity and short analysis time exhibiting detection limits between 80 pg mL−1 and 120 pg mL−1. The result for IL-8 was below the clinical established cut-off of 600 pg mL−1, which revealed the potential of the biosensor to early detection of oral cancer. The detection limit was also comparable to other previously reported immunosensors performed with bulky instrumentation or using industrial inorganic photodetectors. The optical detection sensitivity of the polythiophene-C70 OPDs were enhanced by optimizing the thickness of the photoactive layer and anode interfacial layer prior to the saliva immunoassays. Further, the biosensor was tested with unspiked human saliva samples, and the results of measuring IL-8 and IL-1β were in statistical agreement with those provided by two commercial assays of ELISA. The optical microfluidic biosensor reported hereby offers an attractive and cost-effective tool to diagnostics or screening purposes at the point of care.
Tao Dongc, , 1, , Nuno Miguel Matos Piresa, b, 1
a Institute of Applied Micro-Nano Science and Technology, Chongqing Key Laboratory of Micro-Nano Systems Technology and Smart Sensing, Chongqing Technology and Business University, Nan’an District, Chongqing 400067, China
b Chongqing Engineering Laboratory for Detection, Control and Integrated System, National Research Base of Intelligent Manufacturing Service, Chongqing Technology and Business University, Nan’an District, Chongqing 400067, China
c Institute for Microsystems - IMS, Faculty of Technology, Natural Sciences and Maritime Sciences, University College of Southeast Norway, Postboks 235, 3603 Kongsberg, Norway
Received 15 January 2017, Revised 4 March 2017, Accepted 5 March 2017, Available online 6 March 2017