Label-free aptamer sensor based on silicon microring resonators

We present a label-free DNA aptamer sensor based on silicon microring resonators for the detection of human immunoglobulin E (IgE) and human thrombin. An array of silicon resonators consisting of three sensor microrings and one reference microring was fabricated and its surface sensitivity, detection limit and repeatability were investigated by the deposition of poly (sodium-4-styrenesulfonate) (PSS) and poly (allylamine hydrochloride) (PAH) multilayers. The surface sensitivity and the limit of detection of the fabricated sensor ring are found to be 0.35 nm/ng mm−2 and 26 pg/mm2 in air and 0.24 nm/ng mm−2 and 38 pg/mm2 in water, respectively. We have demonstrated quantitative, sensitive and specific detection of human IgE and thrombin with aptamer modified silicon microring resonators over a broad range of antigen concentrations. The sensor array showed an experimental detection limit of 33 pM and 1.4 nM for IgE and thrombin, respectively. Multiplexing was also performed successfully with a mixed solution of IgE and thrombin and proved the sensor to be highly specific. We believe our silicon microring resonator technology in combination with aptamers offers a low cost solution for various point-of-care applications.