[5p-A409-1~11] 4.2 Bio-and Medical Photonics

▲ [5p-A409-3] Improving detection limit of surface plasmon resonance biosensor using digital method

〇(P)Ming-Yang Pan¹, Kuang-Li Lee¹, Likang Wang², Pei-Kuen Wei^1,3,4 (1.Research Center for Applied Sciences, Academia Sinica, Taiwan, 2.Institute of Photonics Technologies, National Tsing Hua Univ., Taiwan, 3.Department of Optoelectronics, National Taiwan Ocean Univ., Taiwan, 4.Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean Univ., Taiwan)

Keywords:surface plasmon resonance, biosensor, digital detection

Surface plasmon resonance (SPR) sensor has been widely used in detection of biomolecular interaction due to its advantages of label-free and high sensitivity. The ligand-modified sensor surface specifically captures the analyte which results in a small increase of the refractive index that can be measured from the change in the optical response, such as intensity and wavelength. However, in real application of ultralow concentration, the distribution of caperaturing biomolecules on the sensing surface is usually nonuniform. The corresponding signals are averaged by whole detection area that hinder the improvement of limit of detection (LOD). The digital detection method provides an alternative approach for low-concentration detection. By dividing the detection space into many small volumes, isolated signals in each volumes are counted. In this work, we present a silver-capped nanoslit array-based checkerboard nanostructure. The capped nanoslit result in asymmetrical Fano-resonance and high intensity sensitivity due to its narrow FWHM. We have measured the intensity sensitivity as function of number of pitches (N) in nanoslit array. The N=25 array was chosen because it provides high sensitivities (>20,000% per refractive index unit) and small sensing area (12.5μm×12.5μm). Moreover, polarization dependent transmission in this structure makes optical isolation between arrays and results in a crosstalk smaller than 1%. The bovine serum albumin (BSA)/anti-BSA interaction experiments, the LOD of anti-BSA is down to 1 pg/mL using digital method which is approximately 1000 times lower than using traditional analog detection.