A Label-Free Optical Biosensor Based on an Array of Microring Resonators for the Detection of Human Serum Albumin

Abstract

We introduced a label-free sensing system based on an array of microring resonators (MRRs) which was successfully employed for human serum albumin (HSA) detection. The sensing-ring surface was functionalized to immobilize anti-HSA, facilitating HSA binding. Our refractive index sensing system demonstrates high sensitivity at 168 nm/RIU and a low limit of detection (LOD) of 63.54 ng/mL, closely comparable to current HSA detection methods. These findings confirm the potential of MRRs as biocompatible sensors for HSA detection. This system holds great promise as an innovative platform for the detection of HSA, carrying significant importance in medical diagnostics.

Keywords: HSA protein; array of microring resonators; label-free detection; surface functionalization.

Figure 1

(a) Schematic image of the MRR sensors’ optical energy transmission; (b) schematic diagram of the principle of evanescent wave sensing; (c) relative shift changes observed upon analyte binding on the silicon surface; (d) electric field intensity of strip waveguide TM mode.

Figure 2

(a) Schematic image of the MRR sensor; (b) optical microscope image of sensor microrings; (c) optical microscope image of the directional coupler; (d) optical microscope image of grating coupling.

Figure 3

(a) Tunable laser, wavelength range of 1500–1600 nm; (b) polarization controller; (c) photoelectric detector; (d) fiber array; (e) microfluidic channel system; (f) the syringe pump; (g–i) glass bottle for sample, waste liquid storage, and background liquid; (j) photograph of the microfluidic channel system; (k) microfluidic channel; (l) TEC and heat dissipation brass block; (m) chip with fiber array; (n) multidimensional translation platform.

Figure 4

(a) Real-time relative shift observed upon introducing varying concentrations of NaCl aqueous solution; (b) the function curve of relative shift with the concentration of the NaCl aqueous solution.

Figure 5

Schematic illustration of silicon chip surface functionalization, the immobilization of the receptor, and the process of analyte detection.

Figure 6

(a) The dynamic variation in the relative shift of the anti-HSA sensors and sensors without anti-HSA; (b) the relative shift of different solutions for the HSA, IgG, and HCG protein; (c) fit of the experimental results of the anti-HSA sensors.