AuNP array coated substrate for sensitive and homogeneous SERS-immunoassay detection of human immunoglobulin G

Abstract

Owing to the high sensitivity, fast responsiveness and high specificity, immunoassays using surface-enhanced Raman scattering (SERS) as the readout signal displayed great potential in disease diagnosis. In this study, we developed a SERS-immunoassay method for the detection of human immunoglobulin G (HIgG). Upon involving well-ordered AuA on a SERSIA substrate, the LSPR effect was further enhanced to generate a strong and uniform Raman signal through the formation of sandwich structure with the addition of target HIgG and SERSIA tag. Optimization of the assay provided a wide linear range (0.1-200 μg mL^-1) and low limit of detection (0.1 μg mL^-1). In addition, the SERS-immunoassay method displayed excellent specificity and was homogeneous, which guaranteed the practical use of this method in the quantitative detection of HIgG. To validate this assay, human serum was analysed, which demonstrated the potential advantages of SERS-immunoassay technology in clinical diagnostics.

Scheme 1. Schematic illustration of the synthesis of SERSIA tag (A), the fabrication of SERSIA substrate (B), and the SERS-immunoassay method for the detection of HIgG (C).

Fig. 1. TEM images of AuNPs (A), AuNPs/4-ATP@BSA (B), SERSIA tag (C) and their UV-vis spectra (D). Raman spectra of SERSIA tag and 4-ATP solution (E).

Fig. 2. SEM images of the Glass-AuA slide (A1) and bare glass slide (A2). SEM images of SERSIA substrate (B1) and GlassIA substrate (B2). The Raman spectra of Glass-AuA and GlassIA substrate connected with the same amount of HIgG-combined SERSIA tag (C).

Fig. 3. Verification of the SERS-immunoassay for HIgG detection.

Fig. 4. Raman spectra for the detection of HIgG samples with different concentrations (A). The relationship between the peak intensity at 1080 cm⁻¹ and the concentration of HIgG (B).

Fig. 5. Raman spectra (A) and the peak intensities at 1080 cm⁻¹ (B) for the measurement at 15 different spots. SERS-immunoassay results for the detection of Hgb, HSA and HIgG samples (C) and the mixtures of HIgG, Hgb, and HSA (D). The concentration for each species was 10 μg mL⁻¹.

Fig. 6. The Raman spectra for the HIgG detection in real human serum samples. The initial and spiked samples were all 1000× diluted (A). The relationship between the peak intensity at 1080 cm⁻¹ and the concentration of HIgG in human serum samples (B).