SPR detection of protein enhanced by seedless synthesized gold nanorods.

Surface plasmon resonance (SPR) is a label-free, real-time bio-sensing technique with high potential in the diagnostic area, especially when a signal amplification strategy is used to improve the detection limit. We report here a simple method for enhancing the detection limit of bovine serum albumin (BSA), by attaching gold nanorods (AuNRs). AuNRs were obtained by a seedless synthesis technique and characterized using scanning electron microscopy (SEM), UV-VIS spectroscopy, FT-IR spectroscopy and dynamic light scattering (DLS). Finite element method (FEM) simulations were employed to explore the enhancement of the SPR signal by adding AuNRs on the SPR sensor's metallic layer. SPR spectroscopy was used to analyze the changes in the refractive index brought by the immobilization of unconjugated BSA and BSA modified with AuNRs. The results confirmed that the AuNRs conjugated with the protein increase the SPR signal ~ 10 times, leading to a limit of detection of 1.081 × 10-8 M (0.713 μg/mL).