Rational aspect ratio and suitable antibody coverage of gold nanorod for ultra-sensitive detection of a cancer biomarker.
We report a simple, ultra-sensitive, and straightforward method for non-labeling detection of a cancer biomarker, using Rayleigh light scattering spectroscopy of the individual nanosensor based on antibody-antigen recognition and localized surface plasmon resonance (LSPR) λ(max) shifts. By experimentally measuring the refractive index sensitivity of Au nanorods, the Au nanorod with an aspect ratio of ~3.5 was proven optimal for the LSPR sensing. To reduce the steric hindrance effect as well as to immobilize a large amount of ligand on the nanoparticle surface, various mixtures containing different molar ratios of HS(CH(2))(11)(OCH(2)CH(2))(6)OCH(2)COOH and HS(CH(2))(11)(OCH(2)CH(2))(3)OH were applied to form different self-assembled monolayer surfaces. The results showed that the best molar ratio for antibody conjugation was 1 : 10. When using individual Au nanorod sensors for the detection of prostate specific antigen (PSA), the lowest concentration recorded was ~1 aM (~6 × 10(5) molecules), corresponding to LSPR λ(max) shifts of ~4.2 nm. These results indicate that sensor miniaturization down to the nanoscale level, the reduction of steric hindrance, and optimization of size, shape, and aspect ratio of nanorods have led to a significant improvement in the detection limit of sensors.
School of Chemical Engineering, Sungkyunkwan University, Suwon, Korea.
Phuoc Long
PL
Truong
Byung Woo
BW
Kim
Sang Jun
SJ
Sim
D055910:Antibodies, Immobilized / Q000737:chemistry* / Q000276:immunology; D006046:Gold / Q000737:chemistry*; D006801:Humans; D057230:Limit of Detection; D008297:Male; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D017430:Prostate-Specific Antigen / Q000032:analysis* / Q000276:immunology; D011471:Prostatic Neoplasms / Q000175:diagnosis; D020349:Surface Plasmon Resonance / Q000379:methods*
D055910:Antibodies, Immobilized; D006046:Gold; D017430:Prostate-Specific Antigen