Issue 44, 2015

Label-free C-reactive protein SERS detection with silver nanoparticle aggregates

Abstract

In this work, we report a qualitative approach for detecting the adsorption of C-reactive protein on phosphocholine-terminated self-assembled monolayers without the use of any labels. An amplified plasmon of concentration-induced silver nanoparticle aggregates located ∼4.0 nm away from the C-reactive protein via the phosphocholine-terminated self-assembled monolayer linker is considered to be the source of the robust electromagnetic enhancement. The high level (109 to 1010 M−1) of apparent binding constant (KA) of C-reactive protein suggests that the immobilized surface was well-oriented without extreme random stacking. A Raman sensitivity toward the C-reactive protein around 2800–3000 cm−1 was noted, which gradually increased upon the addition of successive layers up to approximately 6–7 layers of phosphocholine-coated silver nanoparticle aggregates, with minimum detection amounts of ∼0.01 ng mL−1 in buffer and ∼0.1 ng mL−1 in 1% serum. A cross-reactivity test confirmed the excellent selectivity and specificity of the measured signals. A computational study based on the finite-difference-time-domain method successfully demonstrated the enhanced (∼1.1 × 106) electromagnetic field of the 2-D silver nanoparticle aggregates as compared with that of isolated particles, and was congruent with the analytical enhancement factor (1.7 × 105).

Graphical abstract: Label-free C-reactive protein SERS detection with silver nanoparticle aggregates

Supplementary files

Article information

Article type
Paper
Submitted
02 Jan 2015
Accepted
09 Apr 2015
First published
09 Apr 2015

RSC Adv., 2015,5, 34720-34729

Label-free C-reactive protein SERS detection with silver nanoparticle aggregates

H. Kim, E. Kim, E. Choi, C. S. Baek, B. Song, C. Cho and S. W. Jeong, RSC Adv., 2015, 5, 34720 DOI: 10.1039/C5RA00040H

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