Label-Free Detection of Human Serum Using Surface-Enhanced Raman Spectroscopy Based on Highly Branched Gold Nanoparticle Substrates for Discrimination of Non-Small Cell Lung Cancer

Figure 3

(a) SERS stability of HGNP substrates measured with 4-MBA (1 × 10⁻⁴ M). 4-MBA-labeled HGNP substrates were stored for several days at room temperature. (b) SERS intensities of the bands at 1080 cm⁻¹ corresponding to the SERS spectra in (a). (c) SERS spectra of 4-MBA at different concentrations (5 × 10⁻¹⁰, 1 × 10⁻⁹, 1 × 10⁻⁸, 1 × 10⁻⁷, 1 × 10⁻⁶, 1 × 10⁻⁵, and 1 × 10⁻⁴ M) absorbed on the HGNP substrates. (d) The Raman intensity of 4-MBA at 1080 cm⁻¹ as a function of the concentration of 4-MBA. The inset is the calibration curve of 4-MBA at the concentration from 1 × 10⁻⁸ to 1 × 10⁻⁴ M. (e) The reproducibility of HGNP substrates measured with 4-MBA (1 × 10⁻⁴ M). (f) The repeatability of the SERS spectrum of serum on the substrate. (g) SERS spectra of unlabeled HGNP substrates.

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