In this study, a high-performance, stable and homogeneous [email protected] /CMC/qPCR flexible film surface-enhanced Raman scattering (SERS) substrate was constructed by synergistically stabilizing and protecting bimetallic core–shell [email protected] nanorods ( [email protected] ) with carboxymethylcellulose (CMC) and fluorescent-quantitative-polymerase-chain-reaction (qPCR) film. The network structure of CMC immobilized and aligned [email protected] through coordination of carboxyl groups with surface Ag atoms to provide intensive and stable ‘hot spots’, and the qPCR bilayer film performed as carrier and barrier to protect [email protected] from oxidation, humidity and optical damage and improved the robustness and stability. The [email protected] /CMC/qPCR film was used for in-situ extraction and SERS detection of thiabendazole on nectarine (0.24 ppm) and lemon (0.27 ppm) with low detection of limits. Furthermore, it retained 98.6% SERS performance after storage for 90 days under ambient conditions, revealing the great potential in promoting the commercialization of the SERS technique for sensitive contaminants sensing with simple fabrication procedures, homogeneity, reproducibility and long-term stability.
The low early diagnosis rate of hepatocellular carcinoma (HCC) severely impacts patient prognosis, making the development of highly sensitive and specific early diagnostic technologies crucial. MicroRNA-221 (miR-221), an aberrantly overexpressed biomarker in HCC, holds significant diagnostic potential. This paper constructed a capillary surface-enhanced Raman scattering (SERS) sensing platform utilizing CRISPR/Cas13a trans-cleavage and double-shell gold-silver nanorods (DS Au-AgNRs) to detect serum miR-221 in HCC patients. DS Au-AgNRs were synthesized and assembled onto aminated capillaries, followed by conjugation of Cy5-labeled single-stranded DNA (ssDNA) to the DS Au-AgNR surface via Au–S bonds. In the presence of miR-221, activated CRISPR/Cas13a trans-cleavage cleaves the ssDNA, releasing Cy5 from the sensor surface and diminishing the SERS signal, enabling miR-221 quantification. The synthesized DS Au-AgNRs exhibit uniform morphology and size, are uniformly distributed on the capillary, and form numerous “hotspots”, thereby significantly enhancing the SERS signal. According to the characteristic peak of Cy5 at 1074 cm−1, a linear relationship is established between the log concentration of miR-221 and the measured SERS intensity (y = −3527.97 × −35369.60, R2 = 0.97767), with a LOD as low as 4.17 × 10−17 M. The sensor demonstrated high specificity and high sensitivity, and its capacity to detect miR-221 expression aligned with qRT-PCR results when analyzing serum samples, confirming that hepatocellular carcinoma patients exhibited significantly higher miR-221 levels compared to healthy individuals. The capillary SERS sensor thus provides an accurate and convenient approach for early HCC diagnosis.
An optimum SERS performance is mainly dependent on the development of innovative substrates that show high spectral reproducibility and stability. The current study involves the synthesis of core–shell nanorods (Au@AgNRs) functionalized with mercaptoacetic acid (MAA) to increase the stability and sensitivity of the substrate for cost-effective and sensitive assessment of paraquat (PQ) residues in fruit samples. The morphological analysis of the substrate using TEM and STEM-EDS images indicated the uniformity in size and structure of the prepared nanoparticles. Further the modified substrate, MAA/Au@AgNRs showed excellent stability and sensitivity in comparison with its unmodified counterpart. For the evaluation of PQ residues in pear and apple fruit samples the modified substrate exhibited R 2 values of 0.9954 and 0.9914 with a low limit of detections of 0.012 and 0.024 ppm, and good percent recoveries of 80–110 % and 81–104 %, respectively. Thus, the study proved the effectiveness of the proposed MAA/Au@AgNRs substrate for assessing residues of herbicide in complex foods.
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