G-quadruplex/hemin (G4/hemin) DNAzymes are biosensing systems, but their application remains limited by an overall low activity and a rather high level of unwarranted background reactions. Here, these issues were addressed through the rational design of F3T-azaC-hemin, a G4-based construct in which the hemin is covalently linked to the G4 core and its binding site flanked with a nucleotide activator, here d(T-azaC). This design led to a G4-DNAzyme whose performances have been ca. 150-fold increased compared to the parent G4-based system. The utility of F3T-azaC-hemin was demonstrated here through the ultrasensitive chemiluminescent detection of miRNA-221. The limit of detection (LOD) has been decreased to the femtomolar range, making it a new and highly efficient molecular tool in the biosensing technology field.
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.
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