Frequently calibrating electrochemical biosensors (ECBs) to obtain acceptable accuracy can be cumbersome for the users. Thus, the achievement of calibration-free operation would effectively lead to commercial applications for ECBs in the real world. Herein, we fabricated a temperature-alternated electrochemical aptamer-based (TAEAB) sensor, producing a cycle of "enhanced-responsive and ∼nonresponsive" state at rapidly alternated interface temperatures (5 and 30 °C, respectively). The ratio of peak currents collected at two temperatures overcomes sensor-to-sensor fabrication variations, obviating sensor calibration prior to use due to its good reproducibility. We then demonstrated the capability of TAEAB sensors for improved, sensitive, and calibration-free measurement of different targets within 7 min, which respectively achieved a detection limit of 0.5 μM procaine in undiluted urine and 1.0 μM adenosine triphosphate in undiluted serum. This generalizable approach ameliorates sensitivity without the complicated amplification step, thus simplifying the operation procedure and reducing the detection time, which will effectively improve the clinical utility of biosensors.
Surface-enhanced
Raman scattering (SERS)-based biosensing has strong
potential owing to its high sensitivity and good selectivity. In this
study, a SERS biosensing platform for microRNA-21 detection was proposed
by combining heating-enhanced duplex-specific nuclease (DSN)-assisted
target recycling amplification and silver nanocube (AgNC)-based SERS
enhancement. The activity of DSN was greatly enhanced by increasing
the surface temperature of a heated Au electrode (HAuE) during the
DSN-assisted target recycling process, resulting in dramatic miRNA-21
amplification detection. 4-Mercaptobenzoic acid (4-MBA) acting as
a Raman reporter was immobilized onto the surface of AgNC to form
a AgNC/4-MBA SERS tag with AgNC providing significantly larger electric
field enhancement and thus excellent SERS applications compared with
conventional silver or gold nanospheres. This enhancement was attributed
to the well-known “lighting rod” effect derived from
the sharp geometrical feature of the edges and corners of AgNCs. These
factors lead to the high sensitivity of the proposed SERS biosensor
for the miRNA-21 measurement. A limit of detection of 2.88 fM (S/N
= 3) was achieved at an electrode temperature of 55 °C, which
was decreased by more than three magnitudes compared with that at
25 °C.
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