Temperature-Controllable Electrodes with a One-Parameter Calibration

Cold-hot Janus electrochemical aptamer-based sensor for calibration-free determination of biomolecules

Real-time, high-frequency measurements of pharmaceuticals, metabolites, exogenous antigens, and other biomolecules in biological samples can provide critical information for health management and clinical diagnosis. Electrochemical aptamer-based (EAB) sensor is a promising analytical technique capable of achieving these goals. However, the issues of insufficient sensitivity, frequent calibration and lack of adapted portable electrochemical device limit its practical application in immediate detection. In response we have fabricated an on-chip-integrated, cold-hot Janus EAB (J-EAB) sensor based on the thermoelectric coolers (TECs). Attributed to the Peltier effect, the enhanced/suppressed current response can be generated simultaneously on cold/hot sides of the J-EAB sensor. The ratio of the current responses on the cold and hot sides was used as the detection signal, enabling rapid on-site, calibration-free determination of small molecules (procaine) as well as macromolecules (SARS-CoV-2 spike protein) in single step, with detection limits of 1 μM and 10 nM, respectively. We have further demonstrated that the J-EAB sensor is effective in improving the ease and usability of the actual detection process, and is expected to provide a universal, low-cost, fast and easy potential analytical tool for other clinically important biomarkers, drugs or pharmaceutical small molecules.

Plasmonic Au nanocube enhanced SERS biosensor based on heated electrode and strand displacement amplification for highly sensitive detection of Dam methyltransferase activity

In this work, a novel "turn-on" mode Au nanocubes (AuNCs) enhanced surface-enhanced Raman scattering (SERS) biosensing platform coupled with heated Au electrode (HAuE) and strand displacement amplification (SDA) strategy was proposed for highly sensitive detection of DNA adenine methylation (Dam) Methyltransferase (MTase) activity. The Dam MTase and DpnI enzyme activities were significantly increased by elevating the HAuE surface temperature, resulting in the rapid production of template DNA for later SDA. During the SDA process, the released single-stranded DNA (ssDNA) could be amplified exponentially, and its concentration was positively related to the Dam MTase activity. The plasmonic AuNCs in SERS tags could provide significant SERS enhancement due to their "lightning rod" effect resulting from the sharp feature of the edges and corners of AuNCs. Because of these factors, the proposed biosensors exhibited high sensitivity in detecting the Dam MTase activity. The limit of detection was estimated to be 8.65 × 10^-5 U mL^-1, which was lower than that in most of the sensors for detection of Dam MTase activity in the literature. This SERS biosensor could also be used to screen inhibitors of Dam MTase and had the potential for detecting Dam MTase activity in real biological samples.

Temperature-Alternated Electrochemical Aptamer-Based Biosensor for Calibration-Free and Sensitive Molecular Measurements in an Unprocessed Actual Sample

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.