Minute level ultra-rapid and thousand copies level high-sensitive pathogen nucleic acid identification based on contactless impedance detection microsensor.

Early screening for pathogens is crucial during pandemic outbreaks. Nucleic acid testing (NAT) is a valuable method for keeping pathogens from spreading. However, the long detection time and large size of the instruments involved significantly limited the efficiency of detection. This work described an integrated NAT microsensor that facilitated rapid and extremely sensitive detection based on nucleic acid amplification (NAA) on a chip. The biochip consisted of two layers incorporating a heater, a thermometer, an interdigital electrode (IDE) and a reaction chamber. The Pt electrode based heater and thermometer were utilized to maintain a specific temperature for the sample in the chamber. The thermometer exhibited a good linear correlation with a sensitivity of 9.36 Ω/°C and the heater achieved a heating efficiency of approximately 6.5 °C/s. Multiple ions were released during NAA, resulting in a decrease in the impedance of the amplification system solution. A large signal of impedance was generated by the released ions due to its linear correlation with the logarithm of the ion concentration. With this detection principle, IDE was employed for real-time monitoring of the in-chip reaction system impedance and NAA process. Specific nucleic acids from two pathogens (SARS-CoV-2, Vibrio vulnificus) were detected with this microsensor. The samples were qualitatively analyzed on microchip within 3 min, with a limit of detection (LOD) of 103 copies/µL. The proposed sensor presented several advantages, including reduced NAT time and increased sensitivity. Consequently, it has shown significant potential in rapid and high-quality nucleic acid testing for the field of epidemic prevention.

A novel microfluidic chip integrated with Pt micro-thermometer for temperature measurement at the single-cell level.

Noninvasive and sensitive thermometry of a single cell during the normal physiological process is crucial for analyzing fundamental cellular metabolism and applications to cancer treatment. However, current thermometers generally sense the average temperature variation for many cells, thereby failing to obtain real-time and continuous data of an individual cell. In this study, we employed platinum (Pt) electrodes to construct an integrated microfluidic chip as a single-cell thermometer. The single-cell isolation unit in the microchip consisted of a main channel, which was connected to the inlet and outlet of a single-cell capture funnel. A single cell can be trapped in the funnel and the remaining cells can bypass and flow along the main channel to the outlet. The best capture ratio of a single MCF7 cell at a single-cell isolation unit was 90 % under optimal condition. The thermometer in the micro-chip had a temperature resolution of 0.007 °C and showed a good linear relationship in the range of 20-40 °C (R2 = 0.9999). Slight temperature increment of different single tumor cell (MCF7 cell, H1975 cell, and HepG2 cell) cultured on the chip was continuously recorded under normal physiological condition. In addition, the temperature variation of single MCF7 cell in-situ after exposure to a stimulus (4 % paraformaldehyde treatment) was also monitored, showing an amplitude of temperature fluctuations gradually decreased over time. Taken together, this integrated microchip is a practical tool for detecting the change in the temperature of a single cell in real-time, thereby offering valuable information for the drug screening, diagnosis, and treatment of cancer.

Rapid and sensitive electrochemiluminescence detection using easily fabricated sensor with an integrated two-electrode system.

The electrochemiluminescence (ECL) behavior of a tri(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)32+)/tripropylamine (TPrA) system was investigated in sensor chips with two kinds of integrated two-electrode systems, which included screen-printed electrodes (SPE) and physical vapor deposition (PVD) electrodes. Firstly, under excitation with an optimal transient potential (TP) within 100 ms, the ECL assay could be carried out on the microchips using an Au & Au electrode system, emitting strong and stable light signal. Secondly, on the PVD chip, the ECL intensity initiated by optimal TP was eight times stronger than the peak light signal emitted by the linear sweep voltammetry model. Finally, the logarithmic ECL intensities exhibited a linear increase with the logarithmic concentrations of Ru(bpy)32+ in both the SPE and PVD chips without any reference electrode (RE). Typically, the integration of an interdigital two-electrode system in the microchip significantly enhanced the ECL sensitivity of Ru(bpy)32+ because the large relative area between the working electrode (WE) and counter electrode (CE) achieved a highly efficient mass transfer. This improvement enabled the establishment of a reliable linear relationship across a wide concentration range, spanning from 1 pM to 1 µM (R2 = 0.998). Therefore, the exceptional ECL response of the Ru(bpy)32+/TPrA system on microfluidic chips using a two-electrode system and the TP excitation model has been demonstrated. This suggests that ECL chips without a RE have broad potential for the rapid and sensitive detection of multiple targets.