Convection Driven Ultrarapid Protein Detection via Nanobody-Functionalized Organic Electrochemical Transistors.

Conventional biosensors rely on the diffusion-dominated transport of the target analyte to the sensor surface. Consequently, they require an incubation step that may take several hours to allow for the capture of analyte molecules by sensor biorecognition sites. This incubation step is a primary cause of long sample-to-result times. Here, alternating current electrothermal flow (ACET) is integrated in an organic electrochemical transistor (OECT)-based sensor to accelerate the device operation. ACET is applied to the gate electrode functionalized with nanobody-SpyCatcher fusion proteins. Using the SARS-CoV-2 spike protein in human saliva as an example target, it is shown that ACET enables protein recognition within only 2 min of sample exposure, supporting its use in clinical practice. The ACET integrated sensor exhibits better selectivity, higher sensitivity, and lower limit of detection than the equivalent sensor with diffusion-dominated operation. The performance of ACET integrated sensors is compared with two types of organic semiconductors in the channel and grounds for device-to-device variations are investigated. The results provide guidelines for the channel material choice in OECT-based biochemical sensors, and demonstrate that ACET integration substantially decreases the detection speed while increasing the sensitivity and selectivity of transistor-based sensors.

Convective polymerase chain reaction in standard microtubes.

Polymerase chain reaction (PCR) is the most widely used method for nucleic acids amplification. To date, a huge number of versatile PCR techniques have been developed. One of the relevant goals is to shorten PCR duration, which can be achieved in several ways. Here, we report on the results regarding nucleic acids amplification by convective PCR (cPCR) in standard 0.2 ml polypropylene microtubes. The following conditions were found to be optimal for such amplification: 1) 70 µl reaction volume, 2) the supply of external temperature 145°Ð¡ for the denaturation zone and 0°Ð¡ for the annealing zone, 3) ∼30° inclination of the microtube main axis, 4) the use of nearby primers, and 5) duration of the reaction 15-20 min. At these conditions, the amplification products are accumulated in an amount sufficient to be registered by gel electrophoresis, and high sensitivity of the reaction comparable to that of conventional PCR is achieved. cPCR provided the reliable detection of SARS-CoV-2 coronavirus RNA isolated from nasopharyngeal swabs of COVID-19 patients.