Selective and easy detection of microcystin-LR in freshwater using a bioactivated sensor based on multiwalled carbon nanotubes on filter paper

Rapid and Easy Detection of Microcystin-LR Using a Bioactivated Multi-Walled Carbon Nanotube-Based Field-Effect Transistor Sensor

In this study, we developed a multi-walled carbon nanotube (MWCNT)-based field-effect transistor (MWCNT-FET) sensor with high sensitivity and selectivity for microcystin-LR (MC-LR). Carboxylated MWCNTs were activated with an MC-LR-targeting aptamer (MCTA). Subsequently the bioactivated MWCNTs were immobilized between interdigitated drain (D) and source (S) electrodes through self-assembly. The top-gated MWCNT-FET sensor was configured by dropping the sample solution onto the D and S electrodes and immersing a Ag/AgCl electrode in the sample solution as a gate (G) electrode. We believe that the FET sensor's conduction path arises from the interplay between the MCTAs, with the applied gate potential modulating this path. Using standard instruments and a personal computer, the sensor's response was detected in real-time within a 10 min time frame. This label-free FET sensor demonstrated an impressive detection capability for MC-LR in the concentration range of 0.1-0.5 ng/mL, exhibiting a lower detection limit of 0.11 ng/mL. Additionally, the MWCNT-FET sensor displayed consistent reproducibility, a robust selectivity for MC-LR over its congeners, and minimal matrix interferences. Given these attributes, this easily mass-producible FET sensor is a promising tool for rapid, straightforward, and sensitive MC-LR detection in freshwater environments.

Electrochemical biosensor using SnO2 colloidal quantum wire for monitoring the interaction of microcystin antigen-antibody

Electrochemical sensors that incorporate immunoassay principles have the ability to monitor dynamic processes of antigen-antibody interactions in real time. In this study, a gold electrode was modified with tin dioxide colloidal quantum wire (SnO2 QWs) and then coated with the leucine/arginine subtype microcystin (MC-LR) antibody. The active site of SnO2 QWs that was not bound by MC-LR antibody was then passivated with bovine serum protein (BSA). When the MC-LR antigen binds specifically to the antibodies on the electrode's surface, it triggers electrochemical reactions and generates electrical signals at specific voltage conditions. The SnO2 QW exhibits excellent electron transport ability, and its ability to form a loose and porous microstructure on the gold electrode surface, which is conducive to the receptor function of the biosensor. The results show a high affinity between the MC-LR antigen and antibody, ranging from 1 pg/mL to 10 ng/mL of MC-LR antigen concentration. The kinetic characteristics of the immune reaction between MC-LR antigen and antibody were elucidated, obtaining a binding constant of 1.399 × 1011 M-1 and a dissociation constant of 7.147 pM, demonstrating the potential of electrochemical biosensing technology in biomolecular interactions.

Sensitive and highly rapid electrochemical measurement of airborne coronaviruses through condensation-based direct impaction onto carbon nanotube-coated porous paper working electrodes

Rapid detection of indoor airborne viruses is critical to prevent the spread of respiratory diseases. Herein, we present sensitive, highly rapid electrochemical measurement of airborne coronaviruses through condensation-based direct impaction onto antibody-immobilized, carbon nanotube-coated porous paper working electrodes (PWEs). Carboxylated carbon nanotubes are drop-cast on paper fibers to make three-dimensional (3D) porous PWEs. These PWEs have higher active surface area-to-volume ratios and electron transfer characteristics than conventional screen-printed electrodes. The limit of detection and detection time of the PWEs for liquid-borne coronaviruses OC43 are 65.7 plaque-forming units (PFU)/mL and 2 min, respectively. The PWEs showed sensitive and rapid detection of whole coronaviruses, which can be ascribed to the 3D porous electrode structure of the PWEs. Moreover, water molecules condense on airborne virus particles during air sampling, and these water-encapsulated virus particles (<4 µm) are impacted on the PWE for direct measurement without virus lysis and elution. The whole detection takes ∼10 min, including air sampling, at virus concentrations of 1.8 and 11.5 PFU/L of air, which can be due to the highly enriching and minimally damaging virus capture on a soft and porous PWE, demonstrating the potential for the rapid and low-cost airborne virus monitoring system.