Competitive smartphone-based portable electrochemical aptasensor system based on an MXene/cDNA-MB probe for the determination of Microcystin-LR

A competitive smartphone-based portable electrochemical aptamer sensing system was developed for MC-LR detection. The platform was composed with a smartphone-controlled portable electrochemical system, a smartphone with custom application and a screen-printed carbon electrode (SPCE). The portable electrochemical system consisted a homemade ARM STM32 with chronoamperometry (CA), cyclic voltammetry (CV) and square wave voltammetry (SWV) modules that had a similar performance to commercial electrochemical workstations. The control of the portable electrochemical system, reception and visualization of the assay results were implemented by a smartphone. SPCE was modified by in situ electrodeposition with gold nanoparticles (AuNPs) and reduced graphene oxide (rGO). Subsequently, the aptamer was incubated onto the SPCE through Au-S bonds. The complementary DNA labeled with methylene blue (cDNA-MB) was conjugated onto the surface of MXene to form the probe for signal amplification. The competitive aptasensor was accomplished when the probe was complemented with the aptamer. The fabricated system exhibited the outstanding capability for the determination of MC-LR over a range of 0.0001-5 nM with a limit of detection of 4 x 10(-5) nM. Furthermore, the system demonstrated acceptable stability, reproducibility, specificity and high recovery rate. The smartphone-based competitive aptasensor system exhibited the merits of portability, low-cost and fast-response to satisfy the demand for on-site detection of MC-LR.