Portable cyanobacteria detection fluorometer with current-conveyor transimpedance amplifiers

A portable fluorometer has been developed for cyanobacteria detection by exploiting commercially available low-cost photodiodes. Particularly, the front-end detection circuit was integrated on-chip by using a 0.11-mm CMOS process to realize the high transimpedance gain of 99.7 dBΩ with low current consumption of 1.4 mA from a single 1.5-V supply, hence providing a low-power solution with small form-factor in the applications of portable cyanobacteria detection. For measuring fluorescence intensity of cyanobacteria, two quantum dots of QD₅₆₅ and QD₆₅₅ were employed into a NanoGene assay for mcyD gene(synthetase of toxic microcystin) detection of Microcystis aeruginosa, resulting in two different readout voltages. Various operational parameters (e.g. distance, angle between laser emission and vial sample, etc) were investigated for the proposed fluorometer. Measurements demonstrated that the mcyD gene hybridized with QD₅₆₅ and QD₆₅₅ was quantitatively detected, i.e. the normalized output voltage (QD₆₅₅/QD₅₆₅) was linearly proportional to the mcyD gene copy numbers (y = 0.25 log x – 0.25). Besides, the wireless transfer of the quantitative data was performed via Bluetooth.