Portable Fluorometer for Cyanobacteria Detection

A portable system for fluorescence measurement has been developed for cyanobacteria detection. Exploiting commercially available low-cost photodiodes and a single 9 V supply, the system was able to measure two fluorescence emissions simultaneously. Output voltages resulting from the fluorescence intensity were measured by utilizing two quantum dots of QD₅₆₅ and QD₆₅₅. These quantum dots were employed into a NanoGene assay for mcyD gene (synthetase of toxic microcystin) detection of Microcystis aeruginosa. We investigated various operational parameters (e.g., distance, angle between laser emission and sample, and so on) for the proposed system. Measurements indicated the highest output voltage signal was obtained at a distance of 0.5 cm with the right angle (90°) between the laser source and a sample vial. Also, the mcyD gene hybridized with QD₅₆₅ and QD₆₅₅ was quantitatively detected by the proposed detection system, i.e., the normalized output voltage (QD₆₅₅/QD₅₆₅) was linearly proportional to the mcyD gene copy numbers (y = 0.41 log x + 6.6, r² = 0.92). Finally, the quantitative data were transferred wirelessly to the readout via Bluetooth.