Design and development of portable fluorescence reader using Silicon photomultiplier (SiPM) sensor

Fluorescent lateral flow assays (LFA) strips have gained popularity for medical diagnostics application by offering fast and reliable response in both qualitative & quantitative readout formats. The fluorescence emission is generated when excited with appropriate optical source, and is dependent on the analyte concentration in the sample spotted on the LFA strips. Quantitative detection requires a LFA reader to carry out accurate and precise measurements of the fluorescence emission. These readers can be of either benchtop or handheld type, and conventionally use either photo multiplier tube (PMT) or avalanche photodiodes (APD) or customized photo diodes. In addition to their proven benefits like high sensitivity, speed and gain, the availability of silicon photomultipliers (SiPM) in micro form factor makes them good choice for developing miniaturized LFA strip readers. In this study, a portable fluorescence reader using SiPM sensor has been designed, which records the fluorescence intensity of the spot on planar surfaces e.g. nitrocellulose membrane (NCM) packaged in the plastic cases. The design and operation details of the benchtop reader using SiPM sensor along with excitation source, focusing and collimating optics and power supplies integrated with general purpose microcontroller board in a mechanical housing are reported in this paper. The testing of the developed reader is done by using mercaptopropionic acid capped cadmium telluride quantum dots (MPA-CdTe QDs) as the fluorescent analytes spotted on NCM packaged plastic strips. The results obtained from the developed portable reader are compared with the standard fluorescence plate reader for QD concentration varying from 60 mu g/mL to 420 mu g/mL and are found to be in good accordance with the response & resolution of the conventional fluorescent plate reader. Further work is under development for testing the developed reader for disease diagnostic applications.