Silicon Photomultipliers as a Low-Cost Fluorescence Detector for Capillary Electrophoresis

Capillary electrophoresis (CE) is a highly efficient separation method capable of handling small sample volumes (~pL) and low (~yoctomole) detection limits, and as such is ideal for applications that require high sensitivity such as single-cell analysis. Low-cost CE instrumentation is quickly expanding but low-cost, open-source fluorescence detectors with ultra-sensitive detection limits are lacking. Silicon photomultipliers (SiPM) are inexpensive, low-footprint detectors with the potential to fill the role as a detector when cost, size, and customization are important. In this work we demonstrate the use of a SiPM in CE with zeptomolar detection limits and a dynamic range spanning five orders of magnitude, comparable to photomultiplier detectors. We characterize the performance of the SiPM as a highly sensitive detector by measuring enzyme activity in single cells. This simple, small footprint, and low-cost (<$130) light detection circuit will be beneficial for open-source, portable, and budget friendly instrumentation requiring high sensitivity.