Development of smartphone-based fluorescence detection system

Abstract

Due to the huge development of technologies in past 20 years, smartphone has been through a huge evolution to be a powerful device with multi-advanced functionality. In this study, we proposed to, by utilizing the ability of CMOS camera on smartphone to capture high-quality pictures with low-light environment as the detector of fluorescence signals, to design and test a smartphone-based fluorescence detection system. Unlike the traditional fluorescence detection methods, a smartphone-based system can provide convenient, low cost and portable detection of fluorescent samples. To assist smartphone to capture clear pictures of fluorescence signal with low background noise, a portable reader that attached on the back of smartphone was designed in this study, which is a cuboid device that provides illuminance signal by using LED for exciting fluorescent samples. It also includes a plano-convex lens and a low-pass filter for the image magnification and reduce noise from surrounding light sources and light source from LED. To further improve the detection results, Noise Reduction Ensemble Averaging (NREA) algorithm was coded in Matlab to significantly enhance the fluorescence signal and reduce noise on the image results. In this study, to verify the proposed functionality of the smartphone detection system, the first experiment was conducted by using 3 different smartphone models (Galaxy S9, Pixel 3 and Oneplus One) to measure the fluorescent signal of a Nanoparticle FITC calibration slide and compare the results with the official referential results. The results from 3 smartphone models showed clear linearity that matches the referential result. To further explore the performance and detection limit of the system on fluorescent samples with lower concentrations, another 2 experiments were conducted by using FITC and Atto-550 samples as the testing objects. For FITC experiment, a 3 steps interrogation method that lowers the range of concentrations of FITC samples for 3 iterations to discover the detection limit of the system on FITC samples by using 3 different phones with different shutter times, and the detection limit is found to be 60 ppb by using Galaxy S9. For the experiment with Atto-550, hydrated and dehydrated Atto-550 samples were measured by using Galaxy S9. The results show the fluorescence signal of hydrated sample is almost unnoticeable even the concentration is 5000ppb. For the dehydrated Atto-550 samples, after 2 steps interrogation, it shows the detection limit is 7 ppb.