Portable Biosensor System and Method Based on Surface Plasmon Resonance (SPR) Fiber Optics and Smartphone for Salmonella Detection

Abstract

The present invention concerns a portable biosensor system and method. This smartphone-integrated fiber-optic biosensor system utilizes a smartphone LED as a light source and an infrared-filtered camera as a detector. Light is transmitted through a polymethyl methacrylate multimode polymer optical fiber to an Au / MgO-coated fiber-optic portion supported by a resin backing. The sensing area is connected to the LED and camera via a polymer fiber-optic cable with an SC to FC type fiber-optic adapter. All components are housed in a three-dimensionally printed polymer prototype housing that holds the smartphone and precisely directs the fiber-optic portion to the sensing area and camera. The biosensor method includes initializing a smartphone application, probing and activating the LED, and delivering light to the Au / MgO-coated sensing area.The system performs calibration by capturing a blank sample image, extracting valid pixels based on the dominant red channel, and calculating the number of pixels, total intensity, and average intensity as a reference. An image of the analyte sample is then captured and analyzed using the same parameters, and the average intensity of the sample is compared with the reference to determine the analyte concentration. The calculation results are stored in the application's local memory and used to determine the detection limit based on the standard deviation of the blank response and the slope of the calibration curve.