A Low-Cost Digital Microscope with Real-Time Fluorescent Imaging Capability

Abstract

This paper describes the development of a prototype of a low-cost digital fluorescent microscope built from commercial off-the-shelf (COTS) components. The prototype was tested to detect malignant tumor cells taken from a living organism in a preclinical setting. This experiment was accomplished by using Alexa Fluor 488 conjugate dye attached to the cancer cells. Our prototype utilizes a torch along with an excitation filter as a light source for fluorophore excitation, a dichroic mirror to reflect the excitation and pass the emitted green light from the sample under test and a barrier filter to permit only appropriate wavelength. The system is designed out of a microscope using its optical zooming property and an assembly of exciter filter, dichroic mirror and transmitter filter. The microscope is connected to a computer or laptop through universal serial bus (USB) that allows real-time transmission of captured florescence images; this also offers real-time control of the microscope. The designed system has comparable features of high-end commercial fluorescent microscopes while reducing cost, power, weight and size.

Fig 1. (a) Block diagram of the fluorescence microscope; (b) absorbance/emission spectra of the sample under test (adapted from [10]).

The excitation filter passes through lights of 400-499nm which is reflected by the dichroic mirror. The peak absorption and peak emission of the sample is 495nm and 519nm respectively. Emitted light is then passed through the dichroic mirror followed by the barrier filter whose band pass wavelength is 520±18nm. Finally a small camera microscope captures the emitted wavelength, forms an image and sends to a computer.

Fig 2. Components of the proposed microscope: (a) Dichroic mirror (b) Exciter filter (c) Pocket microscope (d) Flashlight (e) Barrier Filter.

Fig 3. Fluorescence Microscope (a) Our prototype (b) Commercial microscope [12] (c) Experimental setup showing our proposed microscope connected to computer/laptop.

Fig 4. Results showing (a) Normal cell; (b)-(c) Cancer cells as viewed from our prototype; (d) Same cancer cell when viewed from the commercial microscope (model Olympus IX51).