Automated miniscope for fluorescent cell counting applications

Abstract

Fluorescence microscopy is a powerful biological technique employed in a variety of diagnostic assays. Fluorescence based cell counting is a common way of diagnosing various infections. Despite the high sensitivity and specificity offered by fluorescence microscopy; its utility is restricted as it requires trained personnel to operate instrument and interpret results. Commercially available automated fluorescence microscopy is bulky and expensive. We have developed an automated and compact total internal reflection fluorescence (TIRF) microscopy system, referred to as Miniscope. The Miniscope is a portable, automated, and inexpensive fluorescence based optical system building on a previously reported compact 3D printed TIRF module containing a laser and a prism for a TIRF based sample illumination. The system consists of an aspherical lens, an emission filter, a CMOS camera, a Raspberry Pi, and a micro-stepper motor. It offers automated scanning over an area of 20x20mm² with an optical resolution of 0.76μm/pixel. It can be operated in bright field as well as TIRF mode for image acquisition. As an initial proof-of-concept we have demonstrated its performance using fluorescently labelled HL60 cells spiked in milk samples. Our Miniscope is suitable for providing field deployable diagnostic solutions in resource limited settings due to its compactness, overall low cost and appreciable magnification and resolution.