Seeing and Understanding the Light: Student‐Built Fluorescence Microscopes for Dynamic Calcium Imaging in the Undergraduate Physiology Lab Class

Abstract

Students often treat laboratory equipment as a black box with little knowledge of how scientific instrumentation works to gather data. We are creating interdisciplinary classrooms where students gain confidence to build and understand tools to solve biological questions as future scientists. We describe student construction, use and assessment of our Do‐It‐Yourself (DIY) fluorescence imaging microscope. Students were first introduced to principles of fluorescence microscopy and Drosophila neurogenetics through lecture material, readings and online resources. Mixed teams of 2‐3 Biology and Engineering students assembled their own imaging microscopes with the following parts: 20X objective lens, excitation and emission filters and dichroic mirror, CMOS camera, 3‐D printed holders and housings for these parts, and a student‐built LED light source (total parts/microscope cost ~$1000). Construction was guided by pre‐recorded build videos and assistance from course instructors and teaching assistants. Student teams tested their microscope by collecting images from prepared slides with GFP fluorescence in fly synaptic boutons. Teams also acquired images from living fly larval preparations in two simple experiments. These compared fluorescence intensity before and during application of a high potassium saline that: 1) released GFP‐labelled neuropeptide from fly synaptic boutons, and 2) activated glutamate neurons expressing GCaMP. They analyzed images for fluorescence intensity and adjusted and colorized images with ImageJ. Assessment of the student learning experience was conducted for two Spring 2021 undergraduate laboratory courses at Cornell University (BioNB/BME/ECE 4910, Principles of Neurophysiology and BioNB 4300, Experimental Molecular Biology) and a Fall 2021 undergraduate Neurobiology laboratory course (Neurobiology 340) at Hobart and William Smith colleges. Students rated statements on all the following topics highly positive: knowledge of fluorescence imaging principles, affective experience of building and understanding the instrumentation, working in teams and clarity of guidance during the microscope build and use sessions. We continue our DIY efforts to expand the teaching, learning and research toolbox for physiology students and faculty.