Researchers from the George Washington University, US, have developed a portable and low-cost macroscopic mapping system for all-optical cardiac electrophysiology. Their work was published recently in the Journal of Biomedical Optics.
Previous scientists adopted human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) as a model of the human heart. Such lab-on-a-chip human hearts can be used to study the disruption in these cardiac waves in response to various stimuli, using patient’s own reprogrammed cells. Optical imaging can help visualise the waves, however highly sensitive high-speed cameras are needed for this purpose, and each one of them can be expensive, costing around $100,000.
Against this backdrop, the researchers aimed to develop an efficient and cheaper system for all-optical cardiac electrophysiology. Instead of using electrical stimuli, they triggered voltage, calcium waves, and mechanical contractions in hiPSC-CMs using optogenetic stimulation.
“Optogenetics uses light-sensitive proteins from algae that are genetically expressed in human cells to control them in a manner similar to that realised using electrical impulses. The utilisation of light, however, enables the stimulation of many samples simultaneously in a contactless manner without any wiring. This is not possible with electrical impulses,” explained Emilia Entcheva, a scientist at George Washington University.
To make their system affordable, the researchers used inexpensive high-speed machine vision complementary metal oxide semiconductor (CMOS) cameras, priced 100 times lower than the scientific CMOS cameras typically used for this purpose. The team built a multicamera system, using LEDs and off-the-shelf components for stimulation and control. Using oblique LED illumination made it possible to discern local dye-free signals for small mechanical contractions, while imaging centimetre-scale area.
New all-optical system for testing lab-on-a-chip human heartsNew all-optical system for testing lab-on-a-chip human hearts