Graphene-enabled optical cardiac control in Drosophila melanogaster

Noninvasive cardiac control has stemmed from a need to overcome challenges that come from traditional electric implantable pacemakers, which can require surgery, cause infection and damage to vessels, and require battery replacements. Therefore, new methods are being developed to be able to control heart function noninvasively, specifically, using light. Previously, Drosophila have been used as a model for cardiac optogenetic studies, where the heart was able to be paced both slower and faster than its resting heart rate. This study looks at how reduced graphene oxide (rGO) can be used to increase the heart rate of yellow-white Drosophila pupa using light stimulation from 470 nm (blue light), 617 nm (red light), and 656 nm (near-infrared light). When injected into the heart tube of pupa, it forms aggregates along the heart wall and changes the membrane potential when light is shown, which leads to an increase in heart rate. Our study characterized the heart response to rGO stimulation, utilizing rGO’s broad absorption spectrum. Optical coherence microscopy (OCM) was used to image a cross-section of the heart tube over time, providing information about heart rate, rhythmicity, and morphology. This work is promising for use in both heart disease models, as rGO stimulation does not require prior genetic manipulation, and in larger animal models, where near-infrared light can be used to penetrate the heart when it lies deeper into tissue.