Fig. 1: Integrated Opto-SICM system to study heterocellular connections.

Cardiac fibroblasts were modified to express ChR2-eYFP by adenoviral vector; the ChR2-FB were sparsely co-cultured with non-transformed CMs. An inverted epifluorescence microscope (bottom) was modified to include a controllable light source for optogenetic stimulation (of ChR2-FBs). The microscope was also used to identify ChR2-FBs in pair with CMs for SICM mapping. The SICM system (top), operating in hoping mode, consists of a nanopipette and a control circuit with a current amplifier and real-time feedback to adjust the z-position of the pipette based on measured current. It outputs nano-topographic images to map the ChR2-FB-CM connections and when recording the vertical displacement of the nanopipette it captures CM contractions in response to the optogenetic stimulation. Biorender was used to create parts of this figure.