Lab-on-a-Chip imaging micro-echocardiography (iμEC) for rapid assessment of cardiovascular activity in zebrafish larvae

Analysis of physiological parameters using small model organisms is an attractive approach in pre-clinical drug discovery when studying effects of new drugs or existing drug combinations. Larval zebrafish (Danio rerio) is a small vertebrate model organism that recently emerged as an innovative experimental system for non-invasive and real-time analysis of physiological parameters such as cardiovascular activity. In this work, we demonstrate a new chip-enabled approach to perform non-invasive imaging micro-echocardiography (iμEC) on immobilized larval stages of zebrafish. The iμEC is a new assay for quantification of the temporal cardiac patterns based on analysis of video stream from a high-resolution camera. The chip-based system utilized hydrodynamic trapping principles to actively capture and immobilize individual larvae using a low-pressure suction for real-time iμEC analysis. The system coupled together with an integrated interface provided a new capability to rapidly assess pharmacologically-induced perturbation in cardiac function by real-time and non-invasive monitoring of zebrafish larvae. We demonstrated the application of the technology for proof-of-concept assessment of model cardio-active compounds delivered using continuous micro-perfusion. The optical transparency of larval stages and micro-hydrodynamic immobilization allowed for visualization of cardiac activity after drug treatment in real-time. Results obtained using micro-perfusion also enabled studies on rapid drug withdrawal that are difficult to achieve using existing protocols such as imaging in microtiter plates. This work demonstrates iμEC as a new technique for cardiological experiments utilizing zebrafish models.