Fish on chips: Microfluidic living embryo array for accelerated in vivo angiogenesis assays

Zebrafish (Danio rerio) has recently emerged as a powerful experimental model in molecular medicine and drug discovery. Nevertheless, automated in situ analysis of zebrafish embryos is still in early development. Currently available technologies do not allow for an automated loading, docking and spatial address designation to large numbers of single embryos during imaging. Moreover, microperfusion treatment of large numbers of immobilized zebrafish embryos is still inaccessible. In this work, we describe the proof-of-concept design of a 3D microfluidic embryo array for real-time developmental analysis of transgenic zebrafish embryos. The Lab-on-a-Chip system was fabricated directly in poly(methyl methacrylate) (PMMA) transparent thermoplastic using infrared laser micromachining. The multilayer chip contains a trap-and-release immobilization manifold with an array of micro-mechanical traps that capture single fish embryos. The docking is assisted by the combination of gravitation and low-pressure suction at the bottom plane of the device. The design achieves one-embryo-one-trap for convenient address designation and spatial encoding to each embryo and is capable of high-throughput docking and recovery of single embryos at a large scale. We also present data that the microfluidic embryo array can be readily applied to kinetic analysis of investigational pharmacological agents inhibiting blood vessel growth (angiogenesis) in transgenic Tg(fli1a:EGFP) zebrafish. The work provides a foundation for automated screening of intact metazoan model organisms in drug discovery using Lab-on-a-Chip.