Lab-on-a-chip technology for a non-invasive and real-time visualisation of metabolic activities in larval vertebrates

Abstract

Non-invasive and real-time visualisation of metabolic activities in living small organisms such as zebrafish embryo and larvae has not yet been attempted due to profound analytical limitations of existing technologies. Significant progress in the development of physico-optical oxygen sensors using luminescence quenching by molecular oxygen has recently been made. Sensing using such microsensors is, however, still performed in small glass chambers that hold single specimens and thus not amenable for high-throughput data acquisition.In this work, we present a proof-of-concept approach by using microfluidic Lab-on-a-Chip (LOC) technologies combined with sophisticated optoelectronic sensors. The LOC device is capable of immobilising live zebrafish embryos with continuous flow perfusion, while the sensor uses innovative Fluorescence Ratiometric Imaging (FRIM) technology that can kinetically quantify the temporal patterns of aqueous oxygen gradients at a very fine scale based on signals coming from an optical sensor referred to as a sensor foil. By embedding the sensor foil onto the microfluidic living embryo array system, we demonstrated in situ FRIM on developing zebrafish embryos. Future integration of microfluidic chip-based technologies with FRIM technology represents a noteworthy direction to miniaturise and revolutionise research on metabolism and physiology in vivo.Keywords: Microfluidics, Lab-on-a-Chip, microarrays, zebrafish, embryo, metabolic activity, oxygen, sensor foils, fluorescence ratiometric imaging *e-mail donald.wlodkowic@rmit.edu.au; phone 61 3 992 57157; fax 61 3 992 57110; http://www.rmit.edu.au/staff/donald-wlodkowic

Ecotoxicology Goes on a Chip: Embracing Miniaturized Bioanalysis in Aquatic Risk Assessment

“…Biomicrofluidics has already been widely recognized as emerging technology in research fields, such as analytical chemistry, cell biology, biotechnology, drug discovery, and biomedical research. − However, the application of microfluidics in aquatic ecotoxicology is still in its infancy. ,,, Aquatic ecotoxicity testing enhanced by innovative biomicrofluidic technologies holds a great promise for development of innovative analytical platforms (Figure ).…”

“…LOC systems enabling tests on small metazoan organisms reportedly provide high-throughput low-cost alternatives to conventional macroscale approaches. , They are poised to increase the sensitivity of the bioassays and reduce the overall costs by miniaturization of not only fluid handling components but also detection and data collection systems. , Better control of physicochemical conditions in enclosed circuitries of fluidic channels also allows to reduce the effect of confounding factors of artificial toxicity when testing whole water samples. , Poor-control over parameters, such as changes in toxicant availability to the specimen due to surface adsorption, degradation of tested chemicals, accumulation of metabolites and byproducts, depletion of oxygen and alterations in pH of culture media in standard conditions, introduces significant artifacts in routine bioassays . LOC systems also excel in unprecedented ability to manipulate, cage and position of the specimens, high-throughput as well as high-resolution imaging.…”

“…34−37 However, the application of microfluidics in aquatic ecotoxicology is still in its infancy. 14,18,26,38 Aquatic ecotoxicity testing enhanced by innovative biomicrofluidic technologies holds a great promise for development of innovative analytical platforms (Figure 2).…”

“…17,99 Better control of physicochemical conditions in enclosed circuitries of fluidic channels also allows to reduce the effect of confounding factors of artificial toxicity when testing whole water samples. 18,38 Poor-control over parameters, such as changes in toxicant availability to the specimen due to surface adsorption, degradation of tested chemicals, accumulation of metabolites and byproducts, depletion of oxygen and alterations in pH of culture media in standard conditions, introduces significant artifacts in routine bioassays. 18 LOC systems also excel in unprecedented ability to manipulate, cage and position of the specimens, high-throughput as well as highresolution imaging.…”