Advancing Dynamic Imaging for Microfluidic Stimulated Tissues: Biology, Techniques, and Applications

Using quantitative fluorescence microscopy imaging of cellular activities in intact tissues stimulated in a microfluidic device creates opportunities for studying major diseases such as diabetes and cancer. Despite a number of documented phenotypic traits of these diseases, the underlying pathophysiological mechanisms remain to be elucidated. Conventional biochemical assays have been used to probe mechanistic information; however, these techniques often lack the biological context of the living sample and offer limited spatiotemporal resolution. Here, we show that dynamic imaging of intact ex vivo pancreatic islets and three-dimensional in vitro tumor spheroids on a custom microfluidic platform provides real-time physiological and biological information with subcellular resolution. Using this microfluidic stimulated tissue platform, we developed a novel imaging method relating the redox-associated changes in electron transfer flavoprotein (ETF) autofluorescence to fatty acid oxidation in living pancreatic islets. We found that elevated glucose (>10 mM) decreases the ETF redox state within 20 minutes in islets when presented with a mixed nutrient condition associated with glucolipotoxicity. This observation suggests a glucose-mediated shift in lipid partitioning away from fatty acid oxidation. Furthermore, we found that excess branched-chain amino acid leucine prematurely turns off fatty acid oxidation despite the fasted state and reduces the dynamic glucose response leading to a condition termed metabolic inflexibility. Finally, we imaged the nanoparticle-tissue interactions in tumor spheroids and found that incorporating affinity ligands onto nanoparticles and enhancing convective interstitial fluid flow through the tissue increased the uptake efficiency of nanoparticles by spheroids despite the limitation imposed by diffusion. Overall, our results demonstrate the effectiveness of ETF autofluorescence imaging in monitoring mitochondrial fatty acid oxidation in intact pancreatic islets and the efficiency of a custom microfluidic platform as the pre-animal model for probing nanoparticle-tissue interactions. Future experimental efforts to study other tissue types, physicochemical properties of nanoparticles, imaging techniques, and microfluidic technologies could lead to the development of more sophisticated and effective platforms for medical tissue biopsy or high-throughput rapid screening of nanoparticles to accelerate the clinical translation of nanoparticles.

Department dc:contributor.department

Biomedical Engineering

Year dc:date.issued

2013

Author dc:creator

• Lam, Alan Kwan-Shing

Advisor dc:contributor.advisor

• Rocheleau, Jonathan

• Microscopy Imaging
• Autofluorescence
• Microfluidics
• Nanoparticles
• Pancreatic Islets
• Tumor Spheroids

Language dc:language.iso

en_ca

Handle dc:identifier.uri

http://hdl.handle.net/1807/68895

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/68895