A [Beta]-Camera Integrated with a Microfluidic Chip for Radioassays Based on Real-Time Imaging of Glycolysis in Small Cell Populations

An integrated β-camera and microfluidic chip was developed that is capable of quantitative imaging of glycolysis radioassays using ^sup 18^F-FDG in small cell populations down to a single cell. This paper demonstrates that the integrated system enables digital control and quantitative measurements of glycolysis in B-Raf^sup V600E^-mutated melanoma cell lines in response to specific B-Raf inhibition. Methods: The β-camera uses a position-sensitive avalanche photodiode to detect charged particle-emitting probes within a microfluidic chip. The integrated β-camera and microfluidic chip system was calibrated, and the linearity was measured using 4 different melanoma cell lines (M257, M202, M233, and M229). Microfluidic radioassays were performed with cell populations ranging from hundreds of cells down to a single cell. The M229 cell line has a homozygous B-Raf^sup V600E^ mutation and is highly sensitive to a B-Raf inhibitor, PLX4032. A microfluidic radioassay was performed over the course of 3 days to assess the cytotoxicity of PLX4032 on cellular ^sup 18^F-FDG uptake. Results: The β-camera is capable of imaging radioactive uptake of ^sup 18^F-FDG in microfluidic chips. ^sup 18^F-FDG uptake for a single cell was measured using a radio-activity concentration of 37 MBq/mL during the radiotracer incubation period. For in vitro cytotoxicity monitoring, the β-camera showed that exposure to 1 µM PLX4032 for 3 days decreased the ^sup 18^F-FDG uptake per cell in highly sensitive M229 cells, compared with vehicle controls. Conclusion: The integrated β-camera and microfluidic chip can provide digital control of live cell cultures and allow in vitro quantitative radioassays for multiple samples simultaneously. [PUBLICATION ABSTRACT]