A beta-camera integrated with a microfluidic chip for radioassays based on real-time imaging of glycolysis in small cell populations.

Abstract

An integrated β-camera and microfluidic chip was developed that is capable of quantitative imaging of glycolysis radioassays using (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(V600E)-mutated melanoma cell lines in response to specific B-Raf inhibition. 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(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 (18)F-FDG uptake. The β-camera is capable of imaging radioactive uptake of (18)F-FDG in microfluidic chips. (18)F-FDG uptake for a single cell was measured using a radioactivity 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 (18)F-FDG uptake per cell in highly sensitive M229 cells, compared with vehicle controls. 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.