A novel microfluidic chip for on-site radiation risk evaluation

This paper proposes a microfluidic chip for on-site radiation risk evaluation using immunofluorescence staining for the DNA double-strand break (DSB) marker phosphorylated histone, H2AX (γ-H2AX). The proposed microfluidic chip separates lymphocytes, the cells of the DNA DSB evaluation target, from whole blood based on their size and traps them in the trap structure. The subsequent DNA DSB evaluation, γ-H2AX assay, can be performed on a chip, which saves space and simplifies the complicated operation of the assay, which conventionally requires a large experimental space. Therefore, this chip will enable the biological effect evaluation of radiation exposure to be completed on-site. Bead experiments with samples containing 10 μm and 27 μm diameter beads showed that the proposed chip introduced the sample into the flow channel only by centrifugal force and passively separated the two types of beads by the structure in the flow channel. In addition, bead experiments showed that isolated 10 μm diameter beads were trapped in more than 95% of the 1000 lymphocyte trap structures (LTSs). The feasibility of the proposed method for on-site radiation risk evaluation was demonstrated through cell-based experiments by performing the γ-H2AX assay in human lymphoblastoid TK6 cells. The experiment shows that LTSs in the flow channel are capable of trapping TK6 cells, and γ-H2AX foci which are markers of DNA DSBs are observed in the TK6 cells on the chip. Thus, the results suggest that the proposed microfluidic chip simplifies the γ-H2AX assay protocol and provides a novel method to perform the assay on-site, which is conventionally impracticable.