A radial microfluidic concentration gradient generator with high-density channels for cell apoptosis assay.

An integrated microfluidic concentration gradient chip was developed for generating stepwise concentrations in high-density channels and applied to high-throughput apoptosis analysis of human uterine cervix cancer (HeLa) cells. The concentration gradient was generated by repeated splitting-and-mixing of the source solutions in a radial channel network which consists of multiple concentric circular channels and an increasing number of branch channels. The gradients were formed over hundreds of branches with predictable concentrations in each branch channel.

Immunolabeling and NIR-excited fluorescent imaging of HeLa cells by using NaYF(4):Yb,Er upconversion nanoparticles.

Upconversion fluorescent nanoparticles can convert a longer wavelength radiation (e.g., near-infrared light) into a shorter wavelength fluorescence (e.