Study on uptake of gold nanoparticles by single cells using droplet microfluidic chip-inductively coupled plasma mass spectrometry

Cellular uptake of Au NPs is the premise for their application in drug delivery, cell/tissue imaging and quantitation analysis of biomarkers in the cells. However, conventional methods for cell analysis may lead to the loss of important information from abnormal or atypical cells in the cell population. In this work, with 15, 30 and 60 nm Au NPs@citric acid and Au NPs@DNA as model materials, the cellular uptake of Au NPs in single HeLa cells is studied by using an on-line droplet chip inductively coupled plasma mass spectrometry hyphenated technique. It is found that the average amount of Au uptake for Au NPs@citric acid is higher than that for Au NPs@DNA at high incubation concentrations. The distribution of the number of uptaken Au NPs in single HeLa cells shows a great difference when HeLa cells are incubated with different Au NPs. The percentage of cells uptaking Au NPs in the cell population also reveals a difference in cellular uptake between Au NPs@citric acid and Au NPs@DNA at the single-cell level. To explain the abovementioned phenomenon, the endocytosis mechanisms of Au NPs are investigated. Clathrin-mediated endocytosis is found to be the major internalization pathway for 15 and 30 nm Au NPs@DNA.