Determination of silver nanoparticles in single cells by microwell trapping and laser ablation ICP-MS determination

Silver nanoparticles (AgNPs) are currently one of the most manufactured nanomaterials, and they have been applied in various consumer products due to their distinctive antimicrobial properties. Because of cell heterogeneity, the analysis of AgNPs in single cells after exposure is fundamental for biomedical applications or toxicological assays. Here, we developed a high-throughput method for single cell analysis by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Single cells were efficiently trapped by a polydimethylsiloxane (PDMS) microwell array. Under optimal conditions, 60% microwells contained one single cell and 4% microwells contained two cells or more. The cells in the array were regularly distributed; thus, they could be easily targeted and ablated in a grid pattern and quantitatively analyzed by LA-ICP-MS with a high throughput. The silver mass in single 16HBE cells exposed to AgNPs showed log-normal distribution ranging from 0.80 to 383 fg Ag per cell. The average result from single cells was in good agreement with the result from the digestion of 3.0 x 10(6) cells. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 0.2 fg Ag and 0.7 fg Ag, respectively. Because of its great potential in single cell analysis, LA-ICP-MS can be widely applied for single cell analysis and can offer great benefits for the study of the biological effects of metal NPs at the single-cell level.