Monitoring the death of single BaF3 cells under plasmonic photothermal heating induced by ultrasmall gold nanorods

Abstract

Gold nanorods are very suitable as energy converters for plasmonic photothermal therapy (PPTT) applications. These particles can be accumulated on cells by targeted or non-targeted delivery and subsequently internalized by the cells. Upon photoexcitation, the plasmonic particles create heat that can trigger cell-death mechanisms that are still not fully understood. Here, we used ultrasmall plasmonic gold nanorods, either non-targeted or targeted by functionalization with the aptamer AIR-3A. This aptamer specifically binds to the Interleukin-6 receptor expressed on the investigated BaF3 cell line. After photoexcitation of only individual cells, we monitored and investigated the evolution of cell death in real time on the single-cell level by tracking the temporal development of both the morphology and the absorbance of the cell, which changed due to the uptake of the dye trypan blue. We observed a swelling of the cell during the first few minutes, followed by a subsequent staining due to loss of membrane integrity, before cellular lysis took place. As the most notable difference between the use of targeted and non-targeted gold nanorods, the trypan blue staining period was considerably shorter when the targeted gold nanorods were used. Morphological changes of the cell after irradiation strongly suggest that necrosis is induced. The temporal delay between the start of the necrotic process and the beginning of cell staining indicates that the cell damage initially occurs in the inner cell compartments before the cell membrane is affected.