Single-Nucleobase-Resolved Nanoruler Determines the Surface Energy Transfer Radius on the Living Cell Membrane.

Investigations about surface energy transfer radius ( r 0 ) are limited to the aqueous solution system, and it is quite limited on experimental values of r 0 between dyes and the corresponding gold particle (AuNP) sizes, especially for living cell systems. Hence, the selection of suitable AuNP-dye pairs is restricted when designing nanometal surface energy transfer (NSET) strategies in analytical sciences. Here, we developed a single-nucleobase-resolved NSET strategy to in situ measure the r 0 value between a specific dye and different-sized AuNPs on the living cell membrane. Using the aptamer-dye complex (XQ-2d- n TA-FAM) and antiCD71 antibody-coupled AuNP conjugate (Au@antiCD71) as two working elements to bind two different sites on CD71 receptors on living cell membranes, we modified the n TA spacer between FAM and the terminal of aptamer to change the distance ( r ) from FAM to AuNP center and further adjusted the quenching efficiency (Φ) between them. Different r 0 values of various AuNP-FAM pairs in living cells are determined by this in situ detection strategy. Based on this single-nucleobase-resolved NSET strategy, we established a simple and efficient universal method for measuring r 0 in the living cell system, which greatly expanded the selection range of AuNP-dye pairs during the construction of the NSET model at the nanoscale.