posted on 2022-12-29, 11:29authored byJian Mao, Minmin Xue, Xin Guan, Qian Wang, Zhirui Wang, Guangyong Qin, Hua He
Blinking carbon dots (CDs) have attracted attention as
a probe
for single molecule localization microscopy (SMLM), yet quantitative
analysis is limited because of inept blinking and low signal-to-noise
ratio (SNR). Here we report the design and synthesis of near-infrared
(NIR) blinking CDs with a maximum emission of around 750 nm by weaving
a nitrogen-doped aromatic backbone with surplus carboxyl groups on
the surface. The NIR-CDs allow conjugation to monovalent antibody
fragments for labeling and imaging of cellular receptors as well as
afford increases of 52% in SNR and 33% in localization precision over
visible CDs. Analysis of fluorescent bursts allows for accurate counting
of cellular receptors at the nanoscale resolution. Using NIR-CDs-based
SMLM, we demonstrate oligomerization and internalization of programmed
cell death-ligand 1 by a small molecule inhibitor for checkpoint blockade.
Our NIR-CDs can become a generally applicable probe for quantitative
nanoscopy in chemistry and biology.