Intracellular near-Infrared Microlaser Probes Based on Organic Microsphere–SiO2 Core–Shell Structures for Cell Tagging and Tracking

Conventional near-infrared (NIR) luminescent probes, such as DsRed and Cy5, utilize spontaneous emission (SE) signals, which are broad (fwhm >50 nm) and often have low quantum yield. Herein, we developed smart NIR intracellular whispering-gallery mode (WGM) microlaser probes made by organic microspheres of (E)-3-(4-(diptolylamino)phenyl)-1-(1-hydroxynaphthalen-2-yl)prop-2-en-1-one (DPHP) coated with a silica shell. The overall small diameter (D, adjustable between 2 and 10 μm) and the biocompatible silica shell ensure our core–shell microspheres (CSmSPs) to be engulfed in cells as a microlaser operating around 720 nm with a low threshold of 0.78 μJ/cm2. Considering that WGM mode spacing depending strongly on its size, it will be possible to distinguish millions of individual macrophages through well-defined WGM lasing peaks (fwhm ≤2 nm) of CSmSPs of different sizes. Furthermore, we monitored the transformation of normal macrophages to foamy ones by encoding them with our NIR CSmSPs microlaser probes, whic...