Wavelength Tunable Aqueous CsPbBr3-Based Nanoprobes with Ultrahigh Photostability for Targeted Super-Resolution Bioimaging

Single molecule localization microscopy (SMLM) is indispensable in the visualization of cellular microstructures. However, current SMLM imaging materials, from organic fluorophores to quantum dots, still lack the requirement of increasing need for multiple targets of interest due to their broad emission. Here, by one-step encapsulating hydrophilic cesium lead bromide perovskite nanocrystals (CsPbBr₃ NCs) into functionalized polyethylene glycol (PEG), a core-shell nanocomposite of CsPb(Cl_(1-x)/Br_x)₃@PEG (0 < x < 1) was presented as a wavelength-tunable fluorescent probe with the narrow full width at half-maximum (fwhm) as 11 nm. The layer of functionalized PEG endows CsPbBr₃ NCs with a broad spectral tunability from 521 to 431 nm, superior photostability for several years, and the ability to be further surface functionalized. The CsPb(Cl_(1-x)/Br_x)₃@PEG exhibits a sub-10 nm localization precision and 10-fold enhanced spatial resolution. Using exosomes with small sizes less than 150 nm as the imaging target, CsPb(Cl_(1-x)/Br_x)₃@PEG realized the distinction of two adjacent exosomes by SMLM. Moreover, after being modified with biotin, CsPb(Cl_(1-x)/Br_x)₃@PEG was universally used for SMLM imaging of cellular microstructures. The excellent photostability and narrow fwhm indicated that such a CsPbBr₃-based nanoprobe has great potential as a commercial dye for multitarget super-resolution bioimaging applications.