Targeted NIR Fluorescent Mechanically Interlocked Molecules-Peptide Bioconjugate for Live Cancer Cells Submitochondrial Stimulated Emission Depletion Super-Resolution Microscopy

Abstract

Herein, a water-soluble, ultrabright, near-infrared (NIR) fluorescent, mechanically interlocked molecules (MIMs)-peptide bioconjugate is designed with dual targeting capabilities. Cancer cell surface overexpressed α_Vβ₃ integrin targeting two RGDS tetrapeptide residues is tethered at the macrocycle of MIMs-peptide bioconjugate via Cu(I)-catalyzed click chemistry on the Wang resin, and mitochondria targeting lipophilic cationic TPP⁺ functionality is conjugated at the axle dye. Living carcinoma cell selective active targeting, subsequently cell penetration, mitochondrial imaging, including the ultrastructure of cristae, and real-time tracking of malignant mitochondria by MIMs-peptide bioconjugate (RGDS)₂-Mito-MIMs-TPP⁺ are established by stimulated emission depletion (STED) super-resolved fluorescence microscopy. Water-soluble NIR (RGDS)₂-Mito-MIMs-TPP⁺ is an effective class of MIMs-peptide bioconjugate with promising photophysics; for instance, remarkable photostability and thermal stability, strong and narrow NIR abs/em bands with high quantum yield, ultrabrightness, decent fluorescence lifetime, reasonable stability against cellular nucleophiles, biocompatibility, noncytotoxicity, and dual-targeted living cancer cell submitochondrial imaging ability are all indispensable criteria for targeted super-resolved STED microscopy.