Near-Infrared Fluorescent 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene Probes for One- and Two-Photon Fluorescence Bioimaging

Two new two-photon absorbing near-infrared (NIR) emitting 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives, DDC and SDC, were designed for one- and two-photon fluorescence microscopy imaging. Linear and nonlinear photophysical properties, including UV/Vis absorption, fluorescence, excitation anisotropy, photostability, and two-photon absorption cross sections, of the dyes were investigated to assess the potential of using the new probes as bioimaging agents. Cell viability and colocalization studies of DDC with Lysotracker Red, in COS 7 and HCT 116 cells demonstrated not only low toxicity but also selective targeting of lysosomes. SDC was encapsulated in silica-based nanoparticles for in vitro and ex vivo fluorescence bioimaging. The nanoparticles were modified with an RGD peptide to target α_Vβ₃ integrin. The nanoprobe exhibited good biocompatibility and highly selective uptake in α_Vβ₃ integrin-overexpressing cancers.