Long-Wavelength, Photostable, Two-Photon Excitable BODIPY Fluorophores Readily Modifiable for Molecular Probes

Abstract

Near-infrared (NIR) fluorescent probes are increasingly popular in biological imaging and sensing, as long-wavelength (650-900 nm) excitation and emission have the advantages of minimum photodamage, deep tissue penetration, and minimum interference from autofluorescence in living systems. Here, a series of long-wavelength BODIPY dyes SPC, DC-SPC, DPC, and DC-DPC are synthesized conveniently and efficiently. They exhibit excellent photophysical properties in far red to near-infrared region, including large extinction coefficients, high fluorescence quantum yields, good photostability, and reasonable two-photon absorption cross section. Comparison of single-molecular imaging confirms that DPC is a much more efficient and more photostable NIR fluorophore than the commonly used Cy5. Also importantly, two kinds of convenient functionalization sites have been reserved: the aryl iodide for organometallic couplings and the terminal alkyne groups for click reactions. Further derivatives DC-SPC-PPh3 exhibit specificity to localize in mitochondria. The introduction of triphenylphosphonium (TPP) moieties mediates its hydrophilic-lipophilic balance and makes DC-SPC-PPh3 appropriate for cell labeling. Their long-wavelength emission at ∼650 nm can efficiently avoid the spectral crosstalk with other probes emitting in the visible light region. Superior photostability, low cytotoxicity, and two-photon excitable properties demonstrate its utility as a standard colocalizing agent to estimate the other probes' local distribution.

Strongly Emissive and Photostable Four‐Coordinate Organoboron N,C Chelates and Their Use in Fluorescence Microscopy

“…The magnitude of the obtained TPA cross sections, especially the one of dye 4, compares nicely with that of some of the best performing Bodipy derivatives that were used in TPE fluorescence imaging. [51][52][53] However, the plain Bodipy chromophore has commonly lower TPA cross sections (ca. 10 GM at 900 nm).…”

“…The results demonstrate the applicability of 4 as staining dye and the use of TPE is an additional surplus because of the deeper penetration of near-infrared excitation light into biological tissues. [51][52][53][54][55] …”

Near-infrared fluorescent probes in cancer imaging and therapy: an emerging field

“…After facile functionalization into DC-SPC-PPh3, superior amphipathy, cell membrane permeability, and specific localization in mitochondria were revealed. 32 Stable NIR BODIPY developed via a novel pyrrole was non-cytotoxic and suitable for bio-imaging assay. 33 Squaraine-based NIRF probes Squaraines (squarylium dyes), consisting of a central ringbased core and a zwitterionic structure, were first developed by Treibs and Jacob in 1965.…”

Sensing Inside the Living Cells

“…3.6 ), and the best applicable to cellular research FRET detection is the lifetime imaging. Different two-photon excited probes were developed for visualization of sub-cellular structures and measuring local pH and concentrations of analytes (Lim 2013 ;Zhang et al 2013 ).…”