Vectorization and Intracellular Distribution of a Two‐Photon‐Absorbing, Near‐Infrared‐Emitting π‐Extended Boranil Dye

Abstract

A π‐extended boranil (PEB) dye has been synthesized and its photophysical properties have been recorded in a range of solvents. The dye exhibits an intense solvatochromic fluorescence emission covering the entire visible spectrum and the near infra‐red (NIR) region (from λ=534 to 764 nm) with quantum yields up to 69 %. Embedment of the PEB dye in the amphiphilic block copolymer Cremophor EL® leads to a strong emission (λem=617 nm, Φ=0.33) in PBS buffer. Moreover, two‐photon absorption (TPA) spectroscopy evidenced a large two‐photon (2P) cross section (420 GM), enabling the use of the PEB dye in 2P‐excitation fluorescence microscopy. The cellular uptake and distribution of PEB in HeLa cells was monitored using fluorescence lifetime imaging microscopy (FLIM) and real‐time widefield imaging. It was found that the emission of the dye is strongly influenced by the local environment and that the dye is preferentially internalized in acidic vesicles.

Addressing the autofluorescence issue in deep tissue imaging by two-photon microscopy: the significance of far-red emitting dyes

“…This is plausibly due to the minimal two-photon absorption by the key biomolecules when they are excited around 900 nm. 18 Through autofluorescence analysis, it is concluded that autofluorescence interference is minimal when the images are obtained under excitation at around 900 nm and, above all, when emission is collected from the red emission channel.…”

“…However, currently available fluorophores that satisfy the criteria are rare (Table S5 in the ESI † ). 18 …”

Azabora[5]helicene Charge‐Transfer Dyes Show Efficient and Spectrally Variable Circularly Polarized Luminescence

“…Four-coordinate organoboron chelates [1][2][3] are attractive targets for the design of photostable fluorescent dyes for the most varied applications,i ncluding bioimaging, [4][5][6][7][8][9][10][11][12] sensing, [13][14][15][16][17] and organic light-emitting diodes. [18] Much effort has been dedicated to the development of synthetically flexible platforms which enablet he photophysical fine-tuning of the dyes.…”

Excited‐State Pathways of Four‐Coordinate N,C‐Chelate Organoboron Dyes

“…More recently, three‐coordinate organoboron dyes have been also employed for bioimaging . Four‐coordinate organoboron dyes with chelate ligands, containing N‐ and/or O‐donor atoms, are of elevated interest for the development of optoelectronic devices, such as organic light emitting diodes, as photoaddressable materials, and very frequently as dyes for bioimaging and sensing …”