Synthesis, Properties And Applications Of Functional Near-infrared BODIPY Dyes

In recent year, there has been intense interest in the preparation and study of near-infrared (NIR)-absorbing dyes owing to the spectral coincidence with the tissue transparent window (650-1000 nm). Photons in this region are less absorbed and scattered by tissues, which enables deeper light penetration as well as better signal-to-noise ratio by minimal interference from the background autofluorescence. Near-infrared (NIR) dyes have many applications such as biological imaging, optical sensors for biological, photoelectric materials and photodynamic therapy (PDT)On this basis, a rapid development has occurred to various kinds of fluorescence. Among them, BODIPY dyes attract the most attention duo to their excellent features: fluorescence quantum yields, the relatively moderate redox potential, negligible dependence of the spectroscopic properties on enviro nmental polarity, considerably high photostability and chemical stability. Despite these advantageous features, the spectral properties of the classical BODIPY chromophores locate at the wavelength range from 470 to 530 nm, which greatly limits their application in many aspects. Thus, it’s interesting and a research focus to design and prepare long wavelength-absorbing even NIR-absorbing BODIPY dyes.Heavy metal ions mercury and its derivatives are virulent, and could accumulate in human body, harmful to human. In addition, some ions play a key role in life process, such as H+. A normal intracellular pH (related to H+concentration) is necessary for the running of cells growth, apoptosis, ion transport, as well as cytophagy. Therefore, it would be meaningful to carry on studies on fluorescence probe, absorbing and emitting in the NIR/Biological window, for Hg2+, H+in low concentration.As a reactive intermediate in biochemistry, singlet oxygen performs an important part in the photodynamic therapy (PDT). So far, many deficiencies indwell in the all kinds photosensitizer, such as unstability to light, absorption below 650 nm, high dark toxicity, which has inspired efforts to develop a new generation and more effective PDT photosensitizers.In view of the problems above, we have synthesized a series of thienopyrrole-expanded BODIPY dyes by fusion of aromatic rings to pyrrole units Marked red-shifts have been obtained for these dyes (λmax=-680 nm, λem=-715 nm), entering into the region of NIR/Biological window. In addition, we incorporated 0-NH2 droxybenzene, dimethylaminobenzaldehyde, benzene-15-crown-5 to the meso of BODIPY dyes, respectively, which are applied in fluorescence probe for Hg2+, H*. At last, heavy Br atoms have been introduced into the BODIPY core to enhance the intersystem crossing through heavy atom effect. Meanwhile, in the present of NIR laser light, we have measured the singlet oxygen generation efficiency (φΔ=0.63) and PDT effects in HeLa cells by MTT assays, confocal fluorescence images and flow cytometry analysis. The results demonstrated that the BODIPY with Br substitution, displaying high cytotoxicity in the present of light, but no dark cytotoxicity, would be an excellent NIR PDT photosensitizer.