title: Carbazole-Linked Near-Infrared Aza-BODIPY Dyes as Triplet Sensitizers and Photoacoustic Contrast Agents for Deep-Tissue Imaging.
abstract: Four new N-ethylcarbazole-linked aza-boron-dipyrromethene (aza-BODIPY) dyes (8 a,b and 9 a,b) were synthesized and characterized. The presence of the N-ethylcarbazole moiety shifts their absorption and fluorescence spectra to the near-infrared region, λ≈650-730 nm, of the electromagnetic spectrum. These dyes possess strong molar absorptivity in the range of 3-4×104m-1cm-1with low fluorescence quantum yields. The triplet excited state and singlet oxygen generation of these dyes were enhanced upon iodination at the core position. The core-iodinated dyes 9 a,b showed excellent triplet quantum yields of about 90 and 75 %, with singlet oxygen generation efficiency of about 70 and 60 % relative to that of the parent dyes. Derivatives 8 a,b showed dual absorption profiles, in contrast to dyes 9 a,b, which had the characteristic absorption band of aza-BODIPY dyes. DFT calculations revealed that the electron density was spread over the iodine and dipyrromethene plane of 9 a,b, whereas in 8 a,b the electron density was distributed on the carbazole group and dipyrromethene plane of aza-BODIPY. The uniqueness of these aza-BODIPY systems is that they exhibit efficient triplet-state quantum yields, high singlet oxygen generation yields, and good photostability. Furthermore, the photoacoustic (PA) characteristics of these aza-BODIPY dyes was explored, and efficient PA signals for 8 a were observed relative to blood serum with in vitro deep-tissue imaging, thereby confirming its use as a promising PA contrast agent.
authors.affiliation: Dyestuff Technology Department, Institute of Chemical Technology, Matunga, Mumbai, 400 019, India.
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Gawale
authors.affiliation: Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram, 695 019, Kerala, India.
authors.forename: Nagappanpillai
authors.initials: N
authors.lastname: Adarsh
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore, 637459, Singapore.
authors.forename: Sandeep Kumar
authors.initials: SK
authors.lastname: Kalva
authors.affiliation: Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram, 695 019, Kerala, India.
authors.forename: Joshy
authors.initials: J
authors.lastname: Joseph
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore, 637459, Singapore.
authors.forename: Manojit
authors.initials: M
authors.lastname: Pramanik
authors.affiliation: CSIR-North East Institute of Science and Technology, Jorhat, 785 006, Assam, India.
authors.forename: Danaboyina
authors.initials: D
authors.lastname: Ramaiah
authors.affiliation: Dyestuff Technology Department, Institute of Chemical Technology, Matunga, Mumbai, 400 019, India.
authors.forename: Nagaiyan
authors.identifier: http://orcid.org/0000-0001-7568-5129
authors.initials: N
authors.lastname: Sekar
mesh_terms: D000818:Animals; D001896:Boron Compounds / Q000737:chemistry*; D001940:Breast / Q000473:pathology; D002227:Carbazoles / Q000737:chemistry*; D002645:Chickens; D003287:Contrast Media / Q000138:chemical synthesis / Q000737:chemistry*; D055664:Electrochemical Techniques; D005260:Female; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D061088:Photoacoustic Techniques; D011789:Quantum Theory; D044967:Serum / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D014054:Tomography
chemical_list: D001896:Boron Compounds; D002227:Carbazoles; D003287:Contrast Media; D005456:Fluorescent Dyes; C000613417:azaBDPBA compound; C041514:carbazole; D026082:Singlet Oxygen
keywords: dyes/pigments; fluorescence; imaging agents; oxygen; sensitizers