title: Chlorosome-Inspired Synthesis of Templated Metallochlorin-Lipid Nanoassemblies for Biomedical Applications.
abstract: Chlorosomes are vesicular light-harvesting organelles found in photosynthetic green sulfur bacteria. These organisms thrive in low photon flux environments due to the most efficient light-to-chemical energy conversion, promoted by a protein-less assembly of chlorin pigments. These assemblies possess collective absorption properties and can be adapted for contrast-enhanced bioimaging applications, where maximized light absorption in the near-infrared optical window is desired. Here, we report a strategy for tuning light absorption toward the near-infrared region by engineering a chlorosome-inspired assembly of synthetic metallochlorins in a biocompatible lipid scaffold. In a series of synthesized chlorin analogues, we discovered that lipid conjugation, central coordination of a zinc metal into the chlorin ring, and a 3(1)-methoxy substitution were critical for the formation of dye assemblies in lipid nanovesicles. The substitutions result in a specific optical shift, characterized by a bathochromically shifted (72 nm) Qy absorption band, along with an increase in absorbance and circular dichroism as the ratio of dye-conjugated lipid was increased. These alterations in optical spectra are indicative of the formation of delocalized excitons states across each molecular assembly. This strategy of tuning absorption by mimicking the structures found in photosynthetic organisms may spur new opportunities in the development of biophotonic contrast agents for medical applications.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering and Department of Medical Biophysics, University of Toronto , Toronto, Ontario M5G 1L7, Canada.|Princess Margaret Cancer Centre, University Health Network , Toronto, Ontario M5G 1L7, Canada.
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Ng
authors.affiliation: Princess Margaret Cancer Centre, University Health Network , Toronto, Ontario M5G 1L7, Canada.|Department of Chemistry, Osaka University , Osaka 560-0043, Japan.
authors.forename: Misa
authors.initials: M
authors.lastname: Takada
authors.affiliation: Princess Margaret Cancer Centre, University Health Network , Toronto, Ontario M5G 1L7, Canada.
authors.forename: Kara
authors.initials: K
authors.lastname: Harmatys
authors.affiliation: Princess Margaret Cancer Centre, University Health Network , Toronto, Ontario M5G 1L7, Canada.
authors.forename: Juan
authors.initials: J
authors.lastname: Chen
authors.affiliation: Institute of Biomaterials and Biomedical Engineering and Department of Medical Biophysics, University of Toronto , Toronto, Ontario M5G 1L7, Canada.|Princess Margaret Cancer Centre, University Health Network , Toronto, Ontario M5G 1L7, Canada.
authors.forename: Gang
authors.initials: G
authors.lastname: Zheng
mesh_terms: D000818:Animals; D056831:Coordination Complexes / Q000737:chemistry*; D005453:Fluorescence; D008027:Light; D008055:Lipids / Q000737:chemistry*; D008297:Male; D008647:Mesocricetus; D053758:Nanoparticles / Q000737:chemistry*; D009374:Neoplasms, Experimental / Q000000981:diagnostic imaging; D061848:Optical Imaging; D015388:Organelles / Q000737:chemistry*; D010316:Particle Size; D061088:Photoacoustic Techniques; D011166:Porphyrins / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008055:Lipids; D011166:Porphyrins; C006969:chlorin; D015032:Zinc
keywords: J-aggregate; chlorosome; photoacoustic imaging; porphyrin