title: The effects of aggregation, protein binding and cellular incorporation on the photophysical properties of benzoporphyrin derivative monoacid ring A (BPDMA).
abstract: Absorption, fluorescence and laser flash photolysis spectroscopies were used to investigate the effects of self-aggregation, binding to human serum albumin and incorporation in cancer cells on the photophysics of benzoporphyrin derivative monoacid ring A (BPDMA). Aggregation of BPDMA has been studied in mixtures of methanol and phosphate-buffered saline (PBS). The extent of aggregation was dependent on dye concentration and solvent composition, becoming particularly marked in mixtures containing less than 30% methanol. A dimerization constant Kd or 9 x 10(6) M-1 was determined by fluorescence experiments for BPDMA in pure PBS. In addition to spectral modifications, aggregation induces a lowering of the fluorescence and intersystem crossing quantum yields. Human serum albumin binds BPDMA with an association constant Kb of 5.2 x 10(5) M-1 in PBS. When bound to HSA, BPDMA displays photophysical properties very similar to the monomer in organic solvents. The molar ratio [HSA]/[BPDMA] corresponding to complete binding of the dye was determined to be approximately 10. Efficient generation of the triplet state of BPDMA was also observed from aqueous cellular suspensions containing incorporated photosensitizer.
authors.affiliation: Wellman Laboratories of Photomedicine, Department of Dermatology, Harvard Medical School, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: B M
authors.initials: BM
authors.lastname: Aveline
authors.forename: T
authors.initials: T
authors.lastname: Hasan
authors.forename: R W
authors.initials: RW
authors.lastname: Redmond
mesh_terms: D000818:Animals; D002460:Cell Line; D006801:Humans; D000432:Methanol / Q000737:chemistry; D051379:Mice; D015394:Molecular Structure; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012709:Serum Albumin / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D012709:Serum Albumin; C504224:benzoporphyrin D; D000432:Methanol