title: Enhanced singlet oxygen generation from a porphyrin-rhodamine B dyad by two-photon excitation through resonance energy transfer.
abstract: Mitochondrial-targeting photosensitizers have been associated with effective photodynamic responses. However, most photosensitizers absorb light between 400 and 700 nm, where light penetration through tissues is limited. Two-photon excitation is a rational approach to improve light penetration through tissues. In this report, the two-photon photophysical properties of a porphyrin-rhodamine B conjugate (TPP-Rh), previously demonstrated to target the mitochondria, were evaluated. The properties studied included: two-photon absorption (TPA) cross sections (σ2 ); resonance energy transfer (RET) kinetics and dynamics; and singlet oxygen generation. The conjugation of Rh B to TPP-OH approximately doubled the σ2 of TPP-Rh at 800 nm (40 ± 4 GM) compared with the parent porphyrin, TPP-OH (16 ± 4 GM). Furthermore, the rate of DPBF oxidation by singlet oxygen generated from TPP-Rh was twice as fast compared with that from TPP-OH (73 % versus 33% in 10 min) following two-photon excitation at 800 nm. In addition, a significantly stronger luminescence signal was detected from TPP-Rh, than from TPP-OH at 1270 nm, following two-photon excitation. This study indicates that conjugating photosensitizers to Rh B could provide greater TPA at the near-infrared range in addition to preferential mitochondrial accumulation for improved photodynamic responses.
authors.affiliation: Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Ethel J
authors.initials: EJ
authors.lastname: Ngen
authors.forename: Lixin
authors.initials: L
authors.lastname: Xiao
authors.forename: Pallavi
authors.initials: P
authors.lastname: Rajaputra
authors.forename: Xingzhong
authors.initials: X
authors.lastname: Yan
authors.forename: Youngjae
authors.initials: Y
authors.lastname: You
mesh_terms: D004735:Energy Transfer; D008027:Light; D008928:Mitochondria; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D012235:Rhodamines / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D014466:Ultraviolet Rays
chemical_list: D011166:Porphyrins; D012235:Rhodamines; D026082:Singlet Oxygen; C029773:rhodamine B