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Enhanced Singlet Oxygen Generation from a Porphyrin–Rhodamine B Dyad by Two‐Photon Excitation through Resonance Energy Transfer
Author(s) -
Ngen Ethel J.,
Xiao Lixin,
Rajaputra Pallavi,
Yan Xingzhong,
You Youngjae
Publication year - 2013
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12071
Subject(s) - singlet oxygen , photochemistry , porphyrin , chemistry , photodynamic therapy , two photon excitation microscopy , fluorescence , photosensitizer , singlet state , resonance (particle physics) , rhodamine b , rhodamine , oxygen , photocatalysis , excited state , catalysis , atomic physics , optics , organic chemistry , physics
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 ( σ 2 ); resonance energy transfer (RET) kinetics and dynamics; and singlet oxygen generation. The conjugation of Rh B to TPP‐OH approximately doubled the σ 2 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.