Journal
JOURNAL OF PORPHYRINS AND PHTHALOCYANINES
Volume 12, Issue 12, Pages 1261-1269Publisher
WORLD SCI PUBL CO INC
DOI: 10.1142/S1088424608000649
Keywords
porphyrin; phosphorescence; oxygen; two-photon; FRET; photoinduced electron transfer; triplet state
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Funding
- NIH USA [EB007279, HL081273, P41-RR001348, 2U24-CA083105]
- NATIONAL CANCER INSTITUTE [U24CA083105] Funding Source: NIH RePORTER
- NATIONAL CENTER FOR RESEARCH RESOURCES [P41RR001348] Funding Source: NIH RePORTER
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R01HL081273] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF BIOMEDICAL IMAGING AND BIOENGINEERING [R01EB007279] Funding Source: NIH RePORTER
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Metalloporphyrin-based phosphorescent nanoprobes are being developed for two-photon microscopy of oxygen. In these molecular constructs, the generation of porphyrin triplet states following two-photon excitation is induced by the intramolecular Forster-type resonance energy transfer front a covalently attached 2P antenna. In the earlier developed prototypes, electron transfer between the antenna and the metalloporphyrin strongly interferred with the phosphorescence, reducing the sensitivity and the dynamic range of the sensors. By tuning the distances between the antenna and the core, and adjusting their redox potentials, the unwanted electron transfer could be prevented. An array of phosphorescent Pt porphyrins (energy transfer acceptors) and 2P dyes (energy transfer donors) was screened using dynamic quenching of phosphorescence, and the FRET-pair with the minimal ET rate was identified. This pair, consisting of Coumarin-343 and Pt meso-tetra-(4-alkoxyphenyl)porphyrin, was used to construct a probe in which the antenna fragments were linked to the termini of G3 poly(arylglycine) (AG) dendrimer with PtP core. The folded dendrimer formed an insulating layer between the porphyrin and the antenna, Simultaneously controlling the rate of oxygen quenching (Stern-Volmer oxygen quenching constant). Modification of the dendrimer periphery with oligoethyleneglycol residues made the probe's signal insensitive to the presence of proteins and other macromolecular solutes. Copyright (C) 2008 Society of Porphyrins & Phthalocyanines.
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