Two‐Photon Excitation of 4'‐Hydroxymethyl‐4,5',8‐Trimethylpsoralen

Oh, Dennis H.; Stanley, Robert J.; Lin, Michelle; Hoeffler, Warren K.; Boxer, Steven G.; Berns, Michael W.; Bauer, Eugene A.

doi:10.1111/j.1751-1097.1997.tb01882.x

Cited by 31 publications

(18 citation statements)

References 21 publications

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“…Two-photon phototherapy with psoralen chromophores has been investigated (3), as has the spatial localization of a psoralen-DNA crosslink (4). Two-photon fluorescence microscopy has provided a new avenue to high spatial resolution in 3D visualization of biological structures (5)(6)(7).…”

mentioning

confidence: 99%

Combinatorial discovery of two-photon photoremovable protecting groups

Pirrung

Pieper²,

Kaliappan³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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A design principle for a two-photon photochemically removable protecting group based on sequential one-photon processes has been established. The expected performance of such groups in spatially directed photoactivation͞photodeprotection has been shown by a kinetic analysis. One particular molecular class fitting into this design, the nitrobenzyl ethers of o-hydroxycinnamates, has been presented. An initial demonstration of two-photon deprotection of one such group prompted further optimization with respect to photochemical deprotection rate. This was accomplished by the preparation and screening of a 135-member indexed combinatorial library. Optimum performance for >350 nm deprotection in organic solvent was found with 4,5-dialkoxy and ␣-cyano substitution in the nitrobenzyl group and 4-methoxy substitution in the cinnamate.

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mentioning

confidence: 99%

Combinatorial discovery of two-photon photoremovable protecting groups

Pirrung

Pieper²,

Kaliappan³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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“…Chloroaluminum sulfonated phthalocyanine ͑CASPc͒ is a widely used photodynamic therapy ͑PDT͒ agent 19 and an efficient two-photon fluorophore. The concentration of CASPc was assumed to be 50 M, and the two-photon absorption cross section of CASPc was estimated by comparison of the two-photon fluorescence emission properties of CASPc with that of a known compound, 20 Rhodamine B, whose two-photon cross section has been measured. 9 By numerical integration of the measured two-photon fluorescence emission spectra of CASPc and Rhodamine B ͑data not shown͒, the two-photon cross section of CASPc was estimated to be 1.7 ϫ 10 Ϫ49 cm 4 s͞photon.…”

mentioning

confidence: 99%

Influence of optical properties on two-photon fluorescence imaging in turbid samples

et al. 2000

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A numerical model was developed to simulate the effects of tissue optical properties, objective numerical aperture ͑N.A.͒, and instrument performance on two-photon-excited fluorescence imaging of turbid samples. Model data are compared with measurements of fluorescent microspheres in a tissuelike scattering phantom. Our results show that the measured two-photon-excited signal decays exponentially with increasing focal depth. The overall decay constant is a function of absorption and scattering parameters at both excitation and emission wavelengths. The generation of two-photon fluorescence is shown to be independent of the scattering anisotropy, g, except for g Ͼ 0.95. The N.A. for which the maximum signal is collected varies with depth, although this effect is not seen until the focal plane is greater than two scattering mean free paths into the sample. Overall, measurements and model results indicate that resolution in two-photon microscopy is dependent solely on the ability to deliver sufficient ballistic photon density to the focal volume. As a result we show that lateral resolution in two-photon microscopy is largely unaffected by tissue optical properties in the range typically encountered in soft tissues, although the maximum imaging depth is strongly dependent on absorption and scattering coefficients, scattering anisotropy, and objective N.A..

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“…Therefore, because TPE by its physical nature is capable of concentrating photochemical DNA damage to a preferential volume of space, and TFOs by their chemical nature are capable of placing photodynamic agents at a specific nucleotide in a genome, the combination of these two approaches has potential for manipulating DNA damage in both physical space and nucleotide sequence. We and others have previously reported that psoralens have a measurable two-photon cross section at NIR wavelengths produced by a titanium͞sapphire laser (22,26). However, this earlier work did not demonstrate actual DNA damage.…”

Section: Two-photon Excitation Generates Photoadducts In Cellsmentioning

confidence: 55%

“…We and others have previously documented that the excited state of the psoralen, 4Ј-hydroxymethyl-4,5Ј,8-trimethylpsoralen (HMT), is accessible by near-infrared (NIR) light with a quadratic power dependence that indicates a two-photon process (22,26). After either one-or two-photon excitation, the resulting emission spectra were nearly identical, suggesting that although the selection rules for the two processes are formally different, evolution to the same emitting and potentially chemically reactive excited states could occur.…”

mentioning

confidence: 99%

“…TPE has also been investigated as an approach for creating optical memory storage devices (19,39) and has been suggested as a potential tool for selectively activating photochemotherapeutic agents in tissue (22,24,26). Psoralens, as well as other photodynamic agents used for cutaneous therapy, represent fortuitously attractive targets for TPE with NIR radiation, because skin is the most optically accessible tissue of the body, and these wavelengths are within a spectral window where absorption from melanin and other skin chromophores as well as water is at a minimum (6).…”

mentioning

confidence: 99%

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Spatially localized generation of nucleotide sequence-specific DNA damage

King²,

Boxer³

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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Psoralens linked to triplex-forming oligonucleotides (psoTFOs) have been used in conjunction with laser-induced two-photon excitation (TPE) to damage a specific DNA target sequence. To demonstrate that TPE can initiate photochemistry resulting in psoralen-DNA photoadducts, target DNA sequences were incubated with psoTFOs to form triple-helical complexes and then irradiated in liquid solution with pulsed 765-nm laser light, which is half the quantum energy required for conventional one-photon excitation, as used in psoralen ؉ UV A radiation (320 -400 nm) therapy. Target DNA acquired strand-specific psoralen monoadducts in a light dose-dependent fashion. To localize DNA damage in a model tissue-like medium, a DNA-psoTFO mixture was prepared in a polyacrylamide gel and then irradiated with a converging laser beam targeting the rear of the gel. The highest number of photoadducts formed at the rear while relatively sparing DNA at the front of the gel, demonstrating spatial localization of sequence-specific DNA damage by TPE. To assess whether TPE treatment could be extended to cells without significant toxicity, cultured monolayers of normal human dermal fibroblasts were incubated with tritium-labeled psoralen without TFO to maximize detectable damage and irradiated by TPE. DNA from irradiated cells treated with psoralen exhibited a 4-to 7-fold increase in tritium activity relative to untreated controls. Functional survival assays indicated that the psoralen-TPE treatment was not toxic to cells. These results demonstrate that DNA damage can be simultaneously manipulated at the nucleotide level and in three dimensions. This approach for targeting photochemical DNA damage may have photochemotherapeutic applications in skin and other optically accessible tissues.

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Two‐Photon Excitation of 4'‐Hydroxymethyl‐4,5',8‐Trimethylpsoralen

Cited by 31 publications

References 21 publications

Combinatorial discovery of two-photon photoremovable protecting groups

Combinatorial discovery of two-photon photoremovable protecting groups

Influence of optical properties on two-photon fluorescence imaging in turbid samples

Spatially localized generation of nucleotide sequence-specific DNA damage

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