The two-photon laser-induced fluorescence of the tumor-localizing photosensitizer hematoporphyrin derivative. Resonance-enhanced 750 nm two-photon excitation into the near-UV Soret band.

The tumor-localizing photosensitizer hematoporphyrin derivative (HPD) is shown to undergo a simultaneous two-photon excitation into the near-ultraviolet Soret band system upon intense laser irradiation at 750 nm, a spectral region where there is no significant HPD one-photon absorbance in aqueous solution. Subsequent to this excitation, internal conversion and vibrational relaxation occur, resulting in the population of the vibrationless level of the first electronically excited singlet state. This state relaxes by two channels, the emission of fluorescence in the spectral region 600-700 nm and intersystem crossing into the triplet manifold, followed by near-resonant electronic energy transfer with surrounding oxygen to result in the generation of highly reactive singlet molecular oxygen (1 delta g).

The two-photon induced fluorescence of the tumor localizing photosensitizer hematoporphyrin derivative via 1064 nm photons from a 20 ns Q-switched Nd-YAG laser.

We demonstrate the direct 1064 nm two-photon excitation of hematoporphyrin derivative (HPD), a complex mixture of photosensitizing porphyrins which is selectively retained in tumor tissue and used in cancer photochemotherapy. Although 1064 nm is outside of the one-photon HPD absorption spectrum, two-photon induced fluorescence from HPD was observed following excitation by the 20 ns output of an amplified, Q-switched Nd-YAG laser at peak power levels of 0.1 to 3 GW/cm2.

An analysis of the H2O2-mediated crosslinking of lens crystallins catalyzed by the heme-undecapeptide from cytochrome c.

In contrast to other tissues, the lens exists in a milieu containing relatively high (micromolar) concentrations of H2O2. It has been demonstrated that activation of H2O2 to more-potent oxidant species via the heme-undecapeptide from cytochrome c produces alterations in lens crystallin polypeptides similar to the changes found in cataract. These include crystallin polypeptide crosslinking and the development of a blue fluorescence not attributable to tryptophan.

The non-photosensitized potentiation by the photosensitizer hematoporphyrin of the horseradish peroxidase-catalyzed H2O2-mediated oxidation of NADPH to NADP+.

Horseradish peroxidase is known to oxidize NADPH in a reaction initiated by hydrogen peroxide. The present study demonstrates that the photosensitizer hematoporphyrin acting in a non-photodynamic manner, has a marked potentiating effect on the nucleotide oxidation rate. Over 90 percent of the NADPH oxidation product is enzymatically active NADP+.

Effects of lipid peroxidation products on the rat lens in organ culture: a possible mechanism of cataract initiation in retinal degenerative disease.

Rat lenses in organ culture which are exposed to bovine rod outer segments (ROS) or to the major fatty acid of ROS, docosahexaenoic acid, are impaired in their ability to accumulate radiolabeled compounds which lenses normally accumulate by active processes. The extent of lens damage correlates well with the extent of lipid peroxidation in the culture medium as assessed by the thiobarbituric acid assay. Addition of vitamin E to the medium inhibits the effect on the lens while addition of Fe-ADP complexes potentiates the effect.