The therapeutic properties of light have been known for thousands of years, but it was only in the last century that photodynamic therapy (PDT) was developed. At present, PDT is being tested in the clinic for use in oncology--to treat cancers of the head and neck, brain, lung, pancreas, intraperitoneal cavity, breast, prostate and skin. How does PDT work, and how can it be used to treat cancer and other diseases?

Photodynamic therapy for cancer

The interest in heterogeneous photocatalysis is intense and increasing, as shown by the number of publications on this theme which regularly appear in this journal, and the fact that over 2000 papers have been published on this topic since 1981. This article is an overview of the field of semiconductor photocatalysis : a brief examination of its roots, achievements and possible future. The semiconductor titanium dioxide (TiO 2 ) features predominantly in past and present work on semiconductor photocatalysis; as a result, in the most of the examples selected in this overview to illustrate various points the semiconductor is TiO 2 .

An overview of semiconductor photocatalysis

http://nathan.instras.com/MyDocsDB/doc-557.pdf

Photosensitized singlet oxygen and its applications

Heme-Containing Oxygenases

The use of lasers, over the past few decades, has emerged to be highly promising for cancer therapy modalities, most commonly the photothermal therapy method, which employs light absorbing dyes for achieving the photothermal damage of tumors, and the photodynamic therapy, which employs chemical photosensitizers that generate singlet oxygen that is capable of tumor destruction. However, recent advances in the field of nanoscience have seen the emergence of noble metal nanostructures with unique photophysical properties, well suited for applications in cancer phototherapy. Noble metal nanoparticles, on account of the phenomenon of surface plasmon resonance, possess strongly enhanced visible and near-infrared light absorption, several orders of magnitude more intense compared to conventional laser phototherapy agents. The use of plasmonic nanoparticles as highly enhanced photoabsorbing agents has thus introduced a much more selective and efficient cancer therapy strategy, viz. plasmonic photothermal therapy (PPTT). The synthetic tunability of the optothermal properties and the bio-targeting abilities of the plasmonic gold nanostructures make the PPTT method furthermore promising. In this review, we discuss the development of the PPTT method with special emphasis on the recent in vitro and in vivo success using gold nanospheres coupled with visible lasers and gold nanorods and silica-gold nanoshells coupled with near-infrared lasers.

http://wiki.phy.queensu.ca/shughes/images/0/0f/Cancer_3.pdf

Plasmonic photothermal therapy (PPTT) using gold nanoparticles

Attempted nitrosation of octaethylporphyrin, mesoporphyrin dimethyl ester, and octaethylhaemin with acidified nitrite solutions gives meso-nitro derivatives, and nitrosylation of octaethylhaemin and protohaemin dimethyl ester gives the corresponding nitrosylhaems; under suitable conditions the latter substances nitrosate secondary amines.

Reactions of nitrous acid and nitric oxide with porphyrins and haems. Nitrosylhaems as nitrosating agents

A high performance liquid chromatographic method for the determination of the photodynamic chemotherapeutic agent 5,10,15,20-tetra(m-hydroxyphenyl)chlorin (m-THPC) in human plasma following intravenous infusion is described. The procedure involves extraction of the drug in plasma with methanol/dimethyl sulphoxide (4:1 v/v) containing 5,10,15,20-tetra(p-hydroxyphenyl)chlorin as the internal standard and separation on a C18 reversed phase column with acetonitrile:0.1% trifluoroacetic acid (77:23 v/v) as the mobile phase. The drug was detected specifically and sensitively at its absorption maximum of 423 nm with a detection limit of 15 ng/mL (signal-to-noise ratio of 5). The intra- and inter-assay coefficients of variation (CV) on analysis of a plasma spiked with m-THPC (1 micrograms/mL) were 2.3 and 3.4% (n = 6), respectively.

Determination of 5,10,15,20-tetra-(m-hydroxyphenyl)chlorin in tissues by high performance liquid chromatography.

Chemistry of Vanadyl Porphyrins

This invention provides novel compounds for therapy of tumors susceptible to necrosis when an appropriate compound is administered followed by illumination with light of a wavelength absorbed by the compound, the compounds being dihydro porphyrins of the formula, or the corresponding tetra-hydro porphyrins: ##STR1## where n=1 to 3 and each substituent R, the same or different and at the same or different position in its respective substituent phenyl ring, is an hydroxy group.

Porphyrins and cancer treatment

Evidence is presented which supports the postulate that the photobilirubins IIA and IIB are diastereoisomers in which the C-3 vinyl group has cyclized intramolecularly. The evidence comes principally from proton n.m.r. spectroscopy at 400 MHz and from chemical considerations. The cyclic structures require the E-configuration at the C-4 double bond in the precursor; this is the first structural evidence for the Z leads to E isomerization in bilirubin and supports the view that the precursor (photobilirubin IA or IB) is (4E, 15Z)-bilirubin. Brief irradiation of photobilirubin II gives bilirubin, a new compound (photobilirubin III) and unchanged starting material. The various photoisomers are discussed in terms of their inter-relationships and biological fates.

Raymond Bonnett

Papers

Reactions of nitrous acid and nitric oxide with porphyrins and haems. Nitrosylhaems as nitrosating agents

Determination of 5,10,15,20-tetra-(m-hydroxyphenyl)chlorin in tissues by high performance liquid chromatography.

Chemistry of Vanadyl Porphyrins

Porphyrins and cancer treatment

Concerning the structure of photobilirubin II.