Photodynamic Cancer Therapy - Recent Advances

Journal Article · Thu Sep 22 04:00:00 EDT 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3631802· OSTI ID:21611635

Abrahamse, Heidi ^[1]

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1. Laser Research Centre, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein (South Africa)

The basic principle of the photodynamic effect was discovered over a hundred years ago leading to the pioneering work on PDT in Europe. It was only during the 1980s, however, when 'photoradiation therapy' was investigated as a possible treatment modality for cancer. Photodynamic therapy (PDT) is a photochemotherapeutic process which requires the use of a photosensitizer (PS) that, upon entry into a cancer cell is targeted by laser irradiation to initiate a series of events that contribute to cell death. PSs are light-sensitive dyes activated by a light source at a specific wavelength and can be classified as first or second generation PSs based on its origin and synthetic pathway. The principle of PS activation lies in a photochemical reaction resulting from excitation of the PS producing singlet oxygen which in turn reacts and damages cell organelles and biomolecules required for cell function and ultimately leading to cell destruction. Several first and second generation PSs have been studied in several different cancer types in the quest to optimize treatment. PSs including haematoporphyrin derivative (HpD), aminolevulinic acid (ALA), chlorins, bacteriochlorins, phthalocyanines, naphthalocyanines, pheophorbiedes and purpurins all require selective uptake and retention by cancer cells prior to activation by a light source and subsequent cell death induction. Photodynamic diagnosis (PDD) is based on the fluorescence effect exhibited by PSs upon irradiation and is often used concurrently with PDT to detect and locate tumours. Both laser and light emitting diodes (LED) have been used for PDT depending on the location of the tumour. Internal cancers more often require the use of laser light delivery using fibre optics as delivery system while external PDT often make use of LEDs. Normal cells have a lower uptake of the PS in comparison to tumour cells, however the acute cytotoxic effect of the compound on the recovery rate of normal cells is not known. Subcellular localization of PS is of vital importance when cell death mechanism is identified. Programmed cell death (PCD) viz. apoptosis, necrosis and autophagy have all been identified as inducible cell death mechanisms during PDT. While apoptosis is probably the preferred cell death mechanism, understanding the molecular differences and identifying the cross-talk between these mechanisms are crucial to the development of new PSs aimed at improving the killing efficiency and overall effectiveness of PDT as a cancer treatment modality. This paper reviews the process of PDT cancer therapy, the available PSs, their effectiveness for different cancers as well as the cell death mechanisms identified during PDT of different cancers associated with specific PSs.

• OSTI ID: 21611635
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1380; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
AMINOLEVULINIC ACID
APOPTOSIS
BIOPHYSICS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
DIAGNOSIS
DISEASES
DYES
ELECTROMAGNETIC RADIATION
EMISSION
ENERGY-LEVEL TRANSITIONS
EVALUATION
EXCITATION
FLUORESCENCE
HETEROCYCLIC COMPOUNDS
IRRADIATION
LASER RADIATION
LIGHT EMITTING DIODES
LUMINESCENCE
MEDICINE
NECROSIS
NEOPLASMS
NUCLEAR MEDICINE
ORGANIC ACIDS
ORGANIC COMPOUNDS
PATHOLOGICAL CHANGES
PATIENTS
PHOTOCHEMICAL REACTIONS
PHOTON EMISSION
PHTHALOCYANINES
PHYSICS
RADIATIONS
RADIOLOGY
RADIOTHERAPY
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
THERAPY