Investigation of photoproducts produced from aminolevulinic acid-based photodynamic therapy/diagnosis using mass spectrometry
Photodynamic therapy/diagnosis (PDT/PDD) is one of the prominent cancer treatment/diagnostic techniques owing to its minimally invasive and highly selective nature. In PDT/PDD, a nontoxic drug known as photosensitizer is administrated either systemically, locally, or topically to a patient with cancer. When the photosensitizer is illuminated by a specific wavelength of light in the presence of oxygen, singlet oxygen is generated in PDT, which leads to cell death and tissue destruction, and fluorescence is emitted in PDD, which enables to detect cancer cells.
Unfortunately, such photochemical reactions are accompanied by the production of other substances called photoproducts and are presumed to hinder the cancer therapeutic/diagnostic effects. Previous identifications of photoproducts have been based on their optical properties, which deems insufficient since some photoproducts possess similar optical properties as the photosensitizer.
Mass spectrometry is a technique that separates molecules within a sample based on their mass to charge ratio (m/z) along with their relative abundance by the manipulation of electric and magnetic fields. It enables one identify quantitatively the components of an unknown sample or the quantity of a known molecule within a known sample. Employing this technique for the analysis of the photoproducts, one can identify the photoproducts, their chemical compositions, and their chemical structure.
With the identification of the photoproducts and the accompanying information, it is hoped to determine the effects of the photoproducts on PDT/PDD, the probable necessity to include their formation for PDT/PDD dosimetry, and their consequences on the human body.
