Phthalocyanine Photosensitizers towards Drug-Resistant Pathogens

Author(s)
Vanya Mantareva
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria.

ISBN 978-93-49970-20-5 (Print)
ISBN 978-93-49970-18-2 (eBook)
DOI: https://doi.org/10.9734/bpi/mono/978-93-49970-20-5

The scientific topic of the author’s interests can be titled with the name of the method known as “Photodynamic therapy” (PDT). The research and developments on this scientific theme have originated from the Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, starting in the early 80ty (XX century) and it is associated with the name of Prof. DSc Mariya Shopova. As a result of these studies, an original porphyrin derivative was patented in Bulgaria for application in cancer therapy with the PDT approach.

More advanced scientific studies have been conducted considering the novel challenges in the research and development of up-to-date photosensitive compounds for biomedical applications and other light-associated applications. Photosensitive compounds for PDT have features of absorption in the visible or infrared spectral region, which is typical for compounds with a highly conjugated aromatic structure. In view of the chemical structures, the studies of the new original compounds on the basis of the phthalocyanine ring are presented. They are demarcated as second and third-generation photosensitizers. The collected results showed different successes within the attempts to minimise the main limitation of the known photosensitizers.

The so-called photodynamic action has been observed and used for health maintenance and cure since antiquity. Nowadays, it still remains relevant for new challenging applications such as the present time of drug resistance and the emergency need for an effective therapeutic approach for acute, obstinate illnesses. PDT methodology includes the cascade of well-defined photophysical processes that result in the photochemical reactions. If the pathological conditions, such as pathogenic microorganisms and viruses which are present in the vicinity of the photosensitizer and light, and not to forget enough oxygen saturation for the process.

The first clinically approved photosensitizers have a porphyrin type of structure (hematoporphyrin derivative and its purified version known as Photofrin, and protoporphyrin – PPIX, as a result of the biosynthesis that starts from ALA). Nowadays, PDT is updated to the fast research and development referring to novel photosensitizers, modern light sources and novel approaches for oxygen supplementation.

PDT was invented as a perspective method for new applications. The limitations of the known photosensitizers which need special attention are the high hydrophobicity, limited drug-delivery, insufficient uptake and selectivity and not least, the dark toxicity. These problems still exist and draw the attention of chemistry researchers who need to work further on the knowledge referring to an ideal drug for photodynamic therapy. It is in the focus of the new scientific challenges because of the non-specificity of the photosensibilization mechanisms, which highlights the necessity of different mechanisms of action against pathogens. Moreover, the PDT method has characteristics of a non-conventional, palliative procedure with fast, gentle local effect and is highly effective for critical circumstances in medicine and ecology.

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