Posts tagged: photosensitizer

Ondine Biomedical Inc Proudly Supports The PanAmerican PDT Association

Ondine Biomedical Inc. is a proud supporter of the mission and goals of the PanAmerican Photodynamic Therapy Association. Launched last month, the Association’s purpose is to galvanize the basic science and expertise of photodynamic therapy in the Americas. This will help encourage the study and practice of PDT in the treatment of animal and human diseases.

Many of you may not know that photodynamic therapy has been around for centuries. In fact, the earliest recorded treatment using a photosensitizing agent and a light source occurred in ancient Egypt over 3,000 years ago. Vegetable and plant substances were used as photosensitizers and sunlight was used as the light source. Patients suffering from skin diseases such as vitiligo had the photosensitizers topically applied to the damaged area, and the resulting photochemical reaction restored their tissue to a healthier state. In some cases, it even helped repigment their skin to its normal color.

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Photodynamic Therapy– Is Selective Damage Really that Selective?

Why doesn’t photodynamic therapy (PDT) cause any noticeable damage to human tissue? After all, the reaction causes damage to the bacterial membrane, and human cells have membranes as well.

This was a topic that really grabbed my attention when I first learned about photodynamic therapy.   How is it possible that with the creation of highly reactive molecules are we only limiting cellular destruction to bacterial cells? Although there may be a few different answers to this question, the primary solution is that we are not. Don’t be afraid and swear off photodynamic therapy right away, here me out first. Photodynamic therapy is primarily used as a treatment option for cancers. This treatment is used on cancerous tumours formed in esophageal cancer, lung cancer, skin cancer, as well as many different types. The photosensitizer is accumulated in the tumour either by direct injection or utilizing mutations of the cancerous cells that concentrate the photosensitizer inside the cell. After light is applied, the tumour cells are damaged, but the healthy cells are not greatly harmed. Why? One trait of a cancerous growth is the mutation of certain DNA repair enzymes. (Have a look at this Wikipedia article to give you a small background on DNA repair enzymes) These repair enzymes are responsible for fixing oxidative damage problems caused by free radicals. Scientific researchers, knowing this small fact about most cancerous tumour cells, use PDT and reactive oxygen species to their advantage. A healthy human cell can take some free radical “abuse”, but a tumour cell can only take so much until the cell dies. This fact, coupled with selective photosensitizer accumulation within tumour cells, makes PDT an excellent treatment option in some forms of cancer.

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Photodynamic Disinfection (PDD) is the Antimicrobial application of PDT (aPDT)

The key features of aPDT can be summarized as follows [1]:

  • Broad spectrum of action, since one photosensitizer can act on bacteria, fungi, yeasts and parasitic protozoa
  • Efficacy independent of the resistance pattern of the given microbe
  • Extensive reduction of pathogen counts in minutes, without damaging host cells
  • No selection of resistant strains after multiple treatments
  • Readily available, non-toxic photosensitizers
  • Relatively low-cost light sources for activation of the photosensitizing agent
  • No cytotoxic effects on key sensitive host cells such as human keratinocytes or fibroblasts

The treatment of topical infections has traditionally relied upon antibiotics in either topical or systemic dosage forms. However, the inexorable increase in antibiotic resistance (including to vancomycin and other glycopeptides) has led to the spectre of potentially untreatable infections, and this in turn has led to the development of alternative antimicrobial approaches based on light-activated chemotherapy 2, 3. Photodynamic Disinfection (called antimicrobial PDT by the scientific community) is an extension to traditional photodynamic therapy (PDT) which was originally focused on oncotherapy and intra-ocular indications, utilizing systemically-administered photosensitizers. Read more »

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