Posts tagged: eukaryotes

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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