It goes without saying that the greater the number of organs available for transplant, the better for patients in need of them. A newly-developed technique could help, as it uses light to kill viruses and bacteria that might otherwise make donated organs unsuitable for use.

The process begins with a perfusion procedure developed by thoracic surgeon Marcelo Cypel, at the University of Toronto. That procedure involves replacing the blood in donated lungs with a non-toxic liquid preservative, and while it does indeed reduce viral and bacterial populations, it doesn't eliminate them. This means that recipients of the treated organs still have to be on antibiotic and antiviral medications for three months after the transplant takes place.

Cypel wondered if light could be used to further kill off harmful microbes in those lungs, as ultraviolet light already used to do so in donated blood. To that end, he teamed up with Prof. Vanderlei Bagnato of Brazil's University of São Paulo. Bagnato and his team proceeded to create a machine that does the job, utilizing what's known as biphotonic therapy.

The perfusion process is still utilized in the new technology, but a photosensitive drug is also introduced to the lung, within the liquid preservative. Red light at a wavelength of 660 nanometers is then shone into the biological tissue, where that light's energy is absorbed by the drug's molecules. That energy gets transferred to the oxygen molecules in any viruses that are present, causing them to become oxidized. The result is irreversible damage to the membranes and genetic material of viruses such as hepatitis C and HIV-1, causing their death.

At the same time that the red light is being used on the lung itself, ultraviolet light is also shone on the liquid as it's being continuously circulated through the organ. This contributes to the killing of both viruses and bacteria, that are flushed out of the lung and into the liquid. A single liter of the perfusion solution – which is expensive – can be flushed through an organ hundreds of times.

In lab tests, biphotonic therapy was found to "drastically" reduce the viral load in human lungs that had previously been rejected for transplantation. It's even been trialled on human test subjects, ten of whom received lungs that had been treated using the new technology.

In two of those people, where hepatitis C had been completely eliminated in the organs prior to transplant, no problems subsequently occurred. In the other eight, who received lungs with a reduced number of viruses, the patients' viral loads ended up rising one week after the transplant, ultimately requiring the usual three-month course of antiviral medication.

This indicates the importance of being able to remove all viruses and bacteria from organs, which the scientists are now seeking to do with improvements to the system – they're additionally adapting it for use on livers and kidneys. Once it's ready to go, it may be snapped by either of two multinational corporations that have already expressed an interest in commercializing the technology.

A paper on the research was recently published in the journal Nature Communications.

Source: FAPESP

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