Researchers bioengineer melanin for use in photothermal therapy

Researchers at the Shenzhen Institute of Synthetic Biology in collaboration with the Guangdong Medical University have genetically engineered a bacterium to produce melanin nanoparticles. These nanoparticles can be used in photothermal therapy (PTT), one of the latest treatments for cancer.

The process of producing melanin molecules synthetically is extremely harmful to the environment due to which scaling up the industry is difficult. However, the biosynthetic manufacturing route solves this problem.  In their testing, the researchers found that the melanin nanoparticles were biocompatible and safe for human use.

“Engineered melanin nanoparticles are more efficient than conventional nanoparticles in terms of biocompatibility, stability and are helpful in image guided drug delivery systems,” Dr Hemanth Kumar Manikyam, a cancer and genomics researcher told Happiest Health.

Photothermal therapy

In cancer, due to the abnormal cell growth, a hypoxic environment— a state in which oxygen is not available in sufficient amounts— is created within the cancerous tissue. This leads to altered body functioning and drug resistance among the cancer cells.

PTT uses electromagnetic radiation to increase the temperature of the cancer tissue to kill the cells. This is done by administering molecules that can absorb infrared radiations to produce heat.

Unlike previous therapies, this therapy is minimally invasive and highly targeted. Moreover, it does not affect healthy tissue which is a major drawback in chemotherapy and radiation therapies.

Melanin in PTT and beyond

While materials like carbon nanotubes, graphene, and gold nanorods have been used in PTT, melanin is more suitable as it is extremely stable and has negligible toxicity. This is because melanin is naturally produced by our bodies and is responsible for hair, eye, and skin pigmentation.

The biosynthetic melanin particles produced by the researchers were found to have strong light absorption in the near infra-red region and converted 48.9 per cent of the absorbed light   into heat. This was higher than even synthetically produced melanin.

“Nanomaterials-mediated PTT converts the absorbed light energy into heat through the photothermal conversion characteristic of nanocarrier, causing a rapid increase in local temperature,” says Fei Yan, corresponding author of the study that was published in the Journal of Nanobiotechnology.

Apart from helping to deliver PTT to cure cancer, Dr Manikyam adds that the binding efficiency of engineered melanin nanoparticles with medicines and ions can help detect tumours and metabolically active cells (with abnormality) at early stages, before chronic conditions can develop.