Melanin nanoparticles hinder tumours with new theranostics approach

Nanoparticles loaded with skin pigment helps scientists diagnose and treat tumours simultaneously with therapy/diagnostics: ‘theranostics’.

It is sprayed, in synthetic form, onto NASA spaceships to protect them from radiation. It has also featured in recent research into how its absorptive properties have allowed fungi to adapt and thrive inside the radioactive exclusion zone of the Chernobyl disaster. Now the dark skin pigment Melanin, which protects our body from the sun’s damaging rays by absorbing light and dissipating it as heat, could become an essential tool in the diagnosis and treatment of cancer.

Longevity.Technology: The strength, in our view, of the theranostics approach is that it isn’t presented (at this stage) as an option for curing tumours. The research team are, instead, presenting a highly viable method to find tumours and slow them, making them a widely applicable Longevity option for buying time against many different types of cancer, including the ones for which we don’t currently have a cure.

The TRL score for this Longevity.Technology domain is currently set at: ‘Late proof of concept demonstrated in real life conditions.’
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The TRL score for the technology addressed in this article is: ‘Technology has completed initial trials and demonstrates preliminary safety data.’

This revelation comes from the research of scientists from The Technical University of Munich (TUM) and Helmholtz Zentrum München. Writing in Nature Communications [1], they show how they created melanin-loaded nanoparticles (derived from cell membranes) that helped not just to image tumours in mice, but also to slow their growth.

The team were able to create both of these useful effects at once because of melanin’s ability, rare amongst biological polymers, to produce heat when excited. Their method goes like this: first they inject the melanin (transported in biological nano-containers called outer membrane vesicles or OMVs) directly into the tumour before heating it with pulses of an infrared laser. The heat from the infrared causes the tissue to expand slightly, before cooling and contracting when the beam is switched off, releasing pressure waves of ultrasound as it shrinks back to its original size. As tumours expand and contract at different rates to healthy tissue, the specific ultrasound signature they give off can be used to locate them in the body.

So far so standard photoacoustic imaging: a technique that is new but far from unique to medical research. What makes their contribution exciting is what happened to the melanin during this procedure: when exposed directly to the beam, it absorbed the infrared and dissipated it as heat, causing the temperature of the tumour tissue to rise from 37°C up to a maximum of 56°C. This dramatic temperature shift not only killed some of the tumorous cells, but also provoked a bodily immune response to the inflammation, weakening the cancerous tissue further.

This contrasts strongly with control tumours without the melanin injection, which only reached a maximum temperature of 39°C, and grew at a significantly faster rate than those with. And what’s more, the images produced by the treatment delivered were very sharp, and in high-contrast with the surrounding healthy tissue. What’s more, the OMV transporters are biocompatible, biodegradable and can be easily and inexpensively produced in bacteria, even in large volumes.

Professor Vasilis Ntziachristos, the leader of this research, places his team’s new method among the first of many breakthrough therapies in a new field. “Our melanin nanoparticles fit into the new medical field of theranostics – where therapy and diagnostics are combined. This makes them a highly interesting option for use in clinical practice,” he says [2]. They are now developing their melanin-OMV combo for use in further clinical trials.