Cancer-Hunting Nanorobots Used to Seek and Destroy Tumors

 Nanomedicine  

New research has opened up the possibility of an army of robots travelling around a human body, hunting down and destroying malignant tumors.

R
esearch in Nature Communications presented from the University of California Davis Cancer Center shows the prospect of an army of tiny weaponized robots travelling around a human body, hunting down malignant tumors and destroying them from within being a realistic scenario in the not-to-far-off future. Promising progress is being made in the development of a multi-purpose anti-tumour nanoparticle called “nanoporphyrin” that can help diagnose and treat cancers.

Cancer is the world’s biggest killer. In 2012, an estimated 14.1 million new cancer cases were diagnosed and around 8.2 million people died from cancer worldwide.

Nanotechnology is one such revolutionary cancer-fighting technology.

A nanometre is a very small unit of length, just one billionth of a meter. Nanotechnology looks at building up incredibly tiny, nano-level structures for different functions and applications.

One such nanoparticle-based application is the development of precise cancer diagnostic technology and safe, efficient tumour treatment. The only problem is nanoparticles must be tailored to specific jobs. They can be time-consuming and expensive to research and build.

So how do nanoparticles work? They can be made using inorganic or organic components. Each has different properties:

• -Inorganic nanoparticles often have unique properties that make them useful in applications such as fluorescence probes and magnetic resonance imaging tumor diagnoses;
• -“Soft” organic nanoparticles are the best drug-delivery carriers for tumor treatment, due to their biocompatibility, ability to be chemically modified and their drug-loading capacity. A few “soft” organic nanomedicines including Genexol-PM (paclitaxel-loaded polymeric micelles), Doxil (liposomal doxorubicin) and Abraxane (paclitaxel-loaded human serum albumin nanoaggregate) have been approved or are in clinical trials for the treatment of human cancers.

The new organic nanoparticle – nanoporphyrin – can do all this.

Nanoporphyrin is only 20-30 nanometres in size. If you want to get technical, it’s a self-assembled micelle consisting of cross-linkable amphiphilic dendrimer molecules containing four porphyrins.

“These are amazingly useful particles,” noted co-first author Yuanpei Li, a research faculty member in the Lam laboratory. “As a contrast agent, they make tumors easier to see on MRI and other scans. We can also use them as vehicles to deliver chemotherapy directly to tumors; apply light to make the nanoparticles release singlet oxygen (photodynamic therapy) or use a laser to heat them (photothermal therapy) – all proven ways to destroy tumors.”

If you want to get less technical, it’s a loosely bound group of molecules (or “micelle”) with their hydrophilic (“water-loving”) heads pointing outwards and their hydrophobic (“water-hating”) tails pointing inwards. Each molecule contains organic compounds called porphyrins. Porphyrins can occur naturally, the best-known being heme, the pigment in red blood cells.

Nanoporphyrin’s small size gives it an intrinsic advantage as it can be engulfed by and accumulate in tumor cells, where it can act on two levels:

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On the molecule level, nanoporphyrin can aid diagnosis by enhancing the contrast of tumour tissue in magnetic resonance imaging (MRI), positron emission tomography (PET) and dual modal PET-MRI. (Again, this is a bit technical, but if you’re interested, porphyrin acts as a ligand, which chelates with imaging agent metal ions such as gadolinium (III) or ⁶⁴copper (II).)
on the micelle level, nanoporphyrin can be loaded with anti-tumor drugs to kill malignant tissue. When activated, for example, it can generate heat to “cook” the tumor tissue, and release lethal reactive oxygen species (ROS) at tumor sites.
Armed and dangerous (to tumors)

Functional nanoparticle processes can be similar to those of an armed nano-robot. For example, when a tumour-recognition module is installed in a delivery nano-robot (organic particle), the armed drug-loaded nano-robot particles can target and deliver the drug into tumour tissue. They kill only those cells, while being harmless to surrounding healthy cells and tissues.

If a tumor-recognition module is installed in a probe nano-robot (inorganic particle), the armed nano-robot particles can get into tumor tissue and activate a measurable signal to help doctors better diagnose tumors.

It has been a huge challenge to integrate these functions on the one nanoparticle. It’s difficult to combine the imaging functions and light-absorbing ability for phototherapy in organic nanoparticles as drug carriers. This has, until now, hampered development of smart and versatile “all-in one” organic nanoparticles for tumor diagnosis and treatment.

The production of nanoporphyrin is an efficient strategy in the development of multifunctional, integrated nanoparticles. The same strategy could be used to guide further versatile nanoparticle platforms to reduce nanomedicine costs, develop personalised treatment plans and produce self-assessing nanomedicines.




SOURCE  Monash University, Nanowerk

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