About Nanomedicine

Recently, I was interested in the concept of nanomedicine, and the promises it has for the improved health and better quality of our lives.

What is a nanomedicine?
In order to define nanomedicine, we need to know how the term was coined. ‘Nano’ originates from the Greek equivalent ‘nanos’, which means ‘dwarf’. So they’ve used that word to describe ‘very small’. Today, the standards for ‘very small’ is somewhat different, as ‘nano’ means ten to the power of -9. To define nanomedicine, we’re talking about very small particles of medicinal properties.

But wait! Aren’t drug molecules already ‘at the nanometer size’? That is so totally true. Drug molecules are already at ‘nano’, but they have limited properties with regard to delivery, targeting, and clearance. A drug’s efficacy is largely affected by how much it is being delivered to the target cell- in which traditional drug molecules have been doing a great job at- because they can largely be delivered by simple diffusion.

This clearly isn’t totally about size, but about what ‘nano-sized particles’ can do. Traditional drug molecules act by interactions with receptors, or by simple diffusison into the cell for more interactions. They have limited targeting capabilities, and may result in toxicity becoming apparent. In a nutshell, nanomedicine are therapeutic and diagnostic agents using nanoparticles as a means to treat disease with mitigated side-effects with added properties to help patients quality of life.

Trends in Nanomedicine
Nanomedicine came into clear light when many attempts have been done to use nano-sized delivery systems that are biocompatible. Examples of such delivery systems were antibodies, liposomes, micelles, dendrimers, gold nanoparticles, quantum dots, and more. These particle nanomedicines were primarily used to deliver anti-cancer agents because cancer treatments are highly toxic to even normal cells. That what causes vomiting, nausea, hair loss, symptoms associated with lesser quality of life.
Shortly after using normal liposomes as delivery, it was soon found out it didn’t circulate long enough because of macrophages gobbling up the nanoparticles because they were detectable, and identified as foreign. For a long time, they solved this by controlling the size of the particle so that macrophages did not detect these particles for a long time, but were large enough so that they were not cleared in the renal tracts.
Shortly after this, EPR effect was discovered. EPR effect is the ‘Enhanced permeability and retention effect’. Even without any targeting moieties, particles of the proper size simply concentrate in tumorous areas. Odd? This was due to the vascular-endothelial formation that goes with growth of tumors. But since the formation is faster than the natural rate of growth, the walls of these vessels are not complete, and are porous enough so that red blood cells and small particles are able to go through. (Also vice versa, cancerous cells leak out of these holes into the bloodstream, an identified route for metastasis.)

But after this, not many nanomedicine were able to be clinically accepted. Another trend in the clinic were antibodies for treatment. Nowadays, cell treatments are hot on new pipelines. The trends spell more breakthroughs to the clinic, as patients are always in need of better and cheaper medicine.

Opinion
While the field of nanomedicine is getting started, it is in need of acceleration as there is a lag in translation from research to clinics. There may be missing puzzles to the whole scheme as results in research and results in the clinic may be a mismatch. There can only be speculation in the field as clinical progress in medicine are largely done if there are promising market speculations.

While nanomedicines are largely nano-sized drug carriers at this moment, there are many more interesting trials in the near future.

Reference:

Shi, J., Kantoff, P. W., Wooster, R., & Farokhzad, O. C. (2017). Cancer nanomedicine: Progress, challenges and opportunities. Nature Reviews Cancer, 17(1), 20–37. https://doi.org/10.1038/nrc.2016.108

Bertrand, N., & Leroux, J. (2012). The journey of a drug-carrier in the body : An anatomo-physiological perspective ☆. Journal of Controlled Release, 161(2), 152–163. https://doi.org/10.1016/j.jconrel.2011.09.098

Lammers, T. (2012). Drug delivery research in Europe. Journal of Controlled Release, 161(2), 151. https://doi.org/10.1016/j.jconrel.2012.05.019