Delivering chemotherapeutic drugs to cancer cells is a booming industry by itself. Why? Because cancer cells are like normal cells in a lot of ways and it becomes really hard for the drug to actually differentiate between the two. By the time the drug has some effect on the cancer cells, there are already a notorious few that get away, evolve and become resistant. Additionally, a large portion of the drug molecules are lost in transit as they move through the blood stream and may not even make it to the target cells. So, what becomes clear here is that this is a tricky disease to tackle and requires some strategic drug delivery. A strategy that not only brings efficiency but also allows high specificity. Nano-particles can be one such strategy.
How do nano-particles work?
A nano-particle as the name rightly suggests is a particle that has its size in nano-metres (1-100 nm), which is about 2000 times smaller than the diameter of the human hair. These particles can be in the form of chemical polymers, small lipid molecules, viral particles and so on, onto which the chemotherapeutic drug is loaded and then injected into the blood stream. So, what we want essentially is a molecule that is minuscule, so that it can make its way through the blood stream but also has enough surface area so that it can hold on to a good number of drug molecules. Let’s for convenience compare this to a truck with good cargo space. To ensure the cargo (in this case the drug molecules) stays tightly bound to the truck (the nano-particle), the nano-particle should form stable interactions with the drug molecules as they transit through the bloodstream.
The nano-particle is not a sole traveller in the bloodstream!
What we need to remember is that the nano-particle is not a sole traveller in the blood stream. It travels with millions of other cells like the RBCs, WBCs and other biomolecules all heading in their respective directions. The nano-particle must be relatively inert to its environment to be able to effectively deliver the drug and reduce toxicity.
What happens when the nano-particle reaches the cancer cells?
Once the nano-particles have reached the cancer cells, they should be able to enter the cell and release the drug into the respective compartment in the cell. Additionally, we also want the particles to deliver the drug specifically to the cancer cell while keeping its interaction with normal cells minimal. To enable this, nano-particles are often equipped with molecules which specifically bind to the receptors present on the surface of cancer cells, increasing their interaction with cancer cells as opposed to the normal cells. Once inside the cell, due to the change in the pH, the drug loses its affinity to the nano-particle and is thus released!