The detection and cure of cancer has become increasingly essential as a large number of people continue to succumb annually to this deadly disease. Treatment in the case of cancers poses a unique problem in terms of the high potential toxicity of many of the drugs currently being used in cancer therapy. Additionally, the fact that any method of killing cancerous cells also inevitably causes harm to normal, healthy cells and tissues further complicates the situation. Thus researchers have to find answers to some very crucial questions: First, can they reduce the effective dosage of the drug in question in order to reduce the magnitude of the damage to unwanted tissues? And second, can they control the release of the drug and or localize the drug to a specific set of cells within a tumour or in areas near it, thus preventing tissue damage? These are tough problems to tackle, especially when working with a complex system such as the human body. There is a limit to which one can reduce dosage, since one has to allow for loss of the drug through physiological processes within the body. Too low a dose might end up not really being efficacious. Localization however will end up solving both problems. If the drug can be localised, even relatively smaller doses can prove to be more efficient.

It was when I pondering over these problems that I came across some research carried out in the field of nanotechnology that was concerned with precisely the same problems. Researchers have come very close to solving the problem of localized and metered dosing of a drug within the body. This feat has been achieved by using gold nanocages. These cages are coated with a special type of “smart polymer” which can be induced to open or close using an external signal such as exposure to near-infrared light. These smart polymers are very apt for use in timed release of drugs.

How the process works can be simplified as follows: the opening and shutting of the cage doors depend upon a phenomenon known as Surface Plasmon Resonance. When the cages are created, a few of the electrons are not bound to the gold atoms but remain as a cloud or electron gas. This gas, if exposed to light oscillates as one entity giving rise to the phenomenon of the Surface Plasmon. Further, the wavelength of light at which this oscillation occurs can be changed by changing the thickness of the walls of the Nanocage.

Now comes the role of the smart polymer, in this case poly (N-isopropylacrylamide). The polymer coated on the cage when exposed to a lower critical temperature, the polymer chains become water-loving, Hydrophillic, and they stand out from the cage, sealing it and preventing its content (the anticancer drug in question) from leaking. When the cages are exposed to increased light intensity (higher temperature), the polymer strands start rejecting water, hydrophobic, and they shrink and collapse thus allowing the cage to release its contents. Since there is a direct relation between the intensity and the duration that the light shines on the cages, the amount of drug that is released can be controlled to a remarkable degree.

Smart Polymer being used for Drug Delivery

Smart Polymer being used for Drug Delivery

Tissues in the human body are quite sensitive to near-infrared light. Bearing this in mind, the researchers have optimised controlling temperatures very close to this range so that there is no danger of the tissues getting scorched or burned.

I am sure if we can find some way to coat the smart polymer or components of the gold nanocage with antibodies specific to cancerous cells or tissues; we will very soon have solved the problems of localization and metered dosing in cancer therapy. This might even make it possible to use smaller doses of potentially harmful drugs and hence to optimize treatment.

This is a classic example of small is big!!