The idea of nanomachines was first postulated by Richard Feynman, the avant-garde physicist and Nobel laureate. He hypothesised that there was ample ‘Room at the Bottom.’ He also suggested that human beings were a marvellous biological system — adept at doing things ‘small as big.’ He was ahead of his time — he was not only dreaming of scientific fantasy, but also scientific eventuality.
His vision bid fair to the idea of potential medical applications of nanotechnology — of a programmable nano-robot exhibiting and working on the same page as proteins and cells. Better still, they could be fabricated and introduced into our bodily systems. You get the picture — of petite-sized soldiers of health, or nanomolecules of medicine, roaming the bloodstream, exterminating disease, or slowing down the process of aging, among other things.
Recent advances in medical science attest that most illnesses originate from malfunctioning cells. The destiny of our micron-size cells is, in turn, determined by nanosize molecules — genes and proteins — residing within the cells. All the more reason why nanomedicine targets its ‘tiny, but big’ ammo at specific locations within the cells. Picture this. Conventional drugs, due to their micron-scale size, do not have such abilities — to pass through certain biological barriers. Nanomedicine has the capability to pass through various biological barriers and acquire access to molecules within specific cell compartments.
Nanomaterials, or particles, used in nanomedicine have several unique features unlike conventional drugs. They not only have a tall ratio of surface area to volume, but also the high loading of drugs on nanomaterial carriers. They have the wherewithal to encapsulate dozens of drug molecules inside a single vehicle and direct the release of multiple drugs too. In addition, tiny nanomaterials and particles have revolutionised, refined and redefined medical imaging techniques — at the optical, electronic, magnetic and biological levels.
Let us highlight an example — when nanoparticles are directed at cancer cells, they release drug molecules to treat the cells. Besides, they have the ability to emit light and heat to destroy such cells. This is achieved in a precise, incremental manner — while reducing the damage to healthy cells. You’d call it specific targeting with the added advantage of improved availability and release in a controlled, ‘customised,’ or bespoke manner. New nanomedicine research is geared to developing innovative ways to improve nanoparticles’ biocompatibility and protect them from immune attack and/or guiding them to diseased cells and, most importantly, enabling oral administration methods for nanomedicine that can pass through the gastrointestinal tract, or barrier, without ado.
The most significant advantage of nanomedicine is iron oxide nanoparticles — which can be encrusted with a peptide and targeted to ‘hit’ a cancer tumour. The best part is all electrons in iron oxide nanoparticles — which are less than 20nm — whirl in the same direction. The result is the overall magnetic-field strength is larger and more localised than that of larger drug particles. The superior magnetic field augments magnetic resonance imaging [MRI] and enables the nanoparticles, in the process, to be easily taken up by tumour cells, while diffusing the tumour itself more slowly — for much better analyses, or interpretation.
The use of iron oxide nanoparticles has been approved for liver imaging and in the early diagnosis of heart disease, such as atherosclerosis, or hardening and narrowing of the arteries, no less — the [in]famous trigger for heart attack and stroke — among other forays. What’s more, such nanoparticles can accumulate specifically in the diseased area of the arteries and enable clinicians to monitor the development of arterial plaques, not to speak of their ‘disappearance’ following treatment. The use of nanoparticles has also extended to rapid detection tests for ovulation, pregnancy, flu and HIV virus, including neurological illnesses, among other disorders.
In addition, nanoparticles can destroy cells triggering apoptosis, or programmed cell death, or becoming naturally responsive — in other words, their behaviour in the area of drug release can be controlled by local stimuli, like pH, or acid-base balance, temperature, chemical ‘prompts,’ or remote stimuli like electrical and magnetic fields. To highlight an exemplar — when nanoparticle carriers are made of pH-sensitive polymers, their release into different locations of the gastrointestinal tract can be controlled. This would be a big-plus, because pH conditions vary quite consistently and repeatedly in the gut — the temple of good health and optimal wellness.
You may well ask as to what is the significance of such delivery modes. First things, first. Nanoparticle carriers are made with formulations of timed degraded polymers, including antibodies. This means that drugs can discharge into the colon 3-4 hours after leaving the stomach. When nanoparticle carriers are made of microbially degradable polymers, they can be ‘dispatched’ to the colon by specific colonic bacteria too. Think of programmed drug delivery, and this is it — in all its therapeutic finesse and grandeur.
From the restorative angle, nanostructured materials have been used to regenerate bone, cartilage, vascular, bladder, nervous systems, muscle, skin and other tissues. Besides, ‘nanocoatings’ have been successfully used as dental implants, hip and intervertebral casings, besides stem cell encapsulation. What’s most fascinating today is tissue regeneration — both in terms of diagnostics and regenerative therapeutic medicine.
All is not hunky-dory for programmed nanomedicine, though. Research has corroborated the existence of certain key concerns and their resolution as regards the use of nanoparticles as drug carriers. The first is aimed to prevent phagocytosis, or foreign body removal, by the immune system. To overcome the drawback, nanoparticles are usually coated by polymers, as cited earlier — this technique prolongs circulation time and bioavailability of drugs. Research is in progress to ‘mounting’ a nanoparticle to beat viruses, or viral incursions. The nanoparticle may not be aimed at literally destroying viruses. It is ‘filled and armed’ with an enzyme that delivers the ‘knock-out’ punch. This eliminates the replication of virus molecules in the patient’s bloodstream.
— First published in The Himalayan Times, Nepal
