A recent scientific article in the American Chemical society Journal Nano Letters (June 2010 issue) has disclosed a new method of delivering drugs into the body: magnetic fields. Researchers at the University of Rhode Island are using this system to produce tiny packets of a drug, called nanoparticles, that are enclosed in a structure known as a liposome. Liposomes are tiny, spherical structures made up of fatty acid materials called lipids. The key to this methods success is the self-assembly of the lipids into a three-dimensional shape. One end of the lipid molecule is hydrophilic, meaning that it mixes well with water and doesn’t mind being in a water environment. The other end of the lipid molecule is hydrophobic, meaning that it doesn’t dissolve well in water and dislikes being in a water environment. So, when added to a water solution, a lipid has a bit of an identity crisis; half of it wants to be surrounded by water, and half of it does not.
The secret to resolving this difficulty is for hundreds of the lipids to come together and form a hollow spherical shell-type structure. All of the hydrophobic ends point towards the center of the sphere, and all of the hydrophilic ends point towards the outside of the sphere, where the water is located. The result is a sphere which doesn’t contain any water on the inside, and is comprised of all of the “water-hating” portions of the lipids. The surface of the sphere is entirely hydrophilic, and the resulting supermolecular sphere is therefore comfortable floating in water. This self-assembly takes place instantly and is spontaneous. It’s remarkable in a way, because we see entirely non-intelligent components coming together and seemingly working together for the common benefit – providing shelter for their hydrophobic tails. The resulting “collective” of individual molecules floats in the water as a community, each of the molecules benefitting from having their hydrophobic components protected from the water – hundreds of individual parts working in unision.
This new research takes this behavior of liposomes to a new level. Researchers have now found a a way to use this spontaneously-generated structure to transport drug molecules, only releasing them when triggered by an external signal. This is done by dissolving the drug molecule (which, like most organic compounds, is largely hydrophobic and dislikes water) and the starting material lipid in a fresh solution of water. As the three-dimensional liposome sphere begins to form, the drug molecules (which are stuck with nowhere to go, floating in an ocean of water molecules which they dislike) seek refuge and shelter on the inside of the sphere. There, they are surrounded by fellow hydrophobic molecules, and are quite content. The outside of the sphere (facing the water) is made up of just the hydrophilic portions, which mix well with water. The drug molecule “hides” inside the liposome, and the resulting array of molecules can be dissolved into the blood stream even though the drug itself would not be soluble, if it were by itself. It waits patiently inside the interior of the liposome and is carried along towards whatever target organ the doctors need it to treat.
For the actual drug delivery step, the doctors use an external apparatus outside the body to send an electromagnetic field (operating at radio frequencies, so quite harmless) into the area of the body that they wish to treat. When this field reaches the liposomes, it heats them up; this has the effect of “melting” the shell, as it provides sufficient energy to jostle the individual lipids out of their community arrangement and breaks down the spheres into their component parts once again. This exposes the drug molecule to the organ and allows it to begin its work. Only those drug molecules whose protective shells were hit by the magnetic field will be released. In other parts of the body, the drug remains coated by the liposome and is eventually broken down and secreted without having a chance to ever react with bodily tissues.
This method of selective targeting is very useful for drug treatments such as chemotherapy. Chemotherapy drugs are by design extremely toxic, with the hope that they will kill cancerous cells slightly faster than they kill the patient. By using the magnetic field only on the cancerous tumor, the chemotherapy drug is only released in that specific area; this reduces the collateral damage normally seen in a regular chemotherapy approach. Without the magnetic field there is minimal spontaneous leakage of the drug.
This approach will likely lead to future new discoveries, as it’s already known that different lipids behave different around tumorous cells. If lipids can be incorporated into the three-dimensional sphere that specifically seek out and target cancerous cells, it may be possible to selectively target cancerous growths even if the doctors are not sure where in the body they are located. Simply injecting the lipid:drug complex, allowing the bodys circulation to carry and concentrate them at the tumor sites, followed by total body irradiation with the magnetic field, would selectively seek out and destroy dozens of cancerous tumors throughout the body simultaneously.
These new developments are great news for families fighting cancer and other organ-specific diseeases. Instead of showering the patients body with poison, doctors will soon be able to fire a carefully aimed precision strike. This type of approach will extend patient lifetime and improve patient survival rates, which is the best type of news.