Nanotherapy

Two of the ways in which nanotherapy is being used in medicine will be highlighted here: the encapsulation of existant drugs in polymer coatings, and the usage of magnetic nanomolecules to destroy tumors.

Polymeric encapsulation

The problem with current drug formulations is that they aren't always soluble, and cannot be taken up by our bodies efficiently. Drugs have to pass over membranes and also be transported in the blood stream. Packing drugs into polymeric "packets" make them easier to absorb by the body. The polymers are hydrophilic on one side (water-loving) and hydrophobic on the other (orient themselves away from water) (see below). When the polymers are mixed with the drug particles, they organise themselves around the drug molecules so that the hydrophobic ends surround the drug on the inside, while the hydrophilic ends form the outside shell. This makes the molecule soluble and easier to transport in the blood stream.

These nanomolecules are often adapted with proteins or peptides on the surface in order to target them to the specific area in the body where the drug is supposed to take effect. One way that this is done is by adding antibodies to the shell of the nanomolecule (see below). These antibodies recognise receptors that are expressed specifially on the surface of tumors. This means that, once the nanomolecules have reached the tumor, they bind to the receptors and are taken into the tumor cells by a mechanism called endocytosis. In this way the often highly toxic cancer drugs do not affect other, healthy tissues in the body.

Magnetic nanoparticles

Metal-based nanoparticles can be used to target tumors without affecting other tissues, and without exposing the patient to harmful chemicals used to treat cancer. Magnetic nanoparticles are injected directly into the tumor (such as a brain tumor). The patient is then placed in a magnetic field that makes the magnetic poles of the nanoparticles alternate rapidly, causing an increase in heat. The increased heat causes the nanoparticles to be absorbed into the cancer cells. The magnetic field treatment is repeated, causing a further increase in heat. The particles also oscillate, which destroys the cells. The destroyed cells are excreted by the body. The 1-hour treatment is repeated 6 times, but the nanoparticles are only injected once, which makes this a good alternative to conventional chemotherapy.

Surfing

To know how surfing actually "works", you have to know about planing. You might've heard about cars aquaplaning across pools of water, and drivers thereby losing control of the steering. Planing simply means that an object (like a boat or a car) is lifted up onto the surface of the water and is skimming across it, as opposed to plowing through it. Th object or craft is supported predominantly by hydrodynamic lift (water + movement) rather than hydrostatic lift (bouyancy). As the object moves through the water, it is lifted up, thereby decreasing the contact of the object and the water, decreasing the drag, and allowing greater speed.

Waves are formed by wind blowing on the surface of water. The stronger the wind, and the larger the area it blows on, the bigger the waves are that form. Water molecules closer to the surface move faster than water molecules at depth. This means that the top "layer" of water eventually overruns the lower "layer" of water, creating a wave.


The surf zone (where waves break) is determined by the direction of the swell and the contours of the bottom of the beach. The surf zone forms when the depth of the water is roughly 1.3 times the height of the wave. So a five foot wave will begin to break when the water is about six-and-a-half feet deep.

In order to catch a wave, a surfer has to accelerate up to the speed of the wave (wave velocity). The surfer must place himself further than the position where the waves break, and ensure that his distance from any approaching wave allows him to paddle sufficiently so that he can match his velocity to that of the wave.

After accelerating up to the wave speed, the rider pops up to a standing position and begins planing over the surface of the wave. Since the wave becomes steeper as it advances, the surfer has to move towards the front of the wave where the acceleration is less. Advanced surfers don't simply ride waves straight out to the beach, but travel across waves, in a path that is parallel to the crest. The surfer rides along the position of the wave where the water is starting to rise just before breaking. A surfer can steer a surfboard by shifting their weight between the balls and heels of their feet, along with the help of the fins attached to the bottom of the board.

The native inhabaitants of Hawaii surfed straight out to shore on huge, wooden surf boards that had no fins. When surfing became popular in the USA, modern boards that were a lot lighter, with fins, were developed. In the 80's the short board became popular, and surfers started doing skateboard-inspired jumps on the water.

Alcohol

Ethanol is one of the oldest known drugs. 9000 year-old pottery in China have shown traces of alcohol, indicating that Neolithic humans may have drunk alcoholic beverages.

Alcohol is a depressant - it temporarily diminishes the function of the central nervous system. Alcohol "works" by affecting more than one system in the body, but it has been determined that alcohol stimulates certain receptors in the brain. These receptors (including GABA receptors) decrease neuron activity when a molecule is bound to it. It is also believed that some of these receptors control fear and anxiety, and therefore they are the target of a number of anti-anxiety drugs, like valium.

Ethanol is metabolised in the body like any foodstuff, as it contains sugars and other foodstuffs. Removal of alcohol by the liver is rate-limited, meaning there is a maximal rate that the liver can metabolise alcohol, and after that alcohol will start accumulating in the body untill the liver is given enough time to metabolise all of it.

Space blankets

Space blankets (also called mylar blankets) consist of a thin layer of plastic (often PET), with an extremely thin layer of metal (usually aluminium) over it. The blanket is wrapped around a person with the metallic, reflective side on the inside. The metal reflects visible light as well as infrared light - this is how it reflects body heat back onto the person around which it is wrapped.

Space blankets are also very light and take up very little space. They're wind- and waterproof too, so will keep you dry and warm even when the wind is blowing, or it's raining.

The space blanket was developed by NASA in the 1960's for the US space program. These days it's used in emergencies, first aid, and for camping.

Titanium prosthetic limbs

When a bone in the body has to be replaced, the best material to use is a type of metal. The environment inside your body is not ideal for any sort of metal though - metals corrode and rust. Some metals also cause an allergic reaction.

Many prosthetics these days contain Titanium, as it has a good strength to density ratio. Titanium is also strong, tough, resists corrosion, and is biologically compatible (it doesn't cause allergic reactions). It can be strengthened by alloying it with other elements like aluminium or vanadium. These alloys are used in hip and knee joint replacements, dental implants, and pacemaker cases. It is also used in procedures where the metal is allowes to join the surrounding tissue (see a recent entry in my sister blog).

Economics

The Credit Crunch was partially characterised by people who didn't want to cut their losses and sell, refusing to show a loss. Is this sort of behaviour part of a thought-out plan, or is it instinct?

It turns out that economics "work" in a way that is predictable and hard-wired into our brains. In an experiment where monkeys were taught to use money, the monkeys made decisions that directly reflected decisions that contributed to the Credit Crunch.

Monkeys were taught to use coins in order to buy grapes from laboratory "salesmen".

In the first experiment the monkeys could choose between two options: one salesman sometimes doubled the number of grapes after the sale was made, and sometimes he didn't; the other salesman always added one grape after the sale was made. The second salesman therefore represented a *safe* option with a certain increase in product, while the first salesman represented a *risky* option. Most monkeys bought from the *safe* salesman, preferring a sure increase in the product they bought.

In the second experiment the monkeys had two different choices: one salesman would always sell two grapes, but remove one before handing the grapes over to the monkeys; the other salesman started with three grapes, and either removed two, or none. The first salesman again represented a *safe* option as he always did the same thing, while the second salesman represented a *risky* option as he sometimes handed over less grapes than could be bought from his competitor. Most monkeys bought from the *risky* salesman here, preferring the choice of potentially getting a lot more grapes than they would get from salesman number one.

In the first experiment the monkeys had, in effect, a small amount of money which they could increase by a defined amount (always getting one extra grape), or by an unsure amount (getting no extra grapes, or two extra grapes). Monkeys chose to increase their money by a defined amount.

In the second experiment monkeys had, in effect, a large amount of money which they could have decreased by a defined amount (always getting one less grape than they bought), or by an unsure amount (getting two less grapes than they bought, or not losing any grapes at all). Monkeys chose to avoid the certain loss of money here, and took a risk by buying from the *risky* salesman.

In the Credit Crunch (and in economics in general!) the behaviour of people follow the model highlighted by the monkeys here: when people start off with a small amount of money, they're less likely to take risks with it, rather choosing to increase their money by a defined amount. When people start off with a very large amount of money, they don't want to lose any of it, so they're more likely to take risks with it. They do this even when it is obvious that they might make a massive loss. This is why people are reluctant to sell falling stock or put their houses on the market when prices are dropping. People hate the idea of losing what they have, almost regardless of the implications.

The impulses that lead us are evident in our monkey cousins. This implies that our decision-making skills, and our relationship with risk-taking, was formed many millions of years ago. We have failed to "evolve" out of this particular way of acting and reacting, but this isn't unusual. We also have a great love of fat and sugar, even though over-consumption of these foods lead sto health problems. The one thing that we *do* have is the intellectual capacity to consider situations and make reasoned and considered decisions. Therefore we aren't hostages to our natural instincts.

The research cited in this post was done by Laurie Santos at Yale University. For a 20-minute run-down on her research, be sure to watch her captivating and engaging lecture at http://www.ted.com/talks/laurie_santos.html.

Sustained release drugs

Usually when you eat or drink something, it's digested and absorbed straight away. In the past this was also true for medication. However, a lot of drugs these days are treated or packaged in a way that means the drug is released slowly into the blood stream. This means that you don't have to take the drug as frequently as before. Some of the drugs that work like this include hayfever treatment, pain medication, and anti-depressants. The method is called sustained release.

The simplest way of making a drug sustained-release is by packaging it in some kind of polymer (figure 1). Each grain of medication is coated in a material that dissolves slowly. The granules can be compressed into a tablet, or packed into a capsule. The thickness and type of material determine how slow the drug release will be.




Another way is to mix the drug with an insoluble material (figure 2). The drug gets released as it slowly diffuses out of the insoluble material.











A third method mixes the previous two techniques: the drug is packaged in a material that is partially soluble (figure 3). Parts of the membrane around the drug dissolves, and the drug diffuses out of the coating in this way.















Recently an additional material has been developed, called hydrogel (figure 4). A drug can be packaged in a hydrogel, which will safely transport the drug through the stomach without dissolving. Then, when the hydrogel is in a specific environment (for example, a specific pH), it swells up and the drug can diffuse through pores formed in the coating.










It is important to remember to follow the instructions for taking a specific drug. For example, if you chewed a tablet that was designed to be slow release using technique number 1, as described here, you would destroy its slow-release ability.

The contraceptive implant, Implanon, contains the hormone progestogen. This hormone is released slowly over 3 years. It is imbedded in a polymer called evatane, and the release of the hormone is further controlled by a membrane that ensures a consistent daily dose.