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Medical technology: A silent healer

Akshat RathiLeave a comment

Researchers have developed novel ways to tap the pharmacological potential of an infamous and deadly gas

Carbon monoxide gets a bad rap. The gas, produced by incomplete combustion of hydrocarbons, causes hundreds of deaths every year by poisoning and sends many thousands to hospital. Most of these are the result of leaking cooking and heating equipment, but the colourless, odourless and tasteless substance, known to chemists as CO, has also aided many a suicide. Most horrifically, Nazis used it in gas chambers.

But there is more to the “silent killer”, as CO is sometimes called. It is produced by many cells in the human body, where its molecules play a crucial role in activating enzymes involved in controlling the dilation of blood vessels, and thus blood flow. Mice in which the gene for producing the compound has been knocked out develop faulty organs and die young.

Exploiting this insight, researchers have successfully used CO to treat a number of ailments in lab animals. These include pulmonary hypertension, an otherwise incurable disease in which thickened arteries obstruct the flow of blood, leading to heart failure. The gas can also keep inflammation in check, in particular after organ transplants.

Frederick Montgomery and Duncan Bathe think they have come up with a way to hit the sweet spot. Their Coke-can-sized gizmo, which they devised while working at Ikaria, an American drug firm that both have since left, contains a cartridge of pressurised CO, a tube to deliver the gas to the patient’s nose, and a few buttons to set the required dose. A sensor connected to a nozzle at the end of the tube constantly measures the patient’s breathing rate and adjusts the amount of CO dispensed with each breath. Safety features, including automatic shutdown if anything seems amiss, are meant to eliminate the risk of CO overdose and ensure that none leaks out, endangering others.

Scientists at another American pharmaceutical company, Sangart, meanwhile, have been encasing the gas—or, strictly speaking, CO-ferrying haemoglobin—in a polymer pouch. Kim Vandegriff and her colleagues have been using polymer wrappers a mere nanometre (a billionth of a metre) across. These can be designed to break open only where their payload is needed. Early trials have shown promise in treating sickle-cell anaemia, a disease caused by a faulty haemoglobin gene.

Unlike most drugs, CO is not broken down by the body. Instead, once its job is done, it is transported to the lungs and exhaled. As a result, it produces no side-effects. Given the right dose, then, it can heal silently, too.

First published on economist.com. Also appeared in The Economist. Also available in audio here.

A list of main references is here. Image credit: The Economist

Chemical warfare: Gas-guzzling paint

Akshat RathiLeave a comment

New kinds of paint for military vehicles can detect, absorb and neutralise gases in a chemical-weapon attack

Although there has been no large-scale use of chemical weapons since the Iran-Iraq war in the 1980s, armies need to be prepared for the threat. Part of that preparation means being able to decontaminate people and equipment that have been subject to attack.

The suits and masks worn by soldiers can, if necessary, be thrown away once used, but heavier and more expensive equipment, such as vehicles, cannot be treated in such a cavalier fashion. It needs to be cleaned. At the moment, that is usually done by sloshing it with a solution of hydrogen peroxide. This works, but lugging the stuff around is a nuisance—and so is disposing of it once it has been used. Instead, Britain’s Defence Science and Technology Laboratory, working in collaboration with AkzoNobel, a paints company, proposes to do the job with special paint.

As is often the case with paint jobs, the new anti-chemical-weapon paint needs an undercoat and a top coat. The top coat contains silica gel, an absorbent material that can suck up nerve gas and stop it getting inside a vehicle. This upper layer is available in standard camouflage colours, such as yellow (for deserts) and green (for jungles). The undercoat is made of a polymer that acts like the glue on a Post-it note. It is, in other words, sticky enough to hold the top coat in place, but easily peeled away when that is desirable. If a vehicle gets contaminated its paint can thus be scraped off and dumped by a bunch of squaddies. It can then be repainted without difficulty.

The next stage, currently still in the laboratory, is to develop coatings that change colour when they absorb toxic chemicals, thus alerting soldiers in the area that they are under chemical attack. The details are secret, but a system which responds to mustard gas has been devised, and others are under development. After that, the plan is to modify the coating so that it not only absorbs noxious chemicals, but neutralises them. A group of researchers at the University of Vermont, led by Christopher Landry, have already managed to combine silica gel with a vanadium catalyst to produce a mixture that oxidises mustard gas, rendering it harmless.

In the future, then, military paint will not only hide vehicles from prying eyes, it will also help protect them from one of the most feared forms of attack. The ecstasy of fumbling that follows the cry of “Gas!” may thus become a little less panic-stricken.

First published on economist.com. Also appeared in The Economist. Also available in audio here.

References:

  1. Halabja gas attack in 1988 – BBC
  2. AkzoNobel and DSTL patent
  3. Christopher Landry’s paper – J. Am. Chem. Soc.

Image credit: The Economist

Repairing voices: Good vibrations

Akshat RathiLeave a comment

How to restore people’s voices

Injury, disease or sheer old age mean that as many as 7% of Americans (and, presumably, a similar proportion of the population of other countries) have some kind of voice disorder caused by scarring of their vocal cords. Such scarring makes the cords stiff, and stops them producing sound in the normal way. But that could be overcome if a method were found to restore the cords’ flexibility.

Robert Langer, a pioneering biomedical engineer at the Massachusetts Institute of Technology, and his colleagues think they have one. They have developed a material that mimics the characteristics of natural vocal cords and could thus help restore distorted voices.

To make their new material, Dr Langer and his team took polyethylene glycol, a substance widely used in the cosmetics industry and thus known to be safe, and altered the chemical linkages between its molecules. This allowed them to control the polymer’s viscosity and elasticity. After some trial and error, as they described on August 20th to a meeting of the American Chemical Society held in Philadelphia, they hit on a mixture which matches the traits of human vocal cords. Laboratory tests have shown that when air is blown through a model of the vocal cords made from this material, the model responds in the way that real cords do.

The new polymer gel is not intended to heal scarred tissue, but rather to make the whole tissue flexible enough to restore vibrations to normal. To achieve this Dr Langer proposes to inject the gel under the tissue membrane (a thin layer of cells that covers the vocal cords), forming an additional layer within. Patients with different voices could be treated with gels that had different physical characteristics, in order to produce the desired effect.

There is a limitation. The new gel is prone to degradation and in some cases would need to be topped up regularly. But trials on animals suggest the procedure is safe, and human trials are expected to start soon.

First published in The Economist.

References:

  1. A material to rejuvenate aging and diseased human vocal cords (Press release)
  2. Karajanagi et al, Annals of Otlogy, Rhinology and Laryngology, 2011
  3. InVivo therapeutics

A list of main references here. Image credit: The Economist