A fairy tale for modern medicine

Stephen Harrison highlights the “Cinderella” gases that have a range of applications in medicine and drug discovery but often go unnoticed...

At the mention of medical gases, the first products which usually come to mind are the oxygen used for breathing therapy and the nitrous oxide (laughing gas) used for conscious sedation. Granted, these gases are vital and are used extensively in the healthcare arena. However there is an essential group of “Cinderella” specialty medical gases which are less recognised, but no less critical. These gases are supplied less frequently and in smaller quantities, but are just as vital to patient welfare. The tale of these specialty gases reveals that they are actually used every single day at hospitals, medical laboratories and other associated organisations servicing the medical/healthcare industry. Just like Cinderella in the famous children’s story, this group of gases is small, beautiful and largely unnoticed. However, they are actually at the heart of specialty medical gas supply.

One application of the Cinderella speciality gases is in test gas mixtures. Test gas mixtures are not used in a directly therapeutic way, but aid in understanding the status of patient health. The criteria used in their manufacture also differ from that of therapeutically used medical gases. The same extremely rigorous quality standards apply, but once produced, the content of specialty gases have to be accurately measured to ensure that all components are present and remain at precisely the right levels.

Within this group are the gases used to test or calibrate some of the principal instruments used in hospitals today. The efficient calibration of medical equipment, used either directly or indirectly in the treatment of patients, is imperative. The technology required to produce these specialised and often mixed calibration gases — whether to 100 or 1,000 parts per million— is extremely sophisticated. Maintaining the mixtures at the required levels is just as important. For example, nitrous oxide is a reactive gas with the potential to decay rapidly.

For instance, among the most common tests carried out on patients are lung function tests which harness sophisticated diagnostic instrumentation and mixes of the Cinderella specialty medical gases, containing low levels of carbon monoxide to measure how well the lungs take in air and how well they transport gases such as oxygen from the atmosphere into the body's circulation. The amount of carbon monoxide in the exhaled air is measured and indicates the lung functionality. Since patients’ health status often depends on the accuracy of these readings, highly specialised gas mixes are used to calibrate the equipment on a regular basis. The lung diffusion gases are often dispensed on prescription whether used for inhalation or for calibration of the analytical instrument, since the same gas cylinder is used for both purposes.

Specialty gases and mixtures are also essential for the proper functioning of incubators. These important medical chambers create controlled environmental conditions with elements such as temperature, humidity and oxygen concentration, for the care of vulnerable infants. Incubators are also used to maintain the integrity of body parts and tissue destined for transplants and for growing certain cultures to create an aerobic or anaerobic cell growth environment. This is particularly important when identifying the presence of Methicillin-resistant Staphylococcus aureus (MRSA), the bacterium responsible for several difficult-to-treat infections in humans.

It is very important to have a controlled atmosphere that supports the intended process. When growing aerobe organisms, the ambient atmosphere is based on oxygen or air, and when anaerobe organisms are cultivated the atmospheres are based on nitrogen or carbon dioxide. Both types usually have a carbon source for maximizing the growth. A different type of growth control occurs when sterilizing mixtures are used for the opposite purpose — to get rid of all organisms.

In vitro fertilization eggs and embryos are also stored in IVF incubators. These incubators must have very clean and constant environment. The IVF mixtures are typically either 5% carbon dioxide in air or 5% carbon dioxide, 5% oxygen in nitrogen. As well as contributing to patient wellbeing, incubators are also used to grow many of the plants that are harnessed to grow and synthesize the chemicals used in pharmaceutical preparations. Here temperature, humidity and gas mixtures are also outcome-critical.

 Pure gases, as opposed to gas mixtures, play a significant role in the healthcare and pharmaceutical industries. Within the arena of medical gases and their applications, the diagnostic work conducted using these gases for preventive and diagnostic medicine is an important category.

On-site clinical laboratories or stand-alone contract laboratories contracted to conduct analysis for the hospital are required to carry out sophisticated tests on patient blood and urine samples. These tests could use plate microbiology requiring anaerobic or aerobic gas mixtures for cultivation. Also high-tech instrumentation such as liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC) are often used for diagnostic testing.

LC-MS is a powerful analytical technique used in industries requiring very low detection limits of sometimes unknown samples. The efficient physical separation of chemical substances dissolved in a mobile phase, performed by liquid chromatography, is combined with the mass spectrometer’s ability to sort and identify the components (gaseous ions) in electric and magnetic fields according to their mass-to-charge ratios. The samples analysed by LC-MS are often complex mixtures. LC-MS requires high purity nitrogen to remove the solvent from the sample before introducing in the mass spectrometer. Pure Helium could also be necessary for degassing in the liquid chromatography

HPLC is a form of column chromatography that pumps a sample mixture or analyte in a solvent (known as the mobile phase) at high pressure through a column with chromatographic packing material (stationary phase). HPLC has the ability to separate and identify compounds that are present in any sample that can be dissolved in a liquid in trace concentrations as low as parts per trillion. This equipment also needs high purity gases such as nitrogen or helium to operate accurately.

Another application for the Cinderella gases is in drug discovery. The departure point for drug discovery is identifying a useful new drug candidate molecule from among millions of different molecules. Modern techniques are able to screen candidate molecules down from thousands to just one candidate, in a time span as short as eight weeks.

Identifying and understanding the target receptor and lead compound, or drug candidate, as a means to assault a particular disease, is highly complex and intricate. Researchers need sensitive, fast and stable analytical equipment. “Both the pharmaceutical and biotech industries are heavily dependent on gases and chemicals, from high-purity gases for laboratory use, to process gases for production processes such as chemical synthesis, sterilisation gases and gas mixtures to grow biological cultures,” said Katrin Åkerlindh, Global Product Manager for Specialty Gases & Specialty Equipment at Linde Gas.

Research and development take place in pharmaceutical laboratories using analytical instruments including gas chromatographs with multiple detectors, liquid chromatographs coupled with mass spectrometers (LC-MS), ultraviolet/visible (UV/VIS) spectrometers and nuclear magnetic resonance (NMR) spectrometers. These significantly accelerate research and development cycles, ultimately bringing beneficial drugs onto the market faster than ever before. The effective operation of these instruments depends on the use of the appropriate gases or gas mixtures.

As in healthcare diagnostics, one of the key items of analytical equipment harnessed to test new pharmaceutical chemical compounds is liquid chromatography-mass spectrometry (LC-MS). LC-MS defines and detects the structure of the molecular compound firstly by separating the compounds in the liquid phase chromatograph and then by detecting them in the mass spectrometer. Specialty gases grades of nitrogen are used in LC-MS as a curtain gas. LC-MS units equipped with electrospray ionisation use nitrogen for nebulising, drying and also as a curtain gas.

NMR spectroscopy also has a key role to play in determining chemical structure.  It is able to generate a 3D image or visualisation of the compounds in solution, which allows the structure of molecules to be defined right down to atomic level. This allows researchers to develop a good understanding of the molecule and its function in the human body.

NMR spectroscopy involves placing a sample in a strong homogeneous magnetic field and irradiating it with radio waves of defined frequency. The emitted signals provide information about the local molecular environments of nuclei in the sample, from which structures can be derived. NMR can also be used for determining interactions between molecules and is particularly useful for determining the nature of binding interactions between ligands and macromolecules.

“This information is very important in drug design,” said Åkerlindh. “By understanding how bioactive molecules interact with a target protein or nucleic acid it is, in principle, possible to design ligands with improved affinity and specificity that may make useful drug leads. In addition to this structure-based approach to drug design, NMR is also useful as a screening tool in drug discovery programs to identify ligands that bind to target macromolecules.”

With the immense cost associated with bringing a new pharmaceutical drug to market and the speed at which companies are today required to do this, finding the correct molecular candidate and then being able to trust in the validity of the result is absolutely essential. The purity level of the specialty gases involved in this process, as well as the integrity of gas from the product source to point of use, is therefore critical.

Amid the many breakthroughs and improvements constantly taking place in the drug arena, a fundamental problem has arisen with the potential to affect people all over the world. This is the issue of counterfeit drug production and a prime example is malaria medication. While there are a number of very effective and authentic malaria drugs on the world market, counterfeiting exists in some areas of Asia and Africa. This makes it critical for authorities to test the pharmaceuticals on sale in their markets, randomly and periodically, to ensure they are not potentially harmful counterfeits. Since some of these antimalarial drugs are relatively simple compounds or molecules, simple chemical analysis techniques, based on wet chemistry, can be used to check for the existence of the drugs commonly used to prevent and treat malaria. This illustrates how analytical techniques are also critical to identifying and avoiding malpractice in the manufacture, sales and distribution of drugs, and how a mix of traditional chemistry or modern instrumentation can be appropriate, according to the situation.

Modern drug discovery could not take place without today’s advanced analytical instruments and these instruments could not operate effectively and reliably without high purity specialty gases.