Autoclaving Alternatives for Effective Sterilisation
Jan 29 2016
Author: Marcus Cannon on behalf of Banc Media
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Since Charles Chamberland invented the first autoclave pressure chamber in 1879, the technology has been an almost omnipresent tool to perform sterilisation tasks. Utilised heavily in microbiology, medicine, podiatry, tattooing, body piercing, veterinary science, mycology, dentistry and prosthetics fabrication; autoclaving uses elevated temperatures and pressures to sterilise equipment, chemicals and apparatus.
However, not all laboratories have access to an autoclave to complete such sterilisation tasks. The large costs and physical footprint mean they are often out of the grasp of smaller labs and research teams - though their need for effective sterilisation remains. However, there are a number of alternative sterilisation methods which are equally effective as an autoclave pressure chamber.
Additionally, an autoclave is not immune to malfunction or periods of inactivity, so it is always worthwhile understanding alternative forms of sterilisation which can be used to ensure that research does not slow or discontinue.
Glassware – Dry Heat
Dry heating sterilisation is one of the world’s earliest recognised forms of practiced sterilisation. Utilising hot air, which is free of water vapour (or contains only very small traces), this method accomplishes sterilisation via conduction.
The dry heat destroys microorganisms by causing coagulation of the proteins. All moisture should be removed from the instruments before they are exposed to dry heating methods.
This method is most commonly used on glassware beakers and flasks, which can be sterilised by applying dry heat in an oven. The openings of the flasks and beakers must be comprehensively covered with foil, whilst glass pipettes must be held within a foil pouch. It is important to remove any rubber or cotton lids, tops or plugs prior to covering them with foil.
The glassware within the foil should be placed on a metal tray, then placed in an oven heated to 350°F. After 2-3 hours the tray should be removed from the oven and left to cool. It is important to ensure that pipettes are glass, and not clear plastic.
Dry heating remains an important sterilisation option due to the some items being immune to the effects of an autoclave, making this method a useful backup for all labs and research facilities.
Ozilla Ozone Steriliser
The new kid on the sterilising block, Ozilla Ozone uses ozone gas to purify and sterilise a wide range of materials and pieces of equipment. Eliminating 100% of pathogenic organisms from plastics, glassware and even sensitive electronics; the Ozilla Ozone is capable of completely destroying all airborne and surface contaminants in the affected area.
As an additional benefit, this new technology is capable of leaving the room in which is it used smelling fresh, clean and ready for the next use. Using a special ‘scrubbing’ technique, the Ozilla Ozone Steriliser ensures that all ozone gas is turned back into oxygen.
Leaving no chemical residue, the Ozilla Ozone steriliser is well-suited to the demands of labs which frequently require their instruments to be sterilised. Furthermore, the technology is incredibly safe, not using any liquids, harmful UV rays, harsh chemicals or heat.
Killing 99.7% of 650 different kinds of pathogenic organisms within an hour and a half, the Ozilla Ozone has become a quick and effective tool for sterilisation. The ozone gas is capable of penetrating tiny cavities and crevices, ensuring that contaminants cannot hide from its sterilising power.
Perhaps only practical for one-off experiments, rather than long-term AB testing or extensive research projects; some pieces of equipment and apparatus can be found in disposable form. These disposables can be simply chucked away after every use – reducing the need for sterilisation. Many of these pieces of apparatus will have been sterilised with Ethylene Oxide gas, before being packed into individual blister packs.
This method can have an effect upon the setup of the lab. Whilst it may save the space which would otherwise be designated for an autoclave or other large piece of machinery, it may be necessary to dedicate an area to the continuous supply of disposables. Furthermore, another knock-on effect of using disposable pieces of equipment is the demand to invest in replacements when they are required.
Lab furnishing specialists, InterFocus, offer this advice: “It is vital that any sterilised media brought into the laboratory is kept away from any potential contaminants, ensuring that its sterility is never compromised.”
When completed carefully, chemical baths can be a hugely effective sterilisation method - however this process requires a fair amount of patience and consideration. Amongst the main mistakes which people commit when attempting to sterilise equipment using a chemical bath are failure to complete a comprehensive pre-clean, late administration and premature completion.
It is vital to ensure that any tools used for the pre-clean have been properly sterilised – otherwise it will render the entire operation redundant. Putting the cleaning tools through an ultrasonic cleaner cycle with products such as Alconox can ensure they’re clean and contaminant free.
Only when all the instruments are completely clean is it safe to place them in a glutaraldehyde-based chemical bath. It is vital that no instruments or pieces of equipment are added to the chemical bath midway through the cycle, and no pieces are removed before an appropriate amount of time has passed.
Although considered by many to be a slightly archaic form of sterilisation, some practitioners and professionals continue to sterilise their tools and instruments in liquid antiseptic. Sharp or delicate instruments, certain types of catheters and tubes can be sterilised when exposed to formaldehyde, glutaraldehyde or chlorhexidine.
When exposing instruments to formaldehyde, it is important that they are all carefully cleaned beforehand and then exposed to vapours from paraformaldehyde tablets in a closed container for 48 hours.
The supposed risks of formaldehyde are widely known, with a significant number of studies conducted measuring the relationship between long-term exposure to the chemical and the onset of cancer. This has led to workplaces being forced to restrict the long term exposure to formaldehyde.
The short term effects are significantly less dangerous with some individuals suffering from watery eyes and burning sensations in the eyes, nose and throat when the chemical is present in the air at levels exceeding 0.1 part per million. In fact, a 1997 report by the U.S Consumer Product Safety Commission revealed that formaldehyde is present in both indoor and outdoor air at low levels.
Glutaraldehyde is particularly effective against bacteria, fungi and a large selection of different viruses.
Developed partway through the 19th century by English physicist, John Tyndall, the eponymous Tyndallisation was a commonly used technique by the microbiologists of the 1800s. Tyndall experimented with boiling beef broths to develop a method to sterilise liquids in a safe and comprehensive manner.
His research led him to the basic principles for Tyndallisation, a process by which medias are subjected to relatively short boils at a regular atmospheric pressure. This relatively straightforward method is still suitable for small labs, or research facilities which only require sterilised equipment part of the time.
It is not recommended to attempt to sterilise closed glass containers using this method, without lining them with cotton and capping them with foil – allowing for air to escape without being subjected to contaminants.
The process involves boiling fluids for 10-15 minutes before leaving to cool to room temperature and leaving it to sit for 24 hours. Repeat this process another three or four times, by which time sterilisation should have occurred.
Naturally this method has reduced in popularity due to the requirement to continue the process for up to five days to achieve sterilisation.
Carbon infra-red emitters have been found to help sterilise products through controlled heating. Initially tested on food products, in particular bread at bakeries, the technology is capable of penetrating porous materials and multi-layered germ beds.
Infra-red radiation has long been mooted as a sterilisation alternative for heat resistant instruments which have caused headaches for research teams looking to remove contaminants.
The majority of infra-red sterilising tools are developed on a relatively modest scale, capable of completing ‘on-the-bench’ sterilisation jobs. The BactiZapper instrument is aesthetically closer to a lamp than an autoclave machine, but is capable of sterilising tools and instruments in a matter of seconds.
When used in a laboratory situation, infra-red is suitable for the instant sterilisation of needles, pipettes and various metals and borosilicate glass instruments.
If a lack of space is the reason you or your research team are reluctant to invest in a full size autoclave machine, there are miniature versions of the technology which can help complete the same tasks but on a small scale.
Costing just a few thousand pounds, and requiring minimal space, the miniature autoclaves are well-suited to small and more modest surroundings. BioClave manufacture a number of these machines which are marketed as being convenient and affordable. With widths as small as 14”, these machines are quite mobile and can be stored upon your desktop, assuming minimal space in the lab.
Suited to the sterilization of a wide range of liquids, instruments and medias; the miniature autoclaves offer a comprehensive service which supports a selection of scientific disciplines.
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