by Catherine Shaffer
Because of increases in stem cell research, the market for CO2 incubators has become more interesting—and more discerning. Users are demanding increased performance and sophistication from what used to be a fairly simple warm box. Once upon a time, a rusty, water-jacketed CO2 incubator would suffice for years and years, without the researchers knowing what the conditions were like inside, or what effect those conditions would have on a cell.
Tackling Contamination
In the mid-80s, awareness began to change. NuAire surveyed its customers and learned that their major concerns were contamination and desiccation. “There was a good reason why they said that,” comments Buckner Richerson, vice president of international sales at NuAire, “Because there was a massive contamination problem out there in the industry. Manufacturers at that time were busy trying to figure out what caused it.” Richerson was working at Forma Scientific (now part of Thermo Scientific)
at the time, and their studies determined that horizontal air flow in an incubator was a major contributor to contamination problems, and vertical air flow is far superior in preventing contamination.
NuAire benefited from this information, and in 1986 they launched vertical-flow incubators, leading a new generation of incubators that were more than simple warm boxes, with technology inspired by biosafety cabinets. NuAire incorporated HEPA filtration to create class 100 or class 10 clean air conditions inside their biocabinets, so they decided to duplicate this environment in their incubators. NuAire incubators now include HEPA filtration at four points: the main chamber, the CO2 inlet, the ambient air inlet, and a small filter that keeps the electronics clean. “We've learned the hard way over the years that keeping the electronics clean reduces operational problems. If we just keep it really clean it works a lot longer, things go wrong less often.”
In addition to HEPA filtration, other features added to incubators include germicidal interiors, UV light, and heat sterilization methods. NuAire offers incubators that can be chemically or heat-sterilized, but they have not incorporated UV sterilization technology into their products. This is because it is too hard to determine the necessary dose of UV light to kill all contaminants, and because UV bulbs lose intensity rapidly, beginning with the first day they are used—this adds another level of uncertainty to the dosing of UV light for sterilization.
Binder solves the problem of contamination by using hot air (180°C) sterilization. Their APT.line™ technology and patented Permadry™ system ensure the total absence of condensation. A smooth and seamless interior chamber facilitates cleaning. Says Wolfgang Preter, product manager for Binder, “Our validated and approved hot air sterilization at 180°C [356 ºF] complies with the most important international guidelines to ensure reliable destruction of germs (mycoplasma, RNA/DNA material) that could interfere with your work. Binder incubators offer an easy overnight sterilization cycle that requires no extra work, such as the removal of interior fittings, and without additional maintenance costs for lamps, filters, gas cartridges, or other spare parts.”
New Options in Oxygen Control
Oxygen levels are another area where new features are available. New Brunswick Scientific has added a number of options to their incubators, including three levels of oxygen control. These incubators can accommodate sophisticated and sensitive applications like hypoxic stem cell studies and in vitro fertilization (IVF). “What researchers are finding is that cells behave much differently when they're at in vivo oxygen conditions ... this is uniquely noticeable in things like IVF where if you're able to adjust your O2 control down around 5%, you find that fertilization success rate is much, much higher,” says Ted Andrews, product manager for New Brunswick Scientific.
Another application where oxygen control is important is in tumor biology. As a small tumor rapidly grows, the conditions inside of it also change quickly. The inside of the tumor becomes oxygen-starved and nutrient-starved because the nutrients simply aren't penetrating through the mass. Variable levels of oxygen in the incubator can help researchers study these nuances of tumor growth under different conditions.
Decreasing Desiccation
New Brunswick has also been addressing the problem of desiccation. It takes several days for a cell culture to grow to the point of confluence, and in that time, it is common to have some desiccation of samples in Petri dishes. Finding the right balance of humidity without creating unwanted condensation on the sides of the incubator is a challenge. New Brunswick's active humidification addresses this problem by allowing the user to control the humidity in their incubator. It also offers a rapid humidification feature. The tighter, user-controlled humidification creates a more optimal environment for cell growth.
Precision Temperature Control
Maintaining precise and consistent incubation conditions for microorganisms and cell culture is also crucial. Binder has developed preheating chamber components that deliver a high level of precision. Incubators with gravity, or natural, convection are perfectly suited for the incubation of microorganisms and for microbiological heating and conditioning. These incubators are designed to operate stably over a long term of continuous operation. Incubators with mechanical, or forced, convection are also available and are suited for tasks requiring high specimen volumes and fast temperature recovery times. A powerful air turbine produces the necessary high rate of air flow. In combination with a patented APT.line™ Horizontal Airflow Design, this results in an effective but gentle incubation.
Tetec (Tissue Engineering Technologies) AG is a Tubingen, Germany-based company that uses Binder incubators in the production of their hyaline cartilage transplant material for knee and shoulder joint injuries. Hyaline cartilage protects the joint by cushioning contact between the bones. Implants made of artificial materials have major drawbacks and disadvantages; transplants grown from natural hyaline cartilage are a promising new treatment for these disabling injuries. However, the delicate cartilage cells must be grown under very precise and reliable conditions. The temperature must be controlled to within a tenth of a degree, or the cells may die. Tetec relies on the advanced temperature control system in the Binder line of CO2 incubators to grow their cartilage transplants.
Incubators are used in a wide range of industries and applications, including tissue bioengineering, biotechnology, basic research, clinical research, in vitro fertilization, cosmetic testing, plastic manufacture, food and water testing, microbiology, plant research, and the pharmaceutical industry. Incubator vendors are increasingly offering advanced features originally developed for climate chambers or biosafety cabinets, recognizing that with increasingly sensitive applications there is an increased demand for sophistication in design. New and improved features include technology to prevent contamination and desiccation, and more precise controls over environmental variables like oxygen and temperature. The result is a cleaner, more optimal environment for incubation of biological samples.