Incubator (biology)
An incubator , and incubator , incubator or medical tempering , is a device with which in the biology controlled ambient conditions for various development and growth processes can be created and maintained. It is used to create and maintain a microclimate with closely regulated humidity and temperature conditions.
history
The Dutch physicist, chemist, designer and instrument maker Cornelis Drebbel (1572–1633) is considered to be the inventor of the first modern thermostat , which forms the basis of the incubator. He developed it for alchemical ovens and incubators for hatching chicken eggs. In this case, a fire burned in the incubator under the actual incubator, the hollow walls of which were filled with water. The combustion gases rose on the outside of the walls of the incubator and were able to escape through a smoke vent. To regulate the water temperature, there was a glass temperature sensor in the water-filled bottom of the incubator. A cylindrically shaped part of this elongated glass body was filled with alcohol , a second, U-shaped part with mercury . With the water temperature, the mercury column also moved due to the thermal expansion of the alcohol. With the mercury level on, a floating stick on it was moved. The smoke outlet and thus also the oxygen supply were closed or opened via a lever connected to it, which was used to regulate the fire in the furnace and thus also the temperature.
In the 18th century, it was the French inventor and chicken farmer Jean Simon Bonnemain (~ 1743–1828) who was the first to invent an industrially produced temperature control - again for an incubator that was used in chicken breeding. It is based on the principle that different metals expand differently under the influence of temperature. An iron rod in a lead or zinc pipe acted as a temperature sensor in the water. The lead pipe is closed at the lower end and the iron rod is firmly screwed to this closure. A copper or brass holder is soldered to the upper end of the tube and is connected to the fresh air flap via a lever arm. Since the coefficient of linear expansion of lead is greater than that of iron, the pipe expands more than the iron rod when the temperature rises, the fresh air flap closes and the temperature falls due to the falling oxygen supply.
In the second half of the 19th century, Robert Koch and his institute staff in particular devoted themselves to the development of microbiological methods and techniques. In 1881 he had an incubator built to grow bacteria. A short time later, incubators were already being mass-produced, above all by the Berlin company Lautenschläger. Lautenschläger's "thermoregulator" was based (similar to Drebbel's construction) on the thermal expansion of mercury which was used in a closed system to regulate a gas burner. During this time, incubators were operated exclusively at a constant temperature; temperature control at several temperatures was not yet possible. They were insulated with asbestos or linoleum , a water jacket ensured the transfer of heat into the interior, and gas was used for heating. Double doors, the inner ones made of glass, were already standard. The calibration of the temperature controller, however, was more difficult than today.
With increasing electrification of cities, electrically heated incubators moved into laboratories from the beginning of the 20th century. The control principles remained mechanical for a long time, however, and mercury was often used because its thermal expansion is largely directly proportional to temperature. With the invention of contact thermometers , they were the most common switching measuring probe in temperature control devices well into the 20th century. At first they had fixed contacts and could only switch an electric heater on or off via a relay . In 1926, the Juchheim company from Ilmenau applied for a patent for the first glass contact thermometer, with which variable temperature settings were possible using adjustable metal threads.
From the 1970s onwards, fully electronic controllers, later with the beginning of the digital age, microprocessor-controlled controllers in combination with highly sensitive temperature sensors ensured that temperature control devices today have a precise control behavior. Resistance thermometers with platinum temperature sensors are usually used. Today's devices enable a wide range of temperature control and temperature monitoring. They communicate with other devices or external computers and exchange data with device-specific or higher-level programs. Many devices have internal data loggers in which all measured values and parameters are recorded in a tamper-proof manner over a certain period of time.
Structure and shapes
The incubator has a temperature controller with time control (e.g. constant temperature or temperature gradients by means of heating and / or cooling) and, under certain circumstances, an option for regulating the fresh air supplied. The incubator strictly adheres to the temperature. In order to ensure reproducible test results, temperature constancy and temperature homogeneity are important quality criteria for an incubator even without a fan being operated. Microbiological incubators usually have a temperature range of +5 to +100 ° C. For applications that require temperatures in the range of room temperature and below down to minus degrees, or when the ambient temperature is very high, there are special cooled incubators (e.g. for shelf life tests of food).
The set temperature is adjusted to the optimum temperature of the microorganisms to be incubated. For the gut-dwelling bacterium Escherichia coli , this temperature is 37 ° C. Soil organisms, for example of the genus Pseudomonas , are incubated at 28 ° C. Marine organisms (e.g. Vibrio fischeri ) only need temperatures of 4 to 10 ° C. For agrobacteria , a soil bacterium, on the other hand, a temperature of 21 ° C is optimal.
If the incubator is used for a restriction digest , the temperature depends on the microorganism from which the enzyme was isolated. Since many of the common enzymes are obtained from E. coli , the temperature here is usually 37 ° C.
CO 2 incubators
CO 2 incubators are used to cultivate animal cells and regulate the CO 2 proportion to about 5% (V / V). With in-vitro cultivation, cell and tissue cultures grow in the laboratory in an environment that is as natural as possible, often over several weeks. In a CO 2 incubator, also called a gassing incubator, in addition to temperature, humidity and CO 2 content can also be regulated. With some devices, especially for in vitro fertilization, the oxygen and nitrogen content can also be regulated. Another quality criterion for modern gassing incubators is the possibility of decontaminating or sterilizing the interior including the fittings and sensors. Incubators with special turning devices are used for embryonated hen's eggs .
Incubator closed
Incubator open
CO 2 incubator open
Simple incubator for the small laboratory. It is used to incubate copies and immersion objects.
Incubation shaker
There are also shaking incubators in which the base plate is movable. These incubators are used to prevent the bacteria to be cultivated from forming a mold . With these incubators, the corresponding shaking frequency can be set using the control element.
Compared to a normal incubator, the sample is constantly mixed with an incubation shaker. This promotes cell growth, which may result in shorter test times. The mixing also allows a simulation of processes in the human organism. Depending on the application, test runs of several weeks are required, which is why some incubation shakers are approved for unsupervised operation.
Incubation shakers come in a variety of sizes, from small tabletop models to large floor-standing models. The size of the device depends on the amount of sample to be processed.
Temperature settings are usually possible from −10 ° C to +80 ° C. Highly precise temperature control is essential for medical and biological applications in order to achieve optimal cell growth. That is why several temperature sensors are usually installed under the hood in order to keep the temperature constant with the help of electronic control.
Samples are usually stored in common laboratory glassware, e.g. B. Erlenmeyer flasks or Petri dishes and fixed on the shaking table with clamps or holders.
Incubation shaker with attachment and glassware
Shaking incubator front view
Shaking incubator inside view
Individual evidence
- ↑ a b c d e f g Rüdiger Kramme: Medical technology - procedures - systems - information processing . Springer-Verlag, 2016, ISBN 978-3-662-48771-6 , pp. 733 ( limited preview in Google Book search).
- ↑ John M. Davis: Animal Cell Culture. John Wiley & Sons, 2011, ISBN 978-0-470-97563-3 .
- ↑ vwr.com: Shaking Incubators | VWR , accessed May 18, 2017.