The term "bioreactor" is often used or heard in both research and industrial fields, but:
What is a bioreactor in the first place?
(and) how does it relate to your field of study?
I will attempt to answer these questions in the following article and explain what a bioreactor actually is.
Table of contents
What is a bioreactor?
Types of bioreactors
Bioreactors in the field of regenerative medicine
Intravascular perfusion and external liquid perfusion
What is a bioreactor?
Bioreactors can be described in just a few words.
In the first instance, a bioreactor is a ‘bioreaction tank’. So, the simplest definition is: a bioreactor is a biological reaction tank.
There is also a chemical reactor in bioreactors, which is used for conducting experiments on an industrial scale, such as those listed in high school chemistry textbooks.
In terms of the image (above), as you can see a bioreactor is also a system that continuously supplies experiments in which reagents are placed in a test tube (with pipettes), before a reaction is efficiently induced through pumps, and the like. For example, bioreactors are used, in this way, in the production of sodium chloride and the synthesis of other chemicals.
Bioreactors have developed as reactors, so now they can make organisms do it.
In the field of fermentation, the production of sake is an example of a bioreactor that many laypeople are familiar with. The process of making sake (using rice, koji mold, and yeast) is truly a prime example of a bioreactor. (If you think that the production of alcohol has been done for thousands of years, the idea of reactors may be a first for bioreactors?)
It can be said that bioreactors have the function of making living organisms work, in order to produce (large quantities) of useful substances. Whether or not the alcohol produced in sake is useful is entirely subjective, of course, but you get my point!
Bioreactors in regenerative medicine
In the given context, bioreactors most likely have a history in the fields of fermentation and microorganisms. However, in more recent years, with the development of regenerative medicine, they have also been used as a method for the mass culturing of mammalian cells.
Bioreactors for efficient mass culturing of cells, used both for research or transplantation purposes, are being sold and are being used by many of the manufacturers themselves.
Among the fields where they are seeing the biggest growth in usage, regenerative medicine research has developed dramatically in recent years. The field of tissue engineering has also been developing further and usage in this area is expected to continue to grow.
One of the purposes of tissue engineering is to collect cells and create tissues and organs: a large number of cells are required for such a purpose.
In the bioreactors required by the tissue engineering industry, their main purpose is the growth of tissues and organs. Bioreactors specifically designed for that purpose are therefore required.
Types of bioreactors in the field of regenerative medicine
Bioreactors in the field of regenerative medicine are mainly:
Those that culture cells in large quantities
(or) those that are specifically intended to grow tissues and organs
They are, therefore, divided into two distinct categories...
In a review paper on bioreactors in the field of tissue engineering, it is noted that:
“Bioreactors are generally defined as devices in which biological and/or biochemical processes develop under closely monitored and tightly controlled environmental and operating conditions (e.g. pH, temperature, pressure, nutrient supply and waste removal).” (Martin I. et al. Trends Biotechnol, 22(2) 10, 2004).
It seems that it is necessary to build tissues and organs, while controlling the process with precision and monitoring the physical growth.
Intravascular and external perfusion
There are two main types of bioreactors that are capable of producing tissues and organs: the ‘external liquid perfusion’ type and the ‘intravascular perfusion’ type.
The external fluid perfusion type is mainly suitable for perfusion of tissues with less vascular density (such as bone and cartilage, etc.).
On the other hand, we believe that it is essential to provide nutrition through blood vessels, in so-called organs with high blood vessel density.
There is a connection to the thickness and diffusion of the tissue, but I think that it is more efficient to supply nutrition using the capillaries stretched inside, rather than supplying nutrition from the outside.
It is my belief that "delivering nutrition through blood vessels" can be a method of imitating living organisms, in the same way as they are nutritionally supplied in their natural environment.
However, effectively delivering nutrition through blood vessels is a much more difficult process than when using external liquid perfusion methods, as you would have to do things like inserting (cannulating) tubes into blood vessels, fixing soft organs, and making the control fluid flow the same way as the subject’s blood is naturally flowing.
ALL-IN-ONE bioreactors, are optimized for research on organ production and cultures with Ex-vivo, and can be cultured by supplying nutrients through blood vessels. From the perspective of biomimetics, it is also possible to apply pressure on perfusion organs and tissues.
In addition to regenerative medicine, they can also be used for experiments to analyze organs (in isolation) that are extracted from animals using Ex-vivo. Since the organ culture system is developed from the viewpoint of bioreactors that can be analyzed with cultures for 10 hours to several days, an experimental system that adds the keyword "culture" to physiological experiments can be constructed.
To summarize the above:
Bioreactors are "biological" and "reaction tanks"
First used in the field of fermentation, their development in the field of regenerative medicine is something quite remarkable.
Bioreactors in the field of regenerative medicine are of the external perfusion type and the intravascular perfusion type
The organ culture system of the research bioreactor is a bioreactor that is specialized in intravascular perfusion.
I hope the above is a good explanation of bioreactors (at least an introductory one), and that this was a meaningful read for those who are interested in bioreactors and those who are planning to conduct experiments using them in the future.
Thank you for reading to the end.
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