Pharmaceutical biotechnology
summary
Animal cell biotechnology
Introduction
In a tissue and organ culture, cells keep their differentiated state and special functions. In the case of
more complex tissues and organs, also a balanced relationship between different cell types is
attained.
Cell culture: cells grow as individual units like bacteria and fungi. They may grow in suspension or on
solid surfaces. Usually, they have lost their original function and are dedifferentiated. When are cell
cultures used?
To investigate the physiology and biochemistry of cells.
To study the effect of compounds on the physiology of cells.
For production of artificial tissue.
For the production of high value products, like therapeutic proteins and vaccines.
One of the main advantages of using a cell culture is its consistency and reproducibility, and it is
ethically more correct. A disadvantage is that after a period of growth, conditions may change due to
selection. It is furthermore complex to stimulate the interactions of many different cell types.
Compared to animal cells, the use of genetically modified bacteria, fungi, and yeast offers some
advantages:
Bacteria and yeast can grow to higher biomass densities and they have a higher productivity.
The nutritional requirements of bacteria and yeast are far less complex meaning they can
grow on simple media that are much cheaper.
They have higher growth rates reducing the time needed to perform a large-scale production.
They are less sensitive to shear forces making scale-up easier.
With production in bacteria and fungi it is much easier to make the production process safe
with respect to transfer of diseases.
The main disadvantage is that bacteria, fungi, and yeast cannot perform posttranslational
modifications on proteins. Animal cells can do this, and animal cells excrete the product in the
medium, thereby making downstream processing easier and cheaper. Some bacteria and fungi also
excrete the product into the medium.
, Animal cells derive their nutrients from plants or other animals
and have limited ability to synthesize these building blocks
themselves. This is also why animal cell media are very
complex. Growth and death must be precisely regulated to
maintain a constant size of tissues and organs. Animal cells are
furthermore quite fragile. To prevent cell death due to shear,
caused by aeration and mixing, often shear protective
compounds are added to the medium.
Mammalian cells grow best at a temperature of 37°C, a pH
between 7 and 7.4 and a dissolved oxygen concentration
between 20-80% air saturation (50% is commonly used). The
pH of the culture is maintained by using a bicarbonate buffer.
For insect cells, the conditions are different. They grow at a temperature of 27-28°C and have a much
wider pH range of 6-7. The dissolved oxygen tension usually is between 20 and 80% (30% is
commonly used). The pH in insect cell media is usually controlled by a phosphate buffer.
Figure: a typical growth curve for animal cells in batch compared to E.coli. At the start, cells have to
be inoculated at a minimum cell density, whereas an E.coli culture can be started with one cell.
Animal cells produce certain growth factors required for their own growth. Below a critical density,
not enough of these factors are made and the cells will not grow. After inoculation, there is a lag
phase in which the cells adapt to their new environment. Next, they start growing exponentially until
either the nutrients are exhausted or toxic products become inhibitory. After the exponential phase,
cells enter the stationary phase. Continuous cell lines cannot stay long in this phase and within one or
two days the cells die in the decline phase. To prevent cell death, cells should be diluted into fresh
medium at the end of the exponential phase.
Animal cells are primarily used to produce four types of products:
Viral vaccines
Blood chemistry compounds
Hormones and endocrines
Monoclonal antibodies
Animal cells can also be used for tissue engineering, which is the in vitro generation of new tissue.
In general, glycosylation is the most important posttranslational modification, which is the addition of
branched carbohydrate structures. Glycosylation affects activity, stability, immunogenicity, and in vivo
half-life.
Drug: an article that is intended for use in diagnosing, curing, mitigating, treating or preventing
diseases. A drug can also be intended to affect the structure of any function in the body.
Clinical trials consists of three phases. Before, the drug has to be tested on animals, showing
reasonable safety.
Phase 1: the side effects and pharmacological
actions are established, using 20-50 healthy
humans
Phase 2: to evaluate the effectiveness of the
product, using a small group of patients
summary
Animal cell biotechnology
Introduction
In a tissue and organ culture, cells keep their differentiated state and special functions. In the case of
more complex tissues and organs, also a balanced relationship between different cell types is
attained.
Cell culture: cells grow as individual units like bacteria and fungi. They may grow in suspension or on
solid surfaces. Usually, they have lost their original function and are dedifferentiated. When are cell
cultures used?
To investigate the physiology and biochemistry of cells.
To study the effect of compounds on the physiology of cells.
For production of artificial tissue.
For the production of high value products, like therapeutic proteins and vaccines.
One of the main advantages of using a cell culture is its consistency and reproducibility, and it is
ethically more correct. A disadvantage is that after a period of growth, conditions may change due to
selection. It is furthermore complex to stimulate the interactions of many different cell types.
Compared to animal cells, the use of genetically modified bacteria, fungi, and yeast offers some
advantages:
Bacteria and yeast can grow to higher biomass densities and they have a higher productivity.
The nutritional requirements of bacteria and yeast are far less complex meaning they can
grow on simple media that are much cheaper.
They have higher growth rates reducing the time needed to perform a large-scale production.
They are less sensitive to shear forces making scale-up easier.
With production in bacteria and fungi it is much easier to make the production process safe
with respect to transfer of diseases.
The main disadvantage is that bacteria, fungi, and yeast cannot perform posttranslational
modifications on proteins. Animal cells can do this, and animal cells excrete the product in the
medium, thereby making downstream processing easier and cheaper. Some bacteria and fungi also
excrete the product into the medium.
, Animal cells derive their nutrients from plants or other animals
and have limited ability to synthesize these building blocks
themselves. This is also why animal cell media are very
complex. Growth and death must be precisely regulated to
maintain a constant size of tissues and organs. Animal cells are
furthermore quite fragile. To prevent cell death due to shear,
caused by aeration and mixing, often shear protective
compounds are added to the medium.
Mammalian cells grow best at a temperature of 37°C, a pH
between 7 and 7.4 and a dissolved oxygen concentration
between 20-80% air saturation (50% is commonly used). The
pH of the culture is maintained by using a bicarbonate buffer.
For insect cells, the conditions are different. They grow at a temperature of 27-28°C and have a much
wider pH range of 6-7. The dissolved oxygen tension usually is between 20 and 80% (30% is
commonly used). The pH in insect cell media is usually controlled by a phosphate buffer.
Figure: a typical growth curve for animal cells in batch compared to E.coli. At the start, cells have to
be inoculated at a minimum cell density, whereas an E.coli culture can be started with one cell.
Animal cells produce certain growth factors required for their own growth. Below a critical density,
not enough of these factors are made and the cells will not grow. After inoculation, there is a lag
phase in which the cells adapt to their new environment. Next, they start growing exponentially until
either the nutrients are exhausted or toxic products become inhibitory. After the exponential phase,
cells enter the stationary phase. Continuous cell lines cannot stay long in this phase and within one or
two days the cells die in the decline phase. To prevent cell death, cells should be diluted into fresh
medium at the end of the exponential phase.
Animal cells are primarily used to produce four types of products:
Viral vaccines
Blood chemistry compounds
Hormones and endocrines
Monoclonal antibodies
Animal cells can also be used for tissue engineering, which is the in vitro generation of new tissue.
In general, glycosylation is the most important posttranslational modification, which is the addition of
branched carbohydrate structures. Glycosylation affects activity, stability, immunogenicity, and in vivo
half-life.
Drug: an article that is intended for use in diagnosing, curing, mitigating, treating or preventing
diseases. A drug can also be intended to affect the structure of any function in the body.
Clinical trials consists of three phases. Before, the drug has to be tested on animals, showing
reasonable safety.
Phase 1: the side effects and pharmacological
actions are established, using 20-50 healthy
humans
Phase 2: to evaluate the effectiveness of the
product, using a small group of patients
