Animal Cell Culture and Bioreactors: A Comprehensive Guide
Safety Measures in DNA Technology
Scientists have established safety guidelines for DNA technology. One key measure involves using genetically modified microorganisms that cannot survive outside the laboratory environment.
Dolly the Sheep and Cloning
In 1997, Dolly the sheep became the first cloned mammal. The process involved fusing an adult cell’s nucleus with an enucleated sheep egg and incubating it in a surrogate.
Airlift Bioreactors
Airlift bioreactors offer several advantages, including low shear rates, efficient mixing, high oxygenation capacity, and effective mass and heat transfer. They do not rely on impeller systems for mixing.
Hayflick’s Phenomenon
Hayflick’s Phenomenon describes the limited number of times cells can divide and grow normally before entering senescence.
Ethical Considerations of Cloning
Reproductive cloning of human embryos raises ethical concerns. However, therapeutic cloning, which aims to produce embryonic stem cells for medical purposes, has garnered more diverse opinions due to its potential benefits.
Parameters for Animal Cell Culture Growth
Maintaining optimal conditions in animal cell bioreactors is crucial. Key parameters include temperature (around 37°C), pH (around 7.4), and oxygen levels. Mammalian cells have lower growth rates and oxygen requirements compared to microorganisms.
Transfection
Transfection is the process of introducing foreign genes into cells.
Transgenic Animals
Producing transgenic animals involves transfecting eggs or embryos.
DNA Microinjection
DNA microinjection into fertilized eggs typically occurs before the fusion of male and female nuclei.
Established Cell Lines (ECLs)
ECLs exhibit characteristics such as short doubling times, aneuploidy, high-density growth, and minimal spatial orientation.
Shear Forces and Animal Cells
Shear forces can damage animal cells in bioreactors. The sensitivity to shear varies depending on the cell line, age, and growth phase. Cells are generally more fragile during stationary and lag phases.
Tailoring Agitation for Animal Cell Cultures
Optimizing agitation for animal cell cultures involves considerations such as stirring rates, microcarrier usage, vessel shape (flat-bottomed for animal cells), and impeller type (axial flow preferred over radial flow).
Properties of Embryonic Stem Cells
Embryonic stem cells are unspecialized cells with the potential for specialization and differentiation. They exhibit totipotency and robust repopulation capabilities but have a limited capacity for self-renewal.
RNA Interference
RNA interference utilizes double-stranded RNA sequences, typically around 20-28 nucleotides long, to trigger the breakdown or blocking of mRNA.
Challenges of Culturing Eukaryotic Cells
Eukaryotic cells are more challenging to culture than prokaryotes due to their complex media requirements, susceptibility to damage and contamination, slower growth rates, and lower oxygen demands.
Factors Influencing Transfection Efficiency
Several factors impact transfection efficiency, including cell health, DNA quality and quantity, and contamination. The type of media used does not significantly influence transfection efficiency.
Lipofectamine
Lipofectamine is a transfection reagent that forms lipid-DNA complexes, facilitating gene delivery into cells. It exhibits high transfection efficiency, does not induce immunological reactions, and can be used on living tissue.
RNAi Applications
RNAi technology holds promise for various applications, such as reducing the production of harmful proteins from mutated genes.
Microcarriers
Microcarriers are small beads used to provide a surface for anchorage-dependent cells to attach and grow. They increase cell density and product yield while minimizing damage from agitation. However, they do not decrease the surface area available for cell growth.
Methotrexate and Drug Resistance
Methotrexate is an antifolate cancer drug that inhibits dihydrofolate reductase, leading to toxicity by depleting cofactors needed for purine and thymidylate synthesis. Drug resistance can develop through mechanisms such as decreased drug uptake, gene amplification, mutations, and reduced polyglutamate formation.
Small RNAs as Regulators
Small RNAs play crucial roles in regulating various biological processes, including viral infection, cancer, brain development, apoptosis, and fat metabolism.