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Basics of Cell Culture. Part 1: Basic Growth Requirements. Overview. Growing bacterial cells Growing mammalian cells Things in common Unique things. Using Cultured Cells. Cells can be grown as individuals Bacteria and yeast Animal cells Plant cells. Cell Growth Profile.
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Basics of Cell Culture Part 1: Basic Growth Requirements
Overview • Growing bacterial cells • Growing mammalian cells • Things in common • Unique things
Using Cultured Cells • Cells can be grown as individuals • Bacteria and yeast • Animal cells • Plant cells
Primary vs. Secondary Metabolites • Growing cells focus on “primary metabolites” • Required for living and making macromolecules • Only kind in eukaryotic • Cells after log growth phase make secondary metabolites • Often useful to us • Micro-organisms mainly
Cell Culture Requirements • For all cells • Nutrients • Dissolved oxygen • Waste removal (or dilution) • Appropriate pH and temperature • For some cells • Surface for attachment • Growth stimulating signals
Nutritional Requirements • Basics are common to all cells • Energy source (carbon) • Nitrogen source • Salts (Na+, K+, Ca++) • Details vary with specific cells • Bacteria more self-sufficient • Mammalian cells more sensitive, helpless
Carbon source Molasses Malted grain Cellulose Plant oils and fats Wood pulp waste Nitrogen source Corn steep liquor Yeast extracts Peptones Soybean meal Bacterial Media
Other Ingredients • Water • Trace minerals • Inhibitors (if needed) • Dissolved oxygen • Antifoam agents
Oxygen • Must be dissolved, but water has low capacity • Continually supplied from above • Continually supplied from below
Growth Conditions • Proper temperature • Proper pH • Low levels of waste metabolites • Growth conditions are maintained by a fermentor
pH • Cell growth affected by pH • Biphasic curve (rate vs. pH) • Low at low and high • Best in middle • pH is altered by cell growth • Metabolic wastes include acids, ammonia • Control by buffering, medium replacement or adding alkaline or acid
Temperature • Cell growth affected by temperature • Biphasic curve (rate vs. temperature) • Low at low and high temperature • Best in middle (range defined by cell type) • Cell growth produces heat • Regulate temperature of environment • Incubator • Cooling/warming coil • Water jacket
Jacketed Tank (concept) • Resembles a thermos bottle • Container surrounded by hollow space • Difference: inlet and outlet for heat exchange solution
Other Tank Types • Rely on air for mixing • Bubble tank • Sparged air acts to mix • As air rises, mixing occurs • Air-lift tank • Divided tank • Shown at left • Both tend to have foam
Culture Types • Batch • Closed • Open • Advantages • Continuous • Advantages
Mammalian Medium • More complicated recipes • Cells less capable than microbes • Need more “processed” ingredients • May need lipids and amino acids • May need vitamins and hormones • May require serum supplementation • Animal serum provides many “factors” • Growth factors • Attachment factors
Simple Mammalian Medium AMINO ACIDS: L-Arginine-HCl 0.398 L-Cystine 0.200 L-Alanyl-Glutamine 4.03 Glycine 0.399 L-Histidine HCl-H2O 0.20 L-Isoleucine 0.802 L-Leucine 0.802 L-Lysine-HCl 0.798 L-Methionine 0.201 L-Phenylalanine 0.400 L-Serine 0.400 L-Threonine 0.078 L-Tryptophan 0.078 L-Tyrosine 0.398 L-Valine 0.803 + 10% Fetal Bovine Serum INORGANIC SALTS: Calcium Chloride 1.80 Ferric Nitrate 0.000248 Potassium Chloride 5.30 Magnesium 0.813 Sodium Chloride 110.34 Sodium Bicarbonate 44.10 Sodium Phosphate 0.906 OTHER: D-Glucose 5.55 Phenol red 0.0346 Sodium Pyruvate 1.00 VITAMINS: D-Ca pantothenate 0.0083 Choline Chloride 0.0285 Folic Acid 0.00906 i-Inositol 0.04 Niacinamide 0.0328
Serum Supplements • Provide important nutrients • Add growth factors • Recreate “animal” environment • Potential source of infectious agents • Expensive • Lot-to-lot variation
Attachment Surface • Mammalian cells • Most “normal” cells require • Exceptions are blood cells • Glass or treated plastic • Surface charge groups • Proteins in serum help with attachment • Bacteria and yeast grow in suspension • Commonly used insect cells go either way
Surface Growing vs. Suspension Tank withsuspendedcells at aconcentrationof 106/ml 64 plates with 106 cells/plate
Cheating for Suspension (I) Micro-carrier bead allows cells to grow on surface in suspension
Cheating for Suspension (II) Cells can be grown inside hollow fibers bathed in medium
Cell Density • Cells grow best in specific density range • Range is wider for single cell organisms • Narrower for dissociated cells (tissue or organ) • Mammalian cells secrete growth factors • “Conditioned medium” stimulates growth • Density too low and these signals too low • Use gradual increase in culture volume • Small initial volume, large final volume • Density of cells ~ same throughout process
Review • Cells can be grown in vitro • Cells have requirements for growth • Require nutrients, etc. • Require dissolved oxygen • Require “space” • Industrial cell culture uses specialized equipment • Small scale to large scale • Specifics vary with cell needs