Tissue Engineering

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Tissue Engineering
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Plant cells current interest

• pharmaceuticals atropine, codeine, L-dopa,
  morphine, phytotoxin (digitalis), taxol,
  ubiquinone-10, vincristine, vinblastine
• colors or dyes anthocyanins, saffron, shikonin
• flavours vanilla, strawberry, grape, garlic
• fragrances jasmine, lemon, mint, rose

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Paclitaxel (Taxol)

• anticancer drug
• extracted from bark of Pacific yew (Taxus
  brevifolia)
• one patient requires three 100 year old trees
• semisynthetic alternative needles and branches
  of common yews, extract precursor
• presently 30,000L suspension culture

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Totipotency

• capacity to regenerate whole plants from
  undifferentiated cells (common for plants)
• key to micropropagation

somatic embryogenesis
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Tissue culture propagation
root or shoot
plantlet
whole plant
cutting to solid agar development of callus
suspension culture
photobioreactor
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Media

• sucrose as Carbon/Energy source
• inorganic nutrients
• vitamins, growth regulators
• plant hormones (auxins, cytokinins, giberellins)
• 27oC, pH 5.5 in dark
• elicitors (eg. methyl jasmonate) can cause
  rapid accumulation of secondary metabolites

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Cell characteristics

• 10 100 µm (large)
• typically nonphotosynthetic in culture (sucrose
  as C/energy)
• 0.5 mmol O2/h-g (5-15 that of microbes)
• high density culture possible (70 reactor
  volume)
• 90-95 water
• secondary metabolites often retained in vacuole

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Suspension culture characteristics

• lower respiration rate
• shear sensitive (large cells)
• often grow as aggregates
• aggregation may be important to secondary
  metabolism
• CO2 or ethylene may be important
• up to 75,000L reactors have been used

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Bioreactors

• low or moderate densities (lt20 g/L) appropriate
  to airlift
• high cell density require paddle or
  helical-ribbon impeller
• difficult balance between gas composition,
  sparging rate and degree of agitation
• slow growth rate so contamination is problem