Tissue Engineering - Biomaterials III

Biomolecules are molecules such as proteins (VEGF, Insulin etc) thar are necessary to assemble cells. (There is no self-assembly understood)

Two disadvantages include the cost to produce these biomolecules and the half-life of the molecules.

Biomolecules delivered in tissue engineering to assist tissue formation.

The biomolecule may be placed inside the scaffold or the cells that produce the biomolecule may be used.

• Pill/capsule
• Scaffold/biomolecule integration

• Fairly easy preparation
• Good control over size and size distribution
• Good protection of the encapsulated drug
• Longer clearance times

• Extensive use of poly(vinyl alcohol) - PVA may have issues with toxicity
• General toxicity issues unknown
• Limited targeting abilities

• Nanosuspensions & Nanocrystals
• Liposomes
• Solid Lipid Nanoparticles
• Polymeric Nanoparticles

These include: drug-enriched core, solid solution, drug-enriched shell

• Increase stability of volatile drug agents
• Produced relatively easily
• Vast source of chemistries available
• Many have engineered specificity both to the drug and the target - difficult to achieve with other carriers
• Drug-release profiles and triggering dependent on polymer structure.

• Biodegradable/biocompatible
• Structure - mostly copolymers, combining different qualities of their parent polymers

• Benefits include:
• -closest analogue to living tissue
• -capable of binding large amounts of fluids and drugs including proteins
• -swelling ratio controllable by variation in structure (hydrophobic/hydrophilic ratio)
• -small changes in temperature, pH, electric/magnetic field can trigger large volume change/release of drug
• -in many cases, well defined release patterns

• Drawbacks
• -more difficult to characterize/predict behavior
• -not as many defined stoichiometric compounds

• Viral vectors
• -retroviral vectors
• -adenoviral vectors

• Non-viral vectors
• -polymers
• -liposomes

• Other methods
• -electroporation
• -microinjection
• -particle bombardment (gene gun)

• Not effective in vitro
• Inefficient in vivo

Works only certain tissues (ie muscle)

However, they are simple and inexpensive and plasmid delivery is posibly using hydrogels.

Materials that are inspired from nature. Examples include the skin of the shark for it's properties and the structure of honeycombs.

The use of the honeycomb structure has been used for lightweigh and high compression applications. This may be beneficial for the use of loadbearing applications including humanbone. This would also allow for factors such as VEGF and PDGF to be embedded for vascularization.

• Characteristics:
• -Tough
• -Flexible
• -Poor conductor of electricity

• Functions of skin:
• -To protect the body from external insults
• -To contain all body fluids
• -To regulate body temperature
• -To protect from electrical current

• Penetration includes
• -intercellular route
• -follicular route

• Penetration
• Diffusion

• Steady permeation of drug across skin
• Controlled drug delivery
• Good for acid and enzyme reactive drugs
• Minimum risk of side effects
• Limited toxic effects
• Convenience
• Easy drug administration
• Good for lipophillic drug molecules

• Possibility of a local irritation
• Allergic reactions are possible
• Risky for children
• Skin's low permeability
• Molecular size and polarity of drug
• Insufficient bioavailability
• Damage to a transdermal patch

True.

True.

• Cells
• Scaffold
• Biomolecules.