Tissue Engineering - Biomaterials I
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How many cells are in your body?
50 to 100 trillion cells
How many different types of cells are in the human body?
210 distinct human cell types
- Melanocyte... etc
What are the three main tenets of tissue engineering? What is an additional factor that should be considered?
- Growth Factors (Biomolecules)
- ECM/Scaffold (Biomaterials for organization)
The forth factor that should be considered is the environment.
What are some new innovations that will be coming for medicine?
Innovations in biomaterials, biomimetics, biomedicine, bioinformatics
- Intelligent machines
- Technologies for developing countries (such as the cold chain for delivering drugs)
- Infrastructure - water and energy
What is a common believe for the source of diseases?
Grip strength may be a method to measure for aging effects.
What is the Medici Effect?
Groups of people from different backgrounds or disciplines coming together and sharing their ideas. This allows for ideas of one discipline to have an affect on the ideas of another discipline.
What are some of the benefits of materials science and biomedicine for healthcare?
Preventing, detecting, treating and repairing disease, dysfunction and/or aging.
What are some of the benefits of materials science and biomedicine in biomimetics?
Fundamental biology, tissue engineering, shark skin, hydrophobic/hydrophilic beetles
What are some of the benefits of materials science and biomedicine for materials from biology?
Silk, collagen, botanical proteins
What is biomimetics?
Biomimetics is the study of the structure and function of biological systems as models for the design and engineering of materials and machines. It is widely regarded as being synonymous with biomimicry, biomimesis, biognosis and similar to biologically inspired design.
What is an example of biomimetics with shark skin?
The shark skin's grooved scales surface (a rectangular base embedded in the skin with tiny spines) prevents sea plants and organisms from adhering to it, thereby, reducing drag.
What materials were used indiscriminately by early users?
Wood, granite, gold, iron, lead, placenta, skin, nail, hair etc
Signs of inflammation were regarded as positive.
What percent of the human DNA is composed of human DNA?
8% of human DNA contained integrated retrovirus DNA.
Retrovirus infected our ancestors, leaving a legacy of its DNA in our genes.
A study suggests that since the protein encoded by this DNA abounds in placental cells, the protein may have a useful role by preventing a pregnany woman's immune system from rejecting her fetus.
What were some of the new materials that lead to their use in biomaterials science?
Steel, vanadium alloy, stainless steel etc
What are some examples of biomedical materials used in the human body?
- Contact lenses
- Dental implants
- Vascular grafts
- IV catheters
- Cochlear implants
- Drug delivery systems
- Demodialysis products
- Orthopedic implants
What is the hiearchy when considering a biomaterial (7)?
- The influence in the following scale:
- Atomic scale
- Molecular scale
- Cellular scale
What are the four types of biomaterials?
What are important considerations for biomedicine/biomaterials science in terms of purpose?
- Technology must be driven by the biology; materials science serves, it does not lead.
- Fundamental biology is still being investigated.
- Function is everything
- Integration of materials and biology.
What are considerations of biomaterials in terms of function?
- Proper reconstitution of the environment:
- Biochemical (cytokines, chemokines, signaling, capilaries - nutrients)
- Physical (surfaces, circulation, ECM, geometry)
- Mechanical (strength, elasticity, compliance)
- Hierarchical (molecular, micro, meso, macro)
What are some considerations that cause businesses to fail in tissue engineering?
- Scale-up processes
- Regulatory approval (FDA)
- User error.
In a comparision between natural polymers and synthetic polymers, what are some examples of natural polymers and the associated advantages/disadvantages?
- Natural polymners include
- GAGs (glycosaminoglycans)
- Biocompatibile, bioactive
- Easy for cell seeding hydrophilicity
- Difficult to process
- Poor mechanical properties/mechanically weak
In a comparision between natural polymers and synthetic polymers, what are some examples of synthetic polymers and the associated
- Synthetic polymers
- Poly(lactic acid) (PLA)
- Poly(glycolic acid) (PGA)
- Polycaprolactone (PCL)
- Easy to process
- Mechanical, chemical and biodegradation properties can be engineered by molecular design
- Lack of cell-recognition signals
- May invoke inflammation
- Hydrolysis leads to degradation
What is biocompatibility?
May be functionally defined as the acceptance of the material by the surrounding tissues and fluids of the human body and by the body as a whole, and the ability of the material to perform with an appropriate host response in a specific application.
What is systemic toxitity?
Toxicity to tissues some distance away from the intial source.
Toxicity at some distance from the site of initial insult. The mechanisms by which substances are rendered toxic are varied and complex; may be due to:
- Direct chemical toxicity
- Accumulation of products from wear
- Corrosion or degradation
- Excess inflammatory response
Biomaterials should be carefully evaluated and studied for toxicity in vitro
before being implanted. Such testing must include the intact material, as well as the degradation and wear products that may be produced during function.
What is cytotoxicity?
Toxicity towards cells, typically local.
The extent to which the material kills cells in cell cultures.
Measuring cytotoxicity may be done by the following:
- Direct contact - place a piece of material on top of a layer of cells
- Agar diffusion test - a layer of agar between the cells and sample to be tested
- Elution test - the material is soaked in fluid and this fluid is applied to the cell culture
What is the typical use for metal biomaterials?
Load bearing applications and must have sufficient fatigue strength to endure the rigors of daily acitivity (ie walking, chewing etc)
What are some advantages and disadvantages of metallic biomaterials?
- High strength
- Fatigue resistance
- Wear resistance
- Easy fabrication
- Easy to sterilize
- High modulus
- Metal ion sensitivity and toxicity
What is the typical use of ceramic biomaterials?
Ceramic biomaterials are generally used for their hardness and wear resistance for applications such as articulating surfaces in joints and teeth as well as bone bonding surfaces in implants.
What are some advantages and disadvantages to ceramic biomaterials?
- High compression strength
- Wear and corrosion resistance
- High modulus (mismatched with bone)
- Low strength in tension
- Low fracture toughness
- Difficult to fabricate
What is bioinert or nonabsorbable materials?
- Materials that are:
- Non-toxic, noncarcinogenic, nonallergic, relatively noninflammatory, and biocompatible while resisting corrosion and wear.
What are surface-reactives ceramics?
Materials that elicity the tissue ingrowth and bonding for structural integrity.
What are resorbable ceramics?
Materials that are gradually resorbed by the body and taken place by the body's own tissues for form and function.
What are polymer biomaterials?
Polymers are chains of repeating monomer(s) that are easy to tailor to the desired properties. Polymers are typically used for their flexibility and stability but have also been used for low friction surfaces.
What are some advantages and disadvantages to polymeric biomaterials?
- Easy to make complicated items
- Tailorable physical and mechanical properties
- Surface modification
- Immobilize cells
- Some are biodegradable
- Leachable compounds (due to degradation)
- Absorb water and proteins
- Wear and breakdown
- Difficult to sterilize
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