BIOE2010 Exam 1

Polyesters

synthetic fibers that consist of chains containing many esters

Polyamide

condensation polymer in which the monomers are joined through amide linkages

Polyanhydrides

What are the most reactive and hydrolytically unstable polymers used as biomaterials?

polyhydrocarbons

polymer linking simple linear, saturated hydrocarbon

Substituted hydrocarbons

hydrocarbons that have one or more hydrogen atoms replaced with different atoms or groups of atoms

Polyacrylate

Becomes sodium polyacrylate
after neutralizing with NaOH
Water-soluble polymer
Used as thickening, suspending and emulsifying agents in pharmaceuticals and cosmetics and paints and disposable diapers
It does not biodegrade

Polymethacrylates

Hydrogels, contact lenses, dental fillings

polycyanoacrylates

Specialized acrylic monomers that quickly polymerize with the addition of alcohol, water or any weak alkaline product to form an adhesive

Biomaterials

nonviable (not living) material intended to interact with biological systems

Isotropic materials

have the same mechanical properties in every direction

typical materials for biomaterials

Stainless steel, cobalt, chromium, titanium (Ti-6Al-4V)

CNC machine

computer controlled milling machine (used to create precise detailed pieces, and multiples)

CAD/CAM

Computer Aided Drawing-Computer Aided Manufacturing. The instructions stored in a computer that will be translated to very precise operating instructions to a robot, for tasks such as assembling cars or laser-cutting signage.

Additive Manufacturing

the production of physical items by adding layer upon layer, much in the same way an inkjet printer lays down ink

Subtractive Manufacturing

Manufacturing processes based on controlled removal of undesired materials through cutting, drilling or milling to achieve the desired forms. Ex. CNC milling

Formation of Rust

water, oxygen, and metal essential

Problems with metals

Formation of rust, allergic reactions, deterioration of mechanical properties over time, except noble metals like gold and platinum.

Passivation

spontaneous formation of a stable oxide layer that minimizes corrosion (Ti and CoCr alloys)

Pitting Corrosion

defect in surface oxide layer creates a site for the initiation of corrosion

Magnetic nanoparticles

ferromagnetic fluids could possible be used to direct materials around the body

Magnetic nanoshells

absorb incident light energy and convert it to heat especially absorption in the near IR range.

Resorbable metals

Primarily based around Mg alloys
Surface coatings are commonly used to regulate (prolong) corrosion/ degradation

Alloy

A mixture of two or more metals

Raw metal ore

Oxide forms of metals

MAGNEZIX

Compression screw, Mg-Y-RE-Zr(similar to human bone) metal screw that is completely resorbed by the body and replaced with bone tissue

Ceramic properties

Corrosion resistance
Low conductivities (semi-conductors, insulators)
Stiff and Brittle
Mechanical properties consistent with teeth and bone
Bioinert / bioactive
Naturally occurring ceramics can be made in the laboratory (hydroxyapatite found in bone)
Examples: Alumina, Bioglass, Calcium phosphates, Hydroxyapatite

Hydroxyapatite

Mineral compound that is the principal inorganic component of bone and teeth. Used as a stem coating for orthopedic implants.

Homopolymer

composed of a single monomer

Copolymer

a polymer made from two or more different monomers

Types of copolymers

random, alternating, block, graft

Polymer sturcture

Branched
Graft
Linear
Star
Network
Dendrimer

Branched Polymer

A polymer having a molecular structure of secondary chains that extend from the primary main chains.

Graft polymer

a type of copolymer; another type of monomer is attached to the backbone polymer chain

Linear polymer

A polymer produced from bifunctional monomers in which each polymer molecule consists of repeat units joined end to end in a single chain.

Star Polymer

an important miscrostructural architecture that is related to polymer properties, this special type of patterned branching of the polymer chain is similar in form to ladders, dendrimers, and brush polymer branching

Network Polymer

A polymer produced from multifunctional monomers having three or more active covalent bonds, resulting in the formation of three-dimensional molecules.

Dendrimer

man-made molecules about the size of an average protein, and have a branching shape. This shape gives them vast amounts of surface area to which scientists can attach therapeutic agents or other biologically active molecules beginning with an initiator core.

Tm (melting temperature)

temperature at which polymer transforms from an ordered (crystalline or semi-crystalline) structure to an amorphous structure

Tg-glass transition temperature

temperature at which a polymer (semi-crystalline or amorphous) transforms from rigid to rubbery state

Plasticizer

a substance (typically a solvent) added to a synthetic resin to produce or promote plasticity and flexibility and to reduce brittleness by lowering its effective glass transition temperature. allow chains to move alongside each other more easily

Thermoplastics

Plastics that can be melted and remolded over and over again.

Thermosets

become permanently hardened when heat is applied and do not soften upon subsequent heating. Generally chemically cross-linked materials such as vulcanized rubber.

Biodegredation

chemical degradation of a material resulting from the activity of a biological agent (enzyme, cell, micro-organism)

Bioerosion

a water insoluble material that under physiological conditions is converted to a water-soluble material

hydrolysis

Breaking down complex molecules by the chemical addition of water

Ester degredation

hydrolysis and esterase enzymes

Addition Polymerization

a type of polymerization in which the monomers simply add together to form the polymer, with no other products

step growth polymerization

growing chains react with each other to form even longer chains.

Addition polymerization initiators

free radical, cation, anions, catalyst

condensation polymerization

type of polymerization in which the formation of a small molecule, such as water, carbon dioxide, HCl, and methanol, accompanies the extension of the polymer chain( EX Polyanhydride synthesis)

Free Radical Polymerization Steps

initiation (with a peroxide and hv), propagation, termination (when 2 radical ends meet)

Molecular weight distribution

The relative amount of each molecular weight of a material that comprises the entire sample

SEC/GPC

Size exclusion chromatography/gel permeation chromatography, used to separate polymers based on hydrodynamic volume in a porous material, which correlates with molecular weight. The larger the molecule the fatter it moves.

Stress (sigma)

the load divided by the original cross-sectional area normal to the applied load

Strain (epsilon)

change in length per initial length

Modulus of Elasticity (Young's Modulus)

Measure of stiffness of an object, defined as the amount of
strain resulting from applying a given stress.

elastic deformation

region where the material will return to its original shape when the stress is removed

plastic deformation

permanent change in shape by bending and folding

Yield stress (offset yield point)

The stress at which a material begins to deform plastically.

tensile strength

the resistance of a material to breaking under tension

Proportional limit

Point at which the deformation is no longer directly proportional to the applied force. Hooke's Law no longer applies.

Elastic limit

Maximum stress that a material will withstand without permanent deformation.

Fatigue properties

how materials respond to cyclic loading.

stress concentration

a condition in which the maximum normal stress is much greater than the average normal stress due to geometric discontinuity in the structure or concentration of load

Fatigue limit

stress below which there is no fatigue failure whatever the number of cycles

Compression molding

heat and pressure are applied directly to the polymer powder in the mold cavity

Injection molding

A process during which plastic is heated in a machine and forced into a cavity by a screw or ram. The material solidifies and is then ejected.

Blow molding

A solid bottom hollow tube is placed between two mold halves and heated. The heated tube is then expanded into the sides of the mold with compressed air.

Extrusion

A manufacturing process that forces material through a shaped opening.

Melt Spinning

The process of producing fibers by melting polymer chips and extruding the melt (the molten polymer) in fiber form. Coagulation occurs by cooling.

Dry Spinning

a fiber-forming process in which a solution of polymer dissolved in a solvent is extruded; the fiber coagulates as the solvent evaporates. TRY to avoid, often uses very harsh, environmentally unfriendly solvents.

Fiber Drawing

Control rolls that compress, and spin at different rates stretching fiber through a heater sometimes.

Electrospinning

Forming polymer melt into fibers by electrostatic forces
Fibers are irregular, thin, only slightly drawn-must be combined with supporting textile material
Fibers the size of nanometers

Fused Deposition Modeling

Rapid prototyping process in which a filament of wax or polymer is extruded onto the existing part surface from a workhead to complete each new layer.

Stereolithography (SLA)

common rapid prototyping: solid spots are formed in a pool of liquid polymer by focusing laser beams at a single spot in the pool, curing and hardening that spot.

Regenerative tissues

Bone, liver, and peripheral nerve

Extra Cellular Matrix

The substance in which animal tissue cells are embedded, consisting of protein and polysaccharides.

anchorage dependence

The requirement that to divide, a cell must be attached to a solid surface.

integrins

A transmembrane protein that interconnects the extracellular matrix and the cytoskeleton.

Parenchyma

functional tissues of any organ that perform specialized activites, such as the tissues of the bronchioles, alveoli, ducts, and sacs, that perform respiration

stromal component

required for structual integrity and biomechanics
strong tissue
fibroblasts-produce extracellular matrix

Differentiation

process in which cells become specialized in structure and function

Phases of wound healing

inflammatory, proliferative, remodeling

Inflammatory phase

the initial phase of wound healing in which bleeding is reduced as blood vessels in the affected area constrict(~48 hrs)

Remolding phase

Restoration of function and development of mechanical strength (~2/4 wks to year)

Proliferative phase

Second phase of wound healing consisting of three concurrent process:
Granulation tissue formation-replacing of the extracellular matrix
Angiogenesis- formation of new blood vessels to supply new cells with oxygen
Re-epithelization- proliferation of new epithelial cells
(~2wks)

Growth Factors

Regulatory proteins that ensure that the events of cell occur (division, migration, matrix synthesis)

Hemostasis

Step 1- vasospasm, constriction of blood vessels
Step 2- platelet plug formation, platelets bind to sub endothelial collagen, von Willebrand Factor, then platelets activated by release of activator gP IIb/IIIa, Then platelets can bind to fibrogen leading to aggregation platelet plug.
Step 3- Coagulation and the formation of the fibrin clot
intrinsic vs extrinsic

von Willebrand factor

plasma protein secreted by endothelial cells; facilitates adherence of platelets to damaged vessel wall

GP IIb/IIIa

This receptor aggregates platelets and binds to fibrinogen to stabilize the platelet plug:

Fibrinogen

inactive plasma protein that is converted to fibrin in the clotting process

Aggregation (Platelet Plug Formation)

clot formation to prevent leakage of blood vessel.

Intrinsic initiation of coagulation

activated by normally inactive blood proteins after injury initiating a enzymatic chain reaction. LARGEST issue for medical devices chronic response ALWAYS IN CONTACT WITH BLOOD

Extrinsic initiation of coagulation

mediated by tissue factors not present within endothelial cells but in sub-endothelial cells, injury causes exposure to this tissue factor.

Fibrinogen Polymerization

fibrin, provisional matrix, scaffold for repair (clot)

Control of Coagulation

-damaged cells at the site of injury (mast cells) release heparin (glycosaminoglycan)
-heparin binds to anti-thrombin III (thrombin inhibitor) and increases its potency 1000-fold
- thrombin also activates protein C-which deactivates earlier factors in the cascade (negative feedback)

Chemotaxis

movement by a cell or organism in reaction to a chemical stimulus

Phagocytosis

Non-specific defence where phagocytes engulf foreign antigens and digest them using digestive enzymes present in lysosomes

TNF-alpha

Secreted by macrophages
activate cell types and stimulate processes of proliferative phase

TGF-beta1

important fibroblast growth factor in angiogenesis, but also inhibits inflammation and cancer