BIOMATERIALS EXAM 1 - INTRODUCTION TO MATERIALS IN BIOMEDICAL APPLICATIONS

lectures 1-2

what is a biomaterial?

a material intended to interface with biological systems to evaluate, treat, augment, or replace any tissue, organ, or function of the body

stages of biomedical development: (3)

inert, guide biological function, completely replace

example of inert: (2)

glass eye, teeth

example of guide: (2)

hearing aids, contacts

example of replace: (2)

skin graft, artificial tendon

biological responses to biomaterials: (6)

immune response, blood clotting, infection, tumor, calcification, fibrosis

are biological responses desirable or undesirable?

both, depends on the application

ex: calcification in a bone implant vs contact

types of biomaterials

organic (containing carbon) - polymers: natural, synthetic

inorganic (no carbon) - metals, ceramics

metals:

• highly mobile electrons

• conduct electricity, easily form complex shapes

• suitable for orthopedic and dental implants, stents

• also includes alloys, combination of elements

• usually used for strength

ceramics:

• non-direction ionic bonds between electron-donating and electron-accepting elements

• crystalline vs amorphous ceramics

• hard and resistant to degradation

• brittle, only employed for smaller loads

• like frozen chewing gum

• very strong, sometimes more than metal, but brittle

are ionic or covalent bonds stronger?

ionic

polymers:

• long chains held together by directional covalent bonds

• large range of physical and chemical properties

• can form composite materials to improve bulk or surface properties where only one is a polymer

• may not be high in strength

natural polymers:

• can be derived from sources within the body (collagen, fibrin, hyaluronic acid) or outside the body (chitosan, alginate)

• most common in the body is collagen - matrix that holds everything together in the body

• have chemical compositions similar to tissues

• large quantities of these materials, mechanical properties low

• already in nature, humans or animals, so body most likely will not react poorly

synthetic polymers:

• can be mass produced and sterilized without affecting its properties

• physical, chemical, and mechanical properties can be tailored

• reactivity in vivo is not as good as natural

  • so you can make large amounts but may not react well

degradative properties of biomaterials:

can be both good or bad depending on the application; environment and properties are factors

surface properties of biomaterials:

• can make or break assimilation of a biomaterial within an environment (due to protein interaction)

• surface is a few atomic layers on the exterior of the object (can be different from the rest of the object - bulk)

• can be achieved by using special processing methods that only affect outermost layers

• only a couple of nm thick, cells will initially react with it

  • includes physical and chemical characteristics

physical surface properties:

• don’t think of only cells, applies to other applications

  • toilet paper holder with different surface material - antibacterial

why not just change the entire material?

you would change the bulk properties that you still want, ex don’t need the inside of the toilet paper holder to be antibacterial too

chemical surface properties:

• changing the chemical properties of the outermost layers

  • changes how to enviroment responds, how cells/proteins may react

easy experiment to determine hydrophobicity/hydrophilicity

drop of water on sample, the angle that forms with the surface give the relative hydrophobicity/hydrophilicity

would a hydrophobic or hydrophilic polymer be a more appropriate choice for a contact lens application and why? would a melting temperature above or below 37°C be more appropriate for this application and why?

A hydrophilic polymer would be more appropriate to interface with the aqueous environment of the eye. Additionally, a melting temperature above 37°C would be more appropriate, as one would not want the polymer to be molten at body temperature (37°C) in this application.

which material is more hydrophilic and why?

b - the angle is smaller

bulk properties:

• initially surface properties determine initial response, but overtime bulk properties determine long term impact

• include mechanical, physical, and chemical properties

characterization techniques:

• techniques used to understand physical, chemical, and mechanical properties of biomaterials

• quantitative procedures produce a numerical measure of a property (in absolute or relative units)

• qualitative experiments give a general overview of the property of interest without a numerical value

• ex: observing a material under a microscope is qualitative while spectroscopy will give us the exact concentration of a material