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Biomaterials > Ch 1 - Materials for Biomedical Applications > Flashcards

Ch 1 - Materials for Biomedical Applications Flashcards

1
Q

Biomaterial

A
  • Material intended to interface w/ biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body
  • e.g. not a splinter b/c it’s unintentional
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2
Q

Biomaterials science

A
  • Study of biomaterials and their interactions w/ the biological envir.
  • Includes subjects related to materials science (e.g. mech prop’s) and biology (e.g. immunology, toxicology and wound healing)
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3
Q

Biocompatibility

A

Ability of a material to perform w/ an appropriate host response in a specific application

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4
Q

effects of hosts on materials

A
  • Chem. degrad. rate
  • Mech. prop’s
  • Phys. prop’s (e.g. swelling in hydrogels)
  • Implant calcification (e.g. build-up around heart valves → brittle)
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5
Q

effects of materials on hosts

A
  • Toxicity/chem. rxns
  • Approp. size/weight
  • Rejection by immune sys. (inflammatory response)
  • Heating/cooling prop’s
  • Safe failure mode
  • Blood clotting
  • Carcinogenicity
  • Sterility/infection
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6
Q

EX: hip implant

A

• Contains all 3 major biomaterials: metals, ceramics and polymers
• Components:
1 . Stem: goes into femur (metal)
2. Head: ball attaches to stem (ceramic coating?)
3. Acetabular cup: goes into hip socket (polymeric)

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7
Q

Biological response: Inflammation

A
  • Localized blood clotting, infection, implant calcification)
  • Depends on shape/size of implant (scale), location in body, and chem/mech prop’s
      Macro	> 500 um
  Micro	1-200 um
  Nano	< 200 nm
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8
Q

Biological response: Proteins/Cellular

A

Determines overall success of implant (time to failure)

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9
Q

in vitro

A

in glass

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10
Q

in vivo

A

in living system

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11
Q

FDA approval

A

• Biocompatibility testing dictated by ASTM Int’l and ISO
• Approval is NOT for materials (for all uses), it’s for use in the context of devices/drugs
• Steps:
1 . In vitro
2. In vivo w/ healthy animals
3. In vivo w/ diseased animals (if applicable)
4. Controlled clinical trials

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12
Q

Metals

A
  • Inorganic materials w/ non-directional metallic bonds and highly mobile electrons (conductive)
  • Strong, ductile (formable)
  • Apps: orthopedic replacements (load-bearing)
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13
Q

Ceramics

A
  • Inorganic materials w/ non-directional ionic bonds (encourages integration w/ surrounding tissue) b/w electron-donating and electron-accepting elements
  • Very hard and more resistant to degradation than metals, yet quite brittle b/c of ionic bonds
  • Apps: orthopedic implants or dental materials (for small loads)
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14
Q

Polymers

A
  • Organic materials w/ long chains held together by directional covalent bonds, esp. those derived from natural sources (e.g. proteins)
  • i.e. \elastomers, \hydrogels and \composites
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15
Q

Elastomers

A
  • Can sustain large deformation at low stresses and return to initial form upon release of stress
  • i.e. cardiovascular applications
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16
Q

Hydrogels

A
  • Swell in water and retain signif. fraction of water w/o completely dissolving
  • i.e. soft tissue applications
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17
Q

Composite

A
  • Composed of +2 chemically distinct components (typ. one is a \polymer)
  • Often to optimize \bulk or \surface mech prop’s
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18
Q

Naturally-derived polymers

A
  • Derived from sources within the body
  • Typically similar chem compos. to tissue they replace (better integration or remodeling)
  • e.g. \collagen and \fibrin proteins (cartilage and orthopedic apps)
  • e.g. \chitosan and \alginate (wound dressings)
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19
Q

Synthetically-derived polymers

A
  • Easily mass-produced and sterilized
  • Tailored prop’s for specific apps
  • Typ. do not interact w/ tissues directly (cannot direct cell/tissue response)
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20
Q

Processing biomaterials

A

Can affect \bulk and \surface prop’s to produce complex changes

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21
Q

Degradative properties

A
  • Depends on shape/size of implant (scale), location in body, and chem/phys/mech prop’s
  • e.g. inflammation: may be designed or undesired
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22
Q

Surface properties

A
  • Determine protein adsorption (attachment)
  • e.g. \hydrophobicity (water-fearing moieties, chem prop)
  • e.g. surface roughness (trap biological constituents, phys prop)
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23
Q

Material dogma

A

\surface prop’s → protein attachment → cell/tissue response

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24
Q

Bulk properties

A
  • Most important parameter b/c of long-term impact
    • Mech prop’s e.g. strength & stiffness
    • Phys prop’s e.g. \crystallinity & \thermal transitions
25
Q

Anisotropy

A
  • Mech prop’s differ based on direction of loading

* e.g. bones in leg

26
Q

Crystallinity

A

Alters water uptake, which can impact degradation and interaction w/ surrounding cells & proteins

27
Q

Thermal transitions

A

e. g. melting point

* * Must be stable at body temp.

28
Q

Chemical composition

A
  • Typ. a result of the type of bonds in mat’l

* Dictates \bulk properties e.g. \hydrophobicity

29
Q

Quantitative characterization techniques

A
  • \spectroscopy = absorption of energy

* \chromatography = physical separation of molec’s based on chem char’s (e.g. charge or size)

30
Q

Atomic number

A

“Z” = # protons

31
Q

Atomic mass

A

Measured in \atomic mass units (amu = mass/mole)

32
Q

Mole

A

6.02 E23 molec (per mole) = Avogadro’s #

33
Q

Convert amu/molec to g/mol

A

1 amu/molec = 1 g/mol

34
Q

Quantum mechanics (electron movement)

A
  • \Bohr model - electrons orbit nucleus in \orbitals (discrete energy states)
  • \Wave-mechanical model - orbitals indic. the probability that an electron will occupy a certain space around nucleus (\electron clouds = probability functions)
35
Q

Quantum numbers

A
  • Dictate size, shape and orientation of electron probability functions
  • Divides electron shells (Bohr energy states) into subshells (s, p, d, f)
36
Q

Pauli exclusion principle

A

Each state can hold up to 2 electrons (w/ opposite spin) → predict electron config. of an atom

37
Q

Aufbau principle

A

Sequentially adding electrons to energy states (lower to higher)

38
Q

Hund’s rule

A

In subshells w/ mult. energy states (e.g. 3p subshells), each subshell must first be filled w/ 1 electron

39
Q

Closed-shell configuration

A
  • Completely filled orbitals

* Stable, do not participate in most chem rxns

40
Q

Open-shell configuration

A

Partially filled orbitals

41
Q

Valence electrons

A
  • Occupy outermost shell

* Can be shared/exchanged in \open-shell config.

42
Q

Periodic table

A
  • Organizes elem by incr. atomic #

* Based on # valence electrons

43
Q

Electropositive, EP[+]

A

(L) give up electrons to become [+] ions

44
Q

Electronegative, EN[-]

A

(R) accept electrons to become [-] ions

45
Q

Primary bonds

A
  • Sharing/transfer of \valence electrons
  • \ionic, \covalent, \metallic bonds
  • F_tot(r) = F_attr(r) + F_repuls(r) where r0 = bond length (distance at equilibrium)
46
Q

Ionic bond

A
  • Transfer of valence electrons

* ΔEN b/w cation & anion

47
Q

Covalent bond

A

Sharing valence electrons (typ. polymers)

48
Q

σ bonds

A

First bond formed along internuclear axis of 2 atoms (only 1 ∀ pair)

49
Q

π bonds

A
  • Additional (double/triple) bonds

* Not as strong, but can affect rigidity

50
Q

Molecular orbitals

A

Describes energy absorption and excited states of ENTIRE molec (not singular atom)

51
Q

Bonding molecular orbitals

A
  • Wave functions describing electrons of atomic orbitals from 2 atoms overlap in REINFORCING way
  • ↑ probability of finding e- along internuclear axis (attr to nuclei) ∴ highly stable
52
Q

Antibonding molecular orbitals

A
  • Wave functions overlap in DESTRUCTIVE way and cancel each other in region b/w nuclei
  • Greatest e- density found on OPPOSITE sides of nuclei ∴ less stable
53
Q

Metallic bond

A
  • EP[+] elements
  • e- donated to entire structure, “sea of e-“
  • Delocalized \valence electrons → high electrical conductivity
  • NON-directional electron sharing
54
Q

Secondary bonds

A
  • \VDW
  • \dipoles
  • \polar molec’s
  • \H bonds
55
Q

Van der Waals

A

Attraction b/w atoms w/o electron sharing/transfer

56
Q

Dipoles

A

Molec’s w/ portions slightly positively & negatively charged

57
Q

Polar molec’s

A

Permanent dipoles (strongest 2 ° bond)

58
Q

Hydrogen bond

A

Interactions b/w H,+ and O,2-

Biomaterials (6 decks)

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