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Biomaterials > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

What are the advantages of synthetic biodegradable polymers over that of natural ones?

A

Synthetic biodegradable polymers are tailor-able, have predictable behaviors from lot-lot, low immunogenicity concerns, and are a reliable source of raw materials.

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2
Q

What are the factors that accelerate polymer degradation?

A

Less crystallinity

more porosity

smaller device size

more reactive hydrolytic groups in backbone

more hydrophilic backbone
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3
Q

What are biodegradable polymers?

A

Biodegradable polymers are temporary internal fixation which can be partially or fully absorbable. Implants gradually decompose and tissue gradually heals.

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4
Q

What are the four steps of polymer degradation?

A

Water sorption

reduction of mechanical properties (modulus and strength)

reduction of molar mass

Weight loss

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5
Q

Name two effects of bioerosion on polymer properties

A

Weight loss, loss of function, deformation, changes in physicomechanical properties.

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6
Q

Describe two types of bioerosion

A

Bulk erosion: Happens in hydrophilic polymers. Water enters polymer and causes hydrolytic degradation, the component hollows then crumbles and releases acid groups [acid burst] (and swells)

Surface erosion: Happens in Hydrophobic polymers , degradation at surface because water penetration is limited. Thins the component over time. Components last longer than bulk erosion. Lower chance of inflammation because acid byproducts are released gradually. Can occur via enzymatic degradation
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7
Q

Describe the polymers degradation mechanism?

A

?

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8
Q

Give two examples of natural polymers and two examples of synthetic polymers

A

Natural: Chitosan, Collagen

Synthetic: PCL, PGA

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9
Q

What is the difference between surface erosion and bulk erosion?

A

Surface erosion takes place on surface while bulk erosion takes place throughout the material. Surface erosion maintains integrity longer

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10
Q

All polymers are biodegradable? T/F

A

False

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11
Q

All biodegradable polymers are ideally biocompatible? T/F

A

True

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12
Q

State three applications of biodegradable polymers

A

Drug Delivery Systems, Tissue engineering, Sutures

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13
Q

Name three factors that determine the rate of bioerosion

A

Chemical stability of polymer backbone

crystalline v. amorphous morphology

hydrophobicity of monomer
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14
Q

Name two benefits to having biodegradable polymer in the body

A

Can provide growth factors to promote healing (ex. artificial skin)

Can provide a scaffold for remodling that will be replaced by natural tissue
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15
Q

Which one of the following is a biodegradable polymer

A. Polyethylene

B. Polyvinyl Chloride

C. Nylon

D. Polydioxanone

E. Dacron

A

Polydioxanone

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16
Q

Which one is a NOT synthetic polymer?

A. PGA

B. Polydioxanone

C. Collagen

D. Poly (lactic acid)

A

Collagen

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17
Q

In a reaction with a O=C–X–R2, what is X?

A

X can be Oxygen, Nitrogen, or Sulfur.

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18
Q

State two advantages of using a natural polymer versus a synthetic polymer for biodegradable polymer applications.

A

Natural polymers are similar to host tissue, non-toxic, degrade metabolically, can degrade through enzymes of body,

Synthetic Polymers are tailor-able, have predictable behaviors from lot-lot, low immunogenicity concerns, and are a reliable source of raw materials.

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19
Q

Give example of two natural polymers for biomedical applications

A

Elastin: can be used for wound healing to provide more natural elasticity

Collagen: conduits can help restore neurological damage.

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20
Q

What is an example of a protein based polymer?

A

Collagen

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21
Q

What is a GAG as it relates to the definition of a natural polymer?

A

GAG: Glycosaminoglycan

A herteropolysaccharide that contains a 6-carbon sugar and an added amino group. Repeats in a disaccharide unit.

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22
Q

Name two characteristics of Elastin.

A

Highly Hydrophobic

Fibers are only 5-7mm long
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23
Q

Which amino acids are the major components of Collagen type 1 protein?

A

Glycine, Proline, Hydroxyproline

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24
Q

State two biomedical applications of heparin

A

Treatment of DVT (deep vein thrombosis)

Anti-coagulant (blood clot prevention)
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25
Q

What are the most abundant polysaccharides in the human body?

A

GAGs

26
Q

What is a glycoprotein?

A

Proteins containing one or more covalently linked carbohydrate residues

27
Q

Describe the four levels of structural organization of collagen

A

Primary: sequence of amino acids

Secondary: Local configuration of polypeptide chains (bc of stereochemical angles and Hydrogen bonds between peptide residues)

Tertiary: Triple helical collagen molecule. GLobal configurations of polypeptide chains.

Quarternary: repeating supramolecular unit structure (composed of several molecules packed into a specific lattice (basic microfibril unit)

28
Q

Give an example of physical modification of collagen

A

Tertiary structure can be disrupted by heat

29
Q

Give an example of chemical modification of collagen

A

Extract portions of antibodies of collagen in order to reduce immunogenicity

30
Q

Elaborate with example and applications two forms of collagen?

A

Microspheres: small collagen spheres that may encapsulate cells, hormones, and growth factors; may be used for drug delivery systems

Electrospun Fibres: one long continuous collagen fiber, uses an electrical field to control deposition of collagen fibers on substrate. Spun from aqueous solution fed through a thin needle; may be used for scaffolding
31
Q

What is a monosaccharide?

A

Contain between 3-7 C atoms. Includes aldehydes or ketones

32
Q

List three disadvantages of using natural polymers versus synthetic polymers

A

Natural polymers

  1. temperature sensitivity
  2. Inadequate biomechanical properties
  3. Immunogenicity
33
Q

What are Collagenases?

A

Enzymes that breakdown COllagen; can participate in remodeling. Naturally present in healing wounds. Synthesize scars as collagen degrades

34
Q

Natural materials have the ability to be degraded by natural ___, and are ideal for ____ term applications…

A

enzymes

short (term applications)

35
Q

What is the source for obtaining natural polymers?

A

Renewable sources such as plants, animals, microorganisms

36
Q

Name two representative sources of natural biodegradable polymers

A

Polysaccharides and Protein

37
Q

What are 2 protein based natural biodegradable polymers?

A

Elastin and Collagen

38
Q

Give an example of how physical modification of collagen can be carried out

A

Heating can disrupt teritary structure (triple helix)

Porosity can allow migration of host cells into bulk material (can be made by freeze drying)

39
Q

Give an example of chemical modification of collagen to control its biodegradation

A

Chemical cross-linking can prolong degredation.

40
Q

Name two polysaccharide based natural biodegradable polymers

A

Cellulose, Alginate

41
Q

What is a proteoglycan?

A

Glycoprotein with very high carbohydrate content (subunits consist of a core protein to which glycoseaminoglycans are covalently linked)

42
Q
  1. Hydrogels are polymeric structures held together as water swollen gels by ________________ and _______________.
A

primarily covalent links

ionic forces

H bonds

Hydrophobic interactions

Polymer crystallites

Physical entanglements

Combination of 2 or more interactions

43
Q

Name two distinguishing features of hydrogels

A

Polymeric network in which water is dispersed throughout the structure

Water must constitute at least 10% of total weight

44
Q

Name 3 examples of biological hydrogels

A

DNA/RNA

Polysaccharides

Extracellular matrix components

45
Q

State two applications of hydrogels?

A

Controlled/sustained drug release

Lubricating surface coating

46
Q

Define hydrogels

A

Water insoluble, 3D network of polymeric chains which are crosslinked by chemical or physical bonding. Hydrophilic, water is dispersed throughout polymeric network structure. Capable of swelling in aqueous conditions

47
Q

Classify hydrogels based on ionic charges

A

neutral

anionic

cationic

amphyolytic

48
Q

Describe classification of hydrogels based on structure

A

amorphous (chains are randomly arranged)

semicrystalline (dense regions of ordered)

Hydrogen-bonded

49
Q

State the different ways of crosslink formation in hydrogels

A

carbon atom

chemical bridge

van der waals

hydrogen bond

molecular entanglements

50
Q

Define superabsorbent hydrogels?

A

more than 95% of total weight is water

51
Q

Elaborate on how degree of swelling of hydrogels could be quantified by?

A

Ratios:

  1. Sample volume in swollen state: volume in dry state
  2. (Weight degree of swelling ratio)weight of swollen sample: weight of dry sample
52
Q

Give 3 examples of biological hydrogels.

A

DNA/RNA

blood clots

polysaccharides

53
Q

Name three reactions that could induce cross links to form hydrogels

A

Radiation: electron beams, gamma-rays, X-rays, UV light

Chemical: Small molecular weight cross linking agents through di-or multifunctional groups, copolymerization-crosslinking reactions between monomers and a multifunctional monomer that is present in small quantities

54
Q

Why is the degree of swelling important in a hydrogel?

A

For mechanical properties, surface properties and surface mobility, a solute diffusion coefficient through hydrogel

55
Q

Which one of the following is a natural hydrogel forming polymer:

A. polyethelene glycol

B. polylactic acid

C. polysodium alginate

D. polyn-isopropyl acrylamide

A

Polyethelene glycol

56
Q

What percent of water must be in a hydrogel for it to be considered as a super absorbent hydrogel?

A

95%

57
Q

How would a drug be delivered using a hydrogel?

A

Drug gets trapped in hydrogel during polymerization. Drug introduced during swelling in water.

58
Q

State two defects in crosslinked structures of hydrogels?

A

Unreacted Funtionality (small loop at end of a chain)

Chain loops (loops in the middle of a chain or coming off of a chain)

59
Q

State hydrogel classification based on polymer preparation methods

A

Homopolymer (one type of mer)

copolymer (2 types of mer, one hydrophilic)

multipolymer (more than 3 types of mers)

interpenetrating polymeric hydrogels (intermeshing network through swelling)

60
Q

Properties of hydrogels depend on __________ and __________

A

?

Biomaterials (4 decks)

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