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BMEN 511 Midterm 2 > First Half > Flashcards

First Half Flashcards

1
Q

Gas Permeation Chromatography

A

used to measure molecular weights
-size-exclusion chromatography where the smallest molecules pass through bead pores, resulting in a relatively long flow path. The largest molecules flow around beads, resulting in a relatively short flow path

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2
Q

UV Spectroscopy

A

amount of discrete wavelengths of UV or visible light that are absorbed by or transmitted through a sample in comparison to a reference or blank sample

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3
Q

Different microscopy and optical techniques used to study the size of particles

A

-Transmission electron microscopes (TEM), need to dry samples before
-Dynamic light scattering (DLS), particles need to be spherical

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4
Q

Nuclear Magnetic Resonance (NMR) Spectroschopy

A

Non-invasive analytical technique that uses the magnetic properties of atomic nuclei to study the physical, chemical and biological properties of materials

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5
Q

What does NMR provide information on?

A

structure, composition, purity, molecular weight, dynamics, and diffusion properties of polymers and materials

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6
Q

What phases/dimensions can NMR operate in

A

Liquid and solid state, in one-dimensional (1D) and two dimensional (2D) and multidimensional (nD) experiments

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7
Q

Why use nanocarriers for drug delivery?

A

-no modification of the drug
-Targeted
-chemical/biological stability
-hydrophilic/hydrophobic drugs
-Less side effects
-Lower-dose/high efficacy
-Prolonged circulation time

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8
Q

How to engineer a nanocarrier? (Three functional components)

A
  1. Targeting moiety: recognize and bind to a target (physical/chemical)
  2. Carrier: facilitate endocytosis, promote circulation, carry drug
  3. Therapeutic (drug)
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9
Q

Why are natural polymers used?

A

biocompatibility, inherent biodegradability, biological functions

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10
Q

Three major types of natural polymers

A

Proteins, Polysaccharides, Protein/Polysaccharide hybrid polymers

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11
Q

Proteins (Natural Polymer), why are they used, examples

A

Mimic ECM
-directing the migration, growth and organization of cells during tissue regeneration
-wound healing and for stabilization of encapsulated and transplanted cells (collagen, gelatin, fibrin, silk)

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12
Q

Polysaccharides (Natural Polymer), examples

A

Hyaluronic acid, chitosan, cellulose

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13
Q

Protein/polysaccharide hybrid polymers

A

Collagen/HA, laminin/cellulose, gelatin/chitosan, and fibrin/alginate

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14
Q

Advantages of Natural Polymers

A

Collagen: low toxicity, high biocompatibility, biodegradability, good permeability, hyposensitivity, porous structure, low immunogenicity

Fibrin: non-toxic degradation products, high elasticity, excellent biocompatibility, controllable degradation rate, promotes cell attachment

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15
Q

Disadvantages of Natural Polymers

A

Fibrin: shrink, potential disease transmission

Collagen: poor mechanical/ electrical properties

Gelatin: lower melting temperature, rapid dissolution in water

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16
Q

Collagen Advantages (Most commonly used, Natural Polymer)

A

-Major component of ECM in tissues
-surface binding sites (ligands)
-cell attachment/proliferation
-minimal inflammatory
-used in conjunction with natural/synthetic polymers
-degradation rate

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17
Q

How does Collagen break down?

A
  1. Collagen Fibre
    –>Denaturation
  2. Gelatin
    –>Degradation
  3. Peptides
    –>Hydrolysis
  4. Amino Acids
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18
Q

Brittle Bone Syndrome

A

-Single amino acid changes in primary sequence can destabilize or stabilize tertiary and quaternary structure and have a major effect on function
-Primary sequence mutations are a common cause of inherited diseases including “Osteogenesis imperfecta”

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19
Q

Decellularization

A

removes cells from tissues/organs to generate ECM templates, structural and functional proteins that can be used as natural scaffolds for tissue engineering applications
-preserves the overall structure, compositions, shape, certain levels of mechanical integrity

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20
Q

Advantages of Decellularization

A

Reduces foreign body reaction, inflammation, and potential immune rejection

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21
Q

Effective Decellularization methods

A

chemical, enzymatic, physical or combination approaches

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22
Q

Synthetic Polymers Advantages

A

-physiochemical properties are more controllable compared to naturally derived polymers (molecular weight, degradation rate, thermal properties)
-no potential for disease/antigen transmission

23
Q

Synthetic Polymers Disadvantages

A

Usually don’t have cell binding sites, are not bio functional, typically have to be functionalize with different biomolecules using different techniques

24
Q

Crystallization is promoted in polymers with

A

-simple structure
-little or no chain branching
-flexible chains (easy to orient into crystals)
-non-crosslinked/network chains
-highly polar groups with strong dipole-dipole interactions

25
Q

Can polymers crystallize?

A

Polymers can crystallize like small molecules, however due to variations in length, conformation, polymers tend to for semi-crystalline domains

26
Q

Effects of Polymer Crystallization - Mechanical Properties

A

-Stronger
-interchain distance decreases
-strong intermolecular forces
-acts a reinforcement phase (composite)
-enhance mechanical, thermal, electrical properties

27
Q

Effects of Polymer Crystallization - Optical Properties

A

-More opaque
-Crystallites form a separate phase (scatter light)

28
Q

Effects of Polymer Crystallization -Density

A

-More dense
-Chains packed closer together into crystallites

29
Q

Effects of Polymer Crystallization - Solvent Resistance

A

-More solvent-resistant (And resistant to other molecules)
-Improved barrier properties
-Higher intramolecular interactions = harder solvation

30
Q

Degradation considerations

A

-How long must the biomaterial last?
-Is the slow degradation of the biomaterial essential for function?
-Are the degradation products safe (acidic products, heavy metals)

31
Q

Methods of Biodegradation

A

Hydrolysis, Enzymatic degradation, oxidation

32
Q

Bulk erosion

A

Polymer degrades uniformly throughout entire bulk
-catastrophic breakup of the material
-need water, oxygen
-bulk dimensions change minimally prior to failure

33
Q

Surface erosion

A

layer by layer
-mechanical failure of the material less probable
-bulk dimensions change continuously until failure
-catastrophic breakup of material doesn’t occur
-low transport of water/enzyme into bulk (typically)

34
Q

Hydrolysis

A

react with water molecules, break up and produce new chain ends (break into smaller segments)
-polymers with ester or anhydride bonds

35
Q

What is degradation rate influenced by?

A

-hydrophobicity/hydrophilicity
-crystallinity
-monomer structure
-molecular weight
-degree of crosslinking
-material processing

36
Q

Oxidative degradation

A

-abstraction of H to get an ion or radical
-important for breakdown of carbohydrates/synthetic polymers

37
Q

Oxidative degradation examples in polymers

A

-residual free radicals from irradiation (Crosslinking, steralization)
-release of superoxide anion (O2-) and hydrogen peroxide (ROOH) from neutrophils and macrophages

38
Q

Enzymatic Degradation

A

Natural polymers degrade primarily via enzyme action
* collagen by collagenases, lysozyme
* glycosaminoglycans by hyaluronidase, lysozyme
* Cellulose by cellulase

Degradation of synthetic polymers can be driven or enhanced by enzyme action

39
Q

Water-insoluble polymer properties

A

Do not hydrate (bind water)
-mechanically stiffer (“hard”)
-hydrophobic surface, protein adsorption, host response

40
Q

Water-soluble polymers

A

Hydrate, absorb/bind water
-mechanically weaker (soft)
-hydrophilic surface (lower protein adsorption)
-generally more biocompatible (minim natural ECM properties)

41
Q

Hydrogels

A

water swollen networks (crosslinked structures) composed of hydrophilic copolymers. Insoluble due to the presence of chemical (covalent or ionic) or physical crosslinks (entanglements, crystallites, hydrogen bonds)

42
Q

Do hydrogels swell in water?

A

Hydrogels swell in water. Their swelling ratio can be controlled by changing different parameters (degree/type of crosslinking, Mw)

43
Q

Why hydrogells?

A

-mechanical properties/water content similar to natural tissue
-respond to physiological stimuli (pH, temp)
-used to deliver drugs, cells
-tunable properties
-biodegrade at control rates

44
Q

Physically-crosslinked hydrogels

A

noncovalent force
-dispersion forces (van der wall interaction)
-hydrogen bonding
-hydrophobic interactions
-ionic interactions
-chain entanglement

45
Q

Advantages physically crosslinked hydrogels

A

-self assembled
-no reagents needed
-fewer synthesis steps

46
Q

Disadvantages physically crosslinked hydrogels

A

-weaker mechanical properties
-can be diluted in water (dissolution/weakening)
-harder to estimate crosslinking

47
Q

Chemically-Crosslinked Hydrogels

A

Networked a covalent bonding network
-linkages may be degradable or non-degradable
-linkages could be branches from main chain or side chains

48
Q

Advantages chemically crosslinking

A

-Stronger
-Gels are stable in diluting environment
-Gel lifetime can be controlled by degradation rate of chemical linkage in crosslinker
-easier to control density

49
Q

Disadvantages chemical crosslinking

A

-More reagents needed
-More complicated chemistry/synthesis
-UV, redox or high temperatures

50
Q

Chemical crosslinking examples

A
  1. Crosslinking molecules
  2. Polymer/polymer, hybrid polymer
  3. Photosensitive agents
  4. Enzymatic crosslinking
51
Q

Key properties of gels for bioengineering applications

A
  1. In situ/in vitro/in vivo formability
    Gelation of liquid solutions by:
    -irradiation with light
    -temperature changes
    -cross-linking enzymes
    -Prescence of salts
  2. Degradability
  3. Responsive swelling (temp, pH, molecule response swelling, basis of sensors/smart materials)
  4. Tissue like structure/properties
52
Q

Biocompatability

A

The capability of implanted prosthesis to exist in harmony with surrounding tissues. Ability of an implanted material to function in vivo without eliciting detrimental local or systemic responses in the body.

53
Q

Three things to consider with biocompatibility

A
  1. Host
  2. Material Properties
  3. Material Function
54
Q

What responses might happen when a foreign biomaterial is implanted into the body?

A
  1. Clot formation, blood cells and proteins adhere to the surface
  2. Biofilm formation (bacteria adhesion), bacteria and immune cells
  3. Inflammation, immune cells, blood proteins

BMEN 511 Midterm 2 (2 decks)

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