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BME 353 > Hydrogels > Flashcards

Hydrogels Flashcards

1
Q

Hydrogels

A

mimics the physical properties of biological tissues, excellent candidate for various medical and biological applications

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2
Q

Crosslinks may be physical or chemical:

A
  • by reaction of one or more monomers with pendant functional groups
  • hydrogen or ionic bonding
  • van der waals
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3
Q

Classification of Hydrogels

A

based on origin
- natural hydrogels: derived from natural sources such as polysaccharides and proteins (alginate: algae, chitosan: shrimp)
- synthetic hydrogels: created from synthetic polymers such as polyvinyl alcohol (PVA) and polyethyleneglycol (PEG) (should know the structures of these)
- chemically crosslinked hydrogels: exhibit permanent linkages formed by covalent bonds
- physically crosslinked hydrogels: formed through temporary interactions like hydrogen bonding, hydrophobic interactions

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4
Q

Key properties of hydrogels for biomedical applications

A
  • ease of chemical modification
  • in situ formability
    • control over 3D structure/morphology
    • mild conditions for cell/protein encapsulation
  • degradability
  • responsive swelling “smart” hydrogels (contain certain functional group that can respond to change)
  • soft tissue-like structure/properties
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5
Q

Degree of swelling

A

degree of swelling quantified by: (put in weight compare vol or weight to the dry state)
- volume
- weight

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6
Q

why is the degree of swelling important?

A
  • solute diffusion coefficient through the hydrogel, drug delivery system
    - higher degree of swelling faster drug release
    • surface properties and surface mobility
    • optical properties
    • mechanical properties
    • high swelling enhances flexibility, permeability, and drug release but may reduce mechanical strength and stability
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7
Q

polymer-based hydrogel has to have at least

A

10% of total weight for a material to be a hydrogel.

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8
Q

when content of water over 95% of total weight or vol, hydrogel is

A

superabsorbent

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9
Q

Chemically linked hydrogel

A

can maintain shape before and after hydrolyzation, covalent bonds

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10
Q

Gel transitions through in situ crosslinking physical gels

A
  • add ionic crosslinker
  • change temp
  • change pH
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11
Q

Gel transitions through in situ crosslinking covalent gels

A

polymerization initiation (light, temp,… )

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12
Q

Formation of crosslinked hydrogels

A
  1. by polymerization
  2. with cross-linkers (functional group that can join polymer or monomers together)
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13
Q

Hydrogel formation: physical cross-linking

A
  1. heating/cool of a polymer solution
  2. ionic crosslinking
  3. hydrogen bonding
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14
Q

Hydrogel formation: chemical cross-linking

A
  1. chemical cross-linkers
  2. grafting
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15
Q

Synthetic polymers advantages

A
  • precise control over composition
  • can be tailored to give a wide range of properties to meet specific needs
  • large scale production
  • low immunogenicity
  • no biological pathogens or contaminants
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16
Q

Synthetic polymers disadvantages

A
  • low biodegradability
  • can include toxic substances
17
Q

Natural polymers advantages

A
  • generally high biocompatibility
  • intrinsic cellular interactions
  • biodegradable
  • cell controlled degradability
  • low toxicity byproducts
18
Q

Natural polymers disadvantages

A
  • mechanical strength
  • batch variation
  • animal-derived materials may contain pathogens
19
Q

Smart hydrogels

A

respond to environmental stimuli like temp, pH, light, or electric fields

20
Q

thermoresponsive hydrogels

A

swell or shrink in response to change in temp

21
Q

pH-responsive hydrogels

A

swell or shrink in respond to change in pH, used in drug delivery system

22
Q

Polyelectrolytes

A

polymer with charge

23
Q

polycations (polyelectrolyte)

A

used in gene delivery

24
Q

ampoteric polyelectrolytes

A

charged groups, act as either a polyanion or polycation depending on the pH.

25
Q

polyanions (polyelectrolyte)

A

used in drug delivery, thickeners in foods and cosmetics, superabsorbents

26
Q

Polyelectrolytes

A

expand after dissolved in solution, reverse process by adding salt

27
Q

Ionic Strength Sensitivity

A

polyelectrolytes are highly sensitive to the ionic strength of a solution; At low ionic strength, the chains tend to extend due to electrostatic repulsion between the charged groups on the polymer; At higher ionic strength, the charges are screened by counterions, leading to a more coiled or collapsed state.

27
Q

Superabsorbent Polymers

A

Polyelectrolytes like sodium polyacrylate are used in products such as diapers and agricultural soil conditioners, where they can absorb and retain large amounts of water.

28
Q

Which of the following best describes a hydrogel?

A

A 3D polymer network capable of absorbing and retaining water

29
Q

What makes hydrogels particularly useful in biomedical applications?

A

Their ability to mimic the physical properties of biological tissues

30
Q

Which of the following factors primarily governs the mechanical properties of
chemically cross-linked hydrogels?

A

The degree of cross-linking between the polymer chains

31
Q

Why are ionic strength-responsive hydrogels useful in wound healing?
Respond to physiological ions
Strengthen at higher ionic strength
Release drugs in response to pH
Temperature-sensitive drug release

A

Respond to physiological ions

32
Q

True or false: The mechanical strength of a hydrogel decreases as the degree of cross-linking between polymer chains increases.

A

False

33
Q

True or false: pH-responsive hydrogels can change their swelling behavior depending on
the pH of the surrounding environment

A

True

34
Q

True or false: Physically cross-linked hydrogels use covalent bonds, making them stronger
and more durable than chemically cross-linked

A

False

BME 353 (7 decks)

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