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Regenerative Medicine > Lecture 10 - Hydrogels 1 > Flashcards

Lecture 10 - Hydrogels 1 Flashcards

1
Q

What are hydrogels?

A

Hydrogels are hydrophilic polymer networks that are able to swell and retain large amounts of water and maintain three-dimensional swollen structures.

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2
Q

What are the common features of hydrogels?

A

Common features include:
* 3D networks
* Mostly water
* Ability to swell significantly

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3
Q

When is a gel considered a gel?

A

When the components of the liquid phase contribute to a change in viscosity or stiffness.

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4
Q

Define viscosity.

A

Viscosity is a liquid’s resistance to flow.

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5
Q

Define stiffness.

A

Stiffness refers to the mechanical properties of a solid, primarily the elasticity.

Measured by rheology

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6
Q

What is rheology?

A

Rheology is the study of flow and deformation in ‘shear’.

  • Composition
  • Composition governs behaviour

Shear = platforms in opposite directions

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7
Q

What was the first use of hydrogels?

A

Hydrogels were first used in the 1960s to create contact lenses.

Good use in contact lenses as transparent, wettable, permeable to oxygen, biocompatible, comfortable

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8
Q

List some biomedical applications of hydrogels.

A
  • Drug delivery
  • Wound dressings
  • Implant coatings
  • Regenerative medicine
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9
Q

What are the two types of hydrogels used in regenerative medicine?

A
  • Natural
  • Synthetic
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10
Q

Name some natural hydrogels.

A
  • Carrageenan
  • Alginate
  • Fibrin
  • Collagen
  • Agarose
  • Laminin
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11
Q

Name some synthetic hydrogels.

A
  • Poly(lactic acid)
  • Calcium phosphate
  • Synthetic peptides
  • Poly(urethane)
  • Poly(glycolic acid)
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12
Q

What is the role of polymer chains in hydrogels?

A

Hydrogels are composed of polymer chains, and connecting these chains causes gelation.

Connection through chemical bonds or entanglement

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13
Q

What is the difference between chemical and physical gelation?

A

Chemical gelation involves strong/ permanent bonds, while physical gelation involves weak interactions that are potentially reversible.

Chemical geltation difficult to reverse without breaking bonds.
Some physical networks can be reversed (e.g. dilution or temp change)

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14
Q

What are the characteristics of chemically crosslinked hydrogels?

A
  • More stable (mechanically)
  • Tuneable degradation
  • Potentially cytotoxic crosslinking agents
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15
Q

What are the characteristics of physically crosslinked hydrogels?

A
  • Does not require chemical crosslinking agents
  • Potentially avoids cytotoxicity
  • Can be triggered by factors like temperature or pH
  • Weak
  • Potentially reversible
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16
Q

What is dual gelation?

A

Dual gelation refers to the combination of chemical and physical gelation methods, providing the benefits of both.

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17
Q

Fill in the blank: Hydrogels can be designed to provide _______ cues to cells.

A

cell-guiding

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18
Q

True or False: Hydrogels can integrate with native tissue.

A

True

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19
Q

What is tensile strength?

A

Deformation in stretch

It refers to the ability of a material to withstand being pulled or stretched.

20
Q

What is compressive strength?

A

Deformation through ‘crush’

It refers to the ability of a material to withstand being compressed. E.g. ligaments.

21
Q

What is bend strength?

A

Deformation through flexion

It refers to the ability of a material to resist bending forces.

22
Q

What is rheological strength?

A

Deformation in shear

It refers to the ability of a material to resist shear forces.

23
Q

What does porosity in a hydrogel refer to?

A

The presence and characteristics of pores within the material’s structure.

  • How porous is the material?
  • How big/small are the pores?
  • Are these pores interconnected?
24
Q

What factors are considered when characterizing the porosity of a hydrogel?

A
  • How big/small are the pores?
  • Are these pores interconnected?

These factors influence the hydrogel’s properties and applications.

25
What does degradation in a hydrogel imply?
Loss of structure/mechanical strength ## Footnote * Change in the geometry (consider swelling ratio of the hydrogel) * Byproducts and potential toxicity issues) Degradation can affect the hydrogel's performance in applications.
26
What changes occur in a hydrogel during degradation?
* Change in geometry * Swelling ratio of the hydrogel * Byproducts and potential toxicity issues ## Footnote These factors can impact the safety and efficacy of the hydrogel.
27
What does biocompatibility of a hydrogel refer to?
Cell response to material architecture and chemistry ## Footnote It assesses how well the hydrogel interacts with biological tissues. Inflammatory response.
28
How can cells affect hydrogel behavior?
They may accelerate degradation ## Footnote Understanding cell interaction is crucial for designing effective hydrogels. Inflammatory response.
29
What is the first method for utilizing extracellular matrix (ECM)?
Using what we have (the ECM) ## Footnote ECM is already in the body and has the right chemistry and physical structure. Decellularised ECM materials.
30
What is the second method for creating hydrogels?
Creating what we want from scratch ## Footnote This method allows for more control over the material properties. Often inspired by nature using peptide-based materials.
31
What is involved in the decellularisation method?
Create new materials using decellularised tissue * Use the existing protein matrix * Decellularised * Mill into a powder * Reconstitute as a hydrogel * New scaffold for cells * Form any geometry desired (wound specific geometries) ## Footnote Decellularisation preserves the native architecture of the ECM.
32
What was the outcome of using UBM (decellularised urinary bladder matrix from pig) on Liko, the dolphin?
Fully healed after casting as a sheet to fit around the fin ## Footnote UBM stands for decellularised urinary bladder matrix.
33
What is the significance of protein quaternary structure in hydrogels?
Leads back to a specific sequence of amino acids (primary structure) ## Footnote Understanding this structure is important for mimicking natural proteins.
34
What is the first step in creating de novo peptides?
Creating a secondary structure ## Footnote This is essential before developing more complex systems. ECM-like chemistry can be added (functionalisation or decoration) Difficult to create whole proteins but can begin by trying to mimic the secondary structure (peptides a-helicies or b-sheets)
35
What is meant by functionalisation or decoration in hydrogels?
Adding ECM-like chemistry ## Footnote This process helps in controlling the gel behaviour (injectable vs non-injectable systems)
36
What are some methods of hydrogel fabrication?
* Moulding/Casting * Extruding * 3D printing * Bioprinting ## Footnote These methods allow for diverse applications and designs of hydrogels.
37
What is the goal of the Atala Group's research?
3D printing the human kidney ## Footnote This exemplifies advanced applications of hydrogel technology.
38
Why are hydrogels used in drug delivery?
Can be used as a carrier (spaces between polymer chains). High retentoin rate and promotes diffusion upon trigger. ## Footnote Cervidil induces labour for pateints close to time of delivery.
39
Why are hydrogels used for wound dressings?
Material needed that won't dry inside the body. ## Footnote GranuGel used as a giller to maintain moist environment to promote healing.
40
Why are hydrogels required for implant coating?
Acts as an envelope around implant (metal) to prove a cell-friendly material on devices.
41
How is type of hydrogel chosen?
Type dependent on application, e.g. acellular (provides cures for cell ingress) or cell-laden (delivers cells to wound site inducing repair)
42
How do hydrogels physically replicate the ECM?
Stiffness
43
Properties of required of hydrogels for regenerative medicine
* Non-toxic * Mechanically stable / controlled degradation * Provide chemical and physical cues to the cells * Promote healing and tissue reconstruction * Integrate with native tissue (seamless blend) * Promote functionality (cells constantly adapt in environment)
44
Types of natural hydrogens
Algae based: carrageean, alginate, agarose Animal proteins: fibrin, collagen, laminin Decellularised tissues
45
Properties of natural hydrogels
* Fibrous * Non-toxic (mostly) * Can be functionalised with cell-guiding cues
46
Types of synthetic hydrogels
* Poly(lactic) acid * Poly(glycolic) acid * Poly(urethane) * Peptides
47
Properties of synthetic hydrogels
* Can be designed (and therefore controlled) * No batch-batch variation * No animal sacrafice

Regenerative Medicine (12 decks)

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