Lecture 20: Engineering tissues & organs

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Questions and Answers

Which of the following capabilities is NOT associated with Melt Electrospinning Writing (MEW)?

Creating large sheets for tissue engineering

Producing polymer fibers of varying diameters

Generating biomaterials solely from collagen (correct)

Forming tubular structures for bone tissue engineering

What is a key advantage of electrospun fibers produced by MEW?

They mimic the size of native extracellular matrix fibers. (correct)

They are exclusively made from hydrogels.

They are significantly larger than natural fibers.

They have a randomly distributed fiber orientation.

In the context of PEG-based hydrogels, what does customizing mechanical properties refer to?

Altering fiber deposition angles during printing

Using only standard peptide sequences in formulating hydrogels

Changing the shape of the scaffold post-printing

Modifying the stiffness and softness of the hydrogels (correct)

What is essential for scaffolds created by MEW before they are used in laboratory settings?

They need to be sterilized. Signup and view all the answers

Which of the following is a purpose of culturing human osteoclasts on scaffolds?

To allow cells to deposit their own extracellular matrix. Signup and view all the answers

What is a significant characteristic of PEG hydrogels in biomedical applications?

Non-adhesive to cells and proteins Signup and view all the answers

Which method is NOT typically used for crosslinking PEG hydrogels?

Exposure to ultraviolet light Signup and view all the answers

How do PEG hydrogels enhance biocompatibility?

Through their ability to be eliminated from the body Signup and view all the answers

What is a notable feature of peptide amphiphiles (PAs)?

High design flexibility with customizable motifs Signup and view all the answers

What limitations do peptide amphiphiles (PAs) share with Matrigel?

Low mechanical properties Signup and view all the answers

What function do PEG hydrogels serve when used to coat biomaterials?

Induce non-thrombogenic properties Signup and view all the answers

Which characteristic of PEG hydrogels allows for precise tuning of their properties?

The flexibility in their crosslinking methods Signup and view all the answers

What characterizes self-assembly in the context of peptide amphiphiles?

Components spontaneously organize into ordered structures without external intervention. Signup and view all the answers

Which of the following is an example of self-assembly found in nature?

Protein complexes Signup and view all the answers

What role do peptide amphiphile fibers play in developed tumour models?

They serve as scaffolds for cellular organization. Signup and view all the answers

Which of the following characteristics does functionalization of peptide amphiphiles enhance?

The molecular composition and physical properties of the hydrogel. Signup and view all the answers

What is the expected outcome after mixing peptide and cell components for 30 minutes?

Development of free-floating hydrogels. Signup and view all the answers

In the context of drug screening applications, what primary utility do self-assembling peptide amphiphiles serve?

They facilitate tests of tumour cell reactions to various drugs. Signup and view all the answers

How long can hydrogels grown from self-assembling peptide amphiphiles be maintained in 48-well plates?

Four weeks Signup and view all the answers

In matrix analysis, what key focus is studied regarding how components assemble?

The interaction of matrix components at tumour sites Signup and view all the answers

Which feature is NOT typically associated with self-assembling peptide amphiphiles?

Energy-intensive synthesis processes Signup and view all the answers

What initiates the hydrogen swelling process in hydrogels?

Placement in water Signup and view all the answers

What type of water is primarily involved in the initial stages of hydrogel swelling?

Primary bound water Signup and view all the answers

How does the degree of swelling in a hydrogel affect solute diffusion?

More swelling enhances solute diffusion. Signup and view all the answers

What mechanical property of hydrogels is influenced by their swelling state?

Elasticity and stiffness Signup and view all the answers

At what pH level do most pH-sensitive hydrogels swell and collapse?

They swell at high pH and collapse at low pH. Signup and view all the answers

In the context of drug delivery, what happens to hydrogels in the stomach due to low pH?

They remain intact and do not release drugs. Signup and view all the answers

What effect does increased water content in hydrogels have on their optical properties?

Increases transparency and can alter refractive index. Signup and view all the answers

What term describes the additional water uptake once the network swells to a point of equilibrium?

Free water Signup and view all the answers

How does low pH in the colon affect pH-sensitive hydrogels?

It degrades the hydrogel for targeted drug release. Signup and view all the answers

What drives the additional water uptake in a swelling hydrogel until equilibrium is reached?

Osmotic pressure Signup and view all the answers

What is the primary purpose of hydrogels in drug delivery systems?

To absorb water and swell for controlled drug release Signup and view all the answers

Which degradation mechanism is NOT mentioned as a way hydrogels can degrade?

Thermal decomposition Signup and view all the answers

What factor does NOT affect the degradation rate of hydrogels?

Size of hydrogel particles Signup and view all the answers

Which statement correctly describes triggered degradation of hydrogels?

It can be induced by light or mechanical force Signup and view all the answers

What type of degradation is specifically linked to cellular interaction?

Cell-induced degradation Signup and view all the answers

What is a potential characteristic of chemically crosslinked hydrogels?

They can be designed for predefined degradation rates Signup and view all the answers

Which condition does NOT play a role in determining the degradation rate of a hydrogel?

Color of the hydrogel Signup and view all the answers

In terms of degradation, which of the following statements is accurate?

In vitro and in vivo degradation rates differ Signup and view all the answers

What defines programmed degradation in hydrogels?

It is engineered for a specific degradation speed Signup and view all the answers

Which is NOT a characteristic of spatiotemporal control in hydrogel degradation?

All degradation occurs uniformly throughout the hydrogel Signup and view all the answers

Study Notes

Engineering Tissues & Organs - Lecture 20 Notes

Hydrogels are insoluble polymer networks that swell in water. Their composition includes natural or synthetic polymers, and water content varies from at least 30% to over 90%.
Hydrogels are a major class of biomaterials with tissue-like structural properties, generated by crosslinking. This can be chemical (covalent crosslinks) or physical (hydrogen bonds, ionic bonds, self-assembly).
Hydrogels can be pipetted or 3D printed, and cells can be embedded within them.
There are three types of hydrogels: natural, semi-synthetic, and synthetic, depending on the biomaterial source. Examples include:
- Matrigel (a mix of matrix proteins and growth factors, widely used for organoid cultures)
- Collagen type-I (primary component of the extracellular matrix)
- Alginate (polysaccharide from brown algae; used as an adhesive)
- Hyaluronic acid (HA) (major glycosaminoglycan in tumor's ECM)
- Silk fibroin (high β-sheet content and shear thinning; adhesive)
Hydrogels can be chemically or physically crosslinked.
Natural hydrogels are derived from naturally occurring biomaterials.
Synthetic hydrogels are engineered from synthetic polymers.
Hydrogels are widely used in biomedical applications, including coating biomaterials (making them non-thrombogenic), functionalization (using peptides), and drug delivery systems.
Hydrogels can be triggered to degrade at specific timeframes with external cues (e.g., light, and mechanical forces).
Hydrogels can be responsive to environmental stimuli such as pH, temperature, electricity, and chemical reactions (e.g., redox processes).
Plant-based stimulus examples use materials printed using 3D printing technology, and swelling occurs with the introduction of water.
Temperature-dependent biomaterials mimic blooming flower petals by opening and closing with temperature changes; shape memory polymers are utilized.
Bio-robotic grippers use multi-material designs; shape changes are triggered by temperature.
Applications of hydrogels include soft contact lenses, personal care products, agriculture, food, cell encapsulation, and drug delivery.
Hydrogels are used in tissue engineering (cartilage, bone), regenerative medicine, cancer research (organoids & 3D cancer modeling), and drug testing.
In vitro and in vivo degradation rates of hydrogels differ.
Hydrogels can be engineered to be responsive to pH, triggering drug release in specific parts of the gastrointestinal tract.
Degradation of a hydrogel can occur via polymer backbone or side group cleavage, with rates varying depending on environmental conditions/chemistry, or a catalyst.
Hydrogels have varying properties, including solute diffusion, optical properties, and mechanical properties. Swelling and shrinking can influence these properties.
Methods for hydrogel degradation exist which include spatiotemporal control, triggered by light or mechanical force.
3D cell culture methods use hydrogels based on PEG, with variable mechanical properties for different cell types (e.g., soft vs. stiff).
Tissue engineering applications use hydrogels to create scaffolds for various tissues and organs. This allows for patient-derived cells and controlled analyses.
3D bioprinting creates tissue constructs, as well as allows for cell culture using organ-on-a-chip type models. These allow for the study of different diseases, such as studying cancer metastasis and progression. They can also be used for drug screening, and monitoring.
Research focuses on applications of hydrogels in modeling disease such as cancer.
There are many types of hydrogels as well as drawbacks to their use. Some of these limitations include cost, in-house equipment, and cell type considerations which need to be taken into account.

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Dive into the fascinating world of hydrogels in tissue engineering with this quiz based on Lecture 20 notes. Explore the different types of hydrogels, their properties, and applications in embedding cells. Test your understanding of biomaterials and their importance in organoid cultures.