Lecture 9 - Fibrous Scaffold Fabrication

Question 1

Applications of Polymer Nanofibers

Answer 1

• Wound dressing
• Medical prostheses
• Haemostatic devices
• Sensor devices
• Electrical conductors
• Optical applications
• Material reinforcement
• Protective clothing
• Filter media
• Cosmetics
• Drug delivery
• Tissue engineering scaffolds

Question 2

Wound Dressing

Answer 2

• Prevents scar

- Bacterial shielding

Question 3

Medical prostheses

Answer 3

• Lower stress concentration

- Higher fracture strength

Question 4

Haemostatic devices

Answer 4

Higher efficiency in fluid absorption

Question 5

Sensor devices

Answer 5

• High surface area
• Higher sensitivity
• For cells, arteries and veins

Question 6

Electrical Conductors

Answer 6

• Au/Pt fibers

- Ultra small devices

Question 7

Optical Applications

Answer 7

• Free volume

- Liquid crystal optical shutters

Question 8

Material Reinforcement

Answer 8

• Large surface area
• Higher fracture toughness
• Higher delamination resistances

Question 9

Protective Clothing

Answer 9

• Light
• Integrate additional functions
• Breathable fabric that blocks chemicals

Question 10

Filter Media

Answer 10

• Light with specific wavelength

- Higher filter efficiency

Question 11

Cosmetics

Answer 11

• Higher utilization

- Higher transfer rate

Question 12

Drug Delivery

Answer 12

• Increased dissolution rate

- Drug-nanofiber interlace

Question 13

Tissue Engineering Scaffolds

Answer 13

• Adjustable biodegradation rate
• Better cell attachment
• Controllable cell directional growth

Question 14

Tissue Engineering

Answer 14

• ECM proteins (collagen and elastin) exist in nano-fibrous form in vivo
• Electrospinning fabricates nano-fibrous scaffolds having fiber sizes and morphologies closely resembling that of ECM proteins
• Electrospinning also allows the generation of anisotropic scaffolds mimicking the particular structural and mechanical anisotropy of ECM as dictated by its function within the body

Question 15

Nanofibers Directing Neurite Outgrowth

Answer 15

• Neuron
• Cell consists of cell body and its extension neurite (axon + dendrite)
• Dendrites conduct impulses toward cell body and axons conduct impulses away from cell body
• Neurons are able to respond to stimuli, conduct impulses, and communicate with each other (and with other type of cells such as muscle cells)

Question 16

Biodegradable Nanofiber Scaffold by Electrospinning for Bone Tissue Engineering

Answer 16

• Scaffold containing larger pores (via salt crystals or sacrificial fibers)
• PCL + Mesenchymal stem cells (larger - need bigger pores)
• After 4 weeks, continuous film —> successful population of cells on scaffold surface

Question 17

Electrospun Nanofibers for In Vivo Would Healing of Diabetic Ulcers

Answer 17

• Functionalized with immobilized human epidermal growth factor (EGF)
• Start with block copolymer, want to integrate biomolecules
• Electrospin to create crosslinked network
• Introduce NH2
• Surface immobilization with growth factors (enhances biocompatibility)
• Advantage: simple, turn synthetic system into something more biocompatible
• Disadvantage: body attacks quickly, short term response

Question 18

Drug Delivery

Answer 18

• Less expensive than growth factors

- Delivery of specific antibiotic through specific scaffold

Question 19

Controlled Release of GF from Electrospun PCL Scaffold

Answer 19

• Angiogenesis critical for tissue construct survival in vivo
• When implanting engineering tissue in vivo, needs sufficient nutrients and oxygen to survive which can only be provided by blood vessels
• It is necessary to quickly induce blood vessel formation after implantation of engineered tissue (big challenge)
• Angiogenic growth factors are naturally occurring compounds that stimulate blood vessel growth
• Promoting endothelial cell migration crucial for accelerated angiogenesis in tissue constructs (force blood vessels to form
• Mimicking process of chemotaxis during formation of native blood vessels, creating angiogenic growth factor gradient in tissue constructs will stimulate endothelial cell migration and faster angiogenesis

Question 20

Angiogenesis

Answer 20

• Physiological process involving growth of new blood vessels
• Delivers nutrition

Question 21

FGF

Answer 21

Stimulator that promotes proliferation and differentiation of endothelial cells, smooth muscle cells, and fibroblasts

Question 22

VEGF

Answer 22

Stimulator that promotes proliferation of endothelial cells

Question 23

PDGF

Answer 23

Stimulator that recruits smooth muscle cells

Question 24

PCL Scaffold Fabrication

Answer 24

• Syringe Pump A: bFGF solution (growth factors)
• Syringe Pump B: PLGA solution (shell for GF)
• Syringe Pump C: PCL solution (fibers)
• Use concentration gradient of bFGF to interact with cells, other side to attract

Question 25

Gene Delivery

Answer 25

• Genetically engineering to produce better response at wound site
• DNA particle within coating layer
• Step 1: condensation —> polymer chains contract in poor solvents
• Step 2: result from step 1 + polymer chains with hydrophobic head

Question 26

Surface Modified Nonwoven PSU Fiber Mesh by Electrospinning

Answer 26

• PSU fiber
• Treat with O2 plasma
• Soak in acid (MAA)
• Chains attached to surface with COOH groups