Lecture 8 - Fibrous Scaffold Fabrication

Question 1

Fabrication of Natural Polymer-Based Nanofibers

Answer 1

• Electrospun scaffolds usually crosslinked to improve stability (against water/enzymes) and to improve mechanical properties
• Solvents could denature polymer (lose bioactivity)
• Polymer goes through high voltage (20-25kV) which could change microstructure

Question 2

Fabrication of Synthetic Polymer-Based Nanofibers

Answer 2

Can electrospin almost any synthetic polymer based on solvent combine with

Question 3

Electrospinning Gelatin

Answer 3

• Gelatin dissolved at various concentrations in HFIP
• Control diameter by concentration
• Increase concentration, increase diameter

Question 4

Disadvantage of Electrospun Nanofibrous Scaffold

Answer 4

• Densely arranged architecture of fibers and accompanying small pores hinders efficient cellular infiltration and also prevents 3D cellular integration with host tissue in vivo after implantation

Question 5

Salt Leaching

Answer 5

• Use tube surrounding electrospinning needle to incorporate NaCl particles into electrospun nanofibers via gravity at specific intervals
• Layer-by-layer nanofiber constructs containing tiny salt particles were mechanically compressed and molded into desirable 3D shapes
• Required gentle ‘sintering’ to maintain strength upon aqueous exposure
• Pores not perfectly distributed
• Leach out salt with water, leaves sufficient pore size for cells to come in

Question 6

Cryogenic Electrospinning

Answer 6

• Uses ice crystals as part of electrospinning collection device
• Electrospun fibers collected onto ice crystals formed on surface of chilled ground drum within hollow cavity enabling loading/flowing of cooling material such as dry ice or liquid nitrogen
• After drying, ice particles removed and micron-sized pores or voids remain between fibers

Question 7

Sacrificial Fiber

Answer 7

• PCL and poly(ethylene oxide) were co-electrospun to form dual polymer composite fiber aligned scaffold
• PEO dissolved to obtain scaffold having larger pores
• Pore size controlled by PEO fiber diameter and density

Question 8

‘Wet’ Electrospinning

Answer 8

• Liquid reservoir collector such as coagulation bath
• Electrospun nanofibers spraying toward bath loop on top of liquid surface and then dispersed in bath and deposited onto metal electrode at bottom
• Makes foam like structure
• Highly porous sponge is formed following freeze drying

Question 9

Femtosecond Laser Irradiation

Answer 9

• Laser with high intensity and ultrafast irradiance pulsed onto target surface containing electrospun fibers
• Ultrafast heating, melting, and ablation of fibers induced by high laser energy can produce voids in fibers
• Desirable geometric patterns such as grooves or matrix pores fabricated by controlling process parameters such as laser power, pulse, scanning rate, and orientation
• Melting of remaining fibers eliminated

Question 10

UV Irradiation

Answer 10

• Use photolithography through one porous mask to fabricate a microporous patterned nanofiber structure
• Shallow holes etched into nanofibrous mesh beneath porous mask due to UV induced fiber degradation

Question 11

Combining Nanofiber and Microfibers

Answer 11

• Electrospun nanofibers have small pore size, hot melt extruded microfibers exhibit relatively larger pore size
• Combining into composites overcomes electrospun nanofiber shortcomings
• Electrospin nanofibers on top of existing microfiber layer

Question 12

Electric Field Controlled Deposition

Answer 12

• Varying electrode configurations to form specific electric field distribution can control deposition of electrospinning jet
• Auxiliary parallel electrodes applied to fabricate aligned electrospun nanofibers

Question 13

Overcoming Porosity Issues

Answer 13

Simultaneous electrospin fiber and electrospray cells