Hollow Fibers

1
Hollow Fibers
2
Hollow Fibers

• Definition- materials capable of conducting flow
  in an axial direction or providing a conduit to
  guide the regeneration of tissue, and generally
  capable of separating soluble molecules on the
  basis of size and in certain specialized cases on
  the basis of charge (semipermeable), in other
  cases the separation is not molecular but
  cellular.

3
Filtration

• Hollow Fiber Membranes (HFM)
• Selective Separation
• Materials
• Thermoplastics-PS, PAN, PAN-PVC, CA, CN
• Polyurethane

4
Separation Based on Size Exclusion
5
Increased Number of Pores
Concentration
Concentration
Concentration
Concentration
Gradient
Gradient
Gradient
Gradient
Ficks
Law
Ficks
Law
Ficks
Law
Ficks
Law
6
Hollow Fiber Modules
7
(No Transcript)
8
(No Transcript)
9
Applications

• Blood gas oxygenators
• Plasmapheresis
• Dialysis
• Liquid sterilization
• Bioartificial liver
• Bioartificial kidney
• Drug delivery-cell encapsulation
• Biotechnology-bioreactors
• Vascular grafts
• Nerve repair

10
Hemodialysis

• External procedure
• 3 sessions of 4 hrs a week
• Filtration process only

Hollow Fiber Dialyzer Blood flows in and is
cleaned using the process of diffusion and
ultrafiltration.
11
Cell Culture Bioreactor and Purification of
Biologics
12
Bioartificial liver
Based on pig hepatocytes attached to collagen
microcarriers
13
Nerve Track Repair Bridging Substrates
14
Nerve Repair-Entubulation
15
Applications of Cell Replacement Therapy
16
Problems with Conventional Cell Replacement
Therapies

• Immune rejection
• Shortage of donor cells
• Pathogenicity
• Tumor formation
• Non-reversible treatment

17
Cell Encapsulation Technology
Immunoisolation
Waste Products
Nutrients
Immune Response
Cell Secretions
Encapsulation Membrane
18
(No Transcript)
19
Applications of Cell Replacement Therapy
20
Device Concept
21
Cell Encapsulation Therapy
Harvested Tissue
Purification and/or Isolation
Stem/Precursor Cells
Transformed Cell line
Genetic Engineering
In Vitro Expansion
Primary Cells
Implantation of device
Cell Encapsulation device loading
22
Retrievable Cell Delivery Products
23
(No Transcript)
24
HFM Fabrication-Fiber Spinning
25
Phase Inversion

• Controlled precipitation
• Solution--gt porous solid that is interconnected
  and traversed by an interpenetrating pore
  structure which provides channels across the wall
  structure

26
Required Elements

• A polymer of sufficient Mw
• that is, enough length to provide inter chain
  entanglement following precipitation and adhesive
  force to provide the appropriate mechanical
  properties for a particular application

• Polymer
• solvent

• Miscible
• non-solvent

27
Anatomy of a Spinneret
Spinneret
HFM
28
Dry-Jet Wet Spinning
Spinnerette
Nonsolvent Stream
Note Picture not
drawn to scale
Nonsolvent
Polymer
Stream
Solution
Stream
Polymer Solution Stream
Outflow
Stream
Nonsolvent
Bath
29
Polymer Solution
30
The Addition of Non-solvent
31
Precipitation with Chain Entanglement
32
Anatomy of a Spinneret
Spinneret
HFM
33
Various Stages in the Early Life of a HFM
HFM
34
Polymer Rich Zone
Dense Skin
Lumen of Hollow Fiber
35
(No Transcript)
36
Topography of Selective Skin Layer
37
Inner Skin Ultra-topography
38
4 C - 100 H20 Quench
22 C - 100 H20 Quench
35
1000 x 1000 nm
54 C - 50/50 DMF/H20 Quench
54 C - 100 H20 Quench
nm
0
39
Polymer Rich Zone
Dense Skin
Lumen of Hollow Fiber
40
Production Spinning Line
41
Molecular Separation

• Reverse osmosis-Ion selective
• Ultrafiltration-rejection of molecules gt100kD
• Microporous-rejection of cells
• Macroporous-cell permeable

42
(No Transcript)
43
Diffusive Transport Characteristics
44
Increased Number of Pores
Concentration
Concentration
Concentration
Concentration
Gradient
Gradient
Gradient
Gradient
Ficks
Law
Ficks
Law
Ficks
Law
Ficks
Law
45
On a Larger Scale Various Structures are Apparent
and can be controlled by changing Fabrications
conditions
A PAN-PVC Li et al. 1998 B
PAN-PVC Li et al. 1998 C Polyimide
Chung et al. 1992 D Polysulfone
Valette et al.1999 E Cellulose acetate
Hao et al. 1996 F PAN copolymer
Valette et al.1999 G AN69
Valette et al.1999 H PMMA
Valette et al.1999