1. Biomaterials in Nephrology
Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®.
Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion.
Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience.
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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.
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3. Filtration Materials Hollow Fiber Membranes (HFM);
Selective Separation;
Materials
Thermoplastics-PS, PAN, PAN-PVC, CA, CN
Polyurethane
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4. Hollow Fiber Modules
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5. Separation Based on Size Exclusion
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6. 11/15/2018

7. HFM Fabrication -Fiber Spinning
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8. Phase Inversion Controlled precipitation
Solution--> porous solid that is interconnected and traversed by an interpenetrating pore structure which provides channels across the wall structure
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10. 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
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11. Anatomy of a Spinneret Spinneret HFM Note: Picture not drawn to scale
Polymer
Solution
Stream
Nonsolvent
Note: Picture not
drawn to scale
Outflow
Spinneret
HFM

12. 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
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13. Anatomy of a Spinneret Spinneret HFM Note: Picture not drawn to scale
Polymer
Solution
Stream
Nonsolvent
Note: Picture not
drawn to scale
Outflow
Spinneret
HFM

14. Polymer Solution
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15. The Addition of Non-solvent
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16. Precipitation with Chain Entanglement
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17. Anatomy of a Spinneret Spinneret HFM Note: Picture not drawn to scale
Polymer
Solution
Stream
Nonsolvent
Note: Picture not
drawn to scale
Outflow
Spinneret
HFM

18. Various Stages in the Early Life of a HFM

19. Polymer Rich Zone
Dense Skin
Lumen of Hollow Fiber
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21. Topography of Selective Skin Layer
Photodiode
XYZ
piezotranslator
Cantilever and
Probe Tip
Laser
YM is regenerated cellulose
PM is polysulfone
XM is pan-pvc
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22. Inner Skin Ultra-topography
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23. 35 1000 x 1000 nm nm 4° C - 100% H20 Quench 22° C - 100% H20 Quench
54° C - 50/50 DMF/H20 Quench nm

24. Polymer Rich Zone
Dense Skin
Lumen of Hollow Fiber
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25. Production Spinning Line
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26. Molecular Separation Reverse osmosis-Ion selective
Ultrafiltration-rejection of molecules >100kD
Microporous-rejection of cells
Macroporous-cell permeable
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28. Diffusive Transport Characteristics
0.1
1.0
10.0
100.0
1000.0 1 10
100
1000
Molecular Weight (
kDa )
Km (x 10 6
cm/sec)
Water
PAN -
PVC
Hindered Transport Model
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29. Increased Number of Pores
Concentration
Concentration
Concentration
Concentration
Gradient
Gradient
Gradient
Gradient ) c ( P x D = ÷ ø ö ç è æ J s
Fick’s
Fick’s
Fick’s
Fick’s
Law
Law
Law
Law
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30. On a Larger Scale Various Structures are Apparent and can be controlled by changing Fabrications conditions F A C D G B
asymmetric - phase inversion technique - fabrication
Macroscopically it is characterized by a thin densely packed top layer (referred to as the skin layer) supported by a very open porous layer containing elongated voids (referred to as the macrovoid layer).20 While the pore size characteristics of the very thin skin layer (~ 1% of overall membrane thickness, typically mm) confer the permselectivity of the membrane, the macrovoid layer imparts structural integrity to the skin layer. Both single and double skinned varieties have been studied. The structural attributes (i.e., porosity and pore size distribution) of the skin layer are determined during fabrication of the membrane.21 Slight variations in protocol can lead to a significant differences in transport characteristics of the membrane produced.
. ultrafiltration: pressure-driven membrane-based separation process in which particles and dissolved macromolecules smaller than 0.1 µm and larger than about 2 nm are rejected
asmmetric membrane: membrane constituted of two or more structural planes of non-identical morphologies ()
dry-wet phase separation membrane formation: combination of the dry- () and the wet-phase formation processes ()
selective membrane skin: region, often located at the upstream face of an asymmetric membrane, that forms a thin, distinguishable layer primarily responsible for determining the permeability of the asymmetric membrane
dialysis: membrane process in which transport is driven primarily by concentration differences, rather than by pressure or electrical-potential differences, across the thickness of a membrane
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 AN Valette et al.1999
H PMMA Valette et al.1999 E H
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31. Applications Blood gas oxygenators Plasmapheresis Dialysis
Liquid sterilization
Bioartificial liver
Bioartificial kidney
Drug delivery-cell encapsulation
Biotechnology-bioreactors
Vascular grafts
Nerve repair
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32. Hemodialysis Hollow Fiber Dialyzer Blood flows in and is cleaned
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.
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33. Biocompatibility in Hemodialysis
Interaction of blood with dialysis membranes
Activation of humoral enzymatic pathways
Activation of white blood cells and platelets
Cuprophane membranes
Propose a biologically inspired design?
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34. Copyright © 1997 by Annual Reviews Inc. All rights reserved
Annu. Rev. Med :467–76
Copyright © 1997 by Annual Reviews Inc. All rights reserved
ACUTE RENAL FAILURE: Role of
Dialysis Membrane Biocompatibility
Manuel Pascual, MD, Rita D. Swinford, MD,1 and Nina Tolkoff-Rubin, MD
The Renal Unit and Transplantation Unit and 1 Pediatric Nephrology Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
Hemodialysis Membranes: Interleukins, Biocompatibility, and
Middle Molecules
WALTER H. HORL
Department of Medicine, Division of Nephrology, University of Vienna, Vienna, Austria.
J Am Soc Nephrol 13: S62–S71, 2002
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