Biomaterials in Nephrology 6102021 1 Hollow Fibers l

Biomaterials in Nephrology 6/10/2021 1

Hollow Fibers l 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. 6/10/2021 2

Filtration l l Hollow Fiber Membranes (HFM); Selective Separation; Materials l l Thermoplastics-PS, PAN -PVC, CA, CN Polyurethane 6/10/2021 3

Hollow Fiber Modules 6/10/2021 4

Separation Based on Size Exclusion 6/10/2021 5

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HFM Fabrication -Fiber Spinning 6/10/2021 7

Phase Inversion l l Controlled precipitation Solution--> porous solid that is interconnected and traversed by an interpenetrating pore structure which provides channels across the wall structure 6/10/2021 8

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Dry-Jet Wet Spinning Spinnerette Nonsolvent Stream Note: Picture not drawn to scale Nonsolvent Stream Polymer Solution Stream Outflow Stream Nonsolvent Bath 6/10/2021 10

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

Required Elements l 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 6/10/2021 l Polymer & solvent l Miscible non-solvent 12

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

Polymer Solution 6/10/2021 14

The Addition of Non-solvent 6/10/2021 15

Precipitation with Chain Entanglement 6/10/2021 16

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

HFM Various Stages in the Early Life of a HFM

Polymer Rich Zone Dense Skin Lumen of Hollow Fiber 6/10/2021 19

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Topography of Selective Skin Layer Laser Photodiode Cantilever and Probe Tip XYZ piezotranslator 6/10/2021 21

Inner Skin Ultra-topography 6/10/2021 22

4° C - 100% H 20 Quench 22° C - 100% H 20 Quench 35 1000 x 1000 nm 54° C - 100% H 20 Quench 54° C - 50/50 DMF/H 20 Quench n m 0

Polymer Rich Zone Dense Skin Lumen of Hollow Fiber 6/10/2021 24

Production Spinning Line 6/10/2021 25

Molecular Separation Reverse osmosis-Ion selective Ultrafiltration-rejection of molecules >100 k. D Microporous-rejection of cells Macroporous-cell permeable 6/10/2021 26

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Diffusive Transport Characteristics Hindered Transport Model Km (x 10 6 cm/sec) 1000. 0 Water PAN-PVC 100. 0 1. 0 0. 1 1 6/10/2021 10 1000 Molecular Weight (k. Da) 28

Increased Number of Pores Concentration Gradient Fick’s Law 6/10/2021 æ Dc ö Js = Dç ÷ = P( Dc ) è xø 29

On a Larger Scale Various Structures are Apparent and can be controlled by changing Fabrications conditions F A C D G B 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 69 Valette et al. 1999 6/10/2021 H PMMA Valette et al. 1999 H E 30

Applications l l l l l Blood gas oxygenators Plasmapheresis Dialysis Liquid sterilization Bioartificial liver Bioartificial kidney Drug delivery-cell encapsulation Biotechnology-bioreactors Vascular grafts Nerve repair 6/10/2021 31

Hemodialysis External procedure l 3 sessions of 4 hrs a week l Filtration process only Hollow Fiber Dialyzer Blood flows in and is cleaned using the process of diffusion and ultrafiltration. 6/10/2021 32

Biocompatibility in Hemodialysis l l l 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? 6/10/2021 33

Annu. Rev. Med. 1997. 48: 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, Austria. J Am Soc Nephrol 13: S 62–S 71, 2002 6/10/2021 34

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