2011 lecture 13
TRANSCRIPT
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Biomaterials
BME 551 / 551EPE
Tissue Engineering
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Objectives1. Understand how the definitions for biomaterial and biocompatibility
have evolved with time.
2. Discuss how surface chemistry affects cell adhesion and proteinadsorption. Know how these events are important to biomaterialsdevelopment.
3. Compare and contrast bulk degradation and surface degradation.
4. Know the factors that play a role in determining a materialsbiocompatibility.
5. Discuss the advantages/disadvantages of in vitro and in vivobiocompatibility testing.
6. Describe the general methods by which biomaterials are beingdesigned to be biomimetic.
7. Discuss current strategies for tailoring biomaterials for specifictissue-engineering applications (e.g., modularization,
micropatterning, stimuli responsiveness, peptide grafting, etc.)
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Biomaterials:
Evolution of definition.
Synthetic material used to replace part of a living system or to function
in intimate contact with living tissue A systemically and pharmacologically inert substance designed for
implantation within or incorporation with living systems
A nonviable material used in a medical device intended to interact with
biological systems Materials of synthetic as well as natural origin in contact with tissue,
blood, and biological fluids and intended for use for prosthetic,diagnostic, therapeutic, and storage applications without adversely
affect the living organism and its components Any substance (other than drugs) or combination of substances
synthetic or natural in origin which can be used for any period of time,as a whole or as a part of a system, which treats, augments, or replaces
any tissue organ or function of the body
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Biomaterials and Medical DevicesLimitations
Poor tissue integration No growth or adaptation
Adverse reaction (fibrosis) withsurrounding tissue
Loss of mechanical integrity with time
Increased risk of infection
Lack of biologically relevant instructive
properties
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Traditional Biomaterials and
Medical DevicesPreformance Criteria
Biologically inert
Biocompatible
Non-viable
Mechanical strength and function
Amenability to engineering design, manufacturing, andsterilization
.not found naturally within the body
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Next Generation Biomaterials
and Medical DevicesRevised Preformance Criteria
Biologically inert
Biocompatible
Non-viable
Mechanical strength and function Amenability to engineering design, manufacturing, and sterilization
Biodegradable
Induces cell and tissue integration
Smart (i.e., physiologically-responsive)
Instructional (i.e., controls cell fate)
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Types of Biomaterials
Synthetic (metals, polymers, ceramics,
composites) Nature-derived (e.g., plant-derived)
Naturally-derived (e.g., tissue-derived) Semi-synthetic or hybrid
What are the major factors that contribute to
specific biomaterial choices?
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Materials and their Medical Uses
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Question:
What are the important design criteria when
identifying a biomaterial to incorporate as partof tissue engineering design solutions?
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Tailoring Biomaterials
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Biomaterials: Surface Chemistry
Adhesion properties of cells and proteins is
dependent upon surface chemistry (general:
hydrophobic, electrostatic, van der Waals, hydrogenbonding, or specific receptor-ligand)
Cell Adhesion
Protein Adsorption
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Cell-Surface Interface
Specific Interactions receptor-ligand
Non-specific Interactions
hydrophobicity/hydrophilicity Surface topology/architecture
Physical
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Protein Adsorption
There are three main mechanisms by which surfaceproperties can modify the cell response throughprotein adsorption:
Differential affinity of proteins for differentsurfaces
Modulation of the biological activity of the
adsorbed adhesion protein due to conformationalchanges
Substrate activation of a cellular adhesion protein
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Immobilization via Adsorption
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Covalent Bonding and Graft
Polymerization
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Self-Assembled Monolayers
Substrate (glass coverslip or silicon wafer)
pretreated with a thin layer of titanium (1-5
nm); followed by a thin layer of gold (10-200 nm)
Adsorption of alkane thiol (R-SH) solutionor vapors to gold surface
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Self-Assembled Monolayers
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Microcontact Printing
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Biomaterial Processing
Micromachining
Fiber bonding
Solvent casting and particulate leaching Membrane lamination
Melt molding
Electrospinning
Extrusion
Three-dimensional printing Gas foaming
Freeze-drying
Polymer/ceramic composite foams
In situ polymerization; self-assembly
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Electrospinning Process
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Electrospinning Collection Schemes
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