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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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