BIOM 573 - Final Exam

3 Tenants of Ethics

1. place service before profit;

2. honor of the profession before personal advantage;

3. public welfare above all other considerations

Viscoelasticity

fluids resistance to gradual deformation; behavior is dependent on time and temperature; phase lag between input strain and output stress

Creep

deformation increases with constant force with respect to time

Stress Relaxation

stress decreases with constant deformation

Hysteresis

difference in stress values during loading and unloading

Toughness

ability of a material to absorb energy/loading; energy to failure

Resilience

ability of a material to absorb energy when it is deformed elastically

Thermoplastics

can be remolded when heated; lacks crosslinks; mostly linear polymers with some branches and flexible chains

Thermosets

cannot be remolded; has covalent crosslinks => resists vibrational and rotational chain motions

Molecular Characteristics of a Polymer

1. chemistry (monomer composition)

2. size (molecular weight)

3. shape

4. structure

3 Mechanisms of Chemical Degradation for Polymers

1. cleavage of crosslinks;

2. cleavage of side chains;

3. cleavage of polymer backbone

mainly occurs by hydrolysis

Chromatin

Bundle of DNA wrapped around histones that stores the genetic material of a cell

Epigenome

Control of gene expression through local unwinding of chromatin or DNA modification

Stable Oxide Film for Metals

spontaneously forms upon exposure to air and biological fluids; composed primarily of TiO2; resistance to corrosion

Negatives to Stable Oxide Film

thin, making it easier to compromise, and ion particles be released; film is continuously dissolved and reconstructed in aqueous solutions

Polarization Resistance (Rp)

corrosion process of metallic biomaterials in the body generates a current as the metal ion moves from the electrode to the solution, and there is an inherent resistance to this movement of charge

Characteristic Categories for Bioceramics

1. bioinert;

2. biodegradable;

3. bioactive

Properties of Proteins that Affect Protein Adsorption

1. size;

2. charge;

3. structure stability;

4. unfolding rate

Properties of Surfaces that Affect Protein Adsorption

1. topography;

2. composition;

3. hydrophobicity;

4. heterogeneity;

5. potential

The Vromann Effect - Adsorption/Desorption

initially adsorbed protein desorbs, leaving space for protein 2 to adsorb

The Vromann Effect - Competitive Exchange

initially adsorbed protein is displaced by protein 2 which has a stronger binding affinity to the surface

The Vromann Effect - Exchange via Transient Complex Formation

protein 2 embeds itself in previously adsorbed protein 1 to form a transient complex, protein 1 desorbs when exposed to the solution

Cell interaction with foreign surfaces are mediated by:

integrin receptors

T-Cells

Coordinate immune response and kill infected cells; adaptive

B-Cells

produce antibodies to target pathogens; adaptive

Macrophages

engulf pathogens and present antigens; innate; M0 (unpolarized), M1 (pro), M2 (anti)

Neutrophils

rapidly attach and ingest pathogens; innate

Monocytes

precursors to macrophages and dendritic cells; innate

Dendritic Cells

Capture antigens and activate T-cells; bridges innate and adaptive

Biomaterial Development

Delamination Resistance

1. covalently bonding the modified region to the substrate;

2. intermixing the components of the substrate and the surface film

3. compatibilizing (“primer”) layer at the interface

Biomaterial Development

Nonfouling Surfaces

surfaces that resist the adsorption of proteins and/or adhesion of cells

Biomaterial Development

Exopolymer

biopolymer that is secreted by an organism into the environment; produces biofilms that anchor bacteria and are difficult to eradicate by host immune effectors

Biomaterial Development

Driving force for Protein Adsorption

unfolding of the protein on hydrophobic surfaces

Biomaterial Development

Principal Significant Adaptive Responses of Cells

1. hypertrophy: increase in size;

2. hyperplasia: increase in number;

3. atrophy: decrease in size;

4. metaplasia: transformation from one type to another

driven via stimulus

Biomaterial Development

Factors Impacting Biocompatibility

1. toxicology: measurement and effects of material leaching

2. extrinsic microbiologic organisms: contamination (fungus, bacteria, etc.)

3. mechanical effects: rubbing, irritation, compression, stress concentrations, size mismatch, etc.;

4. cell-biomaterial interactions: immune response cascade, short vs long term

Biomaterial Development

3Rs of Animal Models

1. replacement: replace with cell cultures, human volunteers, computers

2. reduce: use minimum number of animals

3. refinement

Tissue Engineering

aims to restore tissue and organ function by employing biological and engineering strategies to clinical problems

Tissue Engineering

Design Criteria

cell source & type → biomaterial → stimuli (mechanical and biochemical)

Tissue Engineering

2 Main Approaches

1. transplantation: tissue grown in vitro consisting of an artificial matrix

2. in situ regeneration: artificial matrix and growth factors act as a template to induce host cell regeneration

Medical Product Lifecycle

Biomaterial Product Classifications

1. devices;

2. drugs;

3. biologic: achieve purpose by means of virus, therapeutic serum, toxin, blood, etc.

Medical Product Lifecycle

Path to clinic for Drugs and Biologics

1. preclinical: in vitro and in vivo animal tests;

2. phase I: tested in small number, safety

3. phase II: larger number, optimizing dosage

4. phase III: effectiveness and side effects

Medical Product Lifecycle

Path to clinic for Devices

1. classify device: risk levels

2. premarket submission

3. nonclinical and clinical testing

4. premarket submission: meet with FDA;

5. post market: tracking, malfunctions