Lecture 6 Notes (BME 296)

Lecture Overview

• Lecture 6: BME 296

Review Questions

• Considerations for Hip Implant Design

  • Choice of Cobalt-Chromium vs. Titanium

    • Cobalt-chromium offers better corrosion resistance.

  • Defect Reduction for Less Plastic Material

    • Investigate the types of defects that can be minimized through material choice.

  • Understanding Titanium's Grain Corrosion

    • Grain corrosion: Issue where titanium grains break down.

Recent Research Highlights

• Genetic Engineering of Proteins

  • Conducted by Toregem Biopharma (funded by Kyoto University)

  • Focus: Antibody (USAG-1) inhibits protein in the mouth to stop "tooth buds" from developing.

  • Initial studies used a mouse model with excessive teeth.

  • Key Study: (A. Murashima-Suginami et al.) on tooth regeneration through BMP signaling.

  • Considerations for Mass Production

    • Potential protein delivery methods (oral vs. other modes).

    • Rationale for using mice in preliminary research.

Exam Preparation

• Potential Exam Date: March 5, Wednesday

  • Coverage: Lectures 1-9

  • Review session scheduled for March 3.

Review Questions for Exam

• Key Polymerization Types

  • What is addition polymerization?

  • What is condensation polymerization?

  • What is genetic engineering?

Polymerization Techniques

Bulk Polymerization

• Definition and Process

  • Simple method involving monomer and monomer-soluble initiator.

  • Heat applied to initiate the reaction.

  • Advantage: High purity; direct mold use.

  • Disadvantage: Exothermic reactions; potential for thermal issues.

  • Examples of Use: PMMA (bone cement).

Solution Polymerization

• Definition and Process

  • Conducted in water or organic solvent (high thermal conductivity).

  • Monomer and initiator must be soluble in selected solvent.

  • Advantages: Effective heat transfer.

  • Disadvantages: Limited polymer yield; requires solvent recovery.

  • Similar to bulk, yielding polymers in solution (e.g., paints).

Suspension Polymerization

• Definition

  • Non-soluble monomers added to a stirred water reactor.

  • Agitation creates monomer droplets containing initiators.

  • Post-reaction: Polymer beads recovered through filtration.

  • Notable Feature: Droplet size depends on water/monomer ratio and agitation speed.

  • Typical Products: Polystyrene beads in Styrofoam.

Emulsion Polymerization

• Definition and Process

  • Starts with an emulsion of water, monomer, and surfactant.

  • Produces small polymer particles (e.g., nanoparticles).

  • Common type: Oil-in-water emulsion.

Differences Between Suspension and Emulsion

• Suspension Polymerization

  • Mechanical process.

• Emulsion Polymerization

  • Chemical process requiring a surfactant.

Polymer Formation Mechanism

• Bulk/Solution: Require soluble reactants.

• Suspension/Emulsion: Require non-soluble reactants.

Carbon-Based Materials

Overview

• Definition

  • Ceramics, specifically graphite, lack a standard unit cell but remain crystalline.

  • Structure: Hexagonal carbon atom planes.

  • Bonding: Covalent bonds between neighbors; Van der Waals interactions between planes.

Properties and Applications of Graphite

• Gas Absorption

  • Important for pyrolytic carbon preparation.

• Characteristics of Pyrolytic Carbon

  • Biocompatibility and thromboresistance.

  • Applications in cardiovascular devices due to durability and wear resistance.

Failure Modes in Carbon-Based Materials

• Research Reference

  • Addressing fatigue and fracture in pyrolytic carbon implants.

• Key Study: Robert O. Ritchie on structural integrity and life prediction.

Material Characterization Techniques

Spectroscopy and Chromatography

• Techniques Overview

  • Spectroscopy measures energy absorption by compounds.

  • Chromatography separates molecules based on chemical characteristics.

X-Ray Diffraction (XRD)

• Purpose and Technique

  • Used for determining crystal structures and calculating attributes like Miller indices.

  • X-rays are comparable in wavelength to atomic distances in solids.

XRD Data Interpretation

• Intensity vs angles

  • Review of diffraction patterns to assess atomic arrangements.

  • Information regarding crystalline phases, lattice parameters, and atomic arrangements.

Additional Analysis Techniques

Ultraviolet and Visible Light Spectroscopy (UV-Vis)

• Methodology

  • Quantitative absorption measurement of chemical substances.

  • Lambert Beer Law: linear relationship between concentration and absorbance to calculate solution concentrations.

  • Applications in biomaterials: quantification of organic materials.

Nuclear Magnetic Resonance Spectroscopy (NMR)

• Principle

  • Uses radio-frequency radiation to excite nuclei of molecules, impacted by magnetic fields.

  • Measured frequencies provide insight into molecular structure and adjacency of atoms.

Mass Spectrometry

• Function

  • Determines atomic/molecular masses through ionization and size-based separation in a magnetic field.

  • Qualitative and quantitative analysis of biomaterials.

Practical Applications of Mass Spectrometry

• Example Study

  • Proteomic analysis of biomaterial surfaces after body fluid exposure using MALDI-TOF mass spectrometry.