MSE 536- SP2025-Introduction & Important Properties of Materials

MSE 536 Advanced Biomaterials

• Course: Advanced Biomaterials

• Semester: Spring 2025

• Instructor: Aline Avanessian

Introduction & Important Properties of Biomaterials

• Overview of the course and the significance of biomaterials in medical applications.

Significant Developments in the History of Biomaterials

• Historical milestones that have shaped the field of biomaterials.

What Are Biomaterials

• Definition: Materials designed to interface with biological systems for evaluation, treatment, augmentation, or replacement of tissues or organs.

  • Types of materials: Synthetic or natural origin used in medical applications.

  • Functions: Support, enhance, or replace damaged tissues or biological functions.

  • Properties: Must be biocompatible, stable, bioactive, and fulfill functions of diseased tissues.

Biomaterials Science

• Interdisciplinary field combining biology, medicine, engineering, and materials science.

• Biomaterials scientists study material properties, interactions, and manufacturing processes.

Interdisciplinary Area

• Development, characterization, and application of biomaterials in biological systems.

Uses of Biomaterials

• Problem Areas:

  • Replacement of damaged parts (e.g., artificial joints).

  • Healing assistance (e.g., sutures).

  • Function improvement (e.g., cardiac pacemakers).

  • Diagnosis and treatment aids (e.g., catheters).

• Examples of Biomaterials:

  • Artificial hip joint, sutures, kidney dialysis machine, cardiac pacemaker.

Biomaterials in Organs and Body Systems

• Organ Examples:

  • Heart: Cardiac pacemaker, artificial heart valve.

  • Eye: Contact lens, intraocular lens.

  • Bone: Bone plate, intramedullary rod.

• System Examples:

  • Skeletal: Bone plates and joint replacements.

  • Muscular: Sutures and muscle stimulators.

Hard Tissue Replacements

• Radiographs demonstrating usage of total hip joint replacements and spinal implants.

• Highlights various implant designs and materials, such as polyethylene and metal alloys.

Soft Tissue Replacement

• Examples of soft tissue replacements include mechanical heart valves and stent-graft implants.

• Different types of sutures and their properties.

Evolution of Biomaterials

• Generational Development:

  • 1st Generation (1950-1970): Bioinert materials (metals, alloys).

  • 2nd Generation (1970-1990): Bioactive/bioresorbable materials (bioceramics, polymers).

  • 3rd Generation (1990-2010): Hybrid and nano-composites.

  • 4th Generation (2010-2030): Biomimetic materials and tissue-engineered scaffolds.

Advanced Technologies

• Nanotechnology: Atoms/molecules manipulation for novel properties.

• Smart Biomaterials: Change behavior based on physiological conditions (e.g., pH-responsive polymers).

  • Self-healing materials: Improve longevity of implants.

Innovations in Biomaterials

• Biodegradable Polymers: Reduce surgical removal needs, e.g., PLA and PGA.

• Bioactive/Biodegradable Ceramics: Interact with biological tissues, promote healing.

Testing & FDA Approval

• Highly regulated integration process for biomaterials to ensure patient safety.

  • Testing: In vitro and in vivo biocompatibility tests.

  • Regulatory Agencies: Ensures safety, efficacy, and security of medical devices.

Regulatory Pathways for Biomaterials

1. Preclinical Testing: In vitro and in vivo studies.

2. Clinical Trials: Testing in human subjects post-preclinical success.

3. Approval Process: Detailed review of data for safety and effectiveness.

4. Post-market Surveillance: Ongoing monitoring for long-term safety.

Important Properties of Biomaterials

1. Biocompatibility: Appropriate host response, no significant immune reaction.

2. Mechanical Properties: Strength, elasticity, fatigue resistance.

3. Degradative Properties: Rate of degradation must align with tissue healing rates.

Biocompatibility

• Ability to function without adverse biological reactions.

• Key factors in evaluating biocompatibility include protein adsorption and immune response.

• Ideal biomaterials should not cause inflammation or toxicity.

Biological Responses to Biomaterials

• Inflammation characteristics and factors impacting biocompatibility:

  • Material type, shape, degradation characteristics, surface properties.

Responses Between Biomaterial and Tissue

1. Toxic: Materials that harm tissue.

2. Bioinert: Physiologically inactive substances.

3. Bioactive: Substances that create bonds with host tissue.

4. Bioresorbable: Materials that dissolve in vivo, allowing tissue replacement.

Mechanical Properties

• Essential to match mechanical demands of the replacements.

• Metals provide strength for load-bearing implants, while polymers are suited for flexible applications.

Stress and Strain

• Stress: Applied loads affecting the material's structure.

• Strain: Changes in dimensions caused by stress.

Stress-Strain Behavior and Elastic Modulus

• Elastic modulus indicates the material's resistance to deformation.

• Higher elastic modulus signifies a stiffer material.

Tensile Testing

• Generates stress-strain curves to analyze material characteristics and responses under tension.

Elastic and Plastic Deformations

• Distinguishing between reversible (elastic) and permanent (plastic) deformations.

• Ductility: The capacity for plastic deformation before fracture.

Stress-Strain Curve

• Different materials exhibit different fracture and deformation behaviors; metals often show ductile behavior.

Fracture Toughness and Types of Fracture

• Measures a material's resistance to stress concentrations; essential for preventing brittle failures.

• Differences between ductile and brittle fractures.

Fatigue

• A primary cause of material failure under fluctuating stress conditions.

• Fatigue life and endurance limit refer to a material's cyclic strength.

Creep

• Permanent deformation occurring under constant stress; critical for longevity in biomedical parts.

• Different stages of creep: primary, secondary, tertiary.

Degradative Properties

• Influence the longevity and effectiveness of biomaterials, matching degradation with tissue healing processes.

Corrosion of Biomaterials

• Metals must resist corrosion; types of corrosion include galvanic, crevice, and pitting corrosion.

Surface Properties

• Surface characteristics impact protein adsorption and subsequent biological responses.

Important Surface Properties

• Surface charge, hydrophobicity, and roughness significantly affect biological interactions.

Other Properties of Biomaterials

• Summary of physical, electrical, and thermal properties affecting function within medical applications.

Summary of General Properties of Biomaterials

• Key requirements include biocompatibility, appropriate physical and mechanical properties, and the ability to be processed and sterilized.

Physical Forms of Biomaterials

• Different forms include fibers, sheets, membranes, and foams, which affect functionality and application.

Types of Bonding in Biomaterials

• Types include covalent, ionic, metallic, secondary bonding, and their significance in biomaterial properties.

Applications of Biomaterials in Medicine

• Implants, tissue engineering, drug delivery, and diagnostic applications.

Classification of Biomaterials

• Categories: Natural vs. Synthetic, with specific examples and their respective advantages and disadvantages.

Metallic Biomaterials

• Characteristics include high corrosion resistance and wear resistance, essential for various medical applications.

Ceramic Biomaterials

• Differentiated by absorbability, reactivity to biological environments, and mechanical properties relevant for implants.

Polymeric Biomaterials

• Advantages include manufacturability, biocompatibility, and biodegradable options for temporary implants.