Biomaterials Flashcards
PMMA
Poly(Methyl methacrylate)
UHMWPE
Ultra-High-Molecular-Weight-Polyethylene
Issues with Hip Implants
Dislocation
Osteolysis
Metal Sensitivity
What Therapeutic Ways Do We Use Biomaterials?
Replace Repair Support Improve Storage Diagnosis Monitoring
Common Classes of Biomaterials
Metals Ceramics Polymers Composites Biologics
Metals
Pros: Strong; tough; ductile; conducts electricity
Cons: May corrode; difficult to make
Examples: Joint replacement; bone plates and screws; electrodes
Ceramics
Pros: Strong in compression; Biocompatible; Wear-resistant
Cons: Brittle; Not resilient
Examples: Dental and joint replacement; Coatings for dental and orthopedic implants
Polymers
Pros: Easy to fabricate and manipulate; Resilient; Can be made transparent
Cons: Not too strong; Can deform with time
Examples: Sutures; Blood vessels; Soft tissues; Lenses
Composites
Pros: Tailor-made
Cons: Difficult to make
Examples: Carbon-fiber reinforced UHMWPE; Particle-reinforced bone cement
Important material properties
Bulk, Surface, and Biological
Metal Examples
Titanium Alloys, Cobalt Chrome, Platinum
Ceramic Examples
Quartz, Alumina
Bioceramic Examples
Alumina, Porcelain, Hydroxyapatite, Bioglass
Polymer Examples
Silicone, Polyethylene, pHEMA, PTFE, PGA
Biodegradables
Must Break Down: Safely and reliably; Relatively quickly; By biological means; Into raw materials of nature; Disappear into nature
Biodegradation Mechanisms
Hydrolysis and Enzymatic Degradation
4 Steps of Degradation
1) Water adsorption and hydrolysis
2) Reduction of molecular weight (polymer length)
3) Reduction of mechanical properties (modulus and strength)
4) Diffusion and phagocytosis by macrophages
Natural biodegradables
Naturals/Biologics, Fibrin, Collagen, Hyaluronic Acid
Stress of Metals
Linear Elastic Region; Yield Strength Point; Deformation; Breaking point
Normal Injury and Healing Steps
1) Injury
2) Bleeding and clotting
3) Provisional Matrix Formation
4) Acute Inflammation
5) Chronic Inflammation
5) Granulation Tissue Formation
6) Tissue Remodeled to Original State
Healing after Biomaterial Implantation Steps
1) Injury
2) Blood-Material Interactions
3) Provisional Matrix Formation
4) Acute Inflammation
5) Chronic Inflammation
5) Granulation Tissue Formation
6) Foreign Body Reaction
7) Fibrous Capsule Development
Macrophages
- Phagocytic cell
- Removes cellular debris
- Becomes frustrated by the presence of foreign materials
- Becomes multinucleated and releases inflammatory cytokines and reactive oxygen intermediates (ROI)
Biomimetic Coatings
Coat implant with biocompatible material
Passive: Low protein binding surfaces; PEG; Alginate
Active: Heparin (anti-coagulant) coated surfaces
Types of Implant Response Resolution
1) Resorption- material degrades
2) Integration- implant and host tissue grow together
3) Encapsulation- implant surrounded by fibrous tissue
Biocompatability Testing
Cyto-Compatibility (Cyto-toxicity) via in vitro testing then animal studies
