Biomaterials Flashcards
Why are biomaterials needed and important?
Because they can help with cartilage damage, hip fracture, drug delivery and wound dressing. The market for this is very big.
What is a biomaterial?
A material intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body
Mention some different biomaterials.
Polymers, Metals, Ceramics, Composites
What is the definition of biocomatibility?
The ability of a material to preform with an appropriate host response in a specific application
What are Standards and what are they used for?
Standards are a document with guidelines that are to be followed. It is a consensus-built, repeatable way of doing something.
What are some factors that are evaluated for medical devices?
- In vitro cytotoxicity
- Immune response
- Biodegradation
- Interaction with blood
- Systemic toxicity (acute and chronic)
Explain the different In vitro cytotoxicity tests
- Direct contact test: determines if a material itself has potential to by cytotoxic
- Indirect contact test: determines if material itself has potential to release agents that may be cytotoxic
- Extraction test: material is extracted at 37 °C with culture medium and the extract is added to cell culture. Determines if a material extract has the potential to cause cell morphology change and/or lysis
Why can’t in vitro tests replace in vivo tests.
Because the in vitro tests do account for coagulation, inflammation, immune response, interactions with ECM. These aspects are very important for determining if the biocompatibility of a material.
Why are protein-cell-biomaterial interactions important?
Because cells don’t interact with a naked surface. There is often an adsorbed protein layer that mediated cellular behavior.
What properties are protein adsorption influenced by?
- Protein properties: size, shape, the distribution of hydrophobic and hydrophilic groups, and the charge distribution
- Surface properties: the topography of the surface, distribution of hydrophobic and hydrophilic groups, and the charge distribution
What is the driving force for protein adsorption?
The increase in entropy (disorder).
What can be the effects of adsorption of a protein to a biomaterial surface on the biological activity of the protein, compared to the activity in solution?
- Partial dehydration of protein and material surface
- Redistribution of charged groups in the interface
- Conformational changes in the protein molecule
Mention one difference between hydrophobic and hydrophilic surfaces.
Hydrophilic surfaces generally allow reversible proteins adsorption
What factors determine the rate of protein diffusion to a biomaterial surface?
Protein concentration and diffusion coefficient
What is the difference between surface and bulk erosion?
Bulk erosion: decrease in molar mass and mechanical properties
Surface erosion: Significant mass loss while the MW and mechanical properties are unchanged
What happens when a biomaterial is implanted?
- The immune response is activated
- The Coagulation system is activated
- The Complement system is activated
What are the consequences of the foreign body response?
- A fibrous capsule froms around the implant that may interfere with the implant
- Macrophages secrete enzymes, acids and ROS that may degrade the biomaterial
Why is the surface of a biomaterial important?
The surface properties determine the adsorption if proteins and cell interactions, therefore influencing the biocompatibility.
Mention some methods for surface modification.
- Wet chemistry: PEO (hydrophobic) inhibit all protein and cell interactions with the surface
- Gas plasma treatment: Gas at low pressure is discharged by high frequency radio waves. Generates reactive species that modifies the surface.
- Silanization
- Self-assembled monolayers
What are some methods for surface analysis?
AFM, SIMS, XPS, water contact angle
What are some advantages of using additive manufacturing?
- Rapid fabrication
- Customized design
- Low cost
- Ideal low volume processing
Describe 3 different additive manufacturing techniques.
Stereolithography: uses a laser to cure a photosensitive resin layer to create a 3D structure.
Extrusion-based AM: Creates a #D structure by extruding material through a nozzle layer-by-layer. There is a liquid to solid transition of the material.
Fused deposition modeling: Extruding a molten layer of material to create a 3D object
What is the definition of a hydrogel?
Insoluble network of polymer chains and/or molecules that swell in aqueous solutions
What is the difference between physical and chemical crosslinking in hydrogels?
Physical crosslinking: non covalent bonds that are non permanent. Can be hydrogen bonds, guest-host complexes.
Chemical crosslinking: covalent bonds that are permanent.
What are some applications of hydrogels?
Recapiulate ECM properties, Cell carriers, Drug carriers
Give some examples of biomedical uses for hydrogels.
- Scaffolds in tissue engineering
- Contact lenses
- Sustained-release delivery systems
- Lubricating surface coating
What is the definition of bioink?
Cells containing material for 3D printing. Hydrogels are well suited for bioink formulations
What are some disadvantages of autografts?
- Facilitates bone ingrowth
- Takes time
- Limited supply
What is the definition of osteoconduction?
Grafting materials form a framework outside the graft during the formation of the new bone. The bone grows on a surface
What is the definition of osteogenesis?
The formation of bone
What is the definition of osteoinduction?
The process by which osteogenesis is induced. Cells within the grafting material are converted into bone-forming cells to form the new bone
What are some alternatives for bone grafts?
- Synthetic scaffolds w/wo stimuli
- Induction: BMPs or matrix derivatives
- Cell-based TE: fresh bone marrow, cultured MSCs.
Why do cell-based RM fail?
The cells die in big implants. Cells do nor survive in an environment without blood
What are some guidelines that regulate the biomaterials biocompatibility from a cell-biomaterial interaction?
- Specific adhesion proteins and cells receptors
- Signal transduction
- Cell differentiation
- Tissue development
- Host immune response mechanism
What are som application of interfacing and modelling?
- Regenerative medicine
- Drug delivery
- Gene therapy
- In vitro tissue and disease models
What are some advantages to 3D cell cultures compared to 2D?
- Natural gradient formation
- Physiologically relevant mechanism forces
- In vivo-like cell morphology and gene expression (mimics the human relevant microenvironment)
What are the ideal chemical, physical and biological characteristics of a biomaterial for engineering of bone tissue?
- Biocompatibility
- Mechanical properties
- Porosity
- Degradable
- Bioactivity
- Chemical stability
