L3 - Biomaterials Flashcards
What is a biomaterial?
Nonviable material used in a medical device, intended to interact with biological systems
What can biomaterials be used for?
Development of scaffolds
What is biocompatibility?
Ability of a material to perform with an appropriate host response in a specific application
What is an appropriate host response?
Resistance to blood clotting and bacterial colonisation and normal healing
What is a polymer?
Large molecule made up of chains or rings of linked monomeric units
What are hydrogels?
Crosslinked polymer networks that are insoluble but swellable in aqueous medium
What are the benefits of hydrogels?
Offer an environment similar to the highly hydrated state of natural tissues
What are the two classes of natural polymers?
Protein based: Collagen, gelatin, silk, fibrin, elastin and soybean
Polysaccharides: Chitosan, alginates, hyaluronan, chondroitin sulfate
What are the pros and cons of natural polymers
P - naturally occurring therefore biofunctional
C - Batch-to-batch variability
What are some common synthetic polymers and what pros/cons do they have?
Polylactic acid (PLA), polyglycolic acid (PGA) and poly(-lactic-co-glycolic) acid (PLGA) Can be designed for a specific purpose but are costly and run the risk of rejection
What is a semi-synthetic polymer?
Hybrid molecule made by incorp of biologically active molecule onto backbone of synthetic polymer
e.g. Semi-synthetic polyethylene-glycol (PEG)-fibrinogen
PEG: density, stiffness and biodegradability
Fib: presents biofunctional domains
Natural vs Synthetic
Natural:
Built in bioactivity BUT purification, cost, immunity, lack of mechanical properties, batch variations
Synthetic:
Controlled mechanical properties and degradation, easy processibility, minimal batch variation BUT difficult to predict biocompatibility
What are the properties of biomaterials?
Physical/mechanical - strength, elasticity and architecture
Chemical: degrad, resorption, water content
Biological: interactions with cells, release of materials
Bulk properties of biomaterials
Strength, toughness, fatigue resistance, stability
What are surface modifications?
Overcoating biomaterial with molecules of different properties to optimise function
Do cells directly interact with the material?
No, a layer of protein (from plasma or growth media) adheres to the surface and the cells interact with this. The surface properties of the material affect what proteins are absorbed
What is a non-fouling material?
Resistant to ab of pt therefore won’t adhere to cells
PEG and zwitterionic polymers
May inhib bact colonisation in medical devices
How to cells adhere?
Through the receptors in their membrane
How do cell responses vary?
The surface density of RGD peptides immobilised can vary which changes the cell response
How are surfaces functionalised?
- Attach biomolecule to polymer
- Immobilization of integrin-binding peptides or entire protein
Explain the study - Geometric control of cell life and death (Chen et al)
Background - angiogen relies of interplay of mech and chem signals. Endo cell growth is critical to angio. Increase in endo spread area accompanied by an increase in cell proliferation
HYPOTHESIS - cell shape controls cell fate in endo cells
Approach - micropatterning of fibronectin islands - cells assume shape of island
Results - extent of spreading determined whether cell underwent prolif or apop
Cells can filter the same set of chemical inputs to produce different functional outputs
Explain the study - Shape-mediated differentiation of MSCs
RQ: Do changes in cell shape regulate commitment of SC to different lineages?
MSCs on islands of different shapes
Results - Flattened, spread cells = osteogenic lineage. Unspread, rounded cells commit to adipogenic lineage
