Scaffolds For Tissue Regeneration Flashcards
What is bone made of?
Composite material Collagen Hydroxyl apatite HA Can withstand cyclic loading Not brittle Viscoelastic
Ideal scaffold for bone replacement
Porous structure Biocompatible Cheaply produced Easily sterilised Mechanical properties similar to host tissue
Ideal scaffold for regenerative graft
Act as template for tissue growth in 3D - macroporous structure
Ideally something that degrades by enzymes/cells
Provides stimulatory signals to cells for regenration
What are the 3 modes of replacement
Autografts: replacing defect site with hosts body parts
Allografts: transplant of bone from another person, same species
Xenografts: source from a different species
What does osteoconductive mean
When bone graft material acts as scaffold for new bone that is started by native bone
Osteoblasts from surrounding bone spread and generate new bone
3 types of artificial bioceramics
Osteoconductive: hydroxyl apatite. Degrades very slowly
Osteoconductive and resorbable: carbonate and silicon, tricalcium phosphate
Osteoinductive and resorbable: bioactive glass, amorphous glass, degrades fast and is very bioactive. Silica can instigate bone cells
What does osteoinductive mean
Stimulation of osteoprogenitor cells that then begin new bone formation
Will trigger formation of new osteoblasts- faster integration of graft
Eg. Bioactive glass
What are 3 bioceramics
Porous hydroxyapatite
Coralline HA
Actifuse - HA powder that can mix with water, silicon substituted HA
How is coralline HA made
Converts coral (97% CaCO3) Can be converted to HA through hydrothermal conversion
What are the features of bioglass
When applied onto structures material dissolves to form apaptite later
Calcium phosphate production = layer of protection
Releases calcium and silica - stimulate bone cells
Describe sol gel process of making bioactive glass
Silicone molecules are hydrolysed
They will bind together by gelling
Forms glass by first forming nanoparticles = pores
Interconnections between pores and rough surface area increases = more SA for silica to dissolve = more bioactive
Can be made at lower temperatures
3 ways of making porous scaffolds
Freeze drying: add water and ethanol to glass and freeze and sublimate, water and ethanol removed = pores
Porogen: mix glass with salt/paraffin, remove with solvent
Gel cast foaming: introduce surfactant and shake and then remove from glass
3D printing
What is the issue with polymer + bioglass scaffolds?
Different degradation rate
Polymers not bioactive
Lack of interaction = loss of mechanical properties
How can we solve the issues of polymer + bioglass
Hybrid of polymer and glass interacting with nanoscale matrix
So small that cells dont recognise difference
Degradation rate is uniform
They are very hard to make, have to find source that can bond to silica
