Flashcards in Lecture 18 - Novel Biomaterials Deck (16)
Aim of tissue engineering
To generate new functional tissue to repair or replace tissues missing due to disease, genetic defects or trauma
Reasons for tisue engineering failing to live up to expectations
Commercial difficulty (EG: can't get funding)
Traditional tissue engineering approach
Immerse support material in support fluid, cells and growth factors.
This is rarely successful.
When is the traditional tissue engineering approach successful?
With avascular, small or relatively 2D tissues
Way to allow engineered tissues blood supply early in development
Using an in vivio bioreactor.
A loop of blood vessel is looped through a plastic sphere. Vascularisation of tissue occurs because of hypoxic environmant
Technical challenges of tissue engineering
1) Blood supply for 3D vascularised tissues
2) Suitable biomimetic matrix materials
3) Delivery of biological signals
Challenge for biomaterials that are to degrade in the body.
Matching the rate of degradation with the rate of tissue growth
Criteria for biomaterials
2) Mechanical properties match target tissue and implantation site (EG: femur replacement will be placed under a lot of stress)
3) Suitable in vivo responses (little inflammation, FBR)
4) Can be shaped into desired structures.
5) Can be safely sterilised (not everything can be autoclaved)
6) Cost-effective, good shelf life
Examples of tailored, porous biomaterials
Foreign body reaction.
1) Layer of proteins adsorbs to material. Proteins denature.
2) Neutrophils, macrophages interrogate material.
3) Material can't be easily phagocytosed, so macrophages join to form giant cells.
4) Fibroblasts arrive, synthesise collagen.
5) Fibrous capsule surrounds material
How can foreign body reaction be avoided?
1) Layer-by-layer assemblies.
2) Amine groups added to surface of material.
3) Hyaluronic acid (-) and chitosan (+) added in sequential layers. This prevents protein adsorption.
Most effective way to release growth factors from a biomaterial
Slowly, over a long period of time
Way to deliver growth factors
Layer growth factor with hyaluronic acid and chitosan onto material.
Use of porous polymer microspheres
Could crystalise solvent of interest (EG: growth factor) into pores, use them as a delivery system
Protein that can be coated onto materials to reduce inflammation