Tissue Engineering: a new healthcare

technology 

Biomaterials

• Biomaterials science may be the most multidisciplinary of all the sciences which encompasses aspects of medicine, biology, chemistry, engineering and materials science.

• Biomaterials are : “Non-viable materials used in a medical devices intended to interact with biological systems” [D.F. Williams, 1987]

Biomaterials: Examples• Joint replacements • Bone plates • Bone cement • Hip Joint• Artificial ligaments and

tendons • Dental implants for

tooth fixation • Blood vessel prostheses • Heart valves • Skin repair devices • Cochlear replacements • Contact lenses

Hip jointHeart valve

Knee joint Skin

Biomaterials at Oxford

Nano-SIMS characterization

of TeethDrug Delivery Systems

Biomaterials Group Materials Dept.

In vitro TestingCell culture

Tissue expanderTissue Engineering

• 3-D scaffolds for tissue engineering

Example - Total Hip Replacement

Computer Graphic Actual femur head removed

Osteoarthritis

Some Artificial Hips

• UHMWPE

• Alumina

• Ti 6Al4V, Co-Cr, 316L stainless steel

Implants – An X-Ray View

New After 10 years

Gap

Bone is resorbed when not stressed.

A gap forms around the blade of the insert.

• 50,000 hip replacements (arthroplasties) in Britain each year.• Hydroxyapatite porous coatings in orthopaedic prostheses: Bioactivity, Osteoconductivity.• Problem: Infections in orthopedic surgery (10% of cases)

Total Hip Joint Replacement

Bioreactorsystem

Scaffold

Biopsy

mechanical stimuli

electrical stimuli

chemical stimuli

Human Cell Suspension

Nutrients, Growth Factors

Implantationoperation

H

Variable Pore Size in Bone

4µm 220µm

Computer-Aided Design of Vasculature

We need a structure which will be space saving, strong and yet porous to allow growth of blood vessels…

Learn from nature and use a HONEYCOMB structure

3-D printing

From Dr. Chaozong Liu Printing video

3D Printing of Biocompatible Molds

Layers of wax and scaffold material build up in 3D

3D Printing of Biocompatible Molds The wax is dissolved at high pressure and low temperature in liquid carbon dioxide…

…this leaves a porous Scaffold

Why collagen?• It is the ideal scaffold material:

is an important ECM molecule and is the major structural component in the body.

posses ideal surface for cell attachment in the body.

biocompatible and degrades into harmless products that are metabolized or excreted.

a very poor antigen , non-toxic.

Collagen processing• This technique allow

the control over pore size and porosity.

• Achieved through variation of freezing temperature and collagen dispersion concentration

Dry collagen scaffold

Advantages of Scaffold formation

• Control of the external structure:

Technology: CT/MRI CAD

Heart valve tissue engineering

Valve cells

Collagen scaffold of heart valve

Heart valve post- implantation