Lecture 11: Medical devices - prostheses

Question 1

1. What is considered the gold standard for implants and why?

Answer 1

Autograft because it’s the own body. More biocompatible.

Question 2

2. Please cite the most common materials used in different implants.

Answer 2

Silicon Alumina Cellulose Titanium Hydroxyapatite Stainless Steel

Hydrogel

Question 3

3. Focusing on an implant surface, describe the order of events that occur after implantation?

Answer 3

1. Water adsorption 2. Protein adsorption 3. Cell adhesion 4. Cell behaviour and ECM formation

Question 4

4. How would you improve protein adsorption on the surface of a metallic implant? and on a polymeric implant?

Answer 4

1. Grafting
2. Multilayer films
3. Coatings
4. Gradient coatings
5. Roughening
6. Patterning

Polymeric has a covalent bond you can do chemical reactions on the surface, metals are different - they have oxide surfaces.

Question 5

5. What are the advantages and disadvantages of physical modifications to an implant surface? and chemical modifications?

Answer 5

Physical modification: ion implantation, thermal oxidation

Advantage: possible to insert selected biologically effective ions, can control concentration and depth.

Disadvantages: potential to create superficial stresses and/or modify preexisting nanometric features.

Chemical modification: electrolytes, voltage, and or put on a strong acid

Advantage: good integration of bone and control which cells can grow, precise control with etching.

Disadvantage: can change the topography, and affect the mechanical properties of the material, and need something more long term.

Question 6

6. If you want to increase cell adhesion on an implant surface how would you do that? Please suggest two methods.

Answer 6

-

Question 7

7. Besides protein and cell adhesion, why is it important for a porous implant to be hydrophilic?

Answer 7

you need blood to diffuse inside the implant. You need to vascularise it. If it is hydrophobic it will not vascularise.

Question 8

8. What are the advantages and disadvantages of allograft, autograft, xenograft and synthetic implants?

Answer 8

Allograft:

Pros: More supply, fewer complications with growing at the donor site.

Cons: Waiting lists, disease transmission.

Autograft:

Pros: best clinical outcome, integrates and lacks immune and disease-related complications.

Cons: Limited supply, and considerable pain and morbidity at the donor site.

Xenograft:

Pros: could potentially provide an unlimited supply of cells, tissues, and organs for humans.

Cons: Diseases, rejection, and ethical issues.

Synthetic implants:

Pros: Reliable, no chance of diseases, easily available

Cons: poor functionality, and longevity, less biocompatible.

Question 9

9. How is decelluarisation done? Mention possible advantages and disadvantages of this method to obtain implants.

Answer 9

Decelluarisation

1. Growth factor + mechanical stimulus
2. Implantation
3. Biopsy
4. Cell isolation
5. Cell cultivation
6. Cell proliferation
7. Scaffold.

problems : cost to decelluarise, structures contain many types of cells.

Question 10

10. Thinking of hip replacement implants, please describe in general terms its parts and which biological response you would like to obtain from each part. How would you notify the surface to obtain this response? Please justify your choices.

Answer 10

1. Head cap

Desired response: Stimulation of tissue integration.

Solution:

2. Base of head -

Question 11

13. How are “Synthetic meat/leather/tissues” created? Please describe as much as you can about the process.

Answer 11

1. Source cells
2. Grow cells
3. Grow sheets
4. Layer sheets
5. Combine layers
6. Tan hide
7. Dye and finish
8. Design