The document discusses a project to develop biodegradable polymer coatings for orthopedic implants using thermal spraying. The experimental setup involved flame spraying polymethylmethacrylate (PMMA) and polyhydroxybutyrate-co-polyhydroxyvalerate (PHB/PHV) onto titanium substrates. Results showed the coatings achieved full substrate coverage with roughness within acceptable levels. Wettability and FTIR tests indicated the coatings maintained polymer biocompatibility. Cell proliferation studies also showed biocompatibility. Next steps include optimizing polycaprolactone coatings and conducting further biological assessments. The goal is to develop a local drug delivery system for orthopedic implants using thermally sprayed bi

1. Ahmed Chebbi

2. Presentation Layout
 Technology background
 The idea behind the project
 Experimental set-up
 Results
 Conclusions
 Next steps

3. Orthopaedic implants: present technology
 To provide for an adequate range of motion
 To transfer the joint load onto the bone
 Osseointegration properties of some
materials (Hydroxyapatite) elicit a specific
biological response at the interface of the
material
 Results in the formation of bond between
the tissues and material.

4. Orthopaedic implants: Limitations and
Challenges
 Thermal spraying used to deposit coatings for
enhanced mechanical behaviour
 Mechanically related limitation such as implant
loosening
 Biologically related limitations such as post-operative
infections
 Solution: Localised Drug Delivery System (DDS)

5. Idea behind the project
 Biocompatible polymers (PMMA , PLLA, etc.) are widely
used as drug delivery system
Advantage: Biocompatible polymers were successfully
thermally sprayed to obtain coating with enhanced
mechanical properties
Drawback: A second operation to remove carrier
 Biodegradable polymer offer a solution but were not
thoroughly investigated with thermal spraying
Thermal spraying of biodegradable polymers for:
A drug delivery purpose
A structural (mechanical) purpose

6. Flame spraying
 Flame spraying used to melt polymer powder and form
coatings on titanium substrates
 Temperature generated up to 3000o C
 Jet velocity up to 100 m/s

7. Experimental set-up and spraying parameters
 Biopolymers: Polymethylmethacrylate (PMMA)
 Biodegradable biopolymer: Polyhydroxybutyrate 98%/
Polyhydroxyvalerate 2% (PHB/PHV)
 screening stage. The experimental design used was the 3level factorial design (33) with 5 midpoint repeats

8. Biopolymers
 PMMA:
Good mechanical properties and
biocompatibility
 PHBV:
 Superior piezoelectricity properties, no
undesirable chronic inflammatory
response after implantation, its
mechanical properties can be changed by
varying the ratio of the respective
monomers (PHBV)

9. DoE Results

10. DoE Results

11. Thickness/Roughness/Adhesion
 Thickness levels affect the degradation rate in vivo.
 Crucial to control thickness in order to control the
amount of drug released
 Roughness affects the degree of cell attachments.
 Bare Titanium disk: Ra~3.1 microns => Polymer
coating: Ra~2.61 microns
 Understanding how adhesion is affected by process
parameters in order to obtain the highest levels of
adhesion.

12. Wetting Properties
 Average contact angle ~ 53o for PHBV/PMMA
 Hydrophilic surfaces are more osteogenic than are
hydrophobic surfaces

13. FTIR Study

14. Cell Proliferation Study
0.6
0.5
OD at 450mm
0.4
3 Days
0.3
5 Days
0.2
0.1
0
Reference
PHB/PHV
PCL
Titanium

15. Conclusions
 Fully covered substrates were obtained
 Sample roughness was not considerably reduced and remained within
advisable levels
 Excellent wetting properties =>precursor of good cell attachment
 Minor chemical degradation
 Polymer biocompatibility maintained
 Better understanding of responses variation in relation to process
factors

16. Next Steps
 DoE for another biodegradable polymer:





Polycaprolactone
Spray optimised parameters for polymer matrix on
titanium
Plasma spray HA coatings
Spray optimised parameters for polymer matrix on
titanium
Conduct weight loss, ph, and conductivity tests
More thorough biological assessment: flueorescent
microscopy, alkaline phophatase, cell proliferation

17. This work is funded by: