#FIRM2013
Jonathan Dawson
University of Southampton, UK
Self-organising clay gels for
regenerative microenvironments
Jon Dawson and Richard Oreffo
Clays for regeneration
Structure &
properties of clay
Laponite: a synthetic clay used in
cosmetics for 25 years
Clay gels self-organise
Protein localisation
1.6
1.2
Control
1.2
Alginate
r2 =0.95
0.8
0.8
0.4
0.4
Laponite
20
40
60
80
1.6
1.2
Control 1.2
Alginate
0.8
0.8
0.4
0.4
r2 =0.96
0
20
40
800
Adsorbed
Protein
600
Ambient
Protein
400
200
60
Laponite
80
Control
Alginate
r2 =0.95
Laponite
0
1.6
Protein Conc
(mg/ml)
Protein in Media
(mg/ml)
0
Protein Uptake
Lysozyme
1.6
20
40
60
80
Control
Alginate
r2 =0.97
0
Time (hrs)
20
800
Protein Conc
(mg/ml)
Albumin
Protein in Media
(mg/ml)
Protein Release
600
400
200
40
Adsorbed
Protein
Ambient
Protein
60
Laponite
80
Clay-films for surface modification
Auto-flourescence
FITC-BSA
Clay-films for BMP2 delivery
1ul
drops of
1% clay
***
10-1
10-2
*
TCP + BMP2
10-3
Clay-gel dot –
ve
Clay-gel dot +
BMP2
10-4
TCP
-ve
TCP
+BMP2
Clay
-ve
Clay
+BMP2
1.2
1
0.8
0.6
0.4
0.2
0
Mean branch-points per cell
HUVEC tubule assay
Mean branch-points per cell
Clay-bound VEGF Function
2.5
** ***
2
1.5
1
0.5
+ve
0
Laponite only
-ve
Laponite +
fibronectin
Unbound
Bound
Residual VEGF (ng/ml)
Clay-bound VEGF Function In vivo
Collagen
Scaffold
Scaffold +
Clay Gel
Following
incubation in
media +/- VEGF
200
100
***
0
VEGF
Control
Collagen
alone
Collagen +
laponite
**
Vessel volume (%)
3
2
1
0
Collagen
alone
Collagen alone
Collagen Collagen
+ laponite + factors
Collagen
+ laponite
+ factors
Collagen + laponite
Vessel number (per mm)
Clay-bound VEGF Function In vivo
*
0.3
0.2
0.1
0
Collagen
alone
Collagen + factors
Collagen Collagen
+ laponite + factors
Collagen
+ laponite
+ factors
Collagen + laponite
factors
+
Conclusions
• Clay gels can provide a one-step procedure for the
encapsulation and delivery of agents without the need for
complex chemical / physical approaches and methods.
• Retention of proteins and microcapsule recovery provides a
versatile mode of generating spatially-controlled biological
microenvironments.
• We have provided proof of concept of the ability clay-gels to
stimulate angiogenesis via localisation of VEGF and
osteogenesis by enhancing the activity of BMP2
• Clay films may allow functionalisation of implant surfaces
for localised/enhanced activity of biomolecules
Acknowledgements
Bone and Joint Research Group, University of Southampton
Surgeons at Southampton General Hospital
BMP2 binding?
Effect of BMP2 vs. Serum Concentration
Effect of cell adhesion/proliferation?
Preserved BMP2 activity…