Transcript Effects of hydroxyapatite particles size on PAH

Effects of hydroxyapatite particle
size on PAH-GMA hydrogel
Venkata Damaraju
Mentor: Dr. Sidney Sit
What is a hydrogel?


Biocompatible jello-like substance
A matrix of polymers



Poly(allylamine hydrochloride) (PAH)
Glycidyl methacrylate (GMA)
Poly (ethylene glycol) diacrylate (PEG-DA)
Uses of hydrogel
Cell and tissue repair/regeneration
 Drug delivery systems
 Wound dressing
 Cornea implants 

Problem?

Cells don’t stick to the hydrogel!
Solution?
Add adhesive peptides
 Add particles 



Particles create pores
Allow cells to filter in and self adhere
Which particles?

Hydroxyapatite



Micro size (~100-300 µm)
Nano size (~100 nm)
Found in bones
My experiment setup
Experimental Group 1
Negative control
Experimental Group 2
Sonicated for 20 min.
Sonicated for 40 min.
Both nano and micro
particles
Both nano and micro
particles
Electrochemical Impedance
Spectroscopy



Non-destructive way of characterizing
the physical properties
Measures the impedance (Resistance)
over a frequency range
Constant AC current of 0.1 mA
Experimental Group 1
Average Impedance (|Z|)
(ohms)
Average Comparision of Experimental Group 1
5000
4000
Control
Micro Particles
3000
Nano Particles
2000
1000
0
1.0E+04
4.0E+04
7.0E+04
Frequency (Hz)
1.0E+05
Experimental Group 2
Average Impedance (|Z|)
(ohms)
Average Comparision of Experimental Group 2
5000
4000
Control
Micro Particles
3000
Nano Particles
2000
1000
0
1.0E+04
4.0E+04
7.0E+04
Frequency (Hz)
1.0E+05
SEM Imaging
Control hydrogel without particles
SEM Images
Hydrogel with hydroxyapatite particles
Conclusion




Addition of particles decreased the
overall impedance
Lower impedance means more pores
Sonication for 40 min gave better
dispersion of particles
SEM shows particles settled in the
hydrogel, but as very small fragments
Future work


Perform cell culture on the hydrogel
with particles
Add other particles to achieve larger
pores
Acknowledgement







Dr. Sidney Sit
Stephanie Tully
Dillip
Praveen
Syeda
Karen Xu
Nicolas McHughes