1. Effects of hydroxyapatite particle size on PAH-GMA hydrogel
Venkata Damaraju
Mentor: Dr. Sidney Sit

2. 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)

3. Uses of hydrogel Cell and tissue repair/regeneration
Drug delivery systems
Wound dressing
 Cornea implants 

4. Problem?
Cells don’t stick to the hydrogel!

5. Solution? Add adhesive peptides Add particles  Particles create pores
Allow cells to filter in and self adhere

6. Which particles? Hydroxyapatite Found in bones
Micro size (~ µm)
Nano size (~100 nm)
Found in bones

7. My experiment setup Negative control Experimental Group 1
Sonicated for 20 min.
Both nano and micro particles
Experimental Group 2
Sonicated for 40 min.
Both nano and micro particles

8. 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

9. Experimental Group 1

10. Experimental Group 2

11. SEM Imaging
Control hydrogel without particles

12. SEM Images
Hydrogel with hydroxyapatite particles

13. 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

14. Future work Perform cell culture on the hydrogel with particles
Add other particles to achieve larger pores

15. Acknowledgement Dr. Sidney Sit Stephanie Tully Dillip Praveen Syeda
Karen Xu
Nicolas McHughes