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 Found in bones Micro size (~100-300 µm) Nano size (~100 nm) Found in bones

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

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

Experimental Group 2

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