Advisor:  Andrés J. García, Ph.D.  (Georgia Institute of Technology)
Committee:
Aránzazu del Campo, Ph.D.  (Max-Planck-Institut für Polymerforschung)
Tom Barker, Ph.D. (Georgia Institute of Technology)
Evan Zamir, Ph.D. (Georgia Institute of Technology)
Cheng Zhu, Ph.D. (Georgia Institute of Technology)

Cells rely on time-dependent binding and activation by the ECM to initiate downstream signal transduction.  It is unknown whether adhesion to a ligand is required throughout various cell processes, or only during a specified time period (“temporal threshold”). Current approaches to ligand presentation often comprise of static, constant densities of ligands.  In contrast, natural cell adhesive interactions with ECMs exhibit spatiotemporal patterns of binding and activation.  Therefore, a key to future research in controlling cell-material interactions will be the development of materials that can respond to external stimuli.  

The objective of this project is to engineer biomaterials that present a UV-labile caged-Arginine-Glycine-Aspartic Acid (RGD) peptide and evaluate its effects on cell activities.   RGD is the minimal adhesive sequence of fibronectin.  In this caged-peptide, a photo-labile group adjacent to the aspartic acid residue of RGD effectively “masks” a cyclo(RGDfk) peptide.  Upon UV irradiation (360 nm), the caging group is released thereby restoring the adhesive activity of the peptide.  We have successfully tethered this caged-RGD to both poly(ethylene glycol)-based hydrogels and PDMS surfaces.  Using these systems, we will be able to dynamically modulate adhesive ligand presentation to elucidate the effects of temporal control on various cell processes.