(527d) Switching the Aggregation of Nanoparticles by pH Dependent Conformational Transitions of a Self-Assembled Polypeptide

Controlling the stable structures of metallic nanoparticles (~1-100nm) on mesoscopic and macroscopic length scales is of great interest in nanobiotechnology. Our interest lies in achieving this control with synthetic biopolymers that are responsive to external stimuli and exploiting biological characteristics such as recognition and conformational change. The long term goal is to create nanometer scale constructs for application in functional devices such as sensors, photonic materials, and biomolecular electronics. In this presentation, we will discuss the reversible aggregation of gold nanoparticles (GNP) induced by pH dependent conformational changes in a monolayer of poly(L-glutamic acid) (PLGA). Disulfide modified poly(L-glutamic acid) (PLGASS) was prepared where the disulfide anchoring group drives chemisorption on a gold surface and leads to the formation of a self-assembled monolayer. Experimental results show that as the PLGA undergoes a change from a random coil to a helical conformation with decrease in pH and protonation, the modified GNP aggregate. The change in aggregation behavior with pH was almost instantaneous and completely reversible. The presentation will focus on the preparation, characterization, and properties of these novel adaptive materials.