AVS 51st International Symposium
    Biomaterial Interfaces Friday Sessions
       Session BI-FrM

Paper BI-FrM4
Conformational Mechanics of Surface Grafted Stimulus-Responsive Polypeptides

Friday, November 19, 2004, 9:20 am, Room 210D

Session: "Active" - Dynamic Biointerfaces
Presenter: A. Valiaev, Duke University
Authors: A. Valiaev, Duke University
D.W. Lim, Duke University
N. Abu-Lail, Duke University
A. Chilkoti, Duke University
S. Zauscher, Duke University
Correspondent: Click to Email
Stimulus-responsive macromolecules have attracted significant research interest due to their potential applications in drug delivery, molecular motors, and nanoscale actuation devices. ELPs are stimuli-responsive biomacromolecules that undergo an inverse phase transition triggered by changes in solvent temperature, pH, or ionic strength. Associated with this transition is a significant conformational collapse and change in surface energy. To date, most research on ELPs has focused on the investigation of bulk properties and their aggregation behavior in solution. Our research is the first, we believe, to provide detailed insight into the mechanisms of elasticity and conformational mechanics of ELPs immobilized as ensembles on surfaces and on the single molecule level. First we performed single-molecule force spectroscopic experiments on elastin-like polypeptides (ELPs) that shed light on their time-dependent structural changes, physico-chemical and mechanical properties. We also present results obtained with a quartz crystal microbalance (QCM), cantilever deflection measurements, and adhesion force spectroscopy on surface immobilized ELP ensembles. QCM enabled us to study the effective mass change and the change in the mechanical dissipation behavior when ELPs collapse and swell as waters of hydrophobic hydration are released or consumed by the surface grafted protein. Experiments with micro-cantilevers decorated on one side with covalently grafted ELPs showed that a phase transition induces a considerable surface stress, leading to significant cantilever bending. Our approach promises to yield simple and sensitive bioanalytical devices, because cantilever bending can be easily measured. Lastly, adhesion force spectroscopy enabled us to quantify surface energetic changes associated with the phase transition behavior of surface grafted ELP ensembles.