(216aj) Protein Adsorption At An Environmentally Responsive Surface: Towards Improved Adsorptive Membrane Materials

We examined molecular level protein adsorption and desorption behavior on poly(acrylic) acid brushes (PAA), an environmentally responsive surface.     PAA brushes are of particular interest because they have been proposed as a promising adsorptive material and can be used as an ion exchange media, controlled in large part by environmental conditions such as pH and conductivity.   This study aimed to characterize and then optimize adsorption kinetics for, egg white chicken lysozyme (PI~ 11) and bovine serum albumin (BSA) (PI~4.8), to PAA brushes.

A new approach using Si-Atom Transfer Radical Polymerization (Si-ATRP) was successfully used for the controlled polymerization of sodium acrylate that with additional sample modification resulted in homogenous PAA brushes.   The effect of varying polymerization conditions, such as molar ratios of polymerization components and initiator concentrations, along with rinsing techniques, were examined.   The surface chemistry of these PAA brushes on modified gold-coated substrates was verified and characterized by FTIR-hATR, ellipsometry, SEM images, AFM, and water contact angle measurements.

The PAA brushes were ‘grafted from’ a gold substrate/chip and used with Surface Plasmon Resonance (SPR) spectroscopy to examine the fundamental interactions and adsorption/desorption kinetics of model proteins to the PAA surface. SPR spectroscopy enabled the detection of molecular level transport phenomena, fundamental adsorption behavior, and intrinsic physicochemical properties at the solid/fluid interface for various microfluidic system conditions.   SPR sensors are frequently used to examine molecular level binding events and are advantageous over many other detection techniques due to their high resolution and real-time, label-free detection abilities.  Seven process variables (including temperature, protein concentration, and buffer conditions), were examined and correlated to performance metrics used for determining optimal adsorption properties.