Design and Implementation of Two-Dimensional Polymer Adsorption Models: Evaluating the Stability of Candida Antartica Lipase B at Solid-Support Interfaces by QCM-D
Sara V. Orski, Santanu Kundu, Richard Gross, Kathryn L. Beers
A two-dimensional model of a solid-supported enzyme catalyst bead is fabricated on a quartz crystal microbalance sensor to measure in situ stability and mechanical properties of Candida Antartica Lipase B (CAL B) layers under varied conditions relating to ring-opening polymerization. The model was fabricated using a dual photochemical approach, where commercially available poly(methyl methacrylate) (PMMA) thin films were crosslinked by a photoactive benzophenone monolayer and blended crosslinking agent. This process produces homogenous, rigid PMMA layers to mimic the acrylic 3D resin in a QCM-D experiment. Adsorption of CAL B to PMMA in QCM-D under varied buffer ionic strengths produces viscoelastic enzyme layers that become rigid as ionic strength increases. The rigid CAL B/PMMA interface demonstrates up to 20% desorption of the catalyst with increasing trace water content. Increased polycaprolactone binding at the enzyme surface was also observed, indicating higher affinity of the polymer for a hydrated enzyme surface. The enzyme layer destabilized with increasing temperature, yielding near complete reversible catalyst desorption in the model. Study of enzyme stability in situ will allow development of better process controls to retain enzymes on the solid support throughout multiple reactions and increase the viability of biocatalysts for commercial polymerizations.