AVS 49th International Symposium
    Biomaterials Wednesday Sessions
       Session BI-WeA

Paper BI-WeA5
Entrapment of Phosphate Ester Hydrolyzing Enzymes in Polyelectrolyte Multilayers Deposited on Glass Beads and Extended Retention of Their Enzymatic Activity

Wednesday, November 6, 2002, 3:20 pm, Room C-201

Session: Polyelectrolyte Surfaces/Cell-Surface Interactions
Presenter: A. Singh, Naval Research Laboratory
Authors: A. Singh, Naval Research Laboratory
Y. Lee, Naval Research Laboratory
I. Stanish, Naval Research Laboratory
T.C. Cheng, Edgewood Research Development & Engineering Center, APG, MD
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Recent advances in multilayer technology involving layer by layer technique indicate its utility in solving complex problems of multidisciplinary nature. We have explored layer-by-layer technology for entrapping enzymes organophosphorus hydrolase and Organophosphorus acid anhydrolase in polyelectrolyte multilayers with a goal to sustain their biological activity for a long period of time under an environment, where native enzymes turned inactive. Thus, phosphate ester-hydrolyzing enzymes were immobilized in multilayers coated on glass beads (30-50 µm). Coatings on Glass beads consist of 3 alternating layers of branched poly (ethyleneimine) (BPEI) and polystyrene sulfonate (PSS) as precursor layers, followed by five alternative layers of BPEI and OPH. Immobilized enzymes were tested for their enzymatic activity and stability at different temperature and under different humidity conditions and found active. Surprisingly, in 15 percent relative humidity environment an enhancement in enzyme activity was observed. Stability of multilayers incorporating enzymes was further improved by laying additional poly (acrylic acid) (PAA) layer on top of the multilayer assemblies and endcapping the enzyme-PAA layer with monomers, such as trimethylsilyl propylethylenediamine (TMSPED), and vinyl benzyl solketol (VBS). TMSPED end-capped OPH enzyme performed better than VBS coated multilayers and was further evaluated through salt stress test (involving 1 M aq. NaCl). An improved performance of end-capped OPH glass beads was demonstrated than their uncapped counterpart. Efforts on the synthesis of novel support beads will also be presented.