title: Activity and lifetime of urease immobilized using layer-by-layer nano self-assembly on silicon microchannels.
abstract: Urease has been immobilized and layered onto the walls of manufactured silicon microchannels. Enzyme immobilization was performed using layer-by-layer nano self-assembly. Alternating layers of oppositely charged polyelectrolytes, with enzyme layers "encased" between them, were deposited onto the walls of the silicon microchannels. The polycations used were polyethylenimine (PEI), polydiallyldimethylammonium (PDDA), and polyallylamine (PAH). The polyanions used were polystyrenesulfonate (PSS) and polyvinylsulfate (PVS). The activity of the immobilized enzyme was tested by pumping a 1 g/L urea solution through the microchannels at various flow rates. Effluent concentration was measured using an ultraviolet/visible spectrometer by monitoring the absorbance of a pH sensitive dye. The architecture of PEI/PSS/PEI/urease/PEI with single and multiple layers of enzyme demonstrated superior performance over the PDDA and PAH architectures. The precursor layer of PEI/PSS demonstrably improved the performance of the reactor. Conversion rates of 70% were achieved at a residence time of 26 s, on d 1 of operation, and >50% at 51 s, on d 15 with a six-layer PEI/urease architecture.
authors.affiliation: Louisiana Tech University, Chemical Engineering Program, 600 W. Arizona, P.O. Box 10348 TS, Ruston, LA 71272, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Forrest
authors.forename: Bill B
authors.initials: BB
authors.lastname: Elmore
authors.forename: James D
authors.initials: JD
authors.lastname: Palmer
mesh_terms: D000327:Adsorption; D020099:Coated Materials, Biocompatible / Q000032:analysis / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D004355:Drug Stability; D004789:Enzyme Activation; D004800:Enzymes, Immobilized / Q000032:analysis / Q000737:chemistry*; D008422:Materials Testing; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry*; D011485:Protein Binding; D012825:Silicon / Q000737:chemistry*; D014510:Urease / Q000032:analysis / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D004800:Enzymes, Immobilized; D014510:Urease; D012825:Silicon