title: Design optimization for bioMEMS studies of enzyme-controlled metabolic pathways.
abstract: Biological microelectromechanical systems (bioMEMS) provide an attractive approach to understanding and modifying enzymatic pathways by separating and interrogating individual reaction steps at localized sites in a microfluidic network. We have previously shown that electrodeposited chitosan enables immobilization of an enzyme at a specific site while maintaining its catalytic activity. While promising as a methodology to replicate metabolic pathways and search for inhibitors as drug candidates, these investigations also revealed unintended (or parasitic) effects, including products generated by the enzyme either (1) in the homogeneous phase (in the liquid), or (2) nonspecifically bound to microchannel surfaces. Here we report on bioMEMS designs which significantly suppress these parasitic effects. To reduce homogeneous reactions we have developed a new packaging and assembly strategy which eliminates fluid reservoirs that are commonly used for fluidic interconnects with external tubing. To suppress reactions by nonspecifically bound enzyme on microchannel walls we have implemented a cross-flow microfluidic network design so that enzyme flow for assembly and substrate/product for reaction share only the region where the enzyme is immobilized at the intended reaction site. Our results show that the signal-to-background ratio of sequential enzymatic reactions increases from 0.72 to 1.28 by eliminating the packaging reservoirs, and increases to 2.43 by separating the flow direction of enzymatic reaction from that of enzyme assembly step. These techniques can be easily applied to versatile microfluidic devices to minimize parasitic reactions in sequential biochemical reactions.
authors.affiliation: Fischell Department of Bioengineering, University of Maryland, College Park, MD, 20742, USA.|Institute for Systems Research (ISR), University of Maryland, College Park, MD, 20742, USA.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Luo
authors.affiliation: Fischell Department of Bioengineering, University of Maryland, College Park, MD, 20742, USA.|Institute for Systems Research (ISR), University of Maryland, College Park, MD, 20742, USA.
authors.forename: Dean
authors.initials: D
authors.lastname: Larios Berlin
authors.affiliation: Institute for Systems Research (ISR), University of Maryland, College Park, MD, 20742, USA.|Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Buckhout-White
authors.affiliation: Fischell Department of Bioengineering, University of Maryland, College Park, MD, 20742, USA.|University of Maryland Biotechnology Institute (UMBI), University of Maryland, College Park, MD, 20742, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Bentley
authors.affiliation: University of Maryland Biotechnology Institute (UMBI), University of Maryland, College Park, MD, 20742, USA.
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Payne
authors.affiliation: Department of Electrical and Computer Engineering, University of Maryland, College Park, MD, 20742, USA.|Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Ghodssi
authors.affiliation: Institute for Systems Research (ISR), University of Maryland, College Park, MD, 20742, USA. rubloff@umd.edu.|Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA. rubloff@umd.edu.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Rubloff
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D004800:Enzymes, Immobilized / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D009699:N-Glycosyl Hydrolases / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D048271:Chitosan; D009699:N-Glycosyl Hydrolases; C019606:adenosylhomocysteine nucleosidase