title: Automating multi-step paper-based assays using integrated layering of reagents.
abstract: We describe a versatile and simple method to perform sequential reactions on paper analytical devices by stacking dry pullulan films on paper, where each film contains one or more reagents or acts as a delay layer. Exposing the films to an aqueous solution of the analyte leads to sequential dissolution of the films in a temporally controlled manner followed by diffusive mixing of the reagents, so that sequential reactions can be performed. The films can be easily arranged for lateral flow assays or for spot tests (reactions take place sequentially in the z-direction). We have tested the general feasibility of the approach using three different model systems to demonstrate different capabilities: 1) pH ramping from low to high and high to low to demonstrate timing control; 2) rapid ready-to-use two-step Simon's assays on paper for detection of drugs of abuse utilizing a 2-layer stack containing two different reagents to demonstrate the ability to perform assays in the z-direction; and 3) sequential cell lysing and colorimetric detection of an intracellular bacterial enzyme, to demonstrate the ability of the method to perform sample preparation and analysis in the form of a spot assay. Overall, these studies demonstrate the potential of stacked pullulan films as useful components to enable multi-step assays on simple paper-based devices.
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Sana
authors.initials: S
authors.lastname: Jahanshahi-Anbuhi
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4L7, Canada. brennanj@mcmaster.ca.
authors.forename: Balamurali
authors.initials: B
authors.lastname: Kannan
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Kevin
authors.initials: K
authors.lastname: Pennings
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4L7, Canada. brennanj@mcmaster.ca.
authors.forename: M
authors.initials: M
authors.lastname: Monsur Ali
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Vincent
authors.initials: V
authors.lastname: Leung
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Karen
authors.initials: K
authors.lastname: Giang
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Jingyun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4L7, Canada. brennanj@mcmaster.ca.
authors.forename: Dawn
authors.initials: D
authors.lastname: White
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton L8S 4K1, Canada.
authors.forename: Yingfu
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Pelton
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4L7, Canada. brennanj@mcmaster.ca.
authors.forename: John D
authors.initials: JD
authors.lastname: Brennan
authors.affiliation: Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. filipec@mcmaster.ca.
authors.forename: Carlos D M
authors.identifier: 0000-0002-7410-3323
authors.initials: CD
authors.lastname: Filipe
mesh_terms: D004048:Diethylamines / Q000032:analysis; D004867:Equipment Design; D004926:Escherichia coli / Q000302:isolation & purification; D005936:Glucans / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D010209:Paper
chemical_list: D004048:Diethylamines; D005936:Glucans; D007202:Indicators and Reagents; C009109:pullulan; C034281:diethylamine