title: Controlled release of reagents in capillary-driven microfluidics using reagent integrators.
abstract: The integration and release of reagents in microfluidics as used for point-of-care testing is essential for an easy and accurate operation of these promising diagnostic devices. Here, we present microfluidic functional structures, which we call reagent integrators (RIs), for integrating and releasing small amounts of dried reagents (ng quantities and less) into microlitres of sample in a capillary-driven microfluidic chip. Typically, a RI is less than 1 mm(2) in area and has an inlet splitting into a central reagent channel, in which reagents can be loaded using an inkjet spotter, and two diluter channels. During filling of the microfluidic chip, spotted reagents reconstitute and exit the RI with a dilution factor that relates to the relative hydraulic resistance of the channels forming the RI. We exemplify the working principle of RIs by (i) distributing ∼100 pg of horseradish peroxidase (HRP) in different volume fractions of a 1 μL solution containing a fluorogenic substrate for HRP and (ii) performing an immunoassay for C-reactive protein (CRP) using 450 pg of fluorescently labeled detection antibodies (dAbs) that reconstitute in ∼5 to 30% of a 1 μL sample of human serum. RIs preserve the conceptual simplicity of lateral flow assays while providing a great degree of control over the integration and release of reagents in a stream of sample. We believe RIs to be broadly applicable to microfluidic devices as used for biological assays.
authors.affiliation: IBM Research-Zurich, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland.
authors.forename: Martina
authors.initials: M
authors.lastname: Hitzbleck
authors.forename: Luc
authors.initials: L
authors.lastname: Gervais
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Delamarche
mesh_terms: D000906:Antibodies / Q000097:blood; D002097:C-Reactive Protein / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry*; D046210:Microfluidic Analytical Techniques; D015394:Molecular Structure; D010316:Particle Size; D013499:Surface Properties
chemical_list: D000906:Antibodies; D007202:Indicators and Reagents; D002097:C-Reactive Protein; D006735:Horseradish Peroxidase