title: Rapid Slow Off-Rate Modified Aptamer (SOMAmer)-Based Detection of C-Reactive Protein Using Isotachophoresis and an Ionic Spacer.
abstract: We present an on-chip electrophoretic assay for rapid protein detection with a SOMAmer (Slow Off-Rate Modified Aptamer) reagent. We used isotachophoresis (ITP) coupled with an ionic spacer to both react and separate SOMAmer-protein complex from free SOMAmer reagent. ITP accelerates the reaction kinetics as the ionic spacer concurrently separates the reaction products. We developed a numerical and analytical model to describe ITP spacer assays, which involve low-mobility, nonfocusing targets that are recruited into the ITP zone by higher-mobility, ITP-focused probes. We demonstrated a proof-of-concept of this assay using C-reactive protein (CRP) in buffer, and achieved a 2 nM limit of detection (LOD) with a combined 20 min assay time (10 min off-chip preparation of reagents and 10 min on-chip run). Our findings suggest that this approach has potential as a simple and rapid alternative to other homogeneous immunoassays. We also explore the extension of this assay to a diluted serum sample spiked with CRP, where we observe decreased sensitivity (an LOD of 25 nM in 20-fold diluted serum). We describe the challenges in extending this assay to complex samples and achieving higher sensitivity and specificity for clinical applications.
authors.affiliation: †Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States.
authors.forename: Charbel
authors.initials: C
authors.lastname: Eid
authors.affiliation: †Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States.
authors.forename: James W
authors.initials: JW
authors.lastname: Palko
authors.affiliation: §SomaLogic, Inc., Boulder, Colorado 80301, United States.
authors.forename: Evaldas
authors.initials: E
authors.lastname: Katilius
authors.affiliation: †Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States.
authors.forename: Juan G
authors.initials: JG
authors.lastname: Santiago
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D002097:C-Reactive Protein / Q000032:analysis*; D007477:Ions; D057625:Isotachophoresis
chemical_list: D052157:Aptamers, Nucleotide; D007477:Ions; D002097:C-Reactive Protein