title: High sensitivity automated multiplexed immunoassays using photonic crystal enhanced fluorescence microfluidic system.
abstract: We demonstrate a platform that integrates photonic crystal enhanced fluorescence (PCEF) detection of a surface-based microspot fluorescent assay with a microfluidic cartridge to achieve simultaneous goals of high analytic sensitivity (single digit pg/mL), high selectivity, low sample volume, and assay automation. The PC surface, designed to provide optical resonances for the excitation wavelength and emission wavelength of Cyanines 5 (Cy5), was used to amplify the fluorescence signal intensity measured from a multiplexed biomarker microarray. The assay system is comprised of a plastic microfluidic cartridge for holding the PC and an assay automation system that provides a leak-free fluid interface during introduction of a sequence of fluids under computer control. Through the use of the assay automation system and the PC embedded within the microfluidic cartridge, we demonstrate pg/mL-level limits of detection by performing representative biomarker assays for interleukin 3 (IL3) and Tumor Necrosis Factor (TNF-α). The results are consistent with limits of detection achieved without the use of the microfluidic device with the exception that coefficients of variability from spot-to-spot are substantially lower than those obtained by performing assays with manual manipulation of assay liquids. The system's capabilities are compatible with the goal of diagnostic instruments for point-of-care settings.
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA.
authors.forename: Yafang
authors.initials: Y
authors.lastname: Tan
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA.
authors.forename: Tiantian
authors.initials: T
authors.lastname: Tang
authors.affiliation: Department of Material Science, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA.
authors.forename: Haisheng
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA.
authors.forename: Chenqi
authors.initials: C
authors.lastname: Zhu
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA; Department of Bioengineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA. Electronic address: bcunning@illinois.edu.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Cunningham
mesh_terms: D015415:Biomarkers / Q000032:analysis; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D005453:Fluorescence; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation* / Q000379:methods; D007377:Interleukin-3 / Q000032:analysis; D056656:Lab-On-A-Chip Devices; D057230:Limit of Detection; D046210:Microfluidic Analytical Techniques / Q000379:methods; D019095:Point-of-Care Systems; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
chemical_list: D015415:Biomarkers; C508596:IL3 protein, human; D007377:Interleukin-3; D014409:Tumor Necrosis Factor-alpha