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Multi-Assay Point-of-Care Platform: Highly Sensitive Time-Resolved Fluorometric Detection in Combination with a Universal “All-In-One” Assay Format

Pettersson, Kim PhD*; von Lode, Piia MSc*; Eriksson, Susann MSc*; Lövgren, Janita PhD; Takalo, Harri PhD

Point of Care: The Journal of Near-Patient Testing & Technology: September 2003 - Volume 2 - Issue 3 - p 225-232
Original Articles

Near-patient testing is gaining ground in areas such as critical care, emergency situations, and primary care. Time-resolved fluorometry (TRF) of lanthanide chelates is a versatile, robust detection technology suitable for highly sensitive immunoassays. The authors describe a TRF-based point-of-care assay technology suitable for a simple multianalyte platform. Sandwich assays using a proprietary, all-in-one, dry reagent technology were optimized for cardiac troponin I, thyroid-stimulating hormone, human chorionic gonadotropin, prostate-specific antigen, and high-sensitivity C-reactive protein measurement. Detector antibodies were labeled with inherently fluorescent europium chelates where the metal ion is coordinated through 9 sites providing high thermodynamic stability and reduced humidity quenching. The antibodies were selected to provide correct specificity, low detection limits, and rapid kinetics (5-minute or 15-minute incubations). Capture antibodies were immobilized to individual microtiter wells and a shielding protein/sugar layer was added and dried followed by 1 μL detector antibody solution. Addition of 10 or 20 μL whole blood or plasma with a simple buffer initiated the reaction. After a final wash, the signal was measured either directly from the wet surface or after a drying step. Corresponding detection limits/ranges were as follows: cardiac troponin I 0.005/100 μg/L, thyroid-stimulating hormone 0.03/50 mIU/L, human chorionic gonadotropin 0.1/10,000 IU/L, prostate-specific antigen 0.05/1000 μg/L, C-reactive protein 0.01/50 mg/L. An ultimately simple and universal test protocol is provided for even very demanding determinations without sacrificing the performance characteristics. A minimum of liquid handling and the unidirectional 1-step assays enable the design of a simple and fully automatic instrument where several measurements from single whole blood or plasma specimens can be obtained in any user-selected combination.

From the *Department of Biotechnology, University of Turku, Finland; and †Innotrac Diagnostics Oy, Turku, Finland.

Reprints: Kim Pettersson, PhD, Department of Biotechnology, University of Turku Tykistökatu 6A, BioCity FIN-20520 Turku 52, Finland (e-mail kim.pettersson@utu.fi).

© 2003 Lippincott Williams & Wilkins, Inc.