A double-bead sandwich assay for protein detection in serum based on Localized Surface Plasmon Resonance

摘要

In this study, the importance of pre-concentration is clearly demonstrated for the covalent immobilization of various proteins to magnetic nanoparticles through mild carbodiimide activation. Additionally, the covalently biofunctionalized magnetic nanoparticles are employed in a double-bead sandwich assay, using gold nanoparticles. The magnetic nanoparticles allow specific capturing of the analyte in biological samples (serum), while the optical properties of the gold nanoparticles provide the signal transduction. We demonstrated that a major improvement in the assay sensitivity was obtained by selecting an optimal gold nanoparticle size (60 nm). A detection limit of 5-8 ng/mL, a sensitivity of 0.6-0.8 (pg/ mL)~(-1) and a dynamic range of 3 orders of magnitude were achieved without any further amplification using the detection of prostate specific antigen in serum as a model system. The proposed assay has the ability to be easily implemented within a microfluidic device for point-of-care applications whereby the readout can be executed by a fast and cheap optical measurement.