Label-free dynamic light scattering assay for C-reactive protein detection using magnetic nanoparticles

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Analytical Chemistry

Background:

• C-reactive protein (CRP) is a key biomarker for inflammation and infection.
• Accurate and accessible CRP detection methods are essential for clinical diagnostics.
• Existing methods often require specific antibodies or complex sample preparation.

Purpose of the Study:

• To develop a simple, label-free method for detecting C-reactive protein (CRP) in diluted saliva.
• To utilize functionalized silica-coated magnetic nanoparticles and dynamic light scattering (DLS) for CRP quantification.
• To assess the sensitivity, selectivity, and reliability of the developed detection method.

Main Methods:

• Employed dynamic light scattering (DLS) with silica-coated Fe3O4 nanoparticles (Fe3O4@SiO2/COOH) functionalized with aminocarboxylate moieties.
• Utilized magnetic separation for easy nanoparticle recovery and redispersion.
• Correlated changes in nanoparticle hydrodynamic diameter (Z-average size) with CRP concentration.

Main Results:

• Achieved label-free CRP detection in diluted saliva samples down to 0.205 mg L−1, below levels found in unhealthy individuals.
• Demonstrated high selectivity of Fe3O4@SiO2/COOH nanoparticles for CRP, with reduced interference from other saliva biomolecules.
• Confirmed CRP adsorption via LC-MS/MS, attributing enhanced affinity to chelating interactions between nanoparticle surface groups and CRP-associated Ca2+ ions.

Conclusions:

• The developed DLS-based method offers a simple, sensitive, and selective approach for label-free CRP detection in saliva.
• Functionalized nanoparticles provide superior performance compared to non-functionalized ones, reducing assay complexity.
• This method holds potential for rapid, point-of-care diagnostics of inflammatory conditions.