Carbon-Coated Superparamagnetic Nanoflowers for Biosensors Based on Lateral Flow Immunoassays

• Published in: Biosensors (Basel) Vol. 10; no. 8; p. 80
• Main Authors: Moyano, Amanda, Serrano-Pertierra, Esther, Salvador, María, Martínez-García, José Carlos, Piñeiro, Yolanda, Yañez-Vilar, Susana, Gónzalez-Gómez, Manuel, Rivas, José, Rivas, Montserrat, Blanco-López, M Carmen
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 22.07.2020; MDPI
• Subjects: Biocompatibility; Biomarkers; Biopsy; Biosensing Techniques; biosensor; Biosensors; Biotin; Black carbon; Carbodiimide; Carbon; Chemical composition; Coatings; Equipment and supplies; exosomes; Extracellular vesicles; Immunoassay; Immunoassay - methods; Immunoassays; Iron oxides; Labels; lateral flow immunoassays; Limit of Detection; Magnetic fields; Magnetic Iron Oxide Nanoparticles; Magnetic properties; Magnetic separation; Membranes; Metal Nanoparticles; Morphology; Nanoparticles; Production processes; Reproducibility of Results; Sensors; superparamagnetic iron oxide nanoflowers; United States; United States > US; Germany; Spain; biosensor; extracellular vesicles; lateral flow immunoassays; exosomes; superparamagnetic iron oxide nanoflowers
• ISSN: 2079-6374; 2079-6374
• DOI: 10.3390/bios10080080

Superparamagnetic iron oxide nanoflowers coated by a black carbon layer (Fe O @C) were studied as labels in lateral flow immunoassays. They were synthesized by a one-pot solvothermal route, and they were characterized (size, morphology, chemical composition, and magnetic properties). They consist of several superparamagnetic cores embedded in a carbon coating holding carboxylic groups adequate for bioconjugation. Their multi-core structure is especially efficient for magnetic separation while keeping suitable magnetic properties and appropriate size for immunoassay reporters. Their functionality was tested with a model system based on the biotin-neutravidin interaction. For this, the nanoparticles were conjugated to neutravidin using the carbodiimide chemistry, and the lateral flow immunoassay was carried out with a biotin test line. Quantification was achieved with both an inductive magnetic sensor and a reflectance reader. In order to further investigate the quantifying capacity of the Fe O @C nanoflowers, the magnetic lateral flow immunoassay was tested as a detection system for extracellular vesicles (EVs), a novel source of biomarkers with interest for liquid biopsy. A clear correlation between the extracellular vesicle concentration and the signal proved the potential of the nanoflowers as quantifying labels. The limit of detection in a rapid test for EVs was lower than the values reported before for other magnetic nanoparticle labels in the working range 0-3 × 10 EVs/μL. The method showed a reproducibility (RSD) of 3% (n = 3). The lateral flow immunoassay (LFIA) rapid test developed in this work yielded to satisfactory results for EVs quantification by using a precipitation kit and also directly in plasma samples. Besides, these Fe O @C nanoparticles are easy to concentrate by means of a magnet, and this feature makes them promising candidates to further reduce the limit of detection.