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

Abstract

Superparamagnetic iron oxide nanoflowers coated by a black carbon layer (Fe3O4@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 Fe3O4@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 × 107 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 Fe3O4@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.

Magnetic Lateral Flow Immunoassay for Small Extracellular Vesicles Quantification: Application to Colorectal Cancer Biomarker Detection

“…The units provided by this sensor are µΩ·mm coming from the cumulative integral of the impedance (µΩ) across the width of the test line (mm). It has been demonstrated that the impedance change is directly proportional to the number of superparamagnetic nanoparticles at the test line, which enables to determine the analyte concentration [ 38 , 41 , 42 ].…”

“…Therefore, magnetic nanoparticles could be a suitable label to both improve detection and achieve quantitative LFIA. Recently, we have developed a quantitative magnetic LFIA for EVs detection [ 38 ]. For this approach, magnetic LFIAs have been coupled to a sensor developed by the authors to get the quantification for different concentration of isolated EVs from human plasma [ 38 , 39 , 40 , 41 , 42 ].…”

Progress and prospects of magnetic iron oxide nanoparticles in biomedical applications: A review

“…Biosensors have also been widely employed in tissue engineering to modulate cell polarity, to tune the cellular functions, detection of biomolecules, and diagnosis of tissue disease 228 . Recently, various hybrid materials prepared using chitosan, gold NPs, graphene, and IONPs have been utilized to design novel biosensors for glucose detection, 229 ROS detection, 230 catecholamine neurotransmitters in brain tissues, 231 extracellular vesicles detection, 232 cellular detection of hydrogen peroxide, 233 glucose/urea detection, 234 tumor necrosis factor‐α, 235 and multiple immune biomarkers 236 in biological samples.…”

Lipid–Polymer Hybrids Encapsulating Iron-Oxide Nanoparticles as a Label for Lateral Flow Immunoassays

“…The biotin-neutravidin complex is one of the strongest non-covalent interactions that due to the high specificity and strong affinity is widely used in immunoassays [21,22]. In this study, the biotin-neutravidin system was applied as model system in order to study the feasibility of using SPIONs in PLGA-PVA/PC as labels for LFIA.…”