Water dispersion of magnetic nanoparticles with selective Biofunctionality for enhanced plasmonic biosensing

Abstract

Magnetic nanoparticles (MNPs) are widely used in biosensing, bioimaging, and drug delivery. However, high quality superparamagnetic nanoparticles with uniform size were usually synthesized by thermal decomposition using organic solvents. To be suitable for biomedical applications, a facile and efficient water dispersion of iron oxide MNPs from solvent using an innovative agent, sodium oleate (NaOL) was described. The monodispersed MNPs (4 and 15 nm respectively) after transfer was biocompatible and stable at a broad temperature range (4–50°C) over months. More importantly, the NaOL coating allows for surface modification with selective functionality, rendering the aqueous MNPs highly customizable for biofunctionalization. Little effect on the superparamagnetism was observed after the water dispersion. To further evaluate its practical application in biosensing, custom MNPs were prepared for specific cardiac troponin I (cTnI) detection for myocardial infarction diagnosis. Specifically, gold nanorod (GNR) biochip was probed by the MNP-captured cTnI target analyte at varying concentrations. The signal transduction of the GNR sensor is based on the localized surface plasmon resonance (LSPR). The application of the MNPs resulted in a significant enhancement of the plasmonic response of the GNRs. As such, the MNP-mediated LSPR biosenisng showed a three times lower sensitivity as compared to the direct cTnI binding without functional MNPs. Computer simulation further elucidated that the enhancement was distance dependent between the MNP and the surface of the nanorod, which corroborated with experimental results.

Microgel assisted Lab-on-Fiber Optrode

“…Analogous issues occur in such applications where the detection of larger analytes with very low limit of detection (LOD) is required. To enhance the sensitivity, gold and magnetic nanoparticles have been proposed as “molecular concentrators” able to localize multiple binding events on a single particle, and successively deliver target analyte from the solution to the sensor surface 9 – 11 . At the same time, approaches exploiting hydrogels (HGs) have been proposed 12 , 13 .…”

Magnetic Graphene Oxide Nanocarrier for Targeted Delivery of Cisplatin: A Perspective for Glioblastoma Treatment

“…Superparamagnetism is crucial for application in biomedicine, because, despite the strong response to an external magnetic field, the absence of residual magnetic properties upon removal of the external field prevents nanoparticles from aggregation in biological environment [49,50,51,52]. γ-Fe 2 O 3 nanoparticles (average size of 10 nm, see Figure 1d,f) were synthesized by annealing of magnetite Fe 3 O 4 prepared by a chemical co-precipitation technique of FeCl 3 and FeCl 2 solutions [53,54], and then coated with oleic acid/sodium oleate to enhance their dispersion in water media and thus the biocompatibility features [55]. Since previously reported data proved the presence of transport systems importing fatty acids into the brain with high affinity and efficiency, it is reasonable to hypothesize that this coating strategy could be appropriate for targeting the blood brain barrier [56].…”

“…On other hand, the strong interaction between CisPt and NGO [60,61,62] resulted in a more extended release over time (F max < 0.8 even after 250 h), with the same affinity (3.54) recorded for either NGO or γ-Fe 2 O 3 @NGO. The presence of γ-Fe 2 O 3 in γ-Fe 2 O 3 @NGO was found to slow the release, with reduced kinetic constant (k R ) and t 1/2 values moving from 19.01 (NGO) to 29.38 (γ-Fe 2 O 3 @NGO) h. This could be ascribed to the hindrance to the drug diffusion from the NGO to the solvent phase by the oleate coating of γ-Fe 2 O 3 nanoparticles [55].…”

Nanomaterials for Healthcare Biosensing Applications

“…Wavelength modulated SPR provided responses from 1.25 ng mL −1 to 4 μg mL −1 of cTnI. Another study dispersed sodium oleate (NaOL) treated MNPs functionalised with cAb in water for the extraction of cTnI for further sensing on a gold nanorod (GNR)-based LSPR chip [183]. The NaOL treatment generated carboxyl groups on the MNP surface, encouraging cAb attachment.…”