Fixed Bed Reactor for Solid-Phase Surface Derivatization of Superparamagnetic Nanoparticles

Abstract

The functionalization of nanoparticles is conditio sine qua non in studies of specific interaction with a biological target. Often, their biological functionality is achieved by covalent binding of bioactive molecules on a preexisting single surface coating. The yield and quality of the resulting coated and functionalized superparamagnetic iron oxide nanoparticles (SPIONs) can be significantly improved and reaction times reduced by using solid-phase synthesis strategies. In this study, a fixed bed reactor with a quadrupole repulsive arrangement of permanent magnets was assayed for SPION surface derivatization. The magnet array around the fixed bed reactor creates very high magnetic field gradients that enables the immobilization of SPIONs with a diameter as low as 9 nm. The functionalization on the surface of immobilized 25 nm 3-(aminopropyl)trimethoxysilane-coated SPIONs (APS-SPIONs) was performed using fluorescein-isothiocyanate directly, and by the SV40 large T-antigen nuclear localization signal peptide (PKKKRKVGC) conjugated to acryloylpoly(ethylene glycol)-N-hydroxysuccinimide, where the PEG reagent is conjugated first to create a functionalized nanoparticle and the peptide is added to the acryloyl group. We show that the yield of reactant grafted on the surface of the APS-coated SPIONs was higher in solid-phase within the fixed bed reactor compared to conventional liquid-phase chemistry. In summary, the functionalization of SPIONs using a magnetically fixed bed reactor was superior to the liquid-phase reaction in terms of the yield, reaction times required for derivatization, size distribution, and scalability.

Magnetic microreactors for efficient and reliable magnetic nanoparticle surface functionalization

“…The iron content of the suspensions was determined by the Prussian blue assay 26 . Thereafter, 50 L of APTES-coated SPIONs (0.020 to 0.100 mg of iron / mL) were dissolved in 100 L hydrochloric acid (6 M) in a 96-well plate.…”

“…PEGylation or cRGD coupling performed in a standard liquid phase synthesis always resulted in aggregation and low reaction yield, which is in agreement with previous studies from our group using large-scale magnetic microreactors. 26 …”

Magnetoliposomes: opportunities and challenges

“…Further careful design is thus imperative (25). In this category, biocompatible SPIONs (10) are conceived as beneficial, alternative targeting tools compared to other NPs, as they are easily synthesized and surface-functionalized (26). Due to their advantageous magnetic properties (9), SPIONs can be used for magnetic targeting, which relies on the delivery of magnetic NPs to the desired target area through the application of a magnetic field gradient (27).…”

Biomedical nanoparticles modulate specific CD4+T cell stimulation by inhibition of antigen processing in dendritic cells

“…Nevertheless, the PVASPIONs utilized for all subsequent investigations were highly colloidally stable in all solutions (e.g. cell culture media) and environments tested (PetriFink and Hofmann 2007). The zeta potential (surface charge) decreased from +16.7 mV to +6.7 mV, indicating significant coupling of both Oregon green and Alexa Fluor 680 fluorochromes to amine groups of the polymer coating.…”