Abstract
The surface functionalization of magnetic nanoparticles improves their physicochemical properties and applicability in biomedicine. Natural polymers, including proteins, are prospective coatings capable of increasing the stability, biocompatibility, and transverse relaxivity (r2) of magnetic nanoparticles. In this work, we functionalized the nanoclusters of carbon-coated iron nanoparticles with four proteins: bovine serum albumin, casein, and gelatins A and B, and we conducted a comprehensive comparative study of their properties essential to applications in biosensing. First, we examined the influence of environmental parameters on the size of prepared nanoclusters and synthesized protein-coated nanoclusters with a tunable size. Second, we showed that protein coating does not significantly influence the r2 relaxivity of clustered nanoparticles; however, the uniform distribution of individual nanoparticles inside the protein coating facilitates increased relaxivity. Third, we demonstrated the applicability of the obtained nanoclusters in biosensing by the development of a nuclear-magnetic-resonance-based immunoassay for the quantification of antibodies against tetanus toxoid. Fourth, the protein coronas of nanoclusters were studied using SDS-PAGE and Bradford protein assay. Finally, we compared the colloidal stability at various pH values and ionic strengths and in relevant complex media (i.e., blood serum, plasma, milk, juice, beer, and red wine), as well as the heat stability, resistance to proteolytic digestion, and shelf-life of protein-coated nanoclusters.
Highlights
Magnetic nanoparticles find application in numerous fields of biomedicine, including drug delivery, tissue engineering, bioimaging, biosensing, and many others [1,2]
The goal of this study is to provide a direct comparison of the colloidal stability, functional activity, and physical-chemical properties of nanoclusters consisting of magnetic carbon-encapsulated iron nanoparticles coated with four proteins widely used in biomedicine: bovine serum albumin (BSA), casein, and gelatins A and B
Protein coatings endow nanoparticles with several favorable properties, enhancing their performance in various biomedical applications
Summary
Magnetic nanoparticles find application in numerous fields of biomedicine, including drug delivery, tissue engineering, bioimaging, biosensing, and many others [1,2]. Nuclear magnetic resonance (NMR)-based biosensing is an area where magnetic nanoparticles are filling an extremely important role. The ability of magnetic nanoparticles to perturb the precession of nuclear spins in surrounding water protons stipulates their application in vivo as a magnetic resonance imaging (MRI) contrast [6] and in vitro as a nanoprobe for NMR-relaxometry [7]. The second approach is based on the binding of magnetic nanoparticles to the target and the removal of unbound particles. In this case, the relaxation time depends on the number of nanoparticles in the sample; this number is proportional to the analyte concentration. Despite great progress in the field of magnetic sensing, improvements in the stability, relaxivity, and biocompatibility of magnetic nanolabels are of great importance for both in vivo and in vitro diagnostics [7,13,14]
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