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Silica encapsulation of ferrimagnetic zinc ferrite nanocubes enabled by layer-by-layer polyelectrolyte deposition.

ABSTRACT: Stable suspensions of magnetic nanoparticles (MNPs) with large magnetic moment, m, per particle have tremendous utility in a wide range of biological applications. However, because of the strong magnetic coupling interactions often present in these systems, it is challenging to stabilize individual, high-moment, ferro- and ferrimagnetic nanoparticles. A novel approach to encapsulate large, that is, >100 nm, ferrimagnetic zinc ferrite nanocubes (ZFNCs) with silica after an intermediary layer-by-layer polyelectrolyte deposition step is described in this paper. The seed ZFNCs are uniform in shape and size and have high saturation mass magnetic moment (?(s) ?100 emu/g, m ? 4 × 10(-13) emu/particle at 150 Oe). For the MNP system described within, successful silica encapsulation and creation of discrete ZFNCs were realized only after depositing polyelectrolyte multilayers composed of alternating polyallylamine and polystyrenesulfonate. Without the intermediary polyelectrolyte layers, magnetic dipole-dipole interactions led to the formation of linearly chained ZFNCs embedded in a silica matrix. Characterization of particle samples was performed by electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, powder X-ray diffraction, dynamic light scattering (hydrodynamic size and ?-potential), and vibrating sample magnetometry. The results of these characterizations, which were performed after each of the synthetic steps, and synthetic details are presented.

SUBMITTER: Park J

PROVIDER: S-EPMC4751990 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Silica encapsulation of ferrimagnetic zinc ferrite nanocubes enabled by layer-by-layer polyelectrolyte deposition.

Park Jooneon J Porter Marc D MD Granger Michael C MC

Langmuir : the ACS journal of surfaces and colloids 20150310 11

Stable suspensions of magnetic nanoparticles (MNPs) with large magnetic moment, m, per particle have tremendous utility in a wide range of biological applications. However, because of the strong magnetic coupling interactions often present in these systems, it is challenging to stabilize individual, high-moment, ferro- and ferrimagnetic nanoparticles. A novel approach to encapsulate large, that is, >100 nm, ferrimagnetic zinc ferrite nanocubes (ZFNCs) with silica after an intermediary layer-by-l ...[more]

PMID: 25756216

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Project description:In the field of bone regeneration, considerable attention has been addressed towards the use of mesoporous bioactive glasses (MBGs), as multifunctional therapeutic platforms for advanced medical devices. In fact, their extremely high exposed surface area and pore volume allow to load and the release of several drugs, while their framework can be enriched with specific therapeutic ions allowing to boost the tissue regeneration. However, due to the open and easily accessible mesopore structure of MBG, the release of the incorporated therapeutic molecules shows an initial burst effect leading to unsuitable release kinetics. Hence, a still open challenge in the design of drug delivery systems based on MBGs is the control of their release behavior. In this work, Layer-by-layer (LbL) deposition of polyelectrolyte multi-layers was exploited as a powerful and versatile technique for coating the surface of Cu-substituted MBG nanoparticles with innovative multifunctional drug delivery systems for co-releasing of therapeutic copper ions (exerting pro-angiogenic and anti-bacterial effects) and an anti-inflammatory drug (ibuprofen). Two different routes were investigated: in the first strategy, chitosan and alginate were assembled by forming the multi-layered surface, and, successively, ibuprofen was loaded by incipient wetness impregnation, while in the second approach, alginate was replaced by ibuprofen, introduced as polyelectrolyte layer. Zeta-potential, TGA and FT-IR spectroscopy were measured after the addition of each polyelectrolyte layer, confirming the occurrence of the stepwise deposition. In addition, the in vitro bioactivity and the ability to modulate the release of the cargo were evaluated. The polyelectrolyte coated-MBGs were proved to retain the peculiar ability to induce hydroxyapatite formation after 7 days of soaking in Simulated Body Fluid. Both copper ions and ibuprofen were co-released over time, showing a sustained release profile up to 14 days and 24 h, respectively, with a significantly lower burst release compared to the bare MBG particles.

Project description:Spinel ferrite nanocubes (NCs), consisting of pure iron oxide or mixed ferrites, are largely acknowledged for their outstanding performance in magnetic hyperthermia treatment (MHT) or magnetic resonance imaging (MRI) applications while their magnetic particle imaging (MPI) properties, particularly for this peculiar shape different from the conventional spherical nanoparticles (NPs), are relatively less investigated. In this work, we report on a non-hydrolytic synthesis approach to prepare mixed transition metal ferrite NCs. A series of NCs of mixed zinc-cobalt-ferrite were prepared and their magnetic theranostic properties were compared to those of cobalt ferrite or zinc ferrite NCs of similar sizes. For each of the nanomaterials, the synthesis parameters were adjusted to obtain NCs in the size range from 8 up to 15 nm. The chemical and structural nature of the different NCs was correlated to their magnetic properties. In particular, to evaluate magnetic losses, we compared the data obtained from calorimetric measurements to the data measured by dynamic magnetic hysteresis obtained under alternating magnetic field (AMF) excitation. Cobalt-ferrite and zinc-cobalt ferrite NCs showed high specific adsorption rate (SAR) values in aqueous solutions but their heating ability was drastically suppressed once in viscous media even for NCs as small as 12 nm. On the other hand, non-stoichiometric zinc-ferrite NCs showed significant but lower SAR values than the other ferrites, but these zinc-ferrite NCs preserved almost unaltered their heating trend in viscous environments. Also, the presence of zinc in the crystal lattice of zinc-cobalt ferrite NCs showed increased contrast enhancement for MRI with the highest T2 relaxation time and in the MPI signal with the best point spread function and signal-to-noise ratio in comparison to the analogue cobalt-ferrite NC. Among the different compositions investigated, non-stoichiometric zinc-ferrite NCs can be considered the most promising material as a multifunctional theranostic platform for MHT, MPI and MRI regardless of the media viscosity in which they will be applied, while ensuring the best biocompatibility with respect to the cobalt ferrite NCs.

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Silica encapsulation of ferrimagnetic zinc ferrite nanocubes enabled by layer-by-layer polyelectrolyte deposition.

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Silica encapsulation of ferrimagnetic zinc ferrite nanocubes enabled by layer-by-layer polyelectrolyte deposition.

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