We present a simple strategy to generate a family of carbon dots/iron oxide nanoparticles (C/Fe-NPs) that relies on the thermal decomposition of iron (III) acetylacetonate in the presence of a highly fluorescent carbon-rich precursor (derived via thermal treatment of ethanolamine and citric acid at 180 °C), while polyethylene glycol serves as the passivation agent. By varying the molar ratio of the reactants, a series of C/Fe-NPs have been synthesized with tuneable elemental composition in terms of C, H, O, N and Fe. The quantum yield is enhanced from 6 to 9% as the carbon content increases from 27 to 36 wt%, while the room temperature saturation magnetization is improved from 4.1 to 17.7 emu/g as the iron content is enriched from 17 to 31 wt%. In addition, the C/Fe-NPs show excellent antimicrobial properties, minimal cytotoxicity and demonstrate promising bioimaging capabilities, thus showing great potential for the development of advanced diagnostic tools.

This paper reports the characterization of iron oxide magnetic nanoparticles obtained via the thermal decomposition of an organometallic precursor, which were then loaded into nanocapsules prepared via the emulsification process in the presence of an amphiphilic derivative of chitosan. The applied synthetic method led to the formation of a hydrophobic layer on the surface of nanoparticles that enabled their loading in the hydrophobic liquid inside of the polymer-based capsules. The average diameter of nanoparticles was determined to be equal to 15 nm, and they were thoroughly characterized using X-ray diffraction (XRD), magnetometry, and Mössbauer spectroscopy. A core–shell structure consisting of a wüstite core and maghemite-like shell was revealed, resulting in an exchange bias effect and a considerable magnetocrystalline anisotropy at low temperatures and a superparamagnetic behavior at room temperature. Importantly, superparamagnetic behavior was observed for the aqueous dispersion of the nanocapsules loaded with the superparamagnetic nanoparticles, and the dispersion was shown to be very stable (at least 48 weeks). The results were analyzed and discussed with respect to the potential future applications of these nanoparticles and nanocapsules based on biopolymers as platforms designed for the magnetically navigated transport of encapsulated hydrophobic substances.

We present a simple strategy to generate a family of carbon dot/iron oxide nanoparticles (C/Fe-NPs) that relies on the thermal decomposition of iron (III) acetylacetonate in the presence of a highly fluorescent carbon-rich precursor, while polyethylene glycol serves as the passivation agent. By varying the molar ratio of the reactants, a series of C/Fe-NPs have been synthesized with tuneable elemental composition in terms of C, H, O, N, Fe. The quantum yield is enhanced from 6% to 9% as the carbon content increases from 27% to 36%, while the room temperature saturation magnetization is improved from 4.1 emu/g to 17.7 emu/g as the iron content is enriched from 17 to 31%. In addition, the C/Fe-NPs show excellent antimicrobial properties, minimal cytotoxicity and demonstrate promising bioimaging capabilities, thus showing great potential for the development of advanced diagnostic tools.

Introduction: Drug delivery systems typically need to be equipped with targeting moieties in order to be efficiently internalized by cells. Alternatively, magnetic nanoparticles (MNs) combined with active compounds may be driven by magnetic field to the site of action. Delivery of hydrophobic drugs using this approach is challenging as it would require coupling of MNs and hydrophobic environment within nanocarriers and triggering of the drug release. Methods: We propose an approach enabling a magnetically induced forced uptake of core-shell nanocapsules carrying hydrophobic actives together with hydrophobized MNs. Such capsules, formed in a facile emulsification process, are composed of amphiphilic cationic or anionic chitosan (shell) and oil-dispersible MNs (oil core). The capsules were characterized using DLS, cryo-TEM. They were loaded with a model fluorescent dye, Nile Red, and pulled into cells applying a static magnetic field. Then, they were treated with an alternating magnetic field to disrupt the capsules thanks to the action of MNs. Results: Cryo-TEM imaging confirmed the presence of MNs inside the capsules (d≈200 nm). Confocal microscopy imaging showed the efficient capsules’ intracellular uptake only after exposition to static magnetic field (some spontaneous uptake was observed for anionic capsules). Then, application of alternating magnetic fields induced rapture of the capsules inside the cells and release of the cargo. Discussion: This approach is very versatile as various lipophilic compounds could be encapsulated, then transported to desired tissues without active or passive targeting and kept there using static magnetic field, limiting undesired side effects of a therapy to the whole organism. The proposed capsules with MNs respond efficiently to magnetic field stimulation – they can be magnetically navigated into the cells and release their cargo after application of alternating magnetic field. This approach opens opportunities for controlled intracellular delivery of hydrophobic actives using easily applicable magnetic stimuli for both delivery and release.