Effect of Cobalt Doping Concentration on the Crystalline Structure and Magnetic Properties of Monodisperse Co_<i>x</i>Fe_3–<i>x</i>O₄ Nanoparticles within Nonpolar and Aqueous Solvents

In this work, we investigate the effect of cobalt substitution on the size evolution, crystal structure, and magnetic properties of Fe₃O₄ nanoparticles. Monodisperse Co_<i>x</i>Fe_3–<i>x</i>O₄ nanoparticles were prepared, using a one-step method, by direct heating process of iron­(III) and cobalt­(II) acetylacetonates in high-boiling-point inert organic solvent. The quantities of precursors added were based on stoichiometric Fe/Co ratio of desired ferrite. Elemental analyses ICP-AES evidenced successful cobalt doping. The doped particles showed a cobalt-deficient composition. Transmission electron microscopy demonstrated the large changes of particle size as a function of cobalt doping. The magnetization measurements showed an unchanged saturation magnetization only up to <i>x</i> = 0.24, beyond which it significantly decreased. To make the as-synthesized nanoparticles suitable for biomedical applications, oleic acid ligands are exchanged with caffeic acid molecules leading to stable nanoparticles in physiological conditions

Carbodiimide versus Click Chemistry for Nanoparticle Surface Functionalization: A Comparative Study for the Elaboration of Multimodal Superparamagnetic Nanoparticles Targeting α_vβ₃ Integrins

Superparamagnetic fluorescent nanoparticles targeting α_vβ₃ integrins were elaborated using two methodologies: carbodiimide coupling and click chemistries (CuACC and thiol–yne). The nanoparticles are first functionalized with hydroxymethylenebisphonates (HMBP) bearing carboxylic acid or alkyne functions. Then, a large number of these reactives functions were used for the covalent coupling of dyes, poly­(ethylene glycol) (PEG), and cyclic RGD. Several methods were used to characterize the nanoparticle surface functionalization, and the magnetic properties of these contrast agents were studied using a 1.5 T clinical MRI. The affinity toward integrins was evidenced by solid-phase receptor-binding assay. In addition to their chemoselective natures, click reactions were shown to be far more efficient than the carbodiimide coupling. The grafting increase was shown to enhance targeting affinity to integrin without imparing MRI and fluorescent properties

Anti-tumor effect of immunizations in C57BL/6 mice bearing subcutaneous tumors.

<p>(a) Mice were injected with E.G7-OVA cells on day 0 and then immunized on days 4 and 18 (arrows) with [pOVA30-melanin + CpG], [melanin + CpG], [pOVA30 + CpG], or [pOVA30-melanin] (n = 10 mice/group with pooled data from two different experiments). (b) Effect of the in vivo CD8 depletion in C57BL/6 mice bearing subcutaneous E.G7-OVA tumors and immunized on days 4 and 18 (arrows) with [melanin + CpG] (n = 4 mice) or [pOVA30-melanin + CpG] (n = 8 mice). The latter group received either anti-CD8 or an isotype-matched control mAb. Tumor growth was assessed twice a week by measuring the size of tumors with calipers. Results are expressed as the mean ± SEM of tumor volumes. * p < 0.05; ** p < 0.001, when compared with control groups.</p

Synthetic melanin bound to subunit vaccine antigens significantly enhances CD8⁺ T-cell responses

<div><p>Cytotoxic T-lymphocytes (CTLs) play a key role in immunity against cancer; however, the induction of CTL responses with currently available vaccines remains difficult. Because several reports have suggested that pigmentation and immunity might be functionally linked, we investigated whether melanin can act as an adjuvant in vaccines. Short synthetic peptides (8–35 amino acids long) containing T-cell epitopes were mixed with a solution of L-Dopa, a precursor of melanin. The mixture was then oxidized to generate nanoparticles of melanin-bound peptides. Immunization with melanin-bound peptides efficiently triggered CTL responses in mice, even against self-antigens and at a very low dose of peptides (microgram range). Immunization against a tumor antigen inhibited the growth of established tumors in mice, an effect that was abrogated by the depletion of CD8⁺ lymphocytes. These results demonstrate the efficacy of melanin as a vaccine adjuvant.</p></div

Preparation and characterization of synthetic melanin and peptide vaccine formulations.

<p>(a) Schematic of the chemical process for obtaining water-soluble peptide-melanin complexes. Evolution over time of b) the UV-visible spectrum during gp100-melanin synthesis and c) the absorbance ratio at 350 and 280 nm (A350/A280) for melanin (black squares) and for gp100-melanin (red circles). (d): TEM image of gp100-melanin after 18 h of incubation time (inset: high magnification). (e) SDS-PAGE showing the migration of the unbound gp100 peptide within the resolving gel after different incubation times in the presence of oxidizing L-Dopa leading to gp100-melanin formation (following electrophoresis, the gels were stained with Coomassie Blue). (f) FTIR spectra in deuterated solution for melanin (black line) and gp100-melanin (red line); the amide II' band at 1455 cm-1 (blue hatching) is characteristic of peptides.</p

Distribution of melanin in draining lymph nodes.

<p>Macroscopic aspect of the draining inguinal lymph nodes (arrows) of BALB/c mice 2 days after injections with gp100-melanin (a) or saline (b). Fontana-Masson staining of a draining lymph node 2 days after injection with gp100-melanin, showing melanin-laden macrophages in the sinuses (c) and in the paracortical area (d).</p

T-cell response after subcutaneous immunizations in C57BL/6 mice.

<p>Mice were immunized with pOVA35 or pOVA35-melanin (pOVA35-Mel), on days 0 and 14 and sacrificed on day 21. Splenocytes were re-stimulated in vitro either with a) the MHC class II epitope (CD4) or b) the MHC class I-epitope (CD8) (non conjugated to melanin). The numbers of IFNg-SFCs (Spot forming cells) were measured. Each point represents an individual mouse (n = 8 mice/group with pooled data from 2 different experiments of 4 mice each). Bars = median. ** p < 0.01 (Mann–Whitney test).</p

Phenotype of SIINFELKL-specific T-cells in mice immunized on days 0 and 14 with [pOVA30 + CpG] or [pOVA30-melanin + CpG].

<p>(a) gating strategy and representative results (in one mouse) for T-Bet, CD62L and granzyme expression. (b) mean ± SD expression of T-bet, CD62L and granzyme within the CD8⁺dextramer⁺ population (n = 8 mice/group, with pooled data from two different experiments of 4 mice each). ** p<0,01; ***p<0,001.</p

Antioxidative Theranostic Iron Oxide Nanoparticles toward Brain Tumors Imaging and ROS Production

Gliomas are the most common primary brain tumor in humans. To date, the only treatment of care consists of surgical removal of the tumor bulk, irradiation, and chemotherapy, finally resulting in a very poor prognosis due to the lack of efficiency in diagnostics. In this context, nanomedicine combining both diagnostic and magnetic resonance imaging (MRI) and therapeutic applications is a relevant strategy referred to theranostic. Magnetic nanoparticles (NP) are excellent MRI contrast agents because of their large magnetic moment, which induces high transverse relaxivity (<i>r</i>₂) characteristic and increased susceptibility effect (T₂*). NP can be also used for drug delivery by coating their surface with therapeutic molecules. Preliminary <i>in vitro</i> studies show the high potential of caffeic acid (CA), a natural polyphenol, as a promising anticancer drug due to its antioxidant, anti-inflammatory, and antimetastatic properties. In this study, the antioxidative properties of iron oxide NP functionalized with caffeic acid (γFe₂O₃@CA NP) are investigated <i>in vitro</i> on U87-MG brain cancer cell lines. After intravenous injection of these NP in mice bearing a U87 glioblastoma, a negative contrast enhancement was specifically observed on 11.7 T MRI images in cancerous tissue, demonstrating a passive targeting of the tumor with these nanoplatforms