Preparing biological specimens for scanning electron microscopy (SEM) can be difficult to implement, as it requires specialized equipment and materials as well as the training of dedicated personnel. Moreover, the procedure often results in damage to the samples to be analyzed. This work presents a protocol for the preparation of biological samples to evaluate the adherence of nanomaterials on the cell surface using SEM. To this end, we used silicon wafers as a substrate to grow cells and replaced difficult steps such as the critical point drying of the samples in order to make the method quicker and easier to perform. The new protocol was tested using two different types of cells, i.e., human osteosarcoma cells and adipose-derived mesenchymal stem cells, and it proved that it can grossly preserve cell integrity in order to be used to estimate nanomaterials’ interaction with cell surfaces.

A ferrofluid based on Fe_67.2Cr_12.5Nb_0.3B₂₀ magnetic particles with a low Curie temperature was prepared. The particles, most of which had dimensions under 60 nm, were dispersed in a calcium gluconate solution, leading to a stable ferrofluid. The obtained ferrofluid had a magnetization of 0.04 to 0.17 emu/cm³, depending on the particles’ concentration, and a viscosity that increased nonlinearly with the applied magnetic field. The ferrofluid appeared to be biocompatible, as it showed low cytotoxicity, even at high concentrations and for long intervals of co-incubation with human cells, demonstrating a good potential to be used for cancer therapies through magnetic hyperthermia as well as magneto-mechanical actuation.

(1) Osteoarthritis (OA) is a progressive joint degenerative disease that currently has no cure. Limitations in the development of innovative disease modifying therapies are related to the complexity of the underlying pathogenic mechanisms. In addition, there is the unmet need for efficient drug delivery methods. Magnetic nanoparticles (MNPs) have been proposed as an efficient modality for the delivery of bioactive molecules within OA joints, limiting the side effects associated with systemic delivery. We previously demonstrated MNP’s role in increasing cell proliferation and chondrogenesis. In the design of intra-articular therapies for OA, the combined NE-MNP delivery system could provide increased stability and biological effect. (2) Proprietary Fe₃O₄ MNPs formulated as oil-in-water (O/W) magneto nanoemulsions (MNEs) containing ascorbic acid and dexamethasone were tested for size, stability, magnetic properties, and in vitro biocompatibility with human primary adipose mesenchymal cells (ADSC), cell mobility, and chondrogenesis. In vivo biocompatibility was tested after systemic administration in mice. (3) We report high MNE colloidal stability, magnetic properties, and excellent in vitro and in vivo biocompatibility. By increasing ADSC migration potential and chondrogenesis, MNE carrying dexamethasone and ascorbic acid could reduce OA symptoms while protecting the cartilage layer.

Currently, various methods based on magnetic nanoparticles are being considered for the treatment of cancer. Among these, magnetic hyperthermia and magneto-mechanical actuation are the most tested physical methods that have shown promising results when applied both separately and in combination. However, combining them with specific drugs can further improve antitumor efficiency. In this study, we performed a systematic analysis to determine the best combination of hyperthermia, magneto-mechanical actuation of silver-coated magnetite nanoparticles (MNP@Ag) and chemotherapy (mitoxantrone) capable of destroying tumor cells in vitro while maintaining normal cells in their state of increased viability. The results showed that of the nine treatment configurations, the only one that satisfied the safety condition for normal cells (fibroblasts) and the highly cytotoxic condition for tumor cells (HeLa) was the combination of all three triggers. This combination led to the decrease in HeLa viability to about 32%, while the decrease in fibroblast viability reached 80%. It was observed that the cytotoxic effect was not a sum of the separate effects of each trigger involved, but the result of a nonlinear conjugation of the triggers in a dynamic regime imposed by the magneto-mechanical actuation of the nanoparticles. We conclude that by using such a treatment approach, the need for chemotherapeutic drugs can be substantially reduced while maintaining their therapeutic performance.

Magnetic nanoparticles (MPs) are emerging as powerful and versatile tools for biotechnology, including cancer research and theranostic applications. Stem cell-mediated magnetic particle delivery has been previously recognized as a modality to target sites of malignancies. Here, we propose the use of adipose-derived mesenchymal cells (ADSC) for the targeted delivery of Fe-Cr-Nb-B magnetic particles to human osteosarcoma (HOS) cells and magneto-mechanical actuation (MMA) for targeting and destroying HOS cells. We show that MPs are easily incorporated by ADSCs and HOS cells, as confirmed by TEM images and a ferrozine assay. MP-loaded ADSCs display increased motility towards tumor cells compared with their unloaded counterparts. MMA of MP-loaded ADSCs induces HOS destruction, as confirmed by the MTT and live/dead assays. MMA enables the release of the MPs towards cancer cells, producing a significant decrease (about 80%) in HOS viability immediately after application. In contrast, normal human dermal fibroblasts’ (NHDFs) viability exposed to similar conditions remains high, showing a differential behavior of normal and malignant cells to MP load and MMA exposure. Taken together, the method could derive successful strategies for in vivo applications in targeting and destroying malignant cells while protecting normal cells.