Magneto-Mechanical Approach in Biomedicine: Benefits, Challenges, and Future Perspectives.

The magneto-mechanical approach is a powerful technique used in many different applications in biomedicine, including remote control enzyme activity, cell receptors, cancer-selective treatments, mechanically-activated drug releases, etc. This approach is based on the use of a combination of magnetic nanoparticles and external magnetic fields that have led to the movement of such nanoparticles with torques and forces (enough to change the conformation of biomolecules or even break weak chemical bonds). However, despite many theoretical and experimental works on this topic, it is difficult to predict the magneto-mechanical effects in each particular case, while the important results are scattered and often cannot be translated to other experiments. The main reason is that the magneto-mechanical effect is extremely sensitive to changes in any parameter of magnetic nanoparticles and the environment and changes in the parameters of the applied magnetic field. Thus, in this review, we (1) summarize and propose a simplified theoretical explanation of the main factors affecting the efficiency of the magneto-mechanical approach; (2) discuss the nature of the MNP-mediated mechanical forces and their order of magnitude; (3) show some of the main applications of the magneto-mechanical approach in the control over the properties of biological systems.

Myxococcus xanthus Encapsulin as a Promising Platform for Intracellular Protein Delivery.

Introducing a new genetically encoded material containing a photoactivatable label as a model cargo protein, based on Myxococcus xanthus (Mx) encapsulin system stably expressed in human 293T cells. Encapsulin from Mx is known to be a protein-based container for a ferritin-like cargo in its shell which could be replaced with an exogenous cargo protein, resulting in a modified encapsulin system. We replaced Mx natural cargo with a foreign photoactivatable mCherry (PAmCherry) fluorescent protein and isolated encapsulins, containing PAmCherry, from 293T cells. Isolated Mx encapsulin shells containing photoactivatable label can be internalized by macrophages, wherein the PAmCherry fluorescent signal remains clearly visible. We believe that a genetically encoded nanocarrier system obtained in this study, can be used as a platform for controllable delivery of protein/peptide therapeutics in vitro.

Temperature-controlled magnetic nanoparticles hyperthermia inhibits primary tumor growth and metastases dissemination.

Magnetic hyperthermia (MHT) is a promising approach for cancer therapy. However, a systematic MHT characterization as function of temperature on the therapeutic efficiency is barely analyzed. Here, we first perform comparative temperature-dependent analysis of the cobalt ferrite nanoparticles-mediated MHT effectiveness in two murine tumors models - breast (4T1) and colon (CT26) cancer in vitro and in vivo. The overall MHT killing capacity in vitro increased with the temperature and CT26 cells were more sensitive than 4T1 when heated to 43 °C. Well in line with the in vitro data, such heating cured non-metastatic CT26 tumors in vivo, while only inhibiting metastatic 4T1 tumor growth without improving the overall survival. High-temperature MHT (>47 °C) resulted in complete 4T1 primary tumor clearance, 25-40% long-term survival rates, and, importantly, more effective prevention of metastasis comparing to surgical extraction. Thus, the specific MHT temperature must be defined for each tumor individually to ensure a successful antitumor therapy.

Synthesis of Iron Oxide Nanoclusters by Thermal Decomposition.

Herein, we report a novel one-step solvothermal synthesis of magnetite nanoclusters (MNCs). In this report, we discuss the synthesis, structure, and properties of MNCs and contrast enhancement in T2-weighted MR images using magnetite nanoclusters. The effect of different organic acids, used as surfactants, on the size and shape of MNCs was investigated. The structure and properties of samples were determined by magnetic measurements, TGA, TEM, HRTEM, XRD, FTIR, and MRI. Magnetic measurements show that obtained MNCs have relatively high saturation magnetization values (65.1-81.5 emu/g) and dependence of the coercive force on the average size of MNCs was established. MNCs were transferred into an aqueous medium by Pluronic F-127, and T2-relaxivity values were determined. T2-Weighted MR phantom images clearly demonstrated that such magnetite nanoclusters can be used as contrast agents for MRI.

Pharmaceutical Approach to Develop Novel Photosensitizer Nanoformulation: An Example of Design and Characterization Rationale of Chlorophyll α Derivative.

In this study, we described physico-chemical properties of novel nanoformulation of photosensitizer-pyropheophorbide α 17-diethylene glycol ester (XL) (chlorophyll α derivative), revealing insights into antitumor activity and maintaining quality, meeting the pharmaceutical approach of new nanoformulation design. Our formulation, based on poly(lactic-co-glycolic acid) (PLGA) nanoparticles, increased XL solubility and selective tumor-targeted accumulation. In our research, we revealed, for the first time, that XL binding to polyvinyl alcohol (PVA) enhances XL photophysical activity, providing the rationale for PVA application as a stabilizer for nanoformulations. Results of FTIR, DSC, and XRD revealed the physical interactions between XL and excipients, including PVA, indicating that the encapsulation maintained XL binding to PVA. The encapsulated XL exhibited higher photophysical activity compared to non-encapsulated substance, which can be attributed to the influence of residual PVA. Gamma-irradiation led to degradation of XL; however, successful sterilization of the samples was achieved through the filtration. Importantly, the encapsulated and sterilized XL retained cytotoxicity against both 2D and 3D tumor cell models, demonstrating the potential of the formulated NP-XL for photodynamic therapy applications, but lacked the ability to reactivate epigenetically silenced genes. These findings provide valuable insights into the design and characterization of PLGA-based nanoparticles for the encapsulation of photosensitizers.

Unveiling the Role of the Properties of Magnetic Nanoparticles for Highly Efficient Low-Frequency Magneto-Mechanical Actuation of Biomolecules.

The role of the properties of magnetic nanoparticles in the remote magneto-mechanical actuation of biomolecules under the influence of external magnetic fields is still of particular interest. Here, a specially designed strategy based on the mechanical destruction of short oligonucleotide duplexes is used to demonstrate the effect of magnetic nanoparticles with different sizes (5-99 nm) on the magnitude of the magneto-mechanical actuations in a low-frequency alternating magnetic field. The results show that the mechanical destruction of complementary chains of duplexes, caused by the rotational-vibrational movements of nanoparticles upon exposure to a magnetic field, has a nonmonotonic dependence on the nanoparticle core size. The main hypothesis of this phenomenon is associated with a key role of magneto-dipole interactions between individual nanoparticles, which blocks the movements of nanoparticles in dense clusters. This result will allow fine-tuning of the magnetic nanoparticle properties for addressing specific magneto-mechanical tasks.

Magnetic Nanoparticles as a Tool for Remote DNA Manipulations at a Single-Molecule Level.

Remote control of cells and single molecules by magnetic nanoparticles in nonheating external magnetic fields is a perspective approach for many applications such as cancer treatment and enzyme activity regulation. However, the possibility and mechanisms of direct effects of small individual magnetic nanoparticles on such processes in magneto-mechanical experiments still remain unclear. In this work, we have shown remote-controlled mechanical dissociation of short DNA duplexes (18-60 bp) under the influence of nonheating low-frequency alternating magnetic fields using individual 11 nm magnetic nanoparticles. The developed technique allows (1) simultaneous manipulation of millions of individual DNA molecules and (2) evaluation of energies of intermolecular interactions in short DNA duplexes or in other molecules. Finally, we have shown that DNA duplexes dissociation is mediated by mechanical stress and produced by the movement of magnetic nanoparticles in magnetic fields, but not by local overheating. The presented technique opens a new avenue for high-precision manipulation of DNA and generation of biosensors for quantification of energies of intermolecular interaction.

Effects of Macromolecular Crowding on Nanoparticle Diffusion: New Insights from Mössbauer Spectroscopy.

In this work, we used Mössbauer spectroscopy as a new approach for experimental quantification of the self-diffusion coefficient (DMössbauer) and hydrodynamic (HD) size of iron-containing nanoparticles (NPs) in complex crowded solutions, mimicking cell cytoplasm. As a probe, we used 9 nm cobalt ferrite NPs (CFNs) dispersed in solutions of bovine serum albumin (BSA) with a volume fraction (φBSA) of 0-0.2. Our results show that the broadening of Mössbauer spectra is highly sensitive to the diffusion of CFNs, while when φBSA = 0.2, the CFN-normalized diffusivity is reduced by 86% compared to that of a protein-free solution. CFN colloids were also studied by dynamic light scattering (DLS). Comparison of the experimental data shows that DLS significantly underestimates the diffusion coefficient of CFNs and, consequently, overestimates the HD size of CFNs at φBSA > 0, which cannot be attributed to the formation of the BSA monolayer on the surface of CFNs.

Development and pharmaceutical evaluation of the anticancer Anthrafuran/Cavitron complex, a prototypic parenteral drug formulation.

To improve the water solubility of the anticancer drug candidate LCTA-2034 (A1), we investigated the formation of complexes of this anthrax[2,3-b]furan congener with the solubilizing 2-hydroxypropyl derivative of ß-cyclodextrin HP-ßCD (Cavitron®). The interaction of A1 with HP-ßCD resulted in the inclusion complex A1/HP-ßCD in 1:1 stoichiometry. The A1/HP-ßCD complex was used to develop a prototype of a lyophilised drug formulation with enhanced (>10-fold) aqueous solubility than A1 and a long-term stability. The use of HP-ßCD decreased the acute toxicity of A1 by >30%. The A1/HP-ßCD drug formulation as well as A1 in equal doses (5×30mg/kg) to increase the lifespan by up to 140% for mice with i.p. transplanted P388 leukaemia. Furthermore, the A1/HP-ßCD formulation demonstrated a significant and reliable antitumor efficacy in a Р388/ADR drug resistant leukaemia and B16/F10 melanoma, proving a perspective of investigations of toxicology, biodistribution and pharmacokinetics.