Magnetic Properties of Iron Oxide Nanoparticles Do Not Essentially Contribute to Ferrogel Biocompatibility

Two series of composite polyacrylamide (PAAm) gels with embedded superparamagnetic Fe₂O₃ or diamagnetic Al₂O₃ nanoparticles were synthesized, aiming to study the direct contribution of the magnetic interactions to the ferrogel biocompatibility. The proliferative activity was estimated for the case of human dermal fibroblast culture grown onto the surfaces of these types of substrates. Spherical non-agglomerated nanoparticles (NPs) of 20-40 nm in diameter were prepared by laser target evaporation (LTE) electrophysical technique. The concentration of the NPs in gel was fixed at 0.0, 0.3, 0.6, or 1.2 wt.%. Mechanical, electrical, and magnetic properties of composite gels were characterized by the dependence of Young's modulus, electrical potential, magnetization measurements on the content of embedded NPs. The fibroblast monolayer density grown onto the surface of composite substrates was considered as an indicator of the material biocompatibility after 96 h of incubation. Regardless of the superparamagnetic or diamagnetic nature of nanoparticles, the increase in their concentration in the PAAm composite provided a parallel increase in the cell culture proliferation when grown onto the surface of composite substrates. The effects of cell interaction with the nanostructured surface of composites are discussed in order to explain the results.

Ferrogels Ultrasonography for Biomedical Applications

Ferrogels (FG) are magnetic composites that are widely used in the area of biomedical engineering and biosensing. In this work, ferrogels with different concentrations of magnetic nanoparticles (MNPs) were synthesized by the radical polymerization of acrylamide in stabilized aqueous ferrofluid. FG samples were prepared in various shapes that are suitable for different characterization techniques. Thin cylindrical samples were used to simulate the case of targeted drug delivery test through blood vessels. Samples of larger size that were in the shape of cylindrical plates were used for the evaluation of the FG applicability as substitutes for damaged structures, such as bone or cartilage tissues. Regardless of the shape of the samples and the conditions of their location, the boundaries of FG were confidently visualized over the entire range of concentrations of MNPs while using medical ultrasound. The amplitude of the reflected echo signal was higher for the higher concentration of MNPs in the gel. This result was not related to the influence of the MNPs on the intensity of the reflected echo signal directly, since the wavelength of the ultrasonic effect used is much larger than the particle size. Qualitative theoretical model for the understanding of the experimental results was proposed while taking into account the concept that at the acoustic oscillations of the hydrogel, the macromolecular net, and water in the gel porous structure experience the viscous Stocks-like interaction.

The Contribution of Magnetic Nanoparticles to Ferrogel Biophysical Properties

Iron oxide γ-Fe₂O₃ magnetic nanoparticles (MNPs) were fabricated by laser target evaporation technique (LTE) and their structure and magnetic properties were studied. Polyacrylamide (PAAm) gels with different cross-linking density of the polymer network and polyacrylamide-based ferrogel with embedded LTE MNPs (0.34 wt.%) were synthesized. Their adhesive and proliferative potential with respect to human dermal fibroblasts were studied. At the same value of Young modulus, the adhesive and proliferative activities of the human dermal fibroblasts on the surface of ferrogel were unexpectedly much higher in comparison with the surface of PAAm gel. Properties of PAAm-100 + γ-Fe₂O₃ MNPs composites were discussed with focus on creation of a new generation of drug delivery systems combined in multifunctional devices, including magnetic field assisted delivery, positioning, and biosensing. Although exact applications are still under development, the obtained results show a high potential of LTE MNPs to be applied for cellular technologies and tissue engineering. PAAm-100 ferrogel with very low concentration of γ-Fe₂O₃ MNPs results in significant improvement of the cells’ compatibility to the gel-based scaffold.