Mechanical, Electrical and Magnetic Properties of Ferrogels with Embedded Iron Oxide Nanoparticles Obtained by Laser Target Evaporation: Focus on Multifunctional Biosensor Applications

Hydrogels are biomimetic materials widely used in the area of biomedical engineering and biosensing. Ferrogels (FG) are magnetic composites capable of functioning as magnetic field sensitive transformers and field assisted drug deliverers. FG can be prepared by incorporating magnetic nanoparticles (MNPs) into chemically crosslinked hydrogels. The properties of biomimetic ferrogels for multifunctional biosensor applications can be set up by synthesis. The properties of these biomimetic ferrogels can be thoroughly controlled in a physical experiment environment which is much less demanding than biotests. Two series of ferrogels (soft and dense) based on polyacrylamide (PAAm) with different chemical network densities were synthesized by free-radical polymerization in aqueous solution with N, N'-methylene-diacrylamide as a cross-linker and maghemite Fe2O3 MNPs fabricated by laser target evaporation as a filler. Their mechanical, electrical and magnetic properties were comparatively analyzed. We developed a giant magnetoimpedance (MI) sensor prototype with multilayered FeNi-based sensitive elements deposited onto glass or polymer substrates adapted for FG studies. The MI measurements in the initial state and in the presence of FG with different concentrations of MNPs at a frequency range of 1-300 MHz allowed a precise characterization of the stray fields of the MNPs present in the FG. We proposed an electrodynamic model to describe the MI in multilayered film with a FG layer based on the solution of linearized Maxwell equations for the electromagnetic fields coupled with the Landau-Lifshitz equation for the magnetization dynamics.This work was supported in part within the framework of the state task of the Ministry of Education and Science of Russia 3.6121.2017/8.9; RFBR grants 16-08-00609-a, 18-08-00178, and by the ACTIMAT ELKARTEK grant of the Basque Country Government. Selected studies were made at SGIKER Common Services of UPV-EHU and URFU Common Services. We thank I.V. Beketov, A.A. Chlenova, S.O. Volchkov, V.N. Lepalovskij, A.M. Murzakaev and A.A. Svalova for special support

Selected features of morpho-functional reactions of eukaryotic microorganisms grown in the presence of maghemite iron oxide nanoparticles obtained by laser target evaporation

Biological activity of iron introduced into nutrient medium as a suspension of iron oxide nanoparticles (MNPs) synthesized by the laser target evaporation was investigated. Exophiala nigrum (E. nigrum) eukaryotes were grown either in the presence or in absence of MNPs. De-aggregated suspensions of Fe2.75O4 MNPs were added in concentrations of 1 to 104 maximum permissive dose (MPD, being 0.3 mg/L of Fe ions in water). Cells were exposed for 24 to 96 hours periods and then plated onto a solid medium. The effect of MNPs was evaluated by the change in the number of cells during exposure and the number and morphology of the colonies. For 1-10 MPD yeast showed unaltered characteristics. For 100 or 1000 MPD for 72 hours of exposure and above the number of cells increases up to 30 times in comparison with the control. A pronounced stimulating effect was revealed at 104 MPD of iron. A significant excess of the number of cells was observed for the first day. At exposures of 72 and 96 hours the differences in the number of cells in comparison with the control were 11 and 30 times, respectively. A change in the colonies morphology was observed at 100 MPD concentration

Methodological aspects of small iron concentrations determination in black yeasts grown in the presence of iron oxide nanoparticles

Nonpathogenic Exophiala nigrum (black yeasts) unicelular organisms of the Baikal Lake were used as a model system for determination of small iron concentrations in the samples grown without or with controlled amount of maghemite nanoparticles (MNPs) in nutrient. MNPs were produced by the electrophysical laser target evaporation technique. Electrostatically stabilized suspensions were prepared using sodium citrate solutions in distilled water. We assumed that one maximum permissive dose of ionic iron in water 1 MPD is equal to 0.3 mg/L. For biological experiments Saburo liquid nutrient medium was prepared with iron concentrations of 0, 102, 103 and 104 MPD. One ml of E. Nigrum cell suspension was added to Saburo liquid nutrient for 24 hours exposure. Followed by sowing onto a solid agar Saburo for 30 days colonies grows. Biosamples for electron microscopy, magnetic and total reflection X-ray fluorescence spectroscopy measurements were collected simultaneously. We were able to comparatively analyze the trace concentrations of iron in the yeast of the order of 10 ppm for control group and 600 ppm for the group grown in the presence of 104 MPD of iron