Synthesis and characterization of citrate-stabilized gold-coated superparamagnetic iron oxide nanoparticles for biomedical applications. - In: Molecules, ISSN 1420-3049, Bd. 25 (2020), 19, 4425, insges. 23 S.
Surface-functionalized gold-coated superparamagnetic iron oxide nanoparticles (Au-SPIONs) may be a useful tool in various biomedical applications. To obtain Au-SPIONs, gold salt was precipitated onto citrate-stabilized SPIONs (Cit-SPIONs) using a simple, aqueous one-pot technique inspired by the Turkevich method of gold nanoparticle synthesis. By the further stabilization of the Au-SPION surface with additional citrate (Cit-Au-SPIONs), controllable and reproducible Z-averages enhanced long-term dispersion stability and moderate dispersion pH values were achieved. The citrate concentration of the reaction solution and the gold/iron ratio was found to have a major influence on the particle characteristics. While the gold-coating reduced the saturation magnetization to 40.7% in comparison to pure Cit-SPIONs, the superparamagnetic behavior of Cit-Au-SPIONs was maintained. The formation of nanosized gold on the SPION surface was confirmed by X-ray diffraction measurements. Cit-Au-SPION concentrations of up to 100 [my]g Fe/mL for 48 h had no cytotoxic effect on Jurkat cells. At a particle concentration of 100 [my]g Fe/mL, Jurkat cells were found to take up Cit-Au-SPIONs after 24 h of incubation. A significantly higher attachment of thiol-containing L-cysteine to the particle surface was observed for Cit-Au-SPIONs (53%) in comparison to pure Cit-SPIONs (7%).
https://doi.org/10.3390/molecules25194425
Collagen-iron oxide nanoparticle based ferrogel: large reversible magnetostrains with potential for bioactuation. - In: Multifunctional materials, ISSN 2399-7532, Volume 3 (2020), number 3, 035001, Seite 1-10
Smart materials such as stimuli responsive polymeric hydrogels offer unique possibilities for tissue engineering and regenerative medicine. As, however, most synthetic polymer systems and their degradation products lack complete biocompatibility and biodegradability, this study aims to synthesize a highly magnetic responsive hydrogel, based on the abundant natural biopolymer collagen. As the main component of vertebratal extracellular matrix, it reveals excellent biocompatibility. In combination with incorporated magnetic iron oxide nanoparticles, a novel smart nano-bio-ferrogel can be designed. While retaining its basic biophysical properties and interaction with living cells, this collagen-nanoparticle hydrogel can be compressed to 38% of its original size and recovers to 95% in suitable magnetic fields. Besides the phenomenology of this scenario, the underlying physical scenarios are also discussed within the framework of network models. The observed reversible peak strains as large as 150% open up possibilities for the fields of biomedical actuation, soft robotics and beyond.
https://doi.org/10.1088/2399-7532/abaa2d
OPM magnetorelaxometry in the presence of a DC bias field. - In: EPJ Quantum Technology, ISSN 2196-0763, Bd. 7 (2020), 12, insges. 14 S.
Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drug targeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP's magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the influence of background magnetic fields on the MNP's relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic fields of up to 100 [my]T. We show that the relaxation parameters alter or may be intentionally altered significantly by applying static fields parallel or antiparallel to the MNPs alignment direction. Further, not only the relaxation process of the MNP's magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation field.
https://doi.org/10.1140/epjqt/s40507-020-00087-3
Age-related differences of motor cortex plasticity in adults: a transcranial direct current stimulation study. - In: Brain stimulation, ISSN 1876-4754, Bd. 13 (2020), 6, S. 1588-1599
Background - Cognitive, and motor performance are reduced in aging, especially with respect to acquisition of new knowledge, which is associated with a neural plasticity decline. Animal models show a reduction of long-term potentiation, but not long-term depression, in higher age. Findings in humans are more heterogeneous, with some studies showing respective deficits, but others not, or mixed results, for plasticity induced by non-invasive brain stimulation. One reason for these heterogeneous results might be the inclusion of different age ranges in these studies. In addition, a systematic detailed comparison of the age-dependency of neural plasticity in humans is lacking so far. - Objective - We aimed to explore age-dependent plasticity alterations in adults systematically by discerning between younger and older participants in our study. - Methods - We recruited three different age groups (Young: 18-30, Pre-Elderly: 50-65, and Elderly: 66-80 years). Anodal, cathodal, or sham transcranial direct current stimulation (tDCS) was applied over the primary motor cortex with 1 mA for 15 min to induce neuroplasticity. Cortical excitability was monitored by single-pulse transcranial magnetic stimulation as an index of plasticity. - Results - For anodal tDCS, the results show a significant excitability enhancement, as compared to sham stimulation, for both, Young and the Pre-Elderly groups, while no LTP-like plasticity was obtained in the Elderly group by the applied stimulation protocol. Cathodal tDCS induced significant excitability-diminishing plasticity in all age groups. - Conclusion - Our study provides further insight in age-related differences of plasticity in healthy humans, which are similar to those obtained in animal models. The decline of LTP-like plasticity in higher age could contribute to cognitive deficits observed in aging.
https://doi.org/10.1016/j.brs.2020.09.004
Investigation of magnetically driven passage of magnetic nanoparticles through eye tissues for magnetic drug targeting. - In: Nanotechnology, ISSN 1361-6528, Bd. 31 (2020), 49, 495101, S. 1-12
This paper elucidates the feasibility of magnetic drug targeting to the eye by using magnetic nanoparticles (MNPs) to which pharmaceutical drugs can be linked. Numerical simulations revealed that a magnetic field gradient of 20 T m^-1 seems to be promising for dragging magnetic multicore nanoparticles of about 50 nm into the eye. Thus, a targeting magnet system made of superconducting magnets with a magnetic field gradient at the eye of about 20 T m^-1 was simulated. For the proof-of-concept tissue experiments presented here the required magnetic field gradient of 20 T m^-1 was realized by a permanent magnet array. MNPs with an optimized multicore structure were selected for this application by evaluating their stability against agglomeration of MNPs with different coatings in water for injections, physiological sodium chloride solution and biological media such as artificial tear fluid. From these investigations, starch turned out to be the most promising coating material because of its stability in saline fluids due to its steric stabilization mechanism. To evaluate the passage of MNPs through the sclera and cornea of the eye tissues of domestic pigs (Sus scrofa domesticus), a three-dimensionally printed setup consisting of two chambers (reservoir and target chamber) separated by the eye tissue was developed. With the permanent magnet array emulating the magnetic field gradient of the superconducting setup, experiments on magnetically driven transport of the MNPs from the reservoir chamber into the target chamber via the tissue were performed. The resulting concentration of MNPs in the target chamber was determined by means of quantitative magnetic particle spectroscopy. It was found that none of the tested particles passed the cornea, but starch-coated particles could pass the sclera at a rate of about 5 ng mm^-2 within 24 h. These results open the door for future magnetic drug targeting to the eye.
https://doi.org/10.1088/1361-6528/abb0b4
ROS-generation and cellular uptake behavior of amino-silica nanoparticles arisen from their uploading by both iron-oxides and hexamolybdenum clusters. - In: Materials science & engineering, ISSN 1873-0191, Bd. 117 (2020), 111305
The present work introduces combination of superparamagnetic iron oxides (SPIONs) and hexamolybdenum cluster ([{Mo6I8}I6]2−) units within amino-decorated silica nanoparticles (SNs) as promising design of the hybrid SNs as efficient cellular contrast and therapeutic agents. The heating generated by SNs doped with SPIONs (Fe3O4SNs) under alternating magnetic field is characterized by high specific absorption rate (SAR = 446 W/g). The cluster units deposition onto both Fe3O4@SNs and “empty” silica nanoparticles (SNs) results in Fe3O4@SNs[{Mo6I8}I6] and SNs[{Mo6I8}I6] with red cluster-centered luminescence and ability to generate reactive oxygen species (ROS) under the irradiation. The monitoring of spin-trapped ROS by ESR spectroscopy technique indicates that the ROS-generation decreases in time for SNs[{Mo6I8}I6] and [{Mo6I8}I6]2− in aqueous solutions, while it remains constant for Fe3O4@SNs[{Mo6I8}I6]. The cytotoxicity is low for both Fe3O4@SNs[{Mo6I8}I6] and SNs[{Mo6I8}I6], while the flow cytometry indicates preferable cellular uptake of the former versus the latter type of the nanoparticles. Moreover, entering into nucleus along with cytoplasm differentiates the intracellular distribution of Fe3O4@SNs[{Mo6I8}I6] from that of SNs[{Mo6I8}I6], which remain in the cell cytoplasm only. The exceptional behavior of Fe3O4@SNs[{Mo6I8}I6] is explained by residual amounts of iron ions at the silica surface.
https://doi.org/10.1016/j.msec.2020.111305
Influence of lens fluorescence on fluorescence lifetime imaging ophthalmoscopy (FLIO) fundus imaging and strategies for its compensation. - In: Translational Vision Science & Technology, ISSN 2164-2591, Bd. 9 (2020), 8, 13, S. 1-10
https://doi.org/10.1167/tvst.9.8.13
Comparison of algorithms to suppress artifacts from the natural lens in fluorescence lifetime imaging ophthalmoscopy (FLIO). - In: Biomedical optics express, ISSN 2156-7085, Bd. 11 (2020), 10, S. 5586-5602
https://doi.org/10.1364/BOE.400059
Ca2+ channel dynamics explain the nonlinear neuroplasticity induction by cathodal transcranial direct current stimulation over the primary motor cortex. - In: European neuropsychopharmacology, ISSN 1873-7862, Bd. 38 (2020), S. 63-72
https://doi.org/10.1016/j.euroneuro.2020.07.011
New frontiers in noninvasive analysis of retinal wall-to-lumen ratio by retinal vessel wall analysis. - In: Translational Vision Science & Technology, ISSN 2164-2591, Bd. 9 (2020), 6, 7, S. 1-8
https://doi.org/10.1167/tvst.9.6.7