Magnetic Particles for Biomedical Applications

Advances in Material-Assisted Electromagnetic Neural Stimulation

Bioelectricity plays a crucial role in organisms, being closely connected to neural activity and physiological processes. Disruptions in the nervous system can lead to chaotic ionic currents at the injured site, causing disturbances in the local cellular microenvironment, impairing biological pathways, and resulting in a loss of neural functions. Electromagnetic stimulation has the ability to generate internal currents, which can be utilized to counter tissue damage and aid in the restoration of movement in paralyzed limbs. By incorporating implanted materials, electromagnetic stimulation can be targeted more accurately, thereby significantly improving the effectiveness and safety of such interventions. Currently, there have been significant advancements in the development of numerous promising electromagnetic stimulation strategies with diverse materials. This review provides a comprehensive summary of the fundamental theories, neural stimulation modulating materials, material application strategies, and pre-clinical therapeutic effects associated with electromagnetic stimulation for neural repair. It offers a thorough analysis of current techniques that employ materials to enhance electromagnetic stimulation, as well as potential therapeutic strategies for future applications.

In-depth investigations of size and occupancies in cobalt ferrite nanoparticles by joint Rietveld refinements of X-ray and neutron powder diffraction data

Combined neutron and X-ray powder diffraction investigations of CoFe₂O₄ are reported, aimed at investigating the robustness, reproducibility and reliability of structural parameters from Rietveld refinement.

Powder X-ray diffraction (PXRD) and neutron powder diffraction (NPD) have been used to investigate the crystal structure of CoFe₂O₄ nanoparticles prepared via different hydro­thermal synthesis routes, with particular attention given to accurately determining the spinel inversion degrees. The study is divided into four parts. In the first part, the investigations focus on the influence of using different diffraction pattern combinations (NPD, Cu-source PXRD and Co-source PXRD) for the structural modelling. It is found that combining PXRD data from a Co source with NPD data offers a robust structural model. The second part of the study evaluates the reproducibility of the employed multipattern Rietveld refinement procedure using different data sets collected on the same sample, as well as on equivalently prepared samples. The refinement procedure gives reproducible results and reveals that the synthesis method is likewise reproducible since only minor differences are noted between the samples. The third part focuses on the structural consequences of (i) the employed heating rate (achieved using three different hydro­thermal reactor types) and (ii) changing the cobalt salt in the precursors [aqueous salt solutions of Co(CH₃COOH)₂, Co(NO₃)₂ and CoCl₂] in the synthesis. It is found that increasing the heating rate causes a change in the crystal structure (unit cell and crystallite sizes) while the Co/Fe occupancy and magnetic parameters remain similar in all cases. Also, changing the type of cobalt salt does not alter the final crystal/magnetic structure of the CoFe₂O₄ nanoparticles. The last part of this study is a consideration of the chemicals and parameters used in the synthesis of the different samples. All the presented samples exhibit a similar crystal and magnetic structure, with only minor deviations. It is also evident that the refinement method used played a key role in the description of the sample.

The Effect of Starch and Magnetite on the Physicochemical Properties of Polyurethane Composites for Hyperthermia Treatment

In this study, modified polyurethanes (PUs) with starch and magnetite were synthesized in the form of scaffolds for potential applications in orthopedics. Polyurethanes were synthesized using a one-step method. PU synthesis was carried out using poly(ε-caprolactone) 2000 as soft segments and 4,4 ${}^{\prime }$ -methylenediphenyl diisocyanate (MDI). Various molar ratios of starch and 1,5-pentanediol (PDO) as crosslinker/chain extender were applied, and the effects of incorporating different amounts of magnetite, as well as the role of PDO to starch ratio, were studied. The use of the additive in the form of magnetic particles was to feature the polyurethane materials for use in hyperthermia. The prepared polyurethanes were investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA) methods. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) analysis and preliminary bioactivity assessment were also performed. The addition of magnetic particles did not cause significant changes in the properties of the obtained materials compared to starch. The tested materials have the potential to be used to fill or replace bone defects in orthopedics, where they can undergo hyperthermia treatment.

Extensional Magnetorheology of Viscoelastic Human Blood Analogues Loaded with Magnetic Particles

This study represents a pioneering work on the extensional magnetorheological properties of human blood analogue fluids loaded with magnetic microparticles. Dynabeads M-270 particles were dispersed in Newtonian and viscoelastic blood analogue fluids at 5% wt. Capillary breakup experiments were performed, with and without the influence of an external magnetic field aligned with the flow direction. The presence of the particles increased the viscosity of the fluid, and that increment was larger when embedded within a polymeric matrix. The application of an external magnetic field led to an even larger increment of the viscosity of the working fluids, as the formation of small aggregates induced an increment in the effective volume fraction of particles. Regarding the liquid bridge stability, the Newtonian blood analogue fluid remained as a Newtonian liquid exhibiting a pinch-off at the breakup time in any circumstance. However, in the case of the viscoelastic blood analogue fluid, the presence of the particles and the simultaneous application of the magnetic field enhanced the formation of the beads-on-a-string structure, as the Ohnesorge number remained basically unaltered, whereas the time of the experiment increased due to its larger viscosity, which resulted in a decrease in the Deborah Number. This result was confirmed with fluids containing larger concentrations of xanthan gum.

R, Trevino De Leo C, Lopez SA, Martirosyan KS, Chew SA. Application of iron oxide nanoparticles to control the release of minocycline for the treatment of glioblastoma

Background: The utilization of iron oxide nanoparticles (Fe3O4 NPs) to control minocycline release rates from poly(lactic-co-glycolic acid) scaffolds fabricated from an easy/economical technique is presented. Results & methodology: A larger change in temperature and amount of minocycline released was observed for scaffolds with higher amounts of Fe3O4 NPs, demonstrating that nanoparticle concentration can control heat generation and minocycline release. Temperatures near a polymer's glass transition temperature can result in the polymer's chain becoming more mobile and thus increasing drug diffusion out of the scaffold. Elevated temperature and minocycline released from the scaffold can work synergistically to enhance glioblastoma cell death. Conclusion: This study suggests that Fe3O4 NPs are promising materials for controlling minocycline release from polymeric scaffolds by magnetic hyperthermia for the treatment of glioblastoma.

Optimization of Microparticle Reagents to Collect and Detect Antibody

Bead reagents are used in a large number of assays in bioscience and biotechnology to collect and purify antibodies by immobilization. Bead-based immunoassays offer high-throughput analysis of multiple antibodies in a single sample. Although a variety of antibody-binding moieties on the collection beads have been studied, the physical and material properties of collection beads have not been optimized to isolate specific antibodies over a broad range of concentrations from complex environments containing cells. We present a study of how to optimally use microparticles coated with protein G to collect low concentrations of IgG antibodies from complex solutions. We study the impact of bead material, bead size, incubation time, and protein G density to more efficiently collect antibodies and detect specific antibodies via fluorescent antigen labeling. The minimum detectable limit and the minimum incubation time for antibody collection are used as metrics to evaluate the collection parameters. We found that larger silica beads can capture more antibodies from a low concentration of sample, with a minimum incubation time of 60 min to equilibrium binding, resulting in a minimum detectable concentration of antibodies of 26 nM. We show that simple biophysical optimization of antibody collection reagents can be used to improve the collection of low concentrations of antibodies in complex environments. We demonstrate that the technology may be useful for monitoring antibody secretions from hybridoma cultures.

Clinical, Radiological, and Histological Assessment of Magnetic Nanoparticles as Pulpotomy Medicament in Primary Molars

Aim and objectives

Aim of the study was to evaluate the success of magnetic nanoparticles (MNPs) as pulpotomy medicament by clinical, radiologic, and histological assessment in primary molars.

Materials and methods

The sample included 30 primary molars from 25 children aged between 3 and 9 years requiring pulpotomy treatment. Pulpotomy was carried out with MNPs. The teeth were evaluated after a period of 3, 6, and 12 months clinically and with the aid of radiographs. After 1 year, 10 teeth were extracted for histological evaluation under field emission scanning electron microscope (FE-SEM; ZEISS, Model No. Supra 55vp).

Results

Of the samples, 98% showed clinical success rate with absence of pain, swelling, mobility, and abscess formation. After 3 months, 98% radiological success with absence of periodontal ligament widening, root resorption, and inter-radicular radiolucency was noted. Histological examination carried out under FE-SEM revealed a zone of odontoblastic proliferation at the interface between MNPs and odontoblastic layer of pulp and viable pulpal cells from the canal orifice till apical foramen.

Conclusion

Magnetic nanoparticles can be recommended as an effective pulpotomy medicament with hard tissue barrier formation and preservation of vitality of remaining radicular pulp.

How to cite this article: Konyala HR, Mareddy AR, Puppala N, Reddy NV, Mallela MK, Susheela KP. Clinical, Radiological, and Histological Assessment of Magnetic Nanoparticles as Pulpotomy Medicament in Primary Molars. Int J Clin Pediatr Dent 2018;11(4):283-287.

Magnetically driven medical devices: a review

A widely accepted definition of a medical device is an instrument or apparatus that is used to diagnose, prevent or treat disease. Medical devices take a broad range of forms and utilize various methods to operate, such as physical, mechanical or thermal. Of particular interest in this paper are the medical devices that utilize magnetic field sources to operate. The exploitation of magnetic fields to operate or drive medical devices has become increasingly popular due to interesting characteristics of magnetic fields that are not offered by other phenomena, such as mechanical contact, hydrodynamics and thermodynamics. Today, there is a wide range of magnetically driven medical devices purposed for different anatomical regions of the body. A review of these devices is presented and organized into two groups: permanent magnetically driven devices and electromagnetically driven devices. Within each category, the discussion will be further segregated into anatomical regions (e.g., gastrointestinal, ocular, abdominal, thoracic, etc.).