Determination of the blocking temperature of magnetic nanoparticles: The good, the bad, and the ugly

A numerically solved two-level Stoner-Wohlfarth model with thermal agitation is used to simulate Zero Field Cooling (ZFC)-Field Cooling (FC) curves of monosize and polysize samples and to determine the best method for obtaining a representative blocking temperature TB value of polysize samples. The results confirm a technique based on the T derivative of the difference between ZFC and FC curves proposed by Micha et al. (the good) and demonstrate its relation with two alternative methods: the ZFC maximum (the bad) and the inflection point (the ugly). The derivative method is then applied to experimental data, obtaining the TB distribution of a polysize Fe3O4 nanoparticle sample suspended in hexane with an excellent agreement with TEM characterization

Growth factor choice is critical for successful functionalization of nanoparticles

Nanoparticles (NPs) show new characteristics compared to the corresponding bulk material. These nanoscale properties make them interesting for various applications in biomedicine and life sciences. One field of application is the use of magnetic NPs to support regeneration in the nervous system. Drug delivery requires a functionalization of NPs with bio-functional molecules. In our study, we functionalized self-made PEI-coated iron oxide NPs with nerve growth factor (NGF) and glial cell-line derived neurotrophic factor (GDNF). Next, we tested the bio-functionality of NGF in a rat pheochromocytoma cell line (PC12) and the bio-functionality of GDNF in an organotypic spinal cord culture. Covalent binding of NGF to PEI-NPs impaired bio-functionality of NGF, but non-covalent approach differentiated PC12 cells reliably. Non-covalent binding of GDNF showed a satisfying bio-functionality of GDNF:PEI-NPs, but turned out to be unstable in conjugation to the PEI-NPs. Taken together, our study showed the importance of assessing bio-functionality and binding stability of functionalized growth factors using proper biological models. It also shows that successful functionalization of magnetic NPs with growth factors is dependent on the used binding chemistry and that it is hardly predictable. For use as therapeutics, functionalization strategies have to be reproducible and future studies are needed

Magnetic nanoparticles for magnetically guided therapies against neural diseases

Neurological pathologies and nerve damage are two problems of significant medical and economic impact because of the hurdles of losing nerve functionality in addition to significant mortality and morbidity, and demanding rehabilitation. There are currently a number of examples of how nanotechnology can provide new solutions for biomedical problems. Current strategies for nerve repair rely on the use of functionalized scaffolds working as nerve guidance channels to improve axonal regeneration and to direct axonal re-growth across the nerve lesion site. Since low invasiveness and high selectivity of the growth stimulation are usually conflicting requirements, new approaches are being pursued in order to overcome such limitations. Engineered magnetic nanoparticles (MNPs) have emerged from this need for noninvasive therapies for both positioning and guiding neural cells in response to an external magnetic field. Here, we review the current state of the use of MNPs for neuroprotective and magnetically guided therapies. We discuss some conceivable outcomes of current magnetically driven strategies seeking integrated platforms for regenerative action on damaged tissues

Cell damage produced by magnetic fluid hyperthermia on microglial BV2 cells

We present evidence on the effects of exogenous heating by water bath (WB) and magnetic hyperthermia (MHT) on a glial micro-tumor phantom. To this, magnetic nanoparticles (MNPs) of 30-40 nm were designed to obtain particle sizes for maximum heating efficiency. The specific power absorption (SPA) values (f = 560 kHz, H = 23.9 kA/m) for as prepared colloids (533-605 W/g) dropped to 98-279 W/g in culture medium. The analysis of the intracellular MNPs distribution showed vesicle-trapped MNPs agglomerates spread along the cytoplasm, as well as large (~0.5-0.9 µm) clusters attached to the cell membrane. Immediately after WB and MHT (T = 46 °C for 30 min) the cell viability was ˜70% and, after 4.5 h, decreased to 20-25%, demonstrating that metabolic processes are involved in cell killing. The analysis of the cell structures after MHT revealed a significant damage of the cell membrane that is correlated to the location of MNPs clusters, while local cell damage were less noticeable after WB without MNPs. In spite of the similar thermal effects of WB and MHT on the cell viability, our results suggest that there is an additional mechanism of cell damage related to the presence of MNPs at the intracellular space

In silico before in vivo: How to predict the heating efficiency of magnetic nanoparticles within the intracellular space

This work aims to demonstrate the need for in silico design via numerical simulation to produce optimal Fe 3 O 4 -based magnetic nanoparticles (MNPs) for magnetic hyperthermia by minimizing the impact of intracellular environments on heating efficiency. By including the relevant magnetic parameters, such as magnetic anisotropy and dipolar interactions, into a numerical model, the heating efficiency of as prepared colloids was preserved in the intracellular environment, providing the largest in vitro specific power absorption (SPA) values yet reported. Dipolar interactions due to intracellular agglomeration, which are included in the simulated SPA, were found to be the main cause of changes in the magnetic relaxation dynamics of MNPs under in vitro conditions. These results pave the way for the magnetism-based design of MNPs that can retain their heating efficiency in vivo, thereby improving the outcome of clinical hyperthermia experiments

The relevance of Brownian relaxation as power absorption mechanism in Magnetic Hyperthermia

The Linear Response Theory (LRT) is a widely accepted framework to analyze the power absorption of magnetic nanoparticles for magnetic fluid hyperthermia. Its validity is restricted to low applied fields and/or to highly anisotropic magnetic nanoparticles. Here, we present a systematic experimental analysis and numerical calculations of the specific power absorption for highly anisotropic cobalt ferrite (CoFe 2 O 4 ) magnetic nanoparticles with different average sizes and in different viscous media. The predominance of Brownian relaxation as the origin of the magnetic losses in these particles is established, and the changes of the Specific Power Absorption (SPA) with the viscosity of the carrier liquid are consistent with the LRT approximation. The impact of viscosity on SPA is relevant for the design of MNPs to heat the intracellular medium during in vitro and in vivo experiments. The combined numerical and experimental analyses presented here shed light on the underlying mechanisms that make highly anisotropic MNPs unsuitable for magnetic hyperthermia

The needs of families who care for individuals with kidney failure on comprehensive conservative care: A qualitative systematic review

Background: Integrating the family of patients with kidney failure on comprehensive conservative care could benefit patients, families, and the health care system. However, there is a knowledge gap in this phenomenon since no systematic review has focused on the families' needs who care for individuals with kidney failure on comprehensive conservative care. Objectives: To understand the primary needs of families who care for people with kidney failure on comprehensive conservative care. Method: A systematic literature review of qualitative studies, followed by a content analysis was carried out. PubMed, CINAHL, and PsycINFO databases were used to search for articles published in English and Spanish between 2010 and 2021. The ENTREQ guideline was used for reporting. Results: Five relevant studies were included in this study. The analysis has allowed identifying key aspects of knowledge, psychological, social and spiritual needs of family members of patients with kidney failure on comprehensive conservative care. Conclusions: This systematic review has revealed that families experience a lack of information and continuity of care by health care professionals. Added to this is the psychological burden they bear due to the feeling of indefinite care in time and uncertainty about the death of their loved one. All this, without the necessary support from their immediate family environment and social institutions. In light of these data, a paradigm shift in society and the health care received by these families is essential

The needs of families who care for individuals with kidney failure on comprehensive conservative care: A qualitative systematic review

Background: Integrating the family of patients with kidney failure on comprehensive conservative care could benefit patients, families, and the health care system. However, there is a knowledge gap in this phenomenon since no systematic review has focused on the families' needs who care for individuals with kidney failure on comprehensive conservative care. Objectives: To understand the primary needs of families who care for people with kidney failure on comprehensive conservative care. Method: A systematic literature review of qualitative studies, followed by a content analysis was carried out. PubMed, CINAHL, and PsycINFO databases were used to search for articles published in English and Spanish between 2010 and 2021. The ENTREQ guideline was used for reporting. Results: Five relevant studies were included in this study. The analysis has allowed identifying key aspects of knowledge, psychological, social and spiritual needs of family members of patients with kidney failure on comprehensive conservative care. Conclusions: This systematic review has revealed that families experience a lack of information and continuity of care by health care professionals. Added to this is the psychological burden they bear due to the feeling of indefinite care in time and uncertainty about the death of their loved one. All this, without the necessary support from their immediate family environment and social institutions. In light of these data, a paradigm shift in society and the health care received by these families is essential