Iron Oxide Nanoparticle Coatings Dictate Cell Outcomes Despite the Influence of Protein Coronas.

A critical issue in nanomedicine is to understand the complex dynamics that dictate the interactions of nanoparticles (NPs) with their biological milieu. The most exposed part of a nanoparticle is its surface coating, which comes into contact with the biological medium and adsorbs proteins, forming what is known as a protein corona (PC). It is assumed that this PC mainly dictates the nanoparticle-cell interactions. As such, we set out to analyze how different coatings on iron oxide nanoparticles (MNPs) affect the composition of the PC that forms on top of them, and how these newly formed coronas influence the uptake of MNPs by macrophages and tumor cells, their subcellular location upon internalization, and their intracellular degradation. We found that different superficial charges of the coatings did not affect the PC composition, with an enrichment in proteins with affinity for divalent ions regardless of the type of coating. The iron oxide core of the MNP might become exposed to the biological medium, influencing the proteins that constitute the PCs. The presence of enzymes with hydrolase activity in the PC could explain the degradation of the coatings when they come into contact with the biological media. In terms of MNP internalization by cells, coatings mainly determine the endocytic pathways used, especially in terms of receptor-mediated endocytosis. However, the increase in hydrodynamic size provoked by the formation of the associated corona drives uptake mechanisms like macropinocytosis. Once inside the cells, the PC protected the NPs in their intracellular transit to lysosomes, where they were fully degraded. This understanding of how coatings and PCs influence different cellular processes will help design improved NPs for biomedical applications, taking into account the influence of the coating and corona on the biology of the NPs.

Factores cardiometabólicos asociados y prevalencia de concentraciones bajas de colesterol HDL y de dislipidemia aterogénica. Estudio SIMETAP-DA / Related cardiometabolic factors and prevalence of low HDL-cholesterol levels and atherogenic dyslipidemia. SIMETAP-AD study

OBJETIVO: Determinar las prevalencias ajustadas por edad y sexo de concentraciones bajas de colesterol HDL (cHDL-bajo) y de dislipidemia aterogénica (DA), y valorar sus asociaciones con factores de riesgo cardiovascular, enfermedad renal crónica, enfermedades cardiovasculares y cardiometabólicas. MÉTODOS: Estudio observacional transversal de base poblacional realizado en atención primaria, con sujetos adultos seleccionados aleatoriamente. Se consideró DA si los pacientes tenían hipertrigliceridemia (triglicéridos≥150mg/dL) y cHDL-bajo (<40mg/dL [hombres],<50mg/dL [mujeres]). Se determinaron las tasas de prevalencia crudas y ajustadas por edad y sexo, y se realizó análisis univariado y multivariante para evaluar los factores cardiometabólicos relacionados. RESULTADOS: Población de estudio con 6.588 adultos (55,9% mujeres) con edad media de 55,1 (±17,5) años. Las medias de cHDL fueron 49,2 (±12,6) mg/dL en hombres y 59,2 (±14,7) mg/dL en mujeres. Las prevalencias crudas de cHDL-bajo y de DA fueron 30,8% (IC95%: 29,7-31,9), y 14,3% (IC95%: 13,5-15,2), respectivamente. Las prevalencias ajustadas de cHDL-bajo fueron 28% en hombres y 31% en mujeres, y de DA fueron 16,4% en hombres y 10,6% en mujeres. El 73% de la población con DA tenía riesgo cardiovascular alto o muy alto. Los factores independientes asociados con cHDL-bajo o con DA fueron diabetes, tabaquismo, obesidad abdominal y obesidad. Los principales factores asociados con cHDL-bajo y con DA fueron hipertrigliceridemia y diabetes, respectivamente. CONCLUSIONES: Casi un tercio de la población adulta presentaba cHDL-bajo y la mitad de ellos cumplía criterios de DA. Los factores cardiometabólicos se asociaban con cHDL-bajo y DA, destacando la hipertrigliceridemia con el cHDL-bajo, y la DM con la DA

AIM: To determine the crude and sex- and age-adjusted prevalence rates of atherogenic dyslipidemia (AD) and low HDL-cholesterol levels (low-HDLc), and to assess their associations with cardiovascular risk factors, chronic kidney disease, cardiovascular and cardiometabolic diseases. METHODS: Population-based cross-sectional study conducted in Primary Care, with randomly selected adult subjects. The AD was considered if the patients had hypertriglyceridemia (triglycerides≥150mg/dL) and low-HDLc (<40mg/dL [men];<50mg/dL [women]). Crude and sex- and age-adjusted prevalence rates were determined, and univariate and multivariate analysis were performed to assess related cardiometabolic factors. RESULTS: Study population with 6,588 adults (55.9% women) with mean age 55.1 (±17.5) years. The mean HDLc levels were 49.2 (±12.6) mg/dL in men and 59.2 (±14.7) mg/dL in women. The crude prevalence rates of low-HDLc and AD were 30.8% (95%CI: 29.7-31.9), and 14.3% (95%CI: 13.5-15.2), respectively. The adjusted prevalence rates of low-HDLc were 28.0% in men and 31.0% in women, and AD were 16.4% in men and 10.6% in women. Seventy-three percent of the population with AD had high or very high cardiovascular risk. The independent factors associated with low HDLc or with AD were diabetes, smoking, abdominal obesity, and obesity. The major factors associated with low HDLc and AD were hypertriglyceridemia and diabetes, respectively. CONCLUSIONS: Almost a third of the adult population had low HDL-C and half of them met AD criteria. Cardiometabolic factors were associated with low HDL-C and AD, highlighting hypertriglyceridemia with low HDLc, and DM with AD

Related cardiometabolic factors and prevalence of low HDL-cholesterol levels and atherogenic dyslipidemia. SIMETAP-AD study. / Factores cardiometabólicos asociados y prevalencia de concentraciones bajas de colesterol HDL y de dislipidemia aterogénica. Estudio SIMETAP-DA.

AIM: To determine the crude and sex- and age-adjusted prevalence rates of atherogenic dyslipidemia (AD) and low HDL-cholesterol levels (low-HDLc), and to assess their associations with cardiovascular risk factors, chronic kidney disease, cardiovascular and cardiometabolic diseases. METHODS: Population-based cross-sectional study conducted in Primary Care, with randomly selected adult subjects. The AD was considered if the patients had hypertriglyceridemia (triglycerides≥150mg/dL) and low-HDLc (<40mg/dL [men];<50mg/dL [women]). Crude and sex- and age-adjusted prevalence rates were determined, and univariate and multivariate analysis were performed to assess related cardiometabolic factors. RESULTS: Study population with 6,588 adults (55.9% women) with mean age 55.1 (±17.5) years. The mean HDLc levels were 49.2 (±12.6) mg/dL in men and 59.2 (±14.7) mg/dL in women. The crude prevalence rates of low-HDLc and AD were 30.8% (95%CI: 29.7-31.9), and 14.3% (95%CI: 13.5-15.2), respectively. The adjusted prevalence rates of low-HDLc were 28.0% in men and 31.0% in women, and AD were 16.4% in men and 10.6% in women. Seventy-three percent of the population with AD had high or very high cardiovascular risk. The independent factors associated with low HDLc or with AD were diabetes, smoking, abdominal obesity, and obesity. The major factors associated with low HDLc and AD were hypertriglyceridemia and diabetes, respectively. CONCLUSIONS: Almost a third of the adult population had low HDL-C and half of them met AD criteria. Cardiometabolic factors were associated with low HDL-C and AD, highlighting hypertriglyceridemia with low HDLc, and DM with AD.

Variability of anesthetic depth in total intravenous anesthesia vs balanced anesthesia using entropy indices: a randomized, crossover, controlled clinical trial / Variabilidad de la profundidad anestésica en anestesia total intravenosa vs. anestesia general balanceada usando índices de entropía. Un ensayo clínico aleatorizado, cruzado y controlado

Abstract Introduction: Total intravenous anesthesia (TIVA) and balanced anesthesia (BA) are the most commonly used anesthetic techniques. The differences are the variability of the depth of anesthesia between these techniques that might predict which one is safer for patients and presents a lower risk of intraoperative awakening. Objective: To determine whether a difference exists in the variability of depth of anesthesia obtained by response entropy (RE). Methods: A crossover clinical trial was conducted on 20 healthy patients receiving upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to (a) target-controlled infusion of propofol using the Schnider model at a target concentration of 2.5 µg/mL for 15 minutes and a 10-minute washout, followed by sevoflurane administration at 0.8 minimal alveolar concentration (MAC) for the reminder of the surgery, or (b) the reverse sequence. Differences in the variability of the depth of anesthesia using RE were evaluated using paired t-test. Results: The treatment effect showed no significant difference in the average values of RE, during TIVA = 97.23 vs BA 97.04 (P = 0.39). Carry Over (-4.98 vs 4.08) and Period (100.3 vs 94.68) effects were not significantly different. Conclusion: The present study suggests that both anesthetic techniques are equivalent in terms of the stability of the depth of anesthesia. It is important to keep testing the determinants of the efficacy of different populations because the individual behaviors of patients might ultimately tip the scale.

Resumen Introducción: La anestesia total intravenosa (TIVA, por sus siglas en inglés) y la anestesia balanceada (AB) son las técnicas anestésicas más comúnmente utilizadas. La diferencia está en la variabilidad de la profundidad de la anestesia entre estas dos técnicas, lo cual pudiera predecir cuál es más segura para los pacientes y representar un menor riesgo de despertar intraoperatorio. Objetivo: Determinar si existe alguna diferencia en la variabilidad de la profundidad de la anestesia obtenida según los índices de entropía de respuesta (ER). Métodos: Se llevó a cabo un estudio clínico cruzado en 20 pacientes sanos que se sometieron a cirugía ortopédica ambulatoria de miembros superiores o inferiores. Los pacientes se asignaron aleatoriamente así: a) infusión controlada por objetivo (TCI, por sus siglas en inglés) de propofol, utilizando el modelo Schnider a una concentración objetivo de 2,5 µg/mL durante 15 min y un período de lavado de 10 minutos, seguido de la administración de sevoflurano a 0,8 de concentración alveolar mínima (CAM) durante el tiempo restante de la cirugía; o b) la secuencia inversa. Las diferencias en la variabilidad de la profundidad de la anestesia utilizando entropía de respuesta se evaluaron utilizando la prueba t pareada. Resultados: El efecto del tratamiento no mostró ninguna diferencia significativa en los valores promedio de entropía de respuesta (ER) durante TIVA = 97,23 vs. AB 97,04 (P = 0,39). Los efectos de arrastre (-4,98 vs. 4,08) y período (100,3 vs. 94,68) no fueron significativamente diferentes. Conclusiones: El presente estudio sugiere que ambas técnicas anestésicas son equivalentes en términos de estabilidad de la profundidad de la anestesia. Es importante continuar probando los factores determinantes de eficacia en las distintas poblaciones, ya que el comportamiento individual de cada paciente pudiera finalmente inclinar la balanza.

Cell-Promoted Nanoparticle Aggregation Decreases Nanoparticle-Induced Hyperthermia under an Alternating Magnetic Field Independently of Nanoparticle Coating, Core Size, and Subcellular Localization.

Magnetic hyperthermia has a significant potential to be a new breakthrough for cancer treatment. The simple concept of nanoparticle-induced heating by the application of an alternating magnetic field has attracted much attention, as it allows the local heating of cancer cells, which are considered more susceptible to hyperthermia than healthy cells, while avoiding the side effects of traditional hyperthermia. Despite the potential of this therapeutic approach, the idea that local heating effects due to the application of alternating magnetic fields on magnetic nanoparticle-loaded cancer cells can be used as a treatment is controversial. Several studies indicate that the heating capacity of magnetic nanoparticles is largely reduced in the cellular environment because of increased viscosity, aggregation, and dipolar interactions. However, an increasing number of studies, both in vitro and in vivo, show evidence of successful magnetic hyperthermia treatment on several different types of cancer cells. This apparent contradiction might be due to the use of different experimental conditions. Here, we analyze the effects of several parameters on the cytotoxic efficiency of magnetic nanoparticles as heat inductors under an alternating magnetic field. Our results indicate that the cell-nanoparticle interaction reduces the cytotoxic effects of magnetic hyperthermia, independent of nanoparticle coating and core size, the cell line used, and the subcellular localization of nanoparticles. However, there seems to occur a synergistic effect between the application of an external source of heat and the presence of magnetic nanoparticles, leading to higher toxicities than those induced by heat alone or the accumulation of nanoparticles within cells.

RGD-Functionalized Fe3O4 nanoparticles for magnetic hyperthermia.

To improve the selectivity of magnetic nanoparticles for tumor treatment by hyperthermia, Fe3O4 nanoparticles have been functionalized with a peptide of the type arginine-glycine-aspartate (RGD) following a "click" chemistry approach. The RGD peptide was linked onto the previously coated nanoparticles in order to target αvß3 integrin receptors over-expressed in angiogenic cancer cells. Different coatings have been analyzed to enhance the biocompatibility of magnetic nanoparticles. Monodispersed and homogeneous magnetite nanoparticles have been synthesized by the seed growth method and have been characterized using X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, transmission electron microscopy and magnetic measurements. The magnetic hyperthermia efficiency of the nanoparticles has also been investigated and cytotoxicity assays have been perfomed for functionalized nanoparticles.

Polyethylenimine-coated SPIONs trigger macrophage activation through TLR-4 signaling and ROS production and modulate podosome dynamics.

Polyethylenimine (PEI) is widely used as transfection agent in preclinical studies, both in vitro and in vivo. Due to their unique chemical and physical properties, SPIONs (superparamagnetic iron oxide nanoparticles) have been thoroughly studied as nanocarriers. PEI appears to activate different immune cells to an inflammatory response (M1/TH1), whereas the SPION-induced response seems to be context-dependent; the immunogenicity of the combination of these components has not been studied. Here we show that PEI-coated SPIONs (PMag) activate macrophages, as determined by measuring IL-12 secretion into culture medium and upregulation of several genes linked to the M1 phenotype. PMag-induced phosphorylation of p38 MAPK, p44/p42 MAPK and JNK, and upregulation of CD40, CD80, CD86 and I-A/I-E activation markers. PMag-induced macrophage activation depended partially on TLR4 (Toll-like receptor 4) and ROS (reactive oxygen species) signaling. Comparison of these responses with the LPS (lipopolysaccharide)-induced phenotype showed differences in gene expression profiling. PMag positively modulated podosome formation in murine macrophages, but hampered gelatin degradation by these cells. In conclusion, PMag induced an M1-like phenotype that was partially dependent on both TLR4 and ROS. These results show the adjuvant potential of PMag and suggest their use in vaccination schedules.

Long term biotransformation and toxicity of dimercaptosuccinic acid-coated magnetic nanoparticles support their use in biomedical applications.

Although iron oxide magnetic nanoparticles (MNP) have been proposed for numerous biomedical applications, little is known about their biotransformation and long-term toxicity in the body. Dimercaptosuccinic acid (DMSA)-coated magnetic nanoparticles have been proven efficient for in vivo drug delivery, but these results must nonetheless be sustained by comprehensive studies of long-term distribution, degradation and toxicity. We studied DMSA-coated magnetic nanoparticle effects in vitro on NCTC 1469 non-parenchymal hepatocytes, and analyzed their biodistribution and biotransformation in vivo in C57BL/6 mice. Our results indicate that DMSA-coated magnetic nanoparticles have little effect on cell viability, oxidative stress, cell cycle or apoptosis on NCTC 1469 cells in vitro. In vivo distribution and transformation were studied by alternating current magnetic susceptibility measurements, a technique that permits distinction of MNP from other iron species. Our results show that DMSA-coated MNP accumulate in spleen, liver and lung tissues for extended periods of time, in which nanoparticles undergo a process of conversion from superparamagnetic iron oxide nanoparticles to other non-superparamagnetic iron forms, with no significant signs of toxicity. This work provides the first evidence of DMSA-coated magnetite nanoparticle biotransformation in vivo.

Biological applications of magnetic nanoparticles.

In this review an overview about biological applications of magnetic colloidal nanoparticles will be given, which comprises their synthesis, characterization, and in vitro and in vivo applications. The potential future role of magnetic nanoparticles compared to other functional nanoparticles will be discussed by highlighting the possibility of integration with other nanostructures and with existing biotechnology as well as by pointing out the specific properties of magnetic colloids. Current limitations in the fabrication process and issues related with the outcome of the particles in the body will be also pointed out in order to address the remaining challenges for an extended application of magnetic nanoparticles in medicine.

Ordered ferrimagnetic form of ferrihydrite reveals links among structure, composition, and magnetism.

The natural nanomineral ferrihydrite is an important component of many environmental and soil systems and has been implicated as the inorganic core of ferritin in biological systems. Knowledge of its basic structure, composition, and extent of structural disorder is essential for understanding its reactivity, stability, and magnetic behavior, as well as changes in these properties during aging. Here we investigate compositional, structural, and magnetic changes that occur upon aging of "2-line" ferrihydrite in the presence of adsorbed citrate at elevated temperature. Whereas aging under these conditions ultimately results in the formation of hematite, analysis of the atomic pair distribution function and complementary physicochemical and magnetic data indicate formation of an intermediate ferrihydrite phase of larger particle size with few defects, more structural relaxation and electron spin ordering, and pronounced ferrimagnetism relative to its disordered ferrihydrite precursor. Our results represent an important conceptual advance in understanding the nature of structural disorder in ferrihydrite and its relation to the magnetic structure and also serve to validate a controversial, recently proposed structural model for this phase. In addition, the pathway we identify for forming ferrimagnetic ferrihydrite potentially explains the magnetic enhancement that typically precedes formation of hematite in aerobic soil and weathering environments. Such magnetic enhancement has been attributed to the formation of poorly understood, nano-sized ferrimagnets from a ferrihydrite precursor. Whereas elevated temperatures drive the transformation on timescales feasible for laboratory studies, our results also suggest that ferrimagnetic ferrihydrite could form naturally at ambient temperature given sufficient time.

Effect of nanoparticle and aggregate size on the relaxometric properties of MR contrast agents based on high quality magnetite nanoparticles.

Colloidal dispersions of monodispersed and high-crystalline magnetite nanoparticles have been used to establish a relationship between magnetic properties and magnetic resonance (MR) relaxometric parameters in vitro. Magnetite nanoparticles with diameters between 4 and 14 nm were synthesized by thermal decomposition of Fe(acac)3 in different organic solvents and transformed to hydrophilic by changing oleic acid for dimercaptosuccinic acid (DMSA). A final treatment in alkaline water was critical to make the suspension stable at pH 7 with xi-potential values of -45 mV and hydrodynamic sizes as low as 50 nm. Samples showed superparamagnetic behavior at room temperature, which is an important parameter for biomedical applications. Susceptibility increased with both particle and aggregate size, and for particles larger than 9 nm, the aggregate size was the key factor controlling the susceptibility. Relaxivity values followed the same trend as the suspension susceptibilities, indicating that the aggregate size is an important factor above a certain particle size governing the proton relaxation times. The highest relaxivity value, r2=317 s(-1) mM(-1), much higher than those for commercial contrast agents with similar hydrodynamic size, was obtained for a suspension consisting of 9 nm particles and 70 nm of hydrodynamic size, and it was assigned to the higher particle crystallinity in comparison to particles prepared by coprecipitation. Therefore, it can be concluded that in addition to the sample crystallinity, both particle size and aggregate size should be considered in order to explain the magnetic and relaxivity values of a suspension.

Core-shell iron-iron oxide nanoparticles synthesized by laser-induced pyrolysis.

Passivated iron nanoparticles (10-30 nm) have been synthesized by laser pyrolysis of a mixture of iron pentacarbonyl and ethylene vapors followed by controlled oxidation. The nanoparticles show a well-constructed iron-iron oxide core-shell structure, in which the thickness and nature (structure similar to maghemite, gamma-Fe2O3) of the shell is found to be independent of the initial conditions. On the other hand, the composition of the core is found to change with the particle size from the alpha-Fe structure to a highly disordered Fe phase (probably containing C atoms in its structure). The dependence of the magnetic properties on the particle size, iron oxide fraction, and temperature was also investigated. In the case of smaller particles, the magnetic data indicate the existence at low temperature of a large exchange anisotropy field, the magnitude of which increases with decreasing temperature in correspondence with the freezing of magnetic moments in the oxide shell.

Fe-based nanoparticulate metallic alloys as contrast agents for magnetic resonance imaging.

Pharmaceutical grade magnetic colloidal dispersions have been prepared from iron alloys synthesized by laser pyrolysis. The colloids were obtained by simultaneous dispersion and coating of the particles with dextran in a strong alkaline solution. Both powders and dispersions have been analyzed in terms of microstructural characteristics, chemical composition and magnetic properties. The powders consist of uniform spherical nanoparticles (12 nm of diameter) showing a metallic core encapsulated into an iron-oxide shell. On the other hand, the colloidal dispersions consist of magnetic particles-aggregates with hydrodynamic sizes of approximately 75 nm. Magnetic resonance images of rats were taken after the intravenously administration of the Fe colloidal dispersions, and compared with those obtained using a commercial iron oxide magnetic resonance imaging contrast agent. The results showed a contrast improvement of 60% in the liver with respect to the commercial sample, which suggests that this product could be a suitable contrast agent for NMR imaging of liver and spleen.