Impact of nanosilver surface electronic distributions on serum protein interactions and hemocompatibility.

The translation of silver-based nanotechnology 'from bench to bedside' requires a deep understanding of the molecular aspects of its biological action, which remains controversial at low concentrations and non-spherical morphologies. Here, we present a hemocompatibility approach based on the effect of the distinctive electronic charge distribution in silver nanoparticles (nanosilver) on blood components. According to spectroscopic, volumetric, microscopic, dynamic light scattering measurements, pro-coagulant activity tests, and cellular inspection, we determine that at extremely low nanosilver concentrations (0.125-2.5µg ml-1), there is a relevant interaction effect on the serum albumin and red blood cells (RBCs). This explanation has its origin in the surface charge distribution of nanosilver particles and their electron-mediated energy transfer mechanism. Prism-shaped nanoparticles, with anisotropic charge distributions, act at the surface level, generating a compaction of the native protein molecule. In contrast, the spherical nanosilver particle, by exhibiting isotropic surface charge, generates a polar environment comparable to the solvent. Both morphologies induce aggregation at NPs/bovine serum albumin ≈ 0.044 molar ratio values without altering the coagulation cascade tests; however, the spherical-shaped nanosilver exerts a negative impact on RBCs. Overall, our results suggest that the electron distributions of nanosilver particles, even at extremely low concentrations, are a critical factor influencing the molecular structure of blood proteins' and RBCs' membranes. Isotropic forms of nanosilver should be considered with caution, as they are not always the least harmful.

Chitosan Coating as a Strategy to Increase Postemergent Herbicidal Efficiency and Alter the Interaction of Nanoatrazine with Bidens pilosa Plants.

The atrazine nanodelivery system, composed of poly(ε-caprolactone) (PCL+ATZ) nanocapsules (NCs), has demonstrated efficient delivery of the active ingredient to target plants in previous studies, leading to greater herbicide effectiveness than conventional formulations. Established nanosystems can be enhanced or modified to generate new biological activity patterns. Therefore, this study aimed to evaluate the effect of chitosan coating of PCL+ATZ NCs on herbicidal activity and interaction mechanisms with Bidens pilosa plants. Chitosan-coated NCs (PCL/CS+ATZ) were synthesized and characterized for size, zeta potential, polydispersity, and encapsulation efficiency. Herbicidal efficiency was assessed in postemergence greenhouse trials, comparing the effects of PCL/CS+ATZ NCs (coated), PCL+ATZ NCs (uncoated), and conventional atrazine (ATZ) on photosystem II (PSII) activity and weed control. Using a hydroponic system, we evaluated the root absorption and shoot translocation of fluorescently labeled NCs. PCL/CS+ATZ presented a positive zeta potential (25 mV), a size of 200 nm, and an efficiency of atrazine encapsulation higher than 90%. The postemergent herbicidal activity assay showed an efficiency gain of PSII activity inhibition of up to 58% compared to ATZ and PCL+ATZ at 96 h postapplication. The evaluation of weed control 14 days after application ratified the positive effect of chitosan coating on herbicidal activity, as the application of PCL/CS+ATZ at 1000 g of a.i. ha-1 resulted in better control than ATZ at 2000 g of a.i. ha-1 and PCL+ATZ at 1000 g of a.i. ha-1. In the hydroponic experiment, chitosan-coated NCs labeled with a fluorescent probe accumulated in the root cortex, with a small quantity reaching the vascular cylinder and leaves up to 72 h after exposure. This behavior resulted in lower leaf atrazine levels and PSII inhibition than ATZ. In summary, chitosan coating of nanoatrazine improved the herbicidal activity against B. pilosa plants when applied to the leaves but negatively affected the root-to-shoot translocation of the herbicide. This study opens avenues for further investigations to improve and modify established nanosystems, paving the way for developing novel biological activity patterns.

Nonlinear dependence (on ionic strength, pH) of surface charge density and zeta potential in microchannel electrokinetic flow.

In this work, a numerical method is proposed to predict the electrokinetic phenomena and combined with an experimental study of the surface charge density (ρs) and zeta potential (ζ) behavior is investigated for borosilicate immersed in KCl and NaCl electrolytes, and for imogolite immersed in KCl, CaCl2, and MgCl2 electrolytes. Simulations and experiments of the electrokinetic flows with electrolyte solutions were performed to accurately determine the electric double layer (EDL), ζ, and ρs at various electrolyte concentrations and pH. The zeta potential was experimentally determined and numerically predicted by solving the coupled governing equations of mass, species, momentum, and electrical field iteratively. Our numerical prediction shows that ζ for borosilicate develops strong nonlinear behavior with the ion concentration following a power-law. Likewise, the ρs obeys a nonlinear behavior, decreasing as the concentration increases. Moreover, for imogolite, both ζ and the ρs behave nonlinearly with the pH. The EDL for borosilicate and imogolite becomes thinner as the electrolyte concentration and pH increase; this behavior is caused by increased ρs, resulting in the higher attraction of the free charges. The reported nonlinear behavior describes more accurately the interaction of the nanoparticle surface charge with the electrolytes and its effect on the electrolyte transport properties.

Simulations of surface charge density changes during the untreated solid tumour growth.

Understanding untreated tumour growth kinetics and its intrinsic behaviour is interesting and intriguing. The aim of this study is to propose an approximate analytical expression that allows us to simulate changes in surface charge density at the cancer-surrounding healthy tissue interface during the untreated solid tumour growth. For this, the Gompertz and Poisson equations are used. Simulations reveal that the unperturbed solid tumour growth is closely related to changes in the surface charge density over time between the tumour and the surrounding healthy tissue. Furthermore, the unperturbed solid tumour growth is governed by temporal changes in this surface charge density. It is concluded that results corroborate the correspondence between the electrical and physiological parameters in the untreated cancer, which may have an essential role in its growth, progression, metastasis and protection against immune system attack and anti-cancer therapies. In addition, the knowledge of surface charge density changes at the cancer-surrounding healthy tissue interface may be relevant when redesigning the molecules in chemotherapy and immunotherapy taking into account their polarities. This can also be true in the design of completely novel therapies.

The Effect of Low Magnesium Concentration on Ictal Discharges In A Non-Synaptic Model.

Magnesium (Mg[Formula: see text] is an essential mineral for several cellular functions. The concentration of this ion below the physiological concentration induces recurrent neuronal discharges both in slices of the hippocampus and in neuronal cultures. These epileptiform discharges are initially sensitive to the application of [Formula: see text]-methyl-D-aspartate (NMDA) receptor antagonists, but these antagonists may lose their effectiveness with prolonged exposure to low [Mg[Formula: see text]], when extracellular Ca[Formula: see text] reduction occurs, typical of ictal periods, indicating the absence of synaptic connections. The study herein presented aimed at investigating the effect of reducing the [Mg[Formula: see text]] during the induction of Nonsynaptic Epileptiform Activities (NSEA). As an experimental protocol, NSEA were induced in rat hippocampal dentate gyrus (DG), using a bath solution containing high-K[Formula: see text] and zero-added-Ca[Formula: see text]. Additionally, computer simulations were performed using a mathematical model that represents electrochemical characteristics of the tissue of the DG granular layer. The experimental results show that the reduction of [Mg[Formula: see text]] causes an increase in the duration of the ictal period and a reduction in the interictal period, intensifying epileptiform discharges. The computer simulations suggest that the reduction of the Mg[Formula: see text] level intensifies the epileptiform discharges by a joint effect of reducing the surface charge screening and reducing the activity of the Na/K pump.

Rational Surface Engineering of Colloidal Drug Delivery Systems for Biological Applications.

The use of colloidal particles as drug delivery carriers holds a great promise in terms of improvement of traditional treatment and diagnosis of human diseases. Nano- and microsized particles of a different composition including organic and inorganic materials can be fabricated with a great control over size, shape and surface properties. Nevertheless, only some few formulations have surpassed the benchtop and reached the bedside. The principal obstacle of colloidal drug delivery systems is their poor accumulation in target tissues, organs and cells, mainly by efficient sequestration and elimination by the mononuclear phagocytic system. Recent evidence suggests that, besides size, the surface character of colloidal systems is the most determinant design parameter that may ultimately guarantee successful biological performance. To approach these issues, materials designers and engineers can make use of multiple strategies and tools to finely modulate the particles' surface towards highly efficient and biocompatible materials. In this article, we provide an overview of the most relevant colloidal drug delivery systems, a summary of the available literature regarding the effects of surface charge, hydrophobicity and softness on biological response, and finally, we review the key points of surface modification strategies with organic, inorganic and biological materials.

Deprotonation and protonation of humic acids as a strategy for the technological development of pH-responsive nanoparticles with fungicidal potential.

Humic acids (HAs) are macromolecules of undefined compositions that vary with origin, the process by which they are obtained and functional groups present in their structure, such as quinones, phenols, and carboxylic acids. In addition to agriculture, there is an increased interest in HAs due to their important pharmacological effects. However, HAs are not readily soluble in water at physiological pH, which may limit their bioavailability. Although primary aggregation forms non-uniform pseudo-micelles, the presence of ionisable groups in the HA molecule makes pH an environmental stimulus for controlled aggregation and precipitation. The aim of this work was to induce HA deprotonation and protonation, without compromising their colloidal dispersion, by means of pH changes as a strategy to produce nanoparticles. Deprotonation and protonation were achieved by treating HAs with sodium hydroxide and acetic acid, respectively, at various concentrations. Non pH-treated HAs at the same concentrations were used as control. The evolution of the treatments was monitored by pH changes in bulk solutions as a function of time. At equilibrium, the conformation of the colloidal structures was characterised by the predominant mean diameter, polydispersity index and absorbance of the solutions. The zeta potential was also measured in protonation assays. Moreover, the fungicidal activity of the nanoparticles was evaluated on the mycelial growth of three fungal genera. The results showed the pH decrease or increment as a function of the balance between hydroxyl and carboxyl groups and of the diffusion rate inside the structures. Deprotonation followed by protonation produced nanosized (100-200nm), electrostatically stable (-30mV) and pH-responsive particles with a polydispersity index <0.5. The protonated nanoparticles significantly inhibited (P≤0.05) the mycelial growth of Candida albicans in vitro, when compared with control, and the fungicidal activity was dose-dependent. No activity was observed for the deprotonated HAs nanoparticles. These results show that deprotonation followed by protonation is an easy and useful strategy for the controlled production of HA nanoparticles, which exhibit a tendency to elicit fungicidal effects, with potential to develop new classes of cosmetics and pharmaceuticals.

Eletroquímica das partículas coloidais e sua relação com a mineralogia de solos altamente intemperizados

The knowledge of the electrochemical properties of the mineral particles of highly weathered soils is indispensable for the advance of the studies in different Soil Science areas, like as, Soils Physics, Conservation and Management, Fertility and Pollution. In this context, the surface charge behavior and its relationship with the mineralogy of variable charge soils is of fundamental importance to the understanding and the improvement of the predictive capability of several phenomena, such as, floculation and dispersion of colloids, cations exchange, anion adsorption, specially phosphates, heavy metals adsorption, etc. Therefore, this literature review aims at to make a scientific approach of the topic "Electrochemistry of colloidal particles and its relationship with the mineralogy of highly weathered soils", in which, the historical evolution of the knowledge in this field is covered and the challenges to the development of the research in this area are raised. Different tendencies and views existing in the literature about Zero Points of Charge (ZPC), Charge Characterization and Measurement, ZPCs Terminology and Simbology and Relationship between Charge and Minerals of the highly weathered soils are also presented. Basic concepts are revisited and new or seldom used concepts in Soil Science are presented and discussed with the objective of improving the understanding and refining the interpretation of such important branch of the Soil Chemistry and Mineralogy field.

O conhecimento das propriedades eletroquímicas das partículas minerais dos solos altamente intemperizados é imprescindível para o avanço dos estudos em diferente áreas da Ciência do Solo, como, Física, Manejo e Conservação, Fertilidade e Poluição do Solo. Nesse contexto, o comportamento das cargas superficiais e seu relacionamento com a mineralogia dos solos de carga variável é de importância fundamental para o entendimento e a melhoria da capacidade preditiva de diversos fenômenos, tais como dispersão e floculação de colóides, troca catiônica, adsorção de ânions, especialmente os fosfatos, adsorção de metais pesados, etc. Assim, essa revisão de literatura faz uma abordagem científica do tema "Eletroquímica das partículas coloidais e sua relação com a mineralogia de solos altamente intemperizados", na qual é contemplado o histórico da evolução do conhecimento nesse campo e os desafios para o aprofundamento das pesquisas futuras na área. As diferentes tendências e posicionamentos existentes na literatura sobre Pontos de Carga Zero (PCZs), Caracterização e Medição de Cargas, Nomenclatura e Simbologia de PCZs e Relacionamento entre Cargas e Minerais de solos altamente intemperizados são também apresentados. Conceituações básicas são revisitadas e conceitos novos ou pouco utilizados na Ciência do Solo são apresentados e discutidos, com o intuito de se melhorar o entendimento e aprimorar a interpretação de tão importante ramo da Química, Mineralogia e Poluição de Solos.

Eletroquímica das partículas coloidais e sua relação com a mineralogia de solos altamente intemperizados

The knowledge of the electrochemical properties of the mineral particles of highly weathered soils is indispensable for the advance of the studies in different Soil Science areas, like as, Soils Physics, Conservation and Management, Fertility and Pollution. In this context, the surface charge behavior and its relationship with the mineralogy of variable charge soils is of fundamental importance to the understanding and the improvement of the predictive capability of several phenomena, such as, floculation and dispersion of colloids, cations exchange, anion adsorption, specially phosphates, heavy metals adsorption, etc. Therefore, this literature review aims at to make a scientific approach of the topic "Electrochemistry of colloidal particles and its relationship with the mineralogy of highly weathered soils", in which, the historical evolution of the knowledge in this field is covered and the challenges to the development of the research in this area are raised. Different tendencies and views existing in the literature about Zero Points of Charge (ZPC), Charge Characterization and Measurement, ZPCs Terminology and Simbology and Relationship between Charge and Minerals of the highly weathered soils are also presented. Basic concepts are revisited and new or seldom used concepts in Soil Science are presented and discussed with the objective of improving the understanding and refining the interpretation of such important branch of the Soil Chemistry and Mineralogy field.

O conhecimento das propriedades eletroquímicas das partículas minerais dos solos altamente intemperizados é imprescindível para o avanço dos estudos em diferente áreas da Ciência do Solo, como, Física, Manejo e Conservação, Fertilidade e Poluição do Solo. Nesse contexto, o comportamento das cargas superficiais e seu relacionamento com a mineralogia dos solos de carga variável é de importância fundamental para o entendimento e a melhoria da capacidade preditiva de diversos fenômenos, tais como dispersão e floculação de colóides, troca catiônica, adsorção de ânions, especialmente os fosfatos, adsorção de metais pesados, etc. Assim, essa revisão de literatura faz uma abordagem científica do tema "Eletroquímica das partículas coloidais e sua relação com a mineralogia de solos altamente intemperizados", na qual é contemplado o histórico da evolução do conhecimento nesse campo e os desafios para o aprofundamento das pesquisas futuras na área. As diferentes tendências e posicionamentos existentes na literatura sobre Pontos de Carga Zero (PCZs), Caracterização e Medição de Cargas, Nomenclatura e Simbologia de PCZs e Relacionamento entre Cargas e Minerais de solos altamente intemperizados são também apresentados. Conceituações básicas são revisitadas e conceitos novos ou pouco utilizados na Ciência do Solo são apresentados e discutidos, com o intuito de se melhorar o entendimento e aprimorar a interpretação de tão importante ramo da Química, Mineralogia e Poluição de Solos.