Mechanism of Water Intrusion into Flexible ZIF-8: Liquid Is Not Vapor.

Zeolitic Imidazolate Frameworks (ZIF) find application in storage and dissipation of mechanical energy. Their distinctive properties linked to their (sub)nanometer size and hydrophobicity allow for water intrusion only under high hydrostatic pressure. Here we focus on the popular ZIF-8 material investigating the intrusion mechanism in its nanoscale cages, which is the key to its rational exploitation in target applications. In this work, we used a joint experimental/theoretical approach combining in operando synchrotron experiments during high-pressure intrusion experiments, molecular dynamics simulations, and stochastic models to reveal that water intrusion into ZIF-8 occurs by a cascade filling of connected cages rather than a condensation process as previously assumed. The reported results allowed us to establish structure/function relations in this prototypical microporous material, representing an important step to devise design rules to synthesize porous media.

An atomistically informed multiscale approach to the intrusion and extrusion of water in hydrophobic nanopores.

Understanding intrusion and extrusion in nanoporous materials is a challenging multiscale problem of utmost importance for applications ranging from energy storage and dissipation to water desalination and hydrophobic gating in ion channels. Including atomistic details in simulations is required to predict the overall behavior of such systems because the statics and dynamics of these processes depend sensitively on microscopic features of the pore, such as the surface hydrophobicity, geometry, and charge distribution, and on the composition of the liquid. On the other hand, the transitions between the filled (intruded) and empty (extruded) states are rare events that often require long simulation times, which are difficult to achieve with standard atomistic simulations. In this work, we explored the intrusion and extrusion processes using a multiscale approach in which the atomistic details of the system, extracted from molecular dynamics simulations, informed a simple Langevin model of water intrusion/extrusion in the pore. We then used the Langevin simulations to compute the transition times at different pressures, validating our coarse-grained model by comparing it with nonequilibrium molecular dynamics simulations. The proposed approach reproduces experimentally relevant features such as the time and temperature dependence of the intrusion/extrusion cycles, as well as specific details about the shape of the cycle. This approach also drastically increases the timescales that can be simulated, reducing the gap between simulations and experiments and showing promise for more complex systems.

Hydrophobically gated memristive nanopores for neuromorphic applications.

Signal transmission in the brain relies on voltage-gated ion channels, which exhibit the electrical behaviour of memristors, resistors with memory. State-of-the-art technologies currently employ semiconductor-based neuromorphic approaches, which have already demonstrated their efficacy in machine learning systems. However, these approaches still cannot match performance achieved by biological neurons in terms of energy efficiency and size. In this study, we utilise molecular dynamics simulations, continuum models, and electrophysiological experiments to propose and realise a bioinspired hydrophobically gated memristive nanopore. Our findings indicate that hydrophobic gating enables memory through an electrowetting mechanism, and we establish simple design rules accordingly. Through the engineering of a biological nanopore, we successfully replicate the characteristic hysteresis cycles of a memristor and construct a synaptic device capable of learning and forgetting. This advancement offers a promising pathway for the realization of nanoscale, cost- and energy-effective, and adaptable bioinspired memristors.

Optimization of the wetting-drying characteristics of hydrophobic metal organic frameworks via crystallite size: The role of hydrogen bonding between intruded and bulk liquid.

HYPOTHESIS: The behavior of Heterogeneous Lyophobic Systems (HLSs) comprised of a lyophobic porous material and a corresponding non-wetting liquid is affected by a variety of different structural parameters of the porous material. Dependence on exogenic properties such as crystallite size is desirable for system tuning as they are much more facilely modified. We explore the dependence of intrusion pressure and intruded volume on crystallite size, testing the hypothesis that the connection between internal cavities and bulk water facilitates intrusion via hydrogen bonding, a phenomenon that is magnified in smaller crystallites with a larger surface/volume ratio. EXPERIMENTS: Water intrusion/extrusion pressures and intrusion volume were experimentally measured for ZIF-8 samples of various crystallite sizes and compared to previously reported values. Alongside the practical research, molecular dynamics simulations and stochastic modeling were performed to illustrate the effect of crystallite size on the properties of the HLSs and uncover the important role of hydrogen bonding within this phenomenon. FINDINGS: A reduction in crystallite size led to a significant decrease of intrusion and extrusion pressures below 100 nm. Simulations indicate that this behavior is due to a greater number of cages being in proximity to bulk water for smaller crystallites, allowing cross-cage hydrogen bonds to stabilize the intruded state and lower the threshold pressure of intrusion and extrusion. This is accompanied by a reduction in the overall intruded volume. Simulations demonstrate that this phenomenon is linked to ZIF-8 surface half-cages exposed to water being occupied by water due to non-trivial termination of the crystallites, even at atmospheric pressure.

Binary mixtures of locally coupled mobile oscillators.

Synchronized behavior in a system of coupled dynamic objects is a fascinating example of an emerged cooperative phenomena which has been observed in systems as diverse as a group of insects, neural networks, or networks of computers. In many instances, however, the synchronization is undesired because it may lead to system malfunctioning, as in the case of Alzheimer's and Parkinson's diseases, for example. Recent studies of static networks of oscillators have shown that the presence of a small fraction of so-called contrarian oscillators can suppress the undesired network synchronization. On the other hand, it is also known that the mobility of the oscillators can significantly impact their synchronization dynamics. Here, we combine these two ideas-the oscillator mobility and the presence of heterogeneous interactions-and study numerically binary mixtures of phase oscillators performing two-dimensional random walks. Within the framework of a generalized Kuramoto model, we introduce two phase-coupling schemes. The first one is invariant when the types of any two oscillators are swapped, while the second model is not. We demonstrate that the symmetric model does not allow for a complete suppression of the synchronized state. However, it provides means for a robust control of the synchronization timescale by varying the overall number density and the composition of the mixture and the strength of the off-diagonal Kuramoto coupling constant. Instead, the asymmetric model predicts that the coherent state can be eliminated within a subpopulation of normal oscillators and evoked within a subpopulation of the contrarians.

Repair of Critical Size Bone Defects Using Synthetic Hydroxyapatite or Xenograft with or without the Bone Marrow Mononuclear Fraction: A Histomorphometric and Immunohistochemical Study in Rat Calvaria.

Bone defects are a challenging clinical situation, and the development of hydroxyapatite-based biomaterials is a prolific research field that, in addition, can be joined by stem cells and growth factors in order to deal with the problem. This study compares the use of synthetic hydroxyapatite and xenograft, used pure or enriched with bone marrow mononuclear fraction for the regeneration of critical size bone defects in rat calvaria through histomorphometric (Masson's staining) and immunohistochemical (anti-VEGF, anti-osteopontin) analysis. Forty young adult male rats were divided into five groups (n = 8). Animals were submitted to critical size bone defects (Ø = 8 mm) in the temporoparietal region. In the control group, there was no biomaterial placement in the critical bone defects; in group 1, it was filled with synthetic hydroxyapatite; in group 2, it was filled with xenograft; in group 3, it was filled with synthetic hydroxyapatite, enriched with bone marrow mononuclear fraction (BMMF), and in group 4 it was filled with xenograft, enriched with BMMF. After eight weeks, all groups were euthanized, and histological section images were captured and analyzed. Data analysis showed that in groups 1, 2, 3 and 4 (received biomaterials and biomaterials plus BMMF), a significant enhancement in new bone matrix formation was observed in relation to the control group. However, BMMF-enriched groups did not differ from hydroxyapatite-based biomaterials-only groups. Therefore, in this experimental model, BMMF did not enhance hydroxyapatite-based biomaterials' potential to induce bone matrix and related mediators.

Complications in the guided bone regeneration technique associated with the d-PTFE membrane: case report / Complicações na técnica de regeneração óssea guiada associada à membrana de PTFE-d: relato de caso

ABSTRACT Guided bone regeneration aims to gain vertical and horizontal bone volume in atrophic ridges, using different regenerative techniques associated with biomaterials, with occasional post-surgical complications. The objective of the case report was to describe the successive approaches to minimize and eliminate the complications presented in the postoperative period of a patient submitted to the guided bone regeneration technique. In the first surgery, the dense expanded polytetrafluoroethylene membrane (d-PTFE), supported by the tent technique and autogenous platelet graft, was used to perform the guided bone regeneration technique. After three months, the membrane was exposed, with the membrane and the retaining screws removed in the seventh month, with the installation of three Internal Hexagon implants in the areas of teeth 13, 14 and 15. The exposed threads were covered with hydroxyapatites resorbable and covered with d-PTFE membrane. A four-month postoperative panoramic radiograph suggested implant osseointegration. The guided bone regeneration technique associated with the d-PTFE membrane enabled bone neoformation, enabling the installation of osseointegrated implants in an aesthetic and functional position. The exposure of the edges of the membrane allowed the penetration of fluids and contamination, suggesting the worsening of the signs of infection and purulent secretion. On the contrary, the exposure of central areas did not cause inflammatory and infectious signs.

RESUMO A regeneração óssea guiada visa o ganho de volume ósseo vertical e horizontal em rebordos atróficos, sendo utilizadas diferentes técnicas regenerativas associadas a biomateriais, podendo apresentar ocasionais complicações pós-cirúrgicas. O objetivo do relato de caso foi descrever as sucessivas abordagens para minimizar e eliminar as complicações apresentadas no pós-operatório de paciente submetida à técnica de regeneração óssea guiada. Na primeira cirurgia foi utilizada a membrana de politetrafluoretileno expandido denso (PTFE-d), suportada pela técnica da tenda e enxerto plaquetário autógeno, para realizar a técnica de regeneração óssea guiada. Após três meses, constatou-se a exposição da membrana, sendo removida a membrana e os parafusos de contenção no sétimo mês, com instalação de três implantes Hexágono Interno nas áreas dos dentes 13, 14 e 15. As roscas expostas foram recobertas com as hidroxiapatitas reabsorvíeis e recobertas com membrana PTFE-d. A radiografia panorâmica pós-operatória de quatro meses sugeriu osseointegração dos implantes. A técnica de regeneração óssea guiada associada à membrana de PTFE-d possibilitou a neoformação óssea propiciando a instalação de implantes osseointegrados em posição estética e funcional. A exposição das bordas da membrana permitiu a penetração de fluídos e contaminação, sugerindo o agravamento dos sinais de infecção e secreção purulenta. Ao contrário, a exposição de áreas centrais, não acarretou sinais inflamatórios e infecciosos.

Expressão e distribuição de CGRP, VEGF e TGF-β na gengiva dos dentes de ratos com periodontite induzida por ligadura: aspectos imunohistoquímicos / Expression and distribution of CGRP, VEGF and TGFß in the gingiva of rats’ teeth with periodontits by ligature induction: immunohistochemical aspects

No momento em que há a agressão tecidual e a defesa inata é deflagrada, mediadores químicos são liberados no local afetado. Esses mediadores podem ser de origem celular tais como CGRP, VEGF e TGFß. Os objetivos desta pesquisa foram avaliar a expressão e distribuição de CGRP, TGFß e VEGF na gengiva do primeiro molar inferior esquerdo de rato no 7° e 14° dias após a indução por ligadura; a expressão e distribuição de CGRP, TGFß e VEGF na gengiva do dente contralateral correspondente sem ligadura, no 7° e 14° dias, e se a indução da periodontite por ligadura no dente experimental provoca uma inflamação na gengiva do dente contralateral correspondente no 7° e 14° dias após a ligadura. Para o desenvolvimento deste trabalho foram selecionados 15 ratos Rattus Novergicus, Albinus, Wistar. O grupo experimental de 12 ratos foi dividido em 2 subgrupos compostos por 6 ratos cada um deles distribuídos da seguinte maneira: os do subgrupo A1 permaneceram com a ligadura no primeiro molar inferior esquerdo por 7 dias e foram sacrificados; os do subgrupo A-2 -permaneceram com a ligadura no primeiro molar inferior esquerdo por 14 dias e foram sacrificados. Outros três animais constituíram o grupo controle. Após o sacrifício dos 12 animais dos grupos experimentais e controle suas mandíbulas foram colocadas em ácido etilenodiaminotetracético (EDTA) neutro para sofrerem descalcificação. Então foram processadas para inclusão em parafina e os cortes histológicos foram corados pela hematoxilina-eosina e submetidos à técnica imunohistoquímica para imunomarcação de CGRP, VEGF e TGFß. Aos 7 dias de ligadura observou-se na lâmina própria gengival, epitélio juncional e epitélio oral, expressiva marcação para CGRP. A expressão de VEGF foi intensa na lamina própria e com pouca ou nenhuma marcação no epitélio oral e juncional. O TGFß apresentou pouca marcação na lâmina própria ou nenhuma marcação no epitélio oral e juncional...

At the time of the tissue aggression the innate defense is triggered and the chemical mediators are released in the affected site. These mediators may have cell origin as the CGRP, VEGF and TGFß. The aim of this research were to evaluate the expression and distribution of the CGRP, VEGF and TGFß in the gingiva of the lower left first molar of rats in the seven and fourteen days after the ligature for inflammation induction; to analyse the expression and distribution of the CGRP, VEGF and TGFß in the gingiva of the correspondent counter lateral tooth without ligature in the seven and fourteen days and if the induction of periodontitis causes gingival inflammation of the counter lateral tooth after seven and fourteen days after ligature. For the development of this work were selected fifteen Rattus Novergicus, Albinus,Wistar. The experimental group of 12 rats was divided into 2 groups consisting of 6 rats each distributed of the following manner: the subgroup A1 remained with ligature in the first molar and left for 7 days before the sacrificed and the subgroup A-2 remained with the ligature for 14 days before the sacrificed. Another 3 animals constituted the control group. After the sacrificed of the 12 experimental and 3 control animals were immersedin neutral ethylenidiaminetetracetic (EDTA) for the decalcification. Then were processed for paraffin embedding. The sections were stained with hematoxylin-eosin and submitted to immunohistochemical techniques to imunostaining for CGRP, VEGF and TGFß. At 7 days of ligature was observed in the gingival lamina propria, junctional epithelium and oral epithelium, strong staining for CGRP. The intensive expression of VEGF occur in the lamina propria and scarce or no staining in the oral and junctional epithelium. The TGFß shows scarce staining in the lamina propria and no staining in the oral and junctional epithelium...

Expressão e distribuição de CGRP, VEGF e TGF-β na gengiva dos dentes de ratos com periodontite induzida por ligadura: aspectos imunohistoquímicos / Expression and distribution of CGRP, VEGF and TGFß in the gingiva of rats’ teeth with periodontits by ligature induction: immunohistochemical aspects

No momento em que há a agressão tecidual e a defesa inata é deflagrada, mediadores químicos são liberados no local afetado. Esses mediadores podem ser de origem celular tais como CGRP, VEGF e TGFß. Os objetivos desta pesquisa foram avaliar a expressão e distribuição de CGRP, TGFß e VEGF na gengiva do primeiro molar inferior esquerdo de rato no 7° e 14° dias após a indução por ligadura; a expressão e distribuição de CGRP, TGFß e VEGF na gengiva do dente contralateral correspondente sem ligadura, no 7° e 14° dias, e se a indução da periodontite por ligadura no dente experimental provoca uma inflamação na gengiva do dente contralateral correspondente no 7° e 14° dias após a ligadura. Para o desenvolvimento deste trabalho foram selecionados 15 ratos Rattus Novergicus, Albinus, Wistar. O grupo experimental de 12 ratos foi dividido em 2 subgrupos compostos por 6 ratos cada um deles distribuídos da seguinte maneira: os do subgrupo A1 permaneceram com a ligadura no primeiro molar inferior esquerdo por 7 dias e foram sacrificados; os do subgrupo A-2 -permaneceram com a ligadura no primeiro molar inferior esquerdo por 14 dias e foram sacrificados. Outros três animais constituíram o grupo controle. Após o sacrifício dos 12 animais dos grupos experimentais e controle suas mandíbulas foram colocadas em ácido etilenodiaminotetracético (EDTA) neutro para sofrerem descalcificação. Então foram processadas para inclusão em parafina e os cortes histológicos foram corados pela hematoxilina-eosina e submetidos à técnica imunohistoquímica para imunomarcação de CGRP, VEGF e TGFß. Aos 7 dias de ligadura observou-se na lâmina própria gengival, epitélio juncional e epitélio oral, expressiva marcação para CGRP. A expressão de VEGF foi intensa na lamina própria e com pouca ou nenhuma marcação no epitélio oral e juncional. O TGFß apresentou pouca marcação na lâmina própria ou nenhuma marcação no epitélio oral e juncional...

At the time of the tissue aggression the innate defense is triggered and the chemical mediators are released in the affected site. These mediators may have cell origin as the CGRP, VEGF and TGFß. The aim of this research were to evaluate the expression and distribution of the CGRP, VEGF and TGFß in the gingiva of the lower left first molar of rats in the seven and fourteen days after the ligature for inflammation induction; to analyse the expression and distribution of the CGRP, VEGF and TGFß in the gingiva of the correspondent counter lateral tooth without ligature in the seven and fourteen days and if the induction of periodontitis causes gingival inflammation of the counter lateral tooth after seven and fourteen days after ligature. For the development of this work were selected fifteen Rattus Novergicus, Albinus,Wistar. The experimental group of 12 rats was divided into 2 groups consisting of 6 rats each distributed of the following manner: the subgroup A1 remained with ligature in the first molar and left for 7 days before the sacrificed and the subgroup A-2 remained with the ligature for 14 days before the sacrificed. Another 3 animals constituted the control group. After the sacrificed of the 12 experimental and 3 control animals were immersedin neutral ethylenidiaminetetracetic (EDTA) for the decalcification. Then were processed for paraffin embedding. The sections were stained with hematoxylin-eosin and submitted to immunohistochemical techniques to imunostaining for CGRP, VEGF and TGFß. At 7 days of ligature was observed in the gingival lamina propria, junctional epithelium and oral epithelium, strong staining for CGRP. The intensive expression of VEGF occur in the lamina propria and scarce or no staining in the oral and junctional epithelium. The TGFß shows scarce staining in the lamina propria and no staining in the oral and junctional epithelium...