Cognitive behavioural therapy for depression, quality of life, and cognitive function in the post-stroke period: systematic review and meta-analysis.

The post-stroke period is associated with a lot of sequelae, including depression, decreased quality of life, and decline of cognitive function. Apart from the pharmacotherapy, it is also important to find a non-pharmacological treatment to relieve the sequelae. Cognitive behavioural therapy (CBT) might be a potential candidate, which can be clarified by a systematic review and meta-analysis. The eligible criteria of enrolled studies in the systematic review and meta-analysis were the randomised clinical trials (RCTs) using CBT to treat post-stroke depression, or with the focus on quality of life or cognitive function in the post-stroke period. The endpoint scores of depression, quality of life, and cognitive function scales were the targeted outcome for the final meta-analysis in the random effects model. Ten RCTs with 432 post-stroke patients receiving CBT and 385 controls were included. The meta-analysis results showed significant improvements in depression severity and quality of life. However, no significant difference between CBT and control groups was found in cognitive function. In addition, significant heterogeneity was derived from the meta-analysis. According to the meta-analysis results, CBT might be beneficial for relieving depression severity and improving quality of life. However, cognitive function might not be influenced by CBT. Further studies with a more consistent CBT design with greater sample sizes should be warranted to clarify and confirm the treatment effects of CBT for post-stroke depression and quality of life.

Metformin enhances neural precursor cells migration and functional recovery after ischemic stroke in mice.

Resident neural precursor cells (NPCs) activation is a promising therapeutic strategy for brain repair. This strategy involves stimulating multiple stages of NPCs development, including proliferation, self-renewal, migration, and differentiation. Metformin, an FDA-approved diabetes drug, has been shown to promote the proliferation and differentiation of NPCs. However, it is still unclear whether metformin promotes the migration of NPCs. EVOS living cell imaging system was used for observing the migration for primary NPCs dynamically in vitro after metformin treatment. For in vivo study, a mouse model of ischemic stroke was established through middle cerebral artery occlusion (MCAO). To label the proliferating cell in subventricular zone, BrdU was injected intraperitoneally into the mice. After co-staining with BrdU and doublecortin (DCX), a marker for NPCs, the migration of Brdu and DCX double positive NPCs was detected along the rostral migratory stream (RMS) and around the infarct area using frozen brain sections. Finally, the rotarod test, corner test and beam walking were performed to evaluate the motor functions of the mice after stroke in different groups. The results showed that metformin enhanced NPCs migration in vivo and in vitro by promoting F-actin assembly and lamellipodia formation. What's more, metformin treatment also significantly reduced the infarct volume and alleviated functional dysfunction after stroke. Mechanistically, metformin promoted NPCs migration via up-regulating the CDC42 expression. Taken together, metformin represents an optimal candidate agent for neural repair that is capable of not only expanding the adult NPC population but also subsequently driving them toward the destination for neuronal differentiation.

Preparation and Applications of Polydimethylsiloxane-Based Fluorescent Materials.

In the past few years, fluorescent materials have received significant attention due to their fascinating luminescent properties and wide-ranging applications. Polydimethylsiloxane (PDMS) has also attracted the interest of many researchers due to its remarkable performances. The combination of fluorescence and PDMS will undoubtedly produce abundant advanced multifunctional materials. Although numerous achievements have been made in this field, there is still no review to summarize the relevant research. This review summarizes the state-of-the-art achievements made in PDMS-based fluorescent materials (PFMs). First, the preparation of PFM is overviewed following a classification according to the fluorescent sources, including organic fluorescent molecules, perovskite, photoluminescent nanomaterials, and metal complexes. Their applications in sensors, fluorescent probes, multifunctional coatings, and anticounterfeiting are then introduced. Finally, the challenges and development trends in the field of PFMs are presented.

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OBJECTIVES: With the rapid development of aging population, the number of elderly patients undergoing posterior lumbar spine surgery continues to increase. Lumbar spine surgery could cause moderate to severe postoperative pain, and the conventional opioid-based analgesia techniques have many side effects, which are barriers to the recovery after surgery of the elderly. Previous studies have demonstrated that erector spinae plane block (ESPB) could bring about favorable analgesia in spinal surgery. As far as the elderly are concerned, the analgesic and recovery effects of ESPB on posterior lumbar spine surgery are not completely clear. This study aims to observe the effects of bilateral ESPB on elderly patients undergoing posterior lumbar spine surgery, and to improve the anesthesia techniques. METHODS: A total of 70 elderly patients of both sex, who were selected from May 2020 to November 2021, scheduled for elective posterior lumbar spine surgery, and in the age of 60-79 years, with American Society of Anesthesiologists class Ⅱ-Ⅲ, were divided into a ESPB group and a control (C) group using a random number table method, with 35 patients each. Before general anesthesia induction, 20 mL 0.4% ropivacaine was injected to the transverse process of L3 or L4 bilaterally in the ESPB group and only saline in the C group. The score of Numerical Rating Scale (NRS) indicating pain at rest and on movement within 48 h after operation, time of first patient control analgesia (PCA), cumulative consumptions of sufentanil within 48 hours, Leeds Sleep Evaluation Questionnaire (LSEQ) scores on the morning of day 1 and day 2 after operation, Quality of Recovery-15 (QoR-15) scores at 24 and 48 h after operation, full diet intake times, perioperative adverse reactions such as intraoperative hypotension, postoperative dizziness, nausea, vomiting, and constipation were compared between the 2 groups. RESULTS: A total of 70 patients were enrolled and 62 subjects completed the study, including 32 in the ESPB group and 30 in the C group. Compared with the C group, the postoperative NRS scores at rest at 2, 4, 6, and 12 h and on movementat at 2, 4, and 6 h were lower, time of first PCA was later, sufentanil consumptions were significantly decreased during 0-12 h and 12-24 h after operation, LSEQ scores on the morning of day 1 and QoR-15 scores at 24 and 48 h after operation were higher, full diet intakes achieved earlier in the ESPB group (all P<0.05). There were no significant differences in the incidences of intraoperative hypotension, postoperative dizziness, nausea, vomiting, and constipation between the 2 groups (all P>0.05). CONCLUSIONS: Providing favorable analgesic effects with reduced opioids consumption, bilateral ESPB for posterior lumbar spine surgery in the elderly patients could also improve postoperative sleep quality, promote gastrointestinal functional restoration, and enhance recovery with few adverse reactions.

Dexmedetomidine Resists Intestinal Ischemia-Reperfusion Injury by Inhibiting TLR4/MyD88/NF-κB Signaling.

BACKGROUND: Intestinal ischemia/reperfusion (I/R) is a common clinical problem that occurs during various clinical pathological processes. Dexmedetomidine (DEX), a widely used anesthetic adjuvant agent, can induce protection against intestinal I/R in vivo; however, the underlying mechanism is not fully understood. In the present study, we aimed to investigate the protective effects of DEX and examine whether its mechanism was associated with the TLR4/MyD88/NF-κB signaling pathway. METHODS: Sprague-Dawley rats were pretreated with DEX and then subjected to I/R-induced intestinal injury. In vivo, intestinal histopathological examination and scoring were performed, the levels of serum intestinal fatty acid-binding protein (I-FABP), intestinal tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and expression levels of TLR4, MyD88, and NF-κB in the intestine were determined. In in vitro experiments, the human colon carcinoma cell line (Caco-2) was incubated with DEX before deprivation/reoxygenation (OGD/R) treatment. The cell viability of Caco-2 cells, the levels of lactate dehydrogenase (LDH), TNF-α, and IL-1ß in the supernatant, as well as protein expression of TLR4, MyD88, and NF-κB in Caco-2 cells, were measured. Statistical analysis was performed using SPSS version 21.0. RESULTS: DEX preconditioning significantly reduced the intestinal pathological Chiu's score, serum I-FABP, intestinal TNF-α, IL-1ß levels, and the protein expression of TLR4, MyD88, and NF-κB in the rats with intestinal I/R injury. Similarly, in vitro, DEX pretreatment protected against OGD/R-induced Caco-2 cell damage and inhibited TLR4/MyD88/NF-κB signaling, as evidenced by increased cell viability, decreased LDH activity, reduced TNF-α and IL-1ß levels, as well as downregulated TLR4, MyD88, and NF-κB protein levels. CONCLUSIONS: Our findings suggested that DEX could reduce intestinal I/R injury in rats and OGD/R damage in Caco-2 cells, and this protection might be attributed to antiinflammatory effects and inhibition of the TLR4/MyD88/NF-κB signaling pathway.

Protective effect of Shenmai injection on doxorubicin-induced cardiotoxicity via regulation of inflammatory mediators.

BACKGROUND: Doxorubicin (DOX) is a chemotherapy drug for malignant tumors. The clinical application of DOX is limited due to its dosage relative cardiotoxicity. Oxidative damage and cardiac inflammation appear to be involved in DOX-related cardiotoxicity. Shenmai injection (SMI), which mainly consists of Panax ginsengC.A.Mey.and Ophiopogon japonicus (Thunb.) Ker Gawl, is widely used for the treatment of atherosclerotic coronary heart disease and viral myocarditis in China. In this study, we investigated the protective effect of Shenmai injection on doxorubicin-induced acute cardiac injury via the regulation of inflammatory mediators. METHODS: Male ICR mice were randomly divided into seven groups: control, DOX (10 mg/kg), SMI (5 g/kg), DOX with pretreatment with SMI (0.5 g/kg, 1.5 g/kg or 5 g/kg) and DOX with post-treatment with SMI (5 g/kg). Forty-eight hours after the last DOX administration, all mice were anesthetized for ultrasound echocardiography. Then, serum was collected for biochemical and inflammatory cytokine detection, and heart tissue was collected for histological and Western blot detection. RESULTS: A cumulative dose of DOX (10 mg/kg) induced acute cardiotoxicity in mice manifested by altered echocardiographic outcome, and increased tumor necrosis factor, interleukin 6 (IL-6), monocyte chemotactic protein 1, interferon-γ, and serum AST and LDH levels, as well as cardiac cytoplasmic vacuolation and myofibrillar disarrangement. DOX also caused the increase in the expression of IKK-α and iNOS and produced a large amount of NO, resulting in the accumulation of nitrotyrosine in the heart tissue. Pretreatment with SMI elicited a dose-dependent cardioprotective effect in DOX-dosed mice as evidenced by the normalization of serum inflammatory mediators, as well as improve dcardiac function and myofibril disarrangement. CONCLUSIONS: SMI could recover inflammatory cytokine levels and suppress the expression of IKK-α and iNOS in vivo, which was increased by DOX. Overall, there was evidence that SMI could ameliorate DOX-induced cardiotoxicity by inhibiting inflammation and recovering heart dysfunction.

Effects of chemically heterogeneous nanoparticles on polymer dynamics: insights from molecular dynamics simulations.

The dispersion of solid nanoparticles within polymeric materials is widely used to enhance their performance. Many scientific and technological aspects of the resulting polymer nanocomposites have been studied, but the role of the structural and chemical heterogeneity of the nanoparticles has just started to be appreciated. For example, simulations of polymer films on planar heterogeneous surfaces revealed unexpected, non-monotonic activation energy to diffusion on varying the surface composition. Motivated by these intriguing results, here we simulate via molecular dynamics a different, fully three-dimensional system, in which the heterogeneous nanoparticles are incorporated in a polymer melt. The nanoparticles are roughly spherical assemblies of strongly and weakly attractive sites, in fractions of f and 1 - f, respectively. We show that the polymer diffusion is still characterized by a non-monotonic dependence of the activation energy on f. The comparison with the case of homogeneous nanoparticles clarifies that the effect of the heterogeneity increases on approaching the polymer glass transition.

Theoretical Model of Time-Temperature Superposition Principle of the Self-Healing Kinetics of Supramolecular Polymer Nanocomposites.

The matrix-free polymer nanocomposites (PNCs) formed by polymer-grafted nanoparticles(NPs) gain enormous attention due to their controllable morphology and robust properties. Herein, through molecular dynamics simulation, such PNCs are successfully constructed, and the dispersion state of the NPs can be tailored by varying the grafting density. By manipulating the interaction strength between the end groups of the grafted polymer chains, the tensile fracture behavior and the chain orientation are examined. It is revealed that both of them fall down at large strain because of the propagation of the cavities. By probing the self-healing kinetics at various self-healing temperature and time, a time-temperature superposition principle, similar to the Williams, Landel and Ferry equation, is proposed. These results could provide some fundamental guidelines for the design and fabrication of high performance PNCs with excellent self-healing functionality.

Transient Receptor Potential Ankyrin 1 and Substance P Mediate the Development of Gastric Mucosal Lesions in a Water Immersion Restraint Stress Rat Model.

BACKGROUND: Activation of substance P (SP) contributes to the development and maintenance of gastric lesions, but the mechanisms underlying the release of SP and SP-mediated damage to the gastric mucosa remain unknown. Transient receptor potential ankyrin 1 (TRPA1) is expressed in SP-positive neurons in the dorsal root ganglion (DRG) and stomach of rats. We hypothesized that water immersion restraint stress (WIRS) may activate and sensitize TRPA1 in DRG neurons, subsequently inducing the release of SP from DRG and stomach cells, causing the development of acute gastric mucosal lesions (AGML). METHODS: Changes in TRPA1 and SP expression in T8-11 DRG sensory neurons and the stomach in an AGML rat model were determined by reverse transcription polymerase chain reaction, western blotting and immunohistochemistry. The SP levels of serum and gastric mucosa were measured by using an enzyme-linked immunosorbent assay (ELISA). Gastric lesions were evaluated by histopathological changes. The TRPA1 antagonist HC-030031 and TRPA1 agonists allyl isothiocyanate were used to verify effect of TRPA1 and SP on AGML. RESULTS: SP and TRPA1 in the DRG and stomach were upregulated, and the serum and gastric mucosa levels of SP were increased after WIRS, which are closely associated with AGML. The release of SP was suppressed and AGML were alleviated following a selective TRPA1 antagonist HC-030031. TRPA1 agonists AITC increased release of SP and led to moderate gastric lesions. We confirmed that WIRS induced the release of SP in the DRG, stomach, serum and gastric mucosa, and in a TRPA1-dependent manner. CONCLUSIONS: Upregulated SP and TRPA1 in the DRG and stomach and increased serum and gastric mucosa SP levels may contribute to stress-induced AGML. TRPA1 is a potential drug target to reduce stress-induced AGML development in patients with acute critical illnesses. This study may contribute to the discovery of drugs for AGML treatment.

Strain rate and temperature dependence of the mechanical properties of polymers: A universal time-temperature superposition principle.

Establishing the Time-Temperature and Frequency-Temperature Superposition Principles (TTSP and FTSP) to describe the mechanical behavior of polymeric materials is always of paramount significance. In this work, by adopting the classic coarse-grained model, we investigate the validity of these superposition principles for a series of networks, such as the pure polymer network, interpenetrating polymer networks composed of stiff and flexible networks (IPNs-SF), interpenetrating polymer networks composed of different cross-linking networks (IPNs-DC), polymer nanocomposites (PNCs), and surface grafted modified PNCs. The study focuses on the three critical mechanical properties such as the stress relaxation, the storage modulus versus the frequency obtained from the dynamic periodic shear deformation, and the uniaxial tensile stress-strain. The glass transition temperature (Tg) is about 0.47 for the simulated polymer network (CL400), and a smooth master curve is obtained for the stress relaxation process by setting the reference temperature Tref = 0.6 via the horizontal shifting process, indicating the validity of TTSP. Furthermore, similar smooth master curves are also achieved for both dynamic periodic shear and uniaxial tensile deformation, which exhibit similar trends and share the identical linear viscoelastic regime in the temperature interval above Tg: 0.55

A Novel Role for Programmed Cell Death Receptor Ligand-1 (PD-L1) in Sepsis-Induced Intestinal Dysfunction.

Studies imply that intestinal barrier dysfunction is a key contributor to morbid events associated with sepsis. Recently, co-inhibitory molecule, programmed death-ligand1 (PD-L1) has been shown to be involved in the regulation of intestinal immune tolerance and/or inflammation. Our previous studies showed that PD-L1 gene deficiency reduced sepsis-induced intestinal injury morphologically. However, it isn't known how PD-L1 expression impacts intestinal barrier dysfunction during sepsis. Here we tested the hypothesis that PD-L1 expressed on intestinal epithelial cells (IECs) has a role in sepsis-induced intestinal barrier dysfunction. To address this, C57BL/6 or PD-L1 gene knockout mice were subjected to experimental sepsis and PD-L1 expression, intestinal permeability, tissue cytokine levels were assessed. Subsequently, septic or non-septic patient colonic samples (assigned by pathology report) were immunohistochemically stained for PD-L1 I a blinded fashion. Finally, human Caco2 cells were used for in vitro studies. The results demonstrated that PD-L1 was constitutively expressed and sepsis significantly up-regulates PD-L1 in IECs from C57BL/6 mice. Concurrently, we observed an increased PD-L1 expression in colon tissue samples from septic patients. PD-L1 gene deficiency reduced ileal permeability, tissue levels of IL-6, TNF-α and MCP-1, and prevented ileal tight junction protein loss compared to WT after sepsis. Comparatively, while Caco2 cell monolayers responded to inflammatory cytokine stimulation also with elevated PD-L1 expression, increased monolayer permeability and altering/decreasing monolayer tight junction protein morphology/expression; these changes were reversed by PD-L1 blocking antibody. Together these data indicate that ligation of ICE PD-L1 plays a novel role in mediating the pathophysiology of sepsis-induced intestinal barrier dysfunction.

Molecular insights into the effect of graphene packing on mechanical behaviors of graphene reinforced cis-1,4-polybutadiene polymer nanocomposites.

Through united-atom molecular dynamics simulations, we build a series of graphene (GP) reinforced cis-1,4-polybutadiene (cis-PB) models with two novel GP structures, intercalated and stacked GP structures, to investigate the effect of different GP packing patterns on the chain structure, chain dynamics, uniaxial tension and visco-elastic behaviors, and correlate the microscopic mechanism with macroscopic mechanical properties. Simulation results show that the interlayer polymer chains in the void of intercalated GPs are strongly confined, leading to higher bond orientation of polymer chains during the stretch process compared with monodisperse systems. And due to this restriction effect, intercalated systems exhibit higher tensile stress under large tensile strain. For stacked systems, the interaction within GP layers and the orientation of the whole stacked GP structure play dominant roles in mechanical and visco-elastic properties. Furthermore, from the results that stacked systems have higher tensile stress and intercalated systems exhibit a higher storage modulus, we can conclude that the GP-GP interaction makes greater contribution than the GP-PB interaction and the chain confinement effect to the tensile behavior, whereas the restriction and orientation of polymer chains become more crucial factors than the GP-GP interaction under shear conditions. This work may provide rational means to tune the mechanical and visco-elastic properties of GP reinforced polymer nanocomposites.

Designing polymer nanocomposites with a semi-interpenetrating or interpenetrating network structure: toward enhanced mechanical properties.

Using short polymer chains and through molecular dynamics simulation, we designed a well-dispersed nanoparticle (NP) network, which was then incorporated with the polymer matrix. First, we examined the effects of the dual-end grafted chains flexibility and density on the spatial distribution of this particular polymer nanocomposites system. By changing the interaction strength between the matrix polymer chains and the dual-end grafted chains in the semi-interpenetrating network system (NP network), we analyzed the interpenetration state between the linear polymer matrix and the NP network via calculating the total interfacial interaction energy. Moreover, the uniaxial tensile stress-strain and orientation behavior influenced by the interaction strength between the matrix polymer and the grafted chains were investigated for both the semi-interpenetrating network system and the interpenetrating network system (NP network and matrix network). Furthermore, for the interpenetrating network system, we modulated the integrity of the NP network ranging from 0% to 100%, corresponding to the gradual transition of the dispersion morphology of the NPs from the aggregation state to the uniform dispersion state, to examine the effect of the NP network on the tensile mechanical behavior. In particular, by simulating the dynamic shear process in the semi-interpenetrating network system, the composites were found to exhibit a lower non-linear behavior (the famous Payne effect), a higher storage modulus, and a lower tangent loss at large strain amplitude with increasing NP network integrity. In general, our results could provide a new approach for the design of high-performance polymer nanocomposites by taking advantage of the semi-interpenetrating or interpenetrating network reinforcing structure.

Influence of Morphology on the Mechanical Properties of Polymer Nanocomposites Filled with Uniform or Patchy Nanoparticles.

In this work we perform molecular-dynamics simulations, both on the coarse-grained and the chemistry-specific levels, to study the influence of morphology on the mechanical properties of polymer nanocomposites (PNCs) filled with uniform spherical nanoparticles (which means without chemical modification) and patchy spherical nanoparticles (with discrete, attractive interaction sites at prescribed locations on the particle surface). Through the coarse-grained model, the nonlinear decrease of the elastic modulus (G') and the maximum of the viscous modulus (G″) around the shear strain of 10% is clearly reproduced. By turning to the polybutadiene model, we examine the effect of the shear amplitude and the interaction strength among uniform NPs on the aggregation kinetics. Interestingly, the change of the G' as a function of the aggregation time exhibited a maximum value at intermediate time attributed to the formation of a polymer-bridged filler network in the case of strong interaction between NPs. By imposing a dynamic periodic shear, we probe the change of the G' as a function of the strain amplitude while varying the interaction strength between uniform NPs and its weight fraction. A continuous filler network is developed at a moderate shear amplitude, which is critically related to the interaction strength between NPs and the weight fraction of the fillers. In addition, we study the self-assembly of the patchy NPs, which form the typical chain-like and sheet-like structures. For the first time, the effect of these self-assembled structures on the viscoelastic and stress-strain behavior of PNCs is compared. In general, in the coarse-grained model we focus on the size effect of the rough NPs on the Payne effect, while some other parameters such as the dynamic shear flow, the interaction strength between NPs, the weight fraction, and the chemically heterogeneous surface of the NPs are explored for the chemistry-specific model.

Controlling the electrical conductive network formation of polymer nanocomposites via polymer functionalization.

By adopting coarse-grained molecular dynamics simulations, the effect of polymer functionalization on the relationship between the microstructure and the electric percolation probability of nanorod filled polymer nanocomposites has been investigated. At a low chain functionalization degree, the nanorods in the polymer matrix form isolated aggregates with a local order structure. At a moderate chain functionalization degree, the local order structure of the nanorod aggregate is gradually broken up. Meanwhile, excessive functionalization chain beads can connect the isolated aggregates together, which leads to the maximum size of nanorod aggregation. At a high chain functionalization degree, it forms a single nanorod structure in the matrix. As a result, the highest percolation probability of the materials appears at the moderate chain functionalization degree, which is attributed to the formation of the tightly connected nanorod network by analyzing the main cluster. In addition, this optimum chain functionalization degree exists at two chain functionalization modes (random and diblock). Lastly, under the tensile field, even though the contact distance between nanorods nearly remains unchanged, the topological structure of the percolation network is broken down. While under the shear field, the contact distance between nanorods increases and the topological structure of the percolation network is broken down, which leads to a decrease in the percolation probability. In total, the topological structure of the percolation network dominates the percolation probability, which is not a necessary connection with the contact distance between nanorods. In summary, this work presents further understanding of the electric conductive properties of nanorod-filled nanocomposites with functionalized polymers.

Destruction and recovery of a nanorod conductive network in polymer nanocomposites via molecular dynamics simulation.

By adopting coarse-grained molecular dynamics simulation, we investigate the effects of end-functionalization and shear flow on the destruction and recovery of a nanorod conductive network in a functionalized polymer matrix. We find that the end-functionalization of polymeric chains can enhance the electrical conductivity of nanorod filled polymer nanocomposites, indicated by the decrease of the percolation threshold. However, there exists an optimal end-functionalization extent to reach the maximum electrical conductivity. In the case of steady shear flow, both homogeneous conductive probability and directional conductive probability perpendicular to the shear direction decrease with the shear rate, while the directional conductive probability parallel to the shear direction increases. Importantly, we develop a semi-empirical equation to describe the change of the homogeneous conductive probability as a function of the shear rate. Meanwhile, we obtain an empirical formula describing the relationship between the anisotropy of the conductive probability and the orientation of the nanorods. In addition, the conductivity stability increases with increasing nanorod volume fraction. During the recovery process of the nanorod conductive network, it can be fitted well by the model combining classical percolation theory and a time-dependent nanorod aggregation kinetic equation. The fitted recovery rate is similar for different nanorod volume fractions. In summary, this work provides some rational rules for fabricating polymer nanocomposites with excellent performance of electrical conductivity.

Dispersion and shear-induced orientation of anisotropic nanoparticle filled polymer nanocomposites: insights from molecular dynamics simulation.

Although a large number of studies have been performed to study the dispersion behavior of spherical nanoparticles (NPs) in the polymer matrix, little effort has been directed to anisotropic NPs via simulation, which is convenient for controlling the physical parameters compared to experiment. In this work we adopt molecular dynamics simulation to study polymer nanocomposites filled with anisotropic NPs such as graphene and carbon nanotubes (CNTs). We investigate the effects of the grafting position, grafting density, the length and flexibility of the grafted chains on the dispersion of graphene and CNTs. In particular, we find that when the grafting position is located on the surface center of the graphene or the middle of the CNT, the dispersion state is the best, leading to the greatest stress-strain behavior. Meanwhile, the mechanical property can be further strengthened by introducing chemical couplings in the interfacial region, by chemically tethering the grafted chains to the matrix chains. To monitor the processing effect, we exert a dynamic periodic shear deformation in the x direction with its gradient in the y direction. Polymer chains are found to align in the x direction, graphene sheets align in the xoz plane and CNTs orientate in the z direction. We study the effects of the shear amplitude, the shear frequency, polymer-NP interaction strength and volume fraction of NPs on the stress-strain behavior. We also observe that the relaxation process following the shear deformation deteriorates the mechanical performance, resulting from the disorientation of polymer chains and NPs. In general, this work could provide valuable guidance in manipulating the distribution and alignment of graphene and CNTs in the polymer matrix.

Stress-strain behavior of block-copolymers and their nanocomposites filled with uniform or Janus nanoparticles under shear: a molecular dynamics simulation.

Although numerous research studies have been focused on studying the self-assembled morphologies of block-copolymers (BCPs) and their nanocomposites, little attention has been directed to explore the relation between their ordered structures and the resulting mechanical properties. We adopt coarse-grained molecular dynamics simulation to study the influence of the morphologies on the stress-strain behavior of pure block copolymers and block copolymers filled with uniform or Janus nanoparticles (NPs). At first, we examine the effect of the arrangement (di-block, tri-block, alternating-block) and the components of the pure block copolymers, and by varying the component ratio between A and B blocks, spherical, cylindrical and lamellar phases are all formed, showing that spherical domains bring the largest reinforcing effect. Then by studying BCPs filled with NPs, the Janus NPs induce stronger bond orientation of polymer chains and greater mechanical properties than the uniform NPs, when these two kinds of NPs are both located in the interface region. Meanwhile, some other anisotropic Janus NPs, such as Janus rods and Janus sheets, are incorporated to examine the effect on the morphology and the stress-strain behavior. These findings deepen our understanding of the morphology-mechanics relation of BCPs and their nanocomposites, opening up a vast number of approaches such as designing the arrangement and components of BCPs, positioning uniform or Janus NPs with different shapes and shear flow to tailor their stress-strain performance.

Tuning the structure and mechanical property of polymer nanocomposites by employing anisotropic nanoparticles as netpoints.

Introducing carbon nanotubes or graphene sheets into polymer matrices has received lots of scientific and technological attention. For the first time, we report a new kind of polymer nanocomposite (PNC) by means of employing anisotropic nanoparticles (NPs) as netpoints (referred to as an end-linked system), namely with NPs acting as netpoints to chemically connect the dual end-groups of each polymer chain to form a network. By taking advantage of this strategy, the anisotropic NPs can be uniformly distributed in the polymer matrix, with the NPs being separated via the connected polymer chains. And the separation distance between NPs, the stress-strain behavior and the dynamic hysteresis loss (HL) can be manipulated by varying the temperature and the polymer chain flexibility. Meanwhile, the physically mixed system is investigated by changing the interaction strength between polymer and NPs, and the temperature. It is emphasized that compared to the physically mixed system, the end-linked system which employs carbon nanotubes or graphene as netpoints possesses good thermal stability because of its thermodynamically stable morphology, exhibiting both excellent static and dynamic mechanical properties. These results help us to design and fabricate high performance and multi-functional PNCs filled with carbon nanotubes or graphene, facilitating the potentially large industrial application of these nanomaterials.

Cannabinoid CB2 Receptor Mediates Nicotine-Induced Anti-Inflammation in N9 Microglial Cells Exposed to ß Amyloid via Protein Kinase C.

BACKGROUND: Reducing ß amyloid- (Aß-) induced microglial activation is considered to be effective in treating Alzheimer's disease (AD). Nicotine attenuates Aß-induced microglial activation; the mechanism, however, is still elusive. Microglia could be activated into classic activated state (M1 state) or alternative activated state (M2 state); the former is cytotoxic and the latter is neurotrophic. In this investigation, we hypothesized that nicotine attenuates Aß-induced microglial activation by shifting microglial M1 to M2 state, and cannabinoid CB2 receptor and protein kinase C mediate the process. METHODS: We used Aß1-42 to activate N9 microglial cells and observed nicotine-induced effects on microglial M1 and M2 biomarkers by using western blot, immunocytochemistry, and enzyme-linked immunosorbent assay (ELISA). RESULTS: We found that nicotine reduced the levels of M1 state markers, including inducible nitric oxide synthase (iNOS) expression and tumor necrosis factor α (TNF-α) and interleukin- (IL-) 6 releases; meanwhile, it increased the levels of M2 state markers, including arginase-1 (Arg-1) expression and brain-derived neurotrophic factor (BDNF) release, in the Aß-stimulated microglia. Coadministration of cannabinoid CB2 receptor antagonist or protein kinase C (PKC) inhibitor partially abolished the nicotine-induced effects. CONCLUSION: These findings indicated that cannabinoid CB2 receptor mediates nicotine-induced anti-inflammation in microglia exposed to Aß via PKC.