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The utilization of thermal energy from different sources is an important development direction for conserving energy. With the development of technology, refined and rapid utilization of thermal energy is required. Traditional thermal conductive materials cannot meet the growing needs of human beings. Therefore, people pay attention to two-dimensional graphene film materials for their thermal conductivity. This review collects current modeling group of thermal transport on graphene, including non-equilibrium Green function (NEGF) theory, molecular dynamics (MD) simulations modeling and Boltzmann transport equation method. These models can well explain several phenomena of phonon transport in graphene. Further, structural defects were discussed and expounded the effect for graphene thermal conductivity, including doping, grain boundary and defects. Deeply understanding of defects on graphene, we can better grasp the thermal conductivity of graphene from the microscopic point of view.

AIM To explore the role of DNA methylation in the innate immunity of the dental pulp, this study investigated the effect of 5-aza-2'-deoxycytidine (AZA) on lipoteichoic acid (LTA)-induced cytokine production and related intracellular signalling pathways in human odontoblast-like cells (hOBs). METHODOLOGY hOBs were cultured and differentiated from human dental pulp tissue, and the odontoblastic phenotype of the cells was detected using immunofluorescence, qRT-PCR and Western blotting. hOBs were pretreated with AZA and then stimulated with 10 μg mL-1 LTA. The levels of 42 cytokines related to immunity and inflammation were examined using a cytokine antibody array and verified using qRT-PCR and ELISA. The effect of AZA on the LTA-induced NF-κB and MAPK signalling pathways was explored using Western blotting. The cells were treated with the specific NF-κB inhibitor PDTC and MAPK inhibitors (the ERK inhibitor U0126, the p38 inhibitor SB203580, and the JNK inhibitor SP600125) to further confirm the role of the signalling pathways in LTA-treated hOBs. DNA immunoprecipitation-PCR was used to examine the dynamic methylation status of the gene promoters of myeloid differentiation primary response 88 (MyD88) and tumour necrosis factor receptor-associated factor 6 (TRAF6) in the LTA-induced hOBs. Statistical analyses of the differences between two groups were performed using Student's t-test. One-way analysis of variance (anova) or repeated-measures anova with a post hoc Dunnett's test was used to assess the differences between multiple sets of data. P

The prevalence of functionalized nanoparticles in biological and clinical fields attracts intensive toxicology investigations. Minimizing the nanoparticles’ biohazard remains a challenge due to the insufficient understanding on the nanoparticle-induced cell death mechanism. In the presented study, we observed the lysosome and genome injuries and so caused cell cycle changes and regulations of retinal ganglion neuron cell 5 (RGC-5) induced by aminated and alkylated nanoparticles. Alkylated nanoparticles induced malignant lysosome and genome damages followed by severe post-self-repair responses. RGC-5 treated with alkylated nanoparticles presented dramatic S phase prolongation resulted from cyclin E accumulation mediated by Fbw7 downregulation, which assisted DNA replication after failed self-repair of the malignantly damaged DNA caused by alkylated nanoparticles. Differently, aminated nanoparticles in RGC-5 induced moderate lysosome and genome injuries and these damages could be repaired in the p21-involved pathway, so that cells did not induce apparent cyclin E accumulation nor Fbw7 downregulation as post-self-repair response. These results helped us to understand the toxicity of analogous nanoparticles on retinal ganglions such as glaucoma treatment. This work provides new insights into nanoparticle functionalization and toxicity in relation to the research on the toxicology and pathology of nerve cells.

Limited understanding of mitochondria disorders that induced by nanoparticles is a stumbling block for anti-cancer drug delivery targeting strategy. In present study, C6 glioma cells were exposed to aminated and alkylated SiO2 nanoparticles for mitochondrion disordering and cell metabolism study. Collective results showed that aminated nanoparticles tend to trigger the cell-repair mechanism in cancer cells while alkylated nanoparticles could cause irreversible damages on cancer cells, although both types of the particles were proved to damage mitochondrion. The underlying mechanism show that aminated nanoparticles induced proton-stuck effect in mitochondrion and self-repairing in cancer cells by up-regulating p21. Otherwise, alkylated nanoparticles damaged mitochondrion and induced phosphorylated cyclin E accumulation lead to Fbw7 down-regulation caused further S phase arrest and severe late apoptosis. This work can help us elucidate the mechanism of the clinic application of nano-drug carriers.

Implantable pressure biosensors show great potential for assessment and diagnostics of pressure-related diseases. Here, we present a structural design strategy to fabricate core/shell polyvinylidene difluoride (PVDF)/hydroxylamine hydrochloride (HHE) organic piezoelectric nanofibers (OPNs) with well-controlled and self-orientated nanocrystals in the spatial uniaxial orientation (SUO) of β-phase-rich fibers, which significantly enhance piezoelectric performance, fatigue resistance, stability, and biocompatibility. Then PVDF/HHE OPNs soft sensors are developed and used to monitor subtle pressure changes in vivo. Upon implanting into pig, PVDF/HHE OPNs sensors demonstrate their ultrahigh detecting sensitivity and accuracy to capture micropressure changes at the outside of cardiovascular walls, and output piezoelectric signals can real-time and synchronously reflect and distinguish changes of cardiovascular elasticity and occurrence of atrioventricular heart-block and formation of thrombus. Such biological information can provide a diagnostic basis for early assessment and diagnosis of thrombosis and atherosclerosis, especially for postoperative recrudescence of thrombus deep within the human body.

Breast cancer is one of the most common cancers in the world, survival rates of breast cancer are rising as screening and treatment improve. Many new technologies applied in the biomedical domain have been born for rapid diagnosis and treatment. In this work, visualization cell microarray chip with three-dimensional (3D) embedded cell scaffold for cell diagnosis and treatment was designed. DNA segment, targeting on breast cancer cells SK-BR-3, were modified with camptothecin and used as model drug. Cell microarray chip system successfully control the diffusion of small molecules and locally introduced the compounds into cells. 3D embedded cell scaffold in the cell array chip afforded an environment with continuous medium supplementary and help controlling the diffusion of small molecules drugs. By cell microarray chip system, SK-BR-3 was targeted screening and killing in one step. Cell microarray chip system can achieve accurate, rapid diagnosis and target treatment of breast cancer cells SK-BR-3 and have a potential to develop to be an effective and accurate drug screen method for evaluating the drug effect of the booming chemicals.

Organic pollution is considered as a long-term, urgent global issue for energy, environmental, and ecological applications. Carbon-based materials have shown great potential in addressing this global issue. However, development of low-cost and high-performance of carbon-based three-dimensional materials has also proven to challenging for removal of organic pollutants from water. Here, we developed a new technique combining a liquid-assisted electrospinning and interface self-assembly of graphene to successfully fabricate novel graphene fluffy nanofibrous scaffold (GFNs) as an efficient organic pollution absorbent. The resultant GFNs with several advantages of distinctive 3D fluffy macro-structure, super porosity, low density, strong mechanical stability, and super hydrophobicity/oleophicity, demonstrated high adsorption capacity for organic solvents (201 times their own weight) and oils (119 times their own weight), as well as excellent recyclability by simple extrusion. Different from conventional graphe...

Misfolded protein aggregates formed by the same (homologous) or different (heterologous/cross) sequences are the pathological hallmarks of many protein misfolding diseases (PMDs) including Alzheimer's disease (AD) and type 2 diabetes (T2D). Different from homologous-amyloid aggregation that is solely associated with a specific PMD, cross-amyloid aggregation (i.e. cross-seeding) of different amyloid proteins is more fundamentally and biologically important for understanding and untangling not only the pathological process of each PMD, but also a potential molecular cross-talk between different PMDs. However, the cross-amyloid aggregation is still a subject poorly explored and little is known about its sequence/structure-dependent aggregation mechanisms, as compared to the widely studied homo-amyloid aggregation. Here, we review the most recent and important findings of amyloid cross-seeding behaviors from in vitro, in vivo, and in silico studies. Some typical cross-seeding phenomena between Aβ/hIAPP, Aβ/tau, Aβ/α-synuclein, and tau/α-synuclein are selected and presented, and the underlying specific or general cross-seeding mechanisms are also discussed to better reveal their sequence-structure-property relationships. The potential use of the cross-seeding concept to design amyloid inhibitors is also proposed. Finally, we offer some personal perspectives on current major challenges and future research directions in this less-studied yet important field, and hopefully this work will stimulate more research to explore all possible fundamental and practical aspects of amyloid cross-seeding.

Due to inhomogeneous molecular structure and inherent flexibility of organic piezoelectric materials, the improvement in piezoelectric performances is extremely challenging. Herein, a novel sheath-gas-assisted electrospinning method was designed to induce rapid recrystallization and a stretching effect on the PVDF molecular chains, which led to significant promotion in the formation of β and γ crystal phases in PVDF nanofibers and the highest piezoelectric properties reported to date for pure organic piezoelectric materials. By using the PVDF nanofibers for energy harvesting in vivo and in vitro, the motion sensor and implantable nanogenerators displayed excellent sensitivity under an extremely low working frequency of ∼0.1 Hz and considerable output voltage of 0.4-0.6 V cm-2 driven by the femoral artery and carotid artery for the first time. Furthermore, we demonstrated that the nanofibers have outstanding biocompatibility and can provide a spontaneous microelectronic stimulation effect to improve the growth of nerve cells. Thus, we envision that the high-performance piezoelectric nanofibers may serve as a powerful tool for developing future flexible force-sensitive microelectric devices and generators for applications in bioelectronics and biomedicine.

The rapid development of a self-powered system (SPS) has aroused an increasing interest in the field of wearable electronics. The current development trend in wearable electronics is toward integration, portability, miniaturization, and sustainability. Hence, a wearable piezoelectric-driven self-powered patterned electrochromic supercapacitor (ESC) is presented here, which is integrated with the energy harvesting, conversion, storage and indication technologies. The patterned polyaniline (PANI) electrodes electrodeposited by coupling cyclic voltammetric and galvanostatic (CV-GS) techniques were assembled as patterned ESC, which served to store the energy and indicate the charging/discharging status simultaneously. With the advantages of flexibility and biocompatibility, the polyvinylidene difluoride (PVDF) nanofibers were fabricated by electrospinning to establish the piezoelectric nanogenerators (PENGs) as the energy-harvesting device, which can be attached to human body to harvest mechanical kinetic ene...

Adipose derived stem cells (ADSCs) have been proved as an abundant and accessible cell source with the ability to differentiate into neuron-like cells. However, the low differentiation efficiency puts forward an important challenge to practical applications in clinic. Considering of the good biocompatibility of graphene-based materials and the potential interaction between graphene and cells mentioned in previous studies, herein, we investigated the effect of graphene oxide (GO) and reduced graphene oxide (rGO) mats on neurogenic differentiation of the ADSCs. We demonstrated the excellent capabilities of graphene-based mats, especially GO to support the neural differentiation of ADSCs. By comparing the observation under an optical microscope and fluorescence microscope, the conversion rate of neuron-like cells reached about 90%. We consider that GO mat is better for promoting the differentiation of ADSCs into neuron-like cells, which compared to rGO based platforms. Meanwhile, we made an analysis of the mechanism by which graphene induced the differentiation of ADSCs to neuron-like cells. The data obtained here highlight the effect of GO mat on neurogenic differentiation of ADSCs and implicate the potential of graphene-based materials in application of neural tissue engineering for the limited self-repair capability of nerve cells.

Understanding the internal cellular processes of micron/nanoparticles will be important for particles toxicity studies or drug-delivery systems designing. The details and mechanisms of the cellular up-take process of micron/nano particles can hardly be described in real-time. In this study, cellular internalization of micron/nanoparticles was investigated by fluorescence spectroscopy, flow cytometry and sum frequency generation vibrational spectroscopy (SFG). Model cell membranes such as substrate supported lipid bilayers and lipid vesicles were used in this research. Especially, SFG was used to examine the behavior of each leaflet of the lipid bilayer while interacting with micron/nanoparticles. Experiments of SFG show direct evidences that micron/nanoparticles attachment lead to the lipid orientation. Vesicle dye-leakage model were used to study long-term interactions on model membrane. Results from this study provide in-depth insight into the molecular interactions between micron/nanoparticles and cell membranes, which will help to understand the particles toxicity and will be useful for the designing of micron/nanoparticles for applications.

Tough, mechanoresponsive hydrogels have broad and significant impacts on fundamental research and practical applications, but have proved to be extremely challenging to develop. The poor solubility of mechanophores makes them difficult to be integrated into a highly hydrophilic network of hydrogels. In this work, we synthesized dimethylacrylate-functionalized spiropyran (SP) mechanophores and used them as crosslinkers to copolymerize with hydrophobic methyl acrylate (MA) monomers and hydrophilic acrylamide (AM) monomers in the presence of surfactant polysorbate 80 (TWEEN 80) micelles, forming poly(AM-co-MA/SP) hydrogels. The mechanical properties of the as-prepared and swollen poly(AM-co-MA/SP) hydrogels strongly depend on network components (AM, MA, and SP concentrations). Thus, the optimal hydrogels can achieve excellent mechanical properties (tensile stress of 1.1 MPa, tensile strain of 6 mm mm−1, elastic modulus of 1.1 MPa, and tearing energy of 3200 J m−2). Due to multi-stimuli responses of SP crosslinkers, the hydrogels exhibited the reversible changes in color and mechanical properties between the force-, heat-, and UV light-induced deformation state and the white light-induced recovery state. Based on their fast, reversible, force-induced color change behavior, we further designed a conceptual hydrogel strain sensor to monitor color change under the stretching and relaxing processes in multiple cycles. This work demonstrates that the presence of dynamically reversible SP crosslinkers and micellar structures is the key to greatly enhance both mechanical and color recoverable properties of poly(AM-co-MA/SP) hydrogels, which could serve as promising smart materials for a variety of applications such as soft robots, electronic skins, and strain/motion/damage sensors.

Diverse chains and cross-linking density of polymers are important for cell proliferation, aging, and death. In this study, by controlling the component ratio of N,N'-methylenebisacrylamide (Bis)/acrylamide (Acr), we prepared polyacrylamide (PAM) hydrogels with three different polymer structures using ultraviolet irradiation. Moreover, we quantified their Flory's cross-linking densities, gel concentrations, and mechanical properties and evaluated their influence to HL-7702 liver cell behavior and metabolism. Results showed that PAM hydrogel at a ratio of Bis/Acr = 1:50 (Acr-50) owned the highest cross-linking density (0.04), which provided abundant binding sites for cell adhesion and allowed for rapid cell proliferation. On the basis of the binding sites, cells had strong traction interaction from fibrillate adhesion with the polymers, allowed easy cell migration, and induced the living cell aggregations with a diameter of 800 μm. Cells in aggregation exhibited healthy cell phenotypes and functions, and also the mitosis of the cells in aggregation is exactly the same with the cells in tissue. It is concluded that cell proliferation, aging, and death can be controlled by adjusting the cross-linking density and diverse chains of matrix hydrogels. This work will be helpful to design new functional soft biomaterials for tissue regeneration in the future.

Electroactive nanofibrous scaffold is a vital tool for the study of the various biological research fields from bioelectronics to regenerative medicine, which can provide cell preferable 3D nanofiber architecture and programmed electrical signal. However, intrinsic non-biodegradability is a major problem that hinders its widespread application in the clinic. Herein, we designed, synthesized, and characterized shell/core poly (3,4-ethylenedioxythiophene) (PEDOT)/chitosan (CS) nanofibers by combining the electrospinning and recrystallization processes. Upon incorporating a trace amount of PEDOT (1.0 wt%), the resultant PEDOT/CS nanofibers exhibited low interfacial charge transfer impedance, high electrochemical stability, high electrical conductivity (up to 0.1945 S/cm), and ultrasensitive piezoelectric property (output voltage of 22.5 mV by a human hair prodding). With such unique electrical and conductive properties, PEDOT/CS nanofibers were further applied to brain neuroglioma cells (BNCs) to stimulate their adhesion, proliferation, growth, and development under an optimal external electrical stimulation (ES) and a pulse voltage of 400 mV/cm. ES-responsive PEDOT/CS nanofibers indeed promoted BNCs growth and development as indicated by a large number and density of axons. The synergetic interplay between external ES and piezoelectric voltage demonstrates new PEDOT-based nanofibers as implantable electroactive scaffolds for numerous applications in nerve tissue engineering, human health monitoring, brain mantle information extraction, and degradable microelectronic devices.

Heterogeneous materials with scientific design have drawn widespread attention for their morphology-dependent properties and synergistic effects in the application of volatile organic compound (VOC) sensing. Here, we report a sequential nucleation strategy to prepare a Co3O4-ZnO/reduced graphene oxide (rGO) heterogeneous composite via the electrostatic adsorption process, chemical coordination step and crystal nucleation procedure. In this approach, the volatility and alkalescence of ammonia effectively avoids spontaneous diffusion and exchange reactions among metal ions with similar radii. Benefitting from the stepwise pathways, the post-generated ZnO exhibits oriented growth along the 2 1 ¯ 1 ¯ 0 > face and a hexagonal morphology, which favors the VOC sensing. Based on this, the synthesized Co3O4-ZnO/rGO ternary composite shows an enhanced response (Ra/Rg) of 3.0 and a faster response/recovery of 19/12 s towards 5 ppm benzaldehyde in the gas phase than the individual and binary ZnO-based systems. Furthermore, it also presents a comparable sensitivity of 7.98 μAcm−2 mM−1 towards benzaldehyde in the liquid phase. These superior sensing abilities of the Co3O4-ZnO/rGO sensor can be attributed to the enhanced oxygen adsorption capacity by the large sensing area of hexagonal ZnO disk, the p-n effects of Co3O4-ZnO on rGO sheets, as well as the excellent characteristics of rGO sheets.

Nitrogen (N)-doped graphene (N-substituted or nitrogenated graphene) (NG) has become a new class of graphene material due to its modified properties such as the tunable work function, n-type semiconductivity, increasing biocompatibility, and, in particular, the synergistic function with various functional materials. However, the preparation of NG by a simple and effective method is still lacking. The modification of NG mainly depends on the N species and the N content. Thus, we focus on the recent progress in preparing methods of 2D NG and the respective key modulating parameters to modulate the N species and the N content. Furthermore, many effective charactering techniques are covered to accurately analyze the properties of N species, and the distribution and topography of N atoms. Also, we review the effect of N species on graphene, especially, the optical and electronic properties. Since constructing 3D structure is considered a promising strategy to prevent the restacking of 2D NG, the summary for preparing 3D NG is made on the basis of methodology of 2D NG. In a word, this review provides a reference for preparing 2D or 3D NG, modulating and characterizing N species, which are greatly contributed to the NG application.

Fabrication of soft piezoelectric nanomaterials is essential for the development of wearable and implantable biomedical devices. However, a big challenge in this soft functional material development is to achieve a high piezoelectric property with long-term stability in a biological environment. Here, a one-step strategy for fabricating core/shell poly(vinylidene difluoride) (PVDF)/dopamine (DA) nanofibers (NFs) with a very high β-phase content and self-aligned polarization is reported. The self-assembled core/shell structure is believed essential for the formation and alignment of β-phase PVDF, where strong intermolecular interaction between the NH2 groups on DA and the CF2 groups on PVDF is responsible for aligning the PVDF chains and promoting β-phase nucleation. The as-received PVDF/DA NFs exhibit significantly enhanced piezoelectric performance and excellent stability and biocompatibility. An all-fiber-based soft sensor is fabricated and tested on human skin and in vivo in mice. The devices show a high sensitivity and accuracy for detecting weak physiological mechanical stimulation from diaphragm motions and blood pulsation. This sensing capability offers great diagnostic potential for the early assessment and prevention of cardiovascular diseases and respiratory disorders.

Development of efficient adsorbent with low cost, simple and green production process, and zero secondary pollution for Cr(VI) removal in industrial applications is a great challenge for modern chemical and materials engineering. Here, we developed a new strategy for preparation of porous polyacrylonitrile (PAN)/graphene oxide (GO) nanofibers by simple one-step electrospinning of PAN/GO solution in N,N-dimethylformamide (DMF)/H2O mixed solvent. The resultant porous PAN/GO nanofibers possessed abundant nanopores (5–200 nm) and thus huge Brunauer-Emmett-Teller (BET) specific surface area (164.2 ± 10.8 m2g−1) and excellent interfacial compatibility. The porous structure maximized the adsorption function of the doped GO nanosheets for Cr(VI) ions, an unprecedented experimental Cr(VI) ions adsorption capacity of 382.5 ± 6.2 mg/g was achieved. And the porous PAN/GO nanofibers also exhibited excellent regeneration, after 20 times adsorption–desorption test, the desorption efficiency of the Cr(VI) ions stably maintained more than 75%. More importantly, compared to the current complex chemical synthesis and material structure design methods of Cr(VI) ions adsorbent, the simple one-step electrospinning fully showed great technical advantages for industrial applications including efficient (100% raw material utilization), green (no any harmful chemical by-products), low cost (only PAN and 1.98 wt% GO). Therefore, we suggested that the porous PAN/GO nanofibers will be a promising candidate in industrial applications as a solid adsorbent for Cr(VI) ions adsorption.

Paclitaxel is broad-spectrum anticancer drug which has been widely used in clinic. However, traditional drug delivery often suffers from the scarcity of resources and systemic toxic side effects caused by the localization to non-tumor areas, rendering cancer treatment extremely challenging. To address this problem, we developed a novel multifunctional drug delivery system of a poly(lactic-co-glycolic acid) (PLGA) drug-loaded magnetic Janus particles (DMJPs) using electrohydrodynamic (EDH) co-jetting. The DMJPs were loaded with three compartments each with distinct function, i.e. paclitaxel for killing cancer cell, Fe3O4 nanoparticles for target location, and rhodamine B for fluorescence tracing, respectively. The Janus structure of the DMJPs, as demonstrated by the loaded nano-quantum dots CdS/ZnS and CdSe/ZnS in different compartments, enhanced not only the drug loading and encapsulation efficiency but also the cumulative release rate of the loaded drugs from DMJPs in different media. More importantly, DMJPs exhibited specific and high toxicity only to human breast cancer cells (MDA-MB-231), but not to mouse embryonic fibroblasts (NIH-3 T3). Consistently, DMJPs induced the higher lethal effect on cancer cells than paclitaxel suspension of high concentrations. Under guidance of external magnetic field, DMJPs can readily target and accumulate on and inside cancer cells for cell elimination. The specific targetability, selectivity, and toxicity of DMJPs on cancer cells would greatly avoid any potential side effects and reduce the overdose of drugs for conventional drug delivery. This work hopefully provides a new drug delivery system for the development of anticancer drug systems for clinical and precision medicine treatment.

Electrospun nanofiber scaffolds have been shown to accelerate the maturation, improve the growth, and direct the migration of cells in vitro. Electrospinning is a process in which a charged polymer jet is collected on a grounded collector; a rapidly rotating collector results in aligned nanofibers while stationary collectors result in randomly oriented fiber mats. The polymer jet is formed when an applied electrostatic charge overcomes the surface tension of the solution. There is a minimum concentration for a given polymer, termed the critical entanglement concentration, below which a stable jet cannot be achieved and no nanofibers will form - although nanoparticles may be achieved (electrospray). A stable jet has two domains, a streaming segment and a whipping segment. While the whipping jet is usually invisible to the naked eye, the streaming segment is often visible under appropriate lighting conditions. Observing the length, thickness, consistency and movement of the stream is useful to predict the alignment and morphology of the nanofibers being formed. A short, non-uniform, inconsistent, and/or oscillating stream is indicative of a variety of problems, including poor fiber alignment, beading, splattering, and curlicue or wavy patterns. The stream can be optimized by adjusting the composition of the solution and the configuration of the electrospinning apparatus, thus optimizing the alignment and morphology of the fibers being produced. In this protocol, we present a procedure for setting up a basic electrospinning apparatus, empirically approximating the critical entanglement concentration of a polymer solution and optimizing the electrospinning process. In addition, we discuss some common problems and troubleshooting techniques.