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A macro-microscopically chemo-mechanical model has been proposed to numerically investigate the expansion response of hardened cement paste (HCP) under external sulfate attack (ESA). In this model, a saturated HCP specimen and a representative volume element (RVE) are regarded as macro- and microscopic objects. At the macroscale, the sulfate diffusion and expansion response in HCP are described by using Fick’s law and continuum mechanics. At the microscale, the growth of sulfate products and its induced mechanical response in RVE are characterized by using reaction kinetics and microporomechanics. Meanwhile, the macro-micro transition of relevant parameters, such as sulfate concentration, mechanical property, and expansive eigenstrain, is constructed to bridge the relationship between the macro and micro scales. Numerical simulation on expansion response of a HCP cylinder immersed in Na2SO4 solution is performed. Results show that, there exist some differences in the macro- and microscopic expansion responses induced by the growth of sulfate products in the pore, and the microscopic hoop tensile stress is responsible for the initiation and propagation of microcracks in the cement paste.

The transport characteristics of a disordered, multilayered MoS2 nanoflake in the insulator regime are studied by electrical and magnetotransport measurements. The MoS2 nanoflake is exfoliated from a bulk MoS2 crystal and the conductance G and magnetoresistance are measured in a four-probe setup over a wide range of temperatures. At high temperatures, we observe that ln G exhibits a −T−1 temperature dependence and the transport in the nanoflake dominantly arises from thermal activation. At low temperatures, where the transport in the nanoflake dominantly takes place via variable-range hopping (VRH) processes, we observe that ln G exhibits a −T−1/3 temperature dependence, an evidence for the two-dimensional (2D) Mott VRH transport. Furthermore, we observe that the measured low-field magnetoresistance of the nanoflake in the insulator regime exhibits a quadratic magnetic field dependence ∼ αB2 with α ∼ T−1, fully consistent with the 2D Mott VRH transport in the nanoflake.

Semiconducting–superconducting hybrids are vital components for the realization of high-performance nanoscale devices. In particular, semiconducting–superconducting nanowires attract widespread interest owing to the possible presence of non-abelian Majorana zero modes, which are quasiparticles that hold promise for topological quantum computing. However, systematic search for Majoranas signatures is challenging because it requires reproducible hybrid devices and reliable fabrication methods. This work introduces a fabrication concept based on shadow walls that enables the in situ, selective, and consecutive depositions of superconductors and normal metals to form normal-superconducting junctions. Crucially, this method allows to realize devices in a single shot, eliminating fabrication steps after the synthesis of the fragile semiconductor/superconductor interface. At the atomic level, all investigated devices reveal a sharp and defect-free semiconducting–superconducting interface and, correspondingly, a hard induced superconducting gap resilient up to 2 T is measured electrically. While the cleanliness of the technique enables systematic studies of topological superconductivity in nanowires, it also allows for the synthesis of advanced nano-devices based on a wide range of material combinations and geometries while maintaining an exceptionally high interface quality.

The coupling action of calcium leaching and chloride attack is an important durability problem for the cement-based materials served in long-termly in the environmental water like seawater or groundwater containing chloride. This paper investigates the influence of calcium leaching on the chloride diffusivity in cement-based materials by the corrosion experiment, in which the hardened cement paste (HCP) specimens are immersed into three corrosion solutions with the same chloride concentration, such as 1 M sodium chloride solution, 1 M ammonium chloride solution and the mixed solution of 1 M sodium chloride and 3 M ammonium nitrate. Some measurements, like the phenolphthalein, saturation-drying weighing, mercury intrusion porosimetry (MIP), Scanning Electron Microscopy (SEM/EDS), X-ray diffraction analysis (XRD) and rapid chloride test (RCT), are used to analyze the leaching behaviors and its influence on the chloride diffusivity of HCP, characterized by leaching depth, pore structure, morphology, calcium-silicon ratio, chloride-silicon ratio, phase composition and free chloride ion content. Results show that, in the calcium leaching process, the compactness, calcium hydroxide content and calcium-silicon ratio of C-S-H gel of HCP decreases with the leaching time. The calcium leaching causes the reduction of the physically chloride-bound ability and the chemically chloride-absorbed ability in HCP, and it results in high chloride diffusivity.

The passive behavior of ductile iron in simulated cement-mortar pore (SCMP) solution with different alkalinity was investigated by electrochemical measurements, such as open circuit potential (OCP), Tafel polarization curve (TP), electrochemical impedance spectroscopy (EIS), and microscopic tests, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that, with increase in immersion time, the SCMP solution with the high pH value can cause the increase of OCP and capacitive loop of ductile iron surface, a morphology of growing surface film, and the high Fe 2+ /Fe 3+ ratios in its surface Iron-oxide compounds, presenting the formation of passive film on the surface of ductile iron. But in the SCMP solution with low pH value, its OCP, TP curve and EIS show no obvious change, and also produce the corrosion morphology of rust with low Fe 2+ /Fe 3+ ratios, indicating loss of surface protection on the ductile iron.

This paper numerically simulates time-dependent mechanical behaviors, such as stress redistribution and bearing capacity degradation, of concrete subjected to the coupled axial loading and sulfate attack. Based on Fick's law and chemical reaction kinetics, a diffusion-reaction model was proposed to obtain the spatial and time-dependent concentration distribution of sulfate ion, gypsum and ettringite. From previous study, a chemical damage, characterized by the volumetric expansion from ettringite formation, is introduced to reflect the influence of sulfate attack on concrete performance. Furthermore, using the plasticity theory and damage mechanics, a coupled chemo-mechanical damage constitutive model was determined by introducing the chemical damage. Finally, a concrete prism is regarded as a research object, to investigate the time-dependent stress and bearing capacity degradation of concrete structures subjected to the coupled axial compression and sulfate attack.

This paper has numerically investigated the changes of loading-induced stress in concrete with the corrosion time in the sulfate-containing environment. Firstly, based on Fick\'s law and reaction kinetics, a diffusion-reaction equation of sulfate ion in concrete is proposed, and it is numerically solved to obtain the spatial and temporal distribution of sulfate ion concentration in concrete by the finite difference method. Secondly, by fitting the existed experimental data of concrete in sodium sulfate solutions, the chemical damage of concrete associated with sulfate ion concentration and corrosion time is quantitatively presented. Thirdly, depending on the plastic-damage mechanics, while considering the influence of sulfate attack on concrete properties, a simplified chemo-mechanical damage model, with stress-based plasticity and strain-driven damage, for concrete under axial loading and sulfate attack is determined by introducing the chemical damage degree. Finally, an axially compressed concrete prism immersed into the sodium sulfate solution is regarded as an object to investigate the time-varying stress in concrete subjected to the couplings of axial loading and sulfate attack.

This paper uses modelling and experiment to perform a quantitative analysis for the gypsum and ettringite formations in cement pastes subjected to sulfate attack. Firstly, based on Fick\'s law and chemical reaction kinetics, a diffusion model of sulfate ions in cement pastes is proposed, and then the model of the gypsum and ettringite formations is established to analyze its contents in cement pastes with corrosion time. Secondly, the corrosion experiment of the specimens with cement pastes immersed into 2.5%, 5.0% and 10.0% Na2SO4 solutions are carried out, and by using XRD-Rietveld method, the phases of powder samples from the specimens are quantitatively analyzed to obtain the contents of gypsum and ettringite in different surface depth, solution concentration and corrosion time. Finally, the contents of gypsum and ettringite calculated by the models are compared with the results from the XRD experiments, and then the effects of surface depth, corrosion time and solution concentration on the gypsum and ettringite formations in cement pastes are discussed.

In order to investigate the influence of slag on the leaching behavior of cement mortar lined in ductile iron pipe in a flowing solution, two types of ductile iron pipe specimens lined with ordinary- and 40% slag- cement mortar are firstly prepared, then, an accelerated leaching experiment on the prepared specimens is carried out by using a 6 M ammonium chloride solution at a flow rate of 0.3 m/s. The parameters of linings at different leaching times, such as porosity, pore size distribution, phase composition and Calcium-Silicon (Ca/Si) ratio, were analyzed by using the saturation-drying weighing method, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and scanning electron microscopy in back scattered electron mode (ESEM-BSE) measurements. Results show that, the mixture of 40% slag in cement-mortar lining can reduce its initial porosity and Calcium-Silicon ratio, and improve its pore size distribution and phase composition. In the accelerated leaching process, the porosity, phase composition and Calcium-Silicon ratio of the slag-cement-mortar lining with 40% slag have smaller change than that of the ordinary-cement-mortar lining without slag, and it indicates that the addition of slag can effectively improve the calcium leaching resistance of cement-mortar lining in ductile iron pipes in water supply engineering. Keywords: Slag, Cement-mortar lining, Calcium leaching, Ductile iron pipe, Flowing solution

In order to obtain quickly the influences of blast furnace slag and water-binder ratio on the leaching behavior of cement-based material and its corrosion resistance in water environments, an accelerated calcium leaching experiment on a slice specimen with slag-cement pastes in 6 M NH4 Cl solution was carried out. Using the saturation-drying weighing method, X-ray diffraction (XRD) and the scanning electron microscope (SEM/EDS) measurement, the influences of water-binder ratio and slag content on the porosity, phase composition, microstructure morphology and Calcium-Silicon ratio of slag-cement pastes in the process of calcium leaching were analyzed. Results show that, compared to cement pastes without slag, the slag-cement paste with the appropriate slag content has a low rate of microstructure deterioration and a good leaching resistance. The optimum slag contents in slag-cement pastes are respectively 40% and 50% corresponding to the low and high water-binder ratio. The porosity, Calcium-Silicon ratio and microstructure morphology of slag-cement pastes exhibit small change in the process of accelerating leaching, and this indicates that the slag-cement pastes with the optimum slag content can provide the best performance of calcium leaching resistance in the soft-water environment.

Expansion of concrete caused by external sulfate attack (ESA) is a multiscale chemomechanical response, mainly including internal stress evolution at the dormant period and significant crac...

Low-dimensional narrow-band-gap III-V semiconductors are key building blocks for the next generation of high-performance nanoelectronics, nanophotonics, and quantum devices. Realizing these various applications requires an efficient methodology that enables the material dimensional control during the synthesis process and the mass production of these materials with perfect crystallinity, reproducibility, low cost, and outstanding electronic and optoelectronic properties. Although advances in one- and two-dimensional narrow-band-gap III-V semiconductors synthesis, the progress toward reliable methods that can satisfy all of these requirements has been limited. Here, we demonstrate an approach that provides a precise control of the dimension of InAs from one-dimensional nanowires to wafer-scale free-standing two-dimensional nanosheets, which have a high degree of crystallinity and outstanding electrical and optical properties, using molecular-beam epitaxy by controlling catalyst alloy segregation. In our approach, two-dimensional InAs nanosheets can be obtained directly from one-dimensional InAs nanowires by silver-indium alloy segregation, which is much easier than the previously reported methods, such as the traditional buffering technique and select-area epitaxial growth. Detailed transmission electron microscopy investigations provide solid evidence that the catalyst alloy segregation is the origination of the InAs dimensional transformation from one-dimensional nanowires to two-dimensional nanosheets and even to three-dimensional complex crosses. Using this method, we find that the wafer-scale free-standing InAs nanosheets can be grown on various substrates including Si, MgO, sapphire, GaAs, etc. The InAs nanosheets grown at high temperature are pure-phase single crystals and have a high electron mobility and a long time-resolved terahertz kinetics lifetime. Our work will open up a conceptually new and general technology route toward the effective controlling of the dimension of the low-dimensional III-V semiconductors. It may also enable the low-cost fabrication of free-standing nanosheet-based devices on an industrial scale.

Concrete deterioration caused by external sulfate attack (ESA) is a macro-microscopically interactive expansion process, including two stages, namely a dormant period and detrimental duration. Based on ESA-induced deterioration mechanism, an integrated macro-microscopic model has been developed to describe the deterioration of concrete. In this model, a critical characteristic related to crystallization pressure is proposed to recognize two stages of ESA, and a criterion of ESA-induced boundary movement in concrete specimen is established by its total damage associated with micro and macroscopic damages. A diffusion-reaction model is constructed to characterize macroscopic sulfate diffusion and microscopic ettringite/gypsum formation in concrete, which are respectively used to determine the crystallization pressure and volume increase. The macro and microscopic mechanical models, combining with the plastic-damage model, are built to analyze the expansion-induced deterioration of concrete. The integrated model is validated by the experimental results of expansion deformation and damage distribution.

Single crystalline InSb nanosheet is an emerging planar semiconductor material with potential applications in electronics, infrared optoelectronics, spintronics and topological quantum computing. Here we report on realization of a quantum dot device from a single crystalline InSb nanosheet grown by molecular-beam epitaxy. The device is fabricated from the nanosheet on a Si/SiO2 substrate and the quantum dot confinement is achieved by top gate technique. Transport measurements show a series of Coulomb diamonds, demonstrating that the quantum dot is well defined and highly tunable. Tunable, gate-defined, planar InSb quantum dots offer a renewed platform for developing semiconductor-based quantum computation technology., Comment: 12 pages, 4 figures

An accelerated leaching experiment, using 6M NH4Cl solution, on specimens of pure cement paste, binary cement paste with different fly ash contents (20, 30, and 50%), and ternary cement pas...

A family of well-defined poly(3-hexylthiophene)-b-poly(5,8-di-p-tolylquinoxaline-2,3-diyl) rod–rod block copolymers was designed and synthesized in one pot via mechanistically distinct, sequential living polymerization using Ni(dppp)Cl2 as a single catalyst. The block copolymerization was demonstrated to proceed in a living/controlled chain-growth manner, affording the desired block copolymers in high yields with tunable compositions, controlled molecular weight, and narrow molecular weight distributions. The resulting block copolymer was revealed to self-assemble into various well-defined supramolecular structures depending on the solvents used such as nano-fibril and spherical nanoparticles. Very interestingly, such a block copolymer displayed highly selective visual detection for cobalt over most other competing metal ions by changing its orange color to light green and bright orange emission to deep green. The detection limit was estimated to be down to 1.0 × 10−7 M and the interference of the other competing metal ions is negligible. Furthermore, such a block copolymer can be applied using test strips, making it a practical, sensitive, and selective probe for cobalt ions.

A series of novel hydroxyl-terminated hyperbranched polyurethanes (HBPUs) were synthesized via stepwise polymerization by diethanolamine (DEOA), isophorone diisocyanate (IPDI) and trimethylolpropane (TMP). It is interesting to note that the HBPUs can be purified by water. The HBPUs were characterized with 1H nuclear magnetic resonance (NMR), 13C NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The average degree of branching (DB) of HBPUs was calculated from the first generation to the fourth generation to be 1.00, 0.74, 0.59 and 0.57 by quantitative 13C NMR, respectively. The branching model and molecular structure of HBPUs were deduced by the 13C NMR and the value of DB. To investigate the changes of hydrogen bonding interaction in HBPUs with a variation in structure of different generations, the deconvolution of FT-IR spectra was carried out using Origin 7.0 software through the Gaussian curve-fitting method. The ratio of hydrogen-bonded -NH and -OH groups of HBPUs was calculated to be 80.8%, 85.1%, 84.8% and 85.4% from the first generation to the fourth generation by deconvoluted -NH and -OH zone, respectively. The interaction of hydrogen bonding and glass transition temperature (Tg) of HBPUs increased with the increase of generation. The trend of thermal stability and Tg coincide with the change of hydrogen-bonded interactions.

According to the operating characteristics of high-power battery pack in practical application, the effects of four factors, which include operating load, state of charge (SOC), ambient temperature and operating temperature, on the temperature uniformity and rising rate of battery pack under natural convection were studied based on Arbin test bench. The results indicate that: the operating load and SOC of battery pack doesn’t affect its temperature uniformity, which was deteriorated as the increasing of operating temperature of battery pack, or improved as the increasing of ambient temperature when the other factor is kept constant. The increment of operating load or ambient temperature could result in a higher temperature rising rate, while the increasing of SOC or operating temperature could lead to a lower temperature rising rate, when the other three factors are kept constant. When the operating temperature or temperature differences achieved threshold value, thermal management system should choose proper extent of forced flow and flow field in accordance with the battery pack’s current operating conditions, in order to ensure the economy of the thermal management system.

For the volume expansive of cement-based materials subjected to sulfate attack, based on microporous mechanics, the model of representative volume element (RVE) is established to analyze the distribution of microcosmic expansive stress in RVE. By homogenization method, the macroscopic equivalent stress of RVE is analyzed. The results show: on the microcosmic scale, the stress of internal sphere in RVE in all directions is compressive, and the radial stress of spherical shell is compressive, but the hoop stress is tensile; on macroscopic scale, the radial equivalent stress is compressive, the hoop equivalent stress is tensile.

During the process of deep drilling with high temperature and high pressure, downhole drilling tools might be exposed to various corrosive mediums, such as water/oil-based drilling fluid systems, dissolved oxygen, H2S/CO2, halogen elements (Cl- and Br-), etc. Halogen elements existing in the drilling fluid are ions promoting corrosion of metals. This effect is mainly manifested in the forms of uniform corrosion, pitting corrosion, stress corrosion cracking, etc. of carbon steel. Quality of the drill pipe is determined by the DP body, joint and welding area of the drill pipe. Reasonable friction welding process and proper post weld heat treatment can make the mechanical property of weld joint satisfy related standards. If process of friction welding or post weld heat treatment is improper, the weld joint will be easily damaged and accidents of pricking, breaking, etc will be likely aroused. This paper carries out an evaluation experiment of chloride cracking on the DP body, joints and weld joints of the high-strength drill pipe (S135) and discusses corrosion of the high-strength drill pipe caused by chloride ions.

The samples were prepared using Cr2O3 micropowder, TiO2 micropowder and m-ZrO2 micropowder as main starting material, polyvinyl alcohol as binder, by a series of processes such as pulping, spraying granulation, machine moulding and cold isostatic pressing, and sintering at 1 500°С for 3 h in nitrogen protected atmosphere furnace (oxygen partial pressure was 10 Pa). Then thermal shock resistance of the samples was tested by wind quenching. Effect of m-ZrO2 (2%-5% in mass) on sintering behavior and thermal shock resistance of Cr2O3 material was investigated. The results show that m-ZrO2 can accelerate the sintering of Cr2O3 material, but excess 2 wt% m-ZrO2 doesn’t work; m-ZrO2 can obviously improve thermal shock resistance of Cr2O3 material, sample containing 3 wt% m-ZrO2 has 34 wind quenching cycles from 1 150°С to room temperature, and sample without m-ZrO2 only has 11 cycles.

Biomimetic growth of calcium phosphate over natural polymer may be an effective approach to constituting an organic/inorganic composite scaffold for bone tissue engineering. In this work, N-methylene phosphochitosan (NMPCS) was prepared via formaldehyde addition and condensation with phosphoric acid in a step that allowed homogeneous modification without obvious deterioration in chitosan (CS) properties. The NMPCS obtained was characterized by using FT-IR and elemental analysis. The macroporous scaffolds were fabricated through a freeze-drying technique. A comparative study on NMPCS and CS scaffold biomimetic mineralization was carried out in different media, i.e, a simulated body fluid (SBF) or alternative CaCl(2) and Na(2)HPO(4) solutions respectively. Apatite formation within NMPCS and CS scaffolds was identified with FT-IR, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffractometery (XRD). The results revealed alternate soaking of the scaffolds in CaCl(2) and Na(2)HPO(4) solutions was better than soaking in SBF solution alone in relation to apatite deposition on the scaffold pore walls. Biomineralization provides an approach to improve nature derived materials, e.g., chitosan derivative NMPCS properties e.g., compressive modulus, etc. SEM image of a NMPCS/apatite composite scaffold.

A novel composite composed of hydroxyapatite (HA) and a network formed via cocrosslinking of chitosan and gelatin with glutaraldehyde was developed. Two preparation methods are described in detail. A porous material, with similar organic–inorganic constituents to that of natural bone, was made by a unique sol–gel method. The formation of the network in the presence of HA was characterized using IR analysis. The morphology of the composites was also examined using SEM. In addition, XRD was applied to estimate the change in the component crystal. The results indicate that the presence of HA does not retard the formation of the chitosan/gelatin network. On the other hand, the polymer matrix has hardly any influence on the high crystallinity of HA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2929–2938, 2000

pH responsive chitosan/gelatin hybrid polymer network (HPN) microspheres were prepared via the inverse emulsion crosslinking method. Cimetidine release from the microspheres was studied. The drug only delivers in acidic medium, while the release rate can be controlled by the HPN composition and the degree of deacetylation.

A novel hydrogel based on a crosslinked chitosan/gelatin with glutaraldehyde hybrid polymer network was prepared. The gel swells in acidic medium and deswells in alkaline medium. A comparative study of the pH-dependent release of levamisole, cimetidine and chloramphenicol was carried out.

Chitosan [(1-4) 2-amino 2-deoxy-β-D-glucan] is a polyaminosacchar-ide, normally obtained by alkaline deacetylation of chitin which is a very abundant naturally occurring polymeric material. It occurs as a principle constituent of the protective cuticles of crustacea and insects and also in the cell walls of some fungi and microorganisms.

LG type vacuum freeze dryer vapor captor is taken as the study object, and a mathematical model of frost heat transfer of the vapor captor was established, the effective heat capacity method was used to simulate the heat transfer processes of vapor captor. Frosting mechanism under low temperature and low pressure condition was investigated, and the changing relation curves of temperature distribution, thickness and density of frost layer on vapor captor coil along with time were obtained. The results show that with the increasing of the frost thickness, the surface temperature of frost layer increase, and the heat transfer coefficient continue to fall, the rate of increase in frost thickness of late stage is faster than the early by 30.3%.

Our objective in this study was to investigate the efficiency of two treatments for poly (L-lactic acid) (PLLA) surface modification with gelatin, via entrapment and coupling, using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The properties of original PLLA, gelatin-entrapped, and coupled PLLA films were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). The water contact angle indicated that the incorporation of gelatin resulted in a change in hydrophilicity, and the ESCA data suggested that the modified PLLA films became enriched with nitrogen atoms. The cytocompatibility of modified PLLA films might be improved. Therefore, we examined the attachment and proliferation of bovine articular chondrocyte seeded on modified PLLA films and virgin films. A whole-cell enzyme-linked immunosorbent assay (cell ELISA) that detects 5-bromo-2'-deoxyuridine (BrdU) incorporation during DNA synthesis and collagen type II secretion was applied to evaluate the chondrocytes on different PLLA films and tissue culture plates (TCPS). Cell viability was estimated by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, and cell function was assessed by measuring glycosaminoglycan (GAG) secreted by chondrocytes. These results implied that gelatin used to modify the PLLA surface through entrapment and coupling could enhance chondrocyte adhesion, proliferation, and function.

The objective of the present study was to investigate the properties of chitosan-gelatin membranes or scaffolds, which were modified by incorporation of hyaluronic acid in the surface or bulk phase through co-crosslinking with N,N-(3-dimethylamino-propyl)-N'-ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in 2-morpholinoethane sulfonic acid (MES) buffer. The comparative study on properties of surface modification (HA(S)) and polyblend membranes (HA(C)) revealed that gelatin was enriched on the surface of HA(C), while hyaluronic acid was enriched on the surface of the HA(S). The HA(S) membranes made by surface modification method had a characteristic surface morphology. The corresponding scaffolds were prepared through freeze-drying. The incorporation of hyaluronic acid improved flexibility and fibroblasts adhesion, while slowing down the rate of biodegradation of chitosan-gelatin scaffold. Human fibroblasts adhered and proliferated well on the membranes or scaffolds in vitro.

Chitosan-gelatin hybrid polymer network scaffolds were prepared via the freeze-drying technique by using the ice microparticle as a porogen. Monolayer and bilayer scaffolds were obtained by using different pre-freezing methods. The novel bilayer scaffolds were prepared via contact with -56 degrees C lyophilizing plate directly, then lyophilized. The properties of chitosan-gelatin scaffolds, such as microstructure, physical and mechanical and degradable properties, were studied. These results suggested that the porosity and pore size of the scaffolds could be modulated with thermodynamic and kinetic parameters of ice formation. The scaffolds prepared from chitosan and gelatin can be utilized as a promising matrix for tissue engineering.

In this study, L929 cell adhesion, proliferation and apoptosis were investigated on chitosan (CS) and chitosan-gelatin (CS-Gel) membranes having different degrees of deacetylation (DD). The mitochondrial activity [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay results demonstrated that the DD played a key role in the L929 cell adhesion. Indeed, the higher the DD of a CS membrane, the stronger the cell adhesion. The cell cycle analysis showed that the CS surface inhibits most of the cells entering the cell cycle and the DD of CS had little effect on the cell cycle progression. On the other hand, this study also confirmed that CS, blended with Gel, induced L929 cells to enter the cell cycle, encouraged proliferation, decreased the degree of apoptosis on the CS membranes, and are comparable to the results from L929 cells on tissue culture plates. In brief, CS modified with Gel improves cytocompatibility by shielding the positively charged CS with a high charge density.

Chitosan is a natural biopolymer obtained by deacetylation of chitin, which is produced from marine shellfish, such as crabs, shrimp, fungal cell wells, and other biological sources. Chemically it is a linear cationic poly(β-(1-4)-2-amino-2-deoxy-d-glucan) derived from chitin, a poly(β-(1-4)-2-acetamido-2-deoxy-D-glucan) by deacetylation. Chitosan is described in terms of the deacetylation degree and average molecular weight. And next to cellulose, it is the second most plentiful biomass and is already known as a biocompatible and biodegradable material. Many researchers have examined tissue response to various chitosan-based implants. Results indicate that these materials evoke minimal foreign body reactions. Gels consist of 3-D polymer networks swollen in swellers, whereas hydrogels swell in water. Smart (intelligent) gels (or hydrogels) can swell or contract in response to stimulus changes, e.g., temperature, pH, ionic strength, chemicals, and fields. Chitosan has been used for developing smart gels via network or/and complex formation. Due to their various properties that depend on environmental variables such as pH, ionic strength, and electric field, these materials have potential applications such as biomaterials, separation membranes, and field responsive materials. Keywords: Supramolecular interactions; Gel formation; Chitosan; Applications; Controlled release; Separation membranes; Immobilization supports; Tissue engineering; Field response materials