Preparation and Characterization of a Novel Tragacanth Gum/Chitosan/Sr-Nano-Hydroxyapatite Composite Membrane.

It is a great challenge to obtain an ideal guided bone regeneration (GBR) membrane. In this study, tragacanth gum (GT) was introduced into a chitosan/nano-hydroxyapatite (CS/n-HA) system. The effects of different component ratios and strontium-doped nano-hydroxyapatite (Sr-HA) on the physical-chemical properties and degradation behavior of the CS/Sr-n-HA/GT ternary composite membrane were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, electromechanical universal tester and in vitro soaking in simulated body fluid (SBF). The results showed that CS could be ionically crosslinked with GT through electrostatic interaction, and Sr-n-HA was loaded via hydrogen bond, which endowed the GT/CS/n-HA composite membrane with good tensile strength and hydrophilicity. In addition, the results of immersion in SBF in vitro showed that CS/n-HA/GT composite membranes had different degradation rates and good apatite deposition by investigating the changes in pH value, weight loss, water absorption ratio, SEM morphology observation and tensile strength reduction. All results revealed that the CS/Sr-n-HA/GT (6:2:2) ternary composite membrane possessed the strongest ionic crosslinking of GT and CS, which was expected to obtain more satisfactory GBR membranes, and this study will provide new applications of GT in the field of biomedical membranes.

Synthesis of sodium alginate/polyacrylamide photochromic hydrogels with quadruple crosslinked networks.

Photochromic hydrogels have great potential for inkless printing, smart display devices, anti-counterfeiting and encryption. However, the short information storage time limits their large-scale application. In this study, a sodium alginate/polyacrylamide photochromic hydrogel with ammonium molybdate as the color change factor was prepared. The addition of sodium alginate was beneficial to the improvement of the fracture stress and elongation at break. In particular, when the content of sodium alginate was 3%, the fracture stress increased from 20 kPa without sodium alginate to 62 kPa. Different photochromic effects and information storage times were achieved by regulating the calcium ion and ammonium molybdate concentration. And the hydrogel with an ammonium molybdate immersion concentration of 6% and calcium chloride immersion concentration of 10% can store information for up to 15 h. At the same time, the hydrogels were able to maintain their photochromic properties over five cycles of "information writing - erasure" and achieved "hunnu" encryption. Therefore, the hydrogel shows excellent information controllable erasure properties and encryption functions, indicating its broad application prospects.

Electrospinning Novel Sodium Alginate/MXene Nanofiber Membranes for Effective Adsorption of Methylene Blue.

Understanding how to develop highly efficient and robust adsorbents for the removal of organic dyes in wastewater is crucial in the face of the rapid development of industrialization. Herein, d-Ti3C2Tx nanosheets (MXene) were combined with sodium alginate (SA), followed by electrospinning and successive Ca2+-mediated crosslinking, giving rise to a series of SA/MXene nanofiber membranes (NMs). The effects of the MXene content of the NMs on the adsorption performance for methylene blue (MB) were investigated systemically. Under the optimum MXene content of 0.74 wt.%, SA/MXene NMs possessed an MB adsorption capacity of 440 mg/g, which is much higher than SA/MXene beads with the same MXene content, pristine MXene, or electrospinning SA NMs. Furthermore, the optimum SA/MXene NMs showed excellent reusability. After the adsorbent was reused ten times, both the MB adsorption capacity and removal rate could remain at 95% of the levels found in the fresh samples, which indicates that the electrospinning technique has great potential for developing biomass-based adsorbents with high efficiency.

Highly-selective solvent-free catalytic isomerization of α-pinene to camphene over reusable titanate nanotubes.

Titanate nanotubes, prepared by the hydrothermal reconstitution and modification with hydrochloric acid, were tested as solid acid catalysts in the isomerization of α-pinene under solvent free conditions. The results showed that titanate nanotubes have better catalytic properties than titanium dioxide nanoparticles, and the camphene was the main product for α-pinene isomerization. The effects of several reaction variables, such as reaction temperature, catalyst dosage, and reaction time, on the conversion of α-pinene and the selectivity to camphene were examined. The highest conversion was up to 97.8% with selectivity to camphene of 78.5% under the mild reaction conditions, and the catalyst also showed outstanding reusability after four runs. It is proposed that appropriate surface acidic sites and opened nanotubular structures are mainly responsible for the excellent catalytic performance of titanate nanotubes materials.

Polymerization mechanism of 4-APN and a new catalyst for phthalonitrile resin polymerization.

The widely used catalysts for phthalonitrile (PN) resin polymerization are aromatic compounds containing -NH2 because of their high catalytic performances. However, the catalytic mechanisms of these catalysts are not very clear. To understand the mechanisms of them, the widely used autocatalytic catalyst 4-(4-aminophenoxy)-phthalonitrile (4-APN) was studied in this paper. The polymerization process of 4-APN was tracked by a multi-purpose method, and ammonia gas was detected during the cross-linking processing for the fist time. Combined with the online IR results of the curing process of 4-APN, the mechanism of ammonia generation was newly proposed. Based on this mechanism, a new catalyst selection strategy was promoted, which is different from the traditional approach to catalyst selection for PN resin polymerization. According to the new strategy, 1,3-diiminoisoindoline (1,3-DII) was selected as a novel catalyst. The results showed that the new catalyst could not only effectively catalyze the polymerization of PN resin, but also has a lower curing temperature than that of organic amine catalysts and can eliminate the release of ammonia gas and the voids in the products caused thereby. Therefore, the results of this study will give important enlightenment to the development of PN catalysts and the development of PN.

A novel green process for tannic acid hydrolysis using an internally sulfonated hollow polystyrene sphere as catalyst.

A polystyrene-hollow sphere catalyst was prepared by treating polystyrene-encapsulated calcium carbonate particles with concentrated hydrochloric acid. This catalyst was characterized using TGA, FT-IR, optical microscope, SEM-EDX and XPS. Evidences from SEM-EDX and XPS analyses indicated that the sulfonate groups were on the inner surface of the polystyrene hollow sphere. The polystyrene hollow spheres were used as catalyst in the hydrolysis of tannic acid. Reaction conditions including the reaction temperature and time, loading of catalyst, ratio of tannic acid to H2O and number of recycles were optimized. A high yield of gallic acid was obtained as the reaction performed under the following conditions: a temperature of 80 °C, a molar ratio of tannic acid to H2O of 1 : 3, and a catalyst loading of 7% w/w (based on the mass of tannic acid). This catalyst showed excellent catalytic performance, easy separation, high stability and good reusability. This work provides a new strategy for the controllable synthesis of polystyrene hollow structures with sulfonic groups on the inner surface and an excellent and prospective catalyst for the production of gallic acid through hydrolysis of tannic acid.

One-step coagulation to construct durable anti-fouling and antibacterial cellulose film exploiting Ag@AgCl nanoparticle- triggered photo-catalytic degradation.

An anti-fouling and antibacterial surface of cellulose film was obtained by one-step coagulation of the cellulose-LiCl/Dimethyl acetamide (DMAc) solution with AgNO3 and polyvinyl pyrrolidone (PVP). The AgCl nanocrystals were embedded on the surface of cellulose film with the assistance of PVP, and the Ag@AgCl was formed due to the partly decomposition of AgCl under the visible-light irradiation. Morphology and size of the Ag@AgCl in cellulose matrix could be regulated by changing the concentration of PVP. From a series of comparative tests, Ag@AgCl could be stably embedded on cellulose film at the concentration of 1wt% PVP, and its photo-degradation efficiency could be still retained 89% after 5-cycle testing. Meanwhile, a dramatic reduction in viable bacteria was also observed within 120min of exposure on this film, and when exposure time was 180min, no active bacteria was observed.This work provided a simple pathway to construct the functional cellulose film which could be applied as packaging materials.

Preparation and characterization of a novel degradable nano-hydroxyapatite/poly(lactic-co-glycolic) composite reinforced with bamboo fiber.

It is a promising and challenging to achieve an ideal poly (lactic-co-glycolic) (PLGA)-based composite. In this paper, bamboo fiber (BF) was firstly designed to incorporate into nano-hydroxyapatite/PLGA (n-HA/PLGA) composite, and a series of novel biodegradable BF/n-HA/PLGA ternary composites with different BF amounts (0wt%, 5wt%, 10wt% and 20wt%) were prepared by solution mixing method. The effect of BF content on the crystallization behavior, interface structure and mechanical property of BF/n-HA/PLGA ternary composite was investigated by X-ray diffraction pattern (XRD), differential scanning calorimeter (DSC) and scanning electron microscope (SEM), comparing with pure PLGA and n-HA/PLGA composite. The results showed that BF further promoted the crystallization of PLGA acting as a heterogeneous nucleation agent, and the addition of 10wt% BF was the best benefit to promote the crystallization. However, the higher addition content of BF caused more agglomeration in n-HA/PLGA matrix, which decreased gradually the mechanical properties of the BF/n-HA/PLGA composite. In conclusion, the addition content of 5wt% BF to n-HA/PLGA matrix was an appropriate proportion, which can achieved the best mechanical reinforce effectiveness, suggesting that BF/n-HA/PLGA composite had more potential in biomedical application than n-HA/PLGA composite.

Preparation and Properties of Bamboo Fiber/Nano-hydroxyapatite/Poly(lactic-co-glycolic) Composite Scaffold for Bone Tissue Engineering.

In this study, bamboo fiber was first designed to incorporate into nano-hydroxyapatite/poly(lactic-co-glycolic) to obtain a new composite scaffold of bamboo fiber/nano-hydroxyapatite/poly(lactic-co- glycolic) (BF/n-HA/PLGA) by freeze-drying method. The effect of their components and some factors consisting of different freeze temperatures, concentrations, and pore-forming agents on the porous morphology, porosity, and compressive properties of the scaffold were investigated by scanning electron microscope, modified liquid displacement method, and electromechanical universal testing machine. The results indicated that the 5% BF/30% n-HA/PLGA composite scaffold, prepared with 5% (w/v) high concentration and frozen at -20 °C without pore-forming agent, had the best ideal porous structure and porosity as well as compressive properties, which far exceed those of n-HA/PLGA composite scaffold. In addition, the in vitro simulated body fluids soaking and cell culture experiment showed the addition of BF into the scaffold accelerated the BF/n-HA/PLGA composite scaffolds degradation and exhibited good cytocompatibility, including attachment and proliferation. All the results of the study show that BF has improved the properties of n-HA/PLGA composite scaffolds and BF/n-HA/PLGA might have a great potential for bone tissue engineering scaffold.

Preparation of native cellulose-AgCl fiber with antimicrobial activity through one-step electrospinning.

The native Cellulose-AgCl fiber have been firstly fabricated by one-step electrospinning of cellulose solution with poly(vinyl pyrrolidone) (PVP) and AgNO3. X-ray diffraction, Scanning electron microscopy (SEM), Energy dispersive spectrometer, Thermo-gravimetric analysis and Fourier transform infrared are used to characterize the crystal structure, morphology and composition of cellulose-AgCl nanocomposites. The results of SEM indicate that the size of AgCl in cellulose fiber matrix is able to be adjusted by the addition of Polyvinylpyrrolidone (PVP). The antimicrobial activity of the nanocomposites fiber is also tested against the model microbes E. coli (Gram-negative) and S. aureus (Gram-positive). The results indicate that cellulose-AgCl nanocomposites have a good antimicrobial activity, which is improving with the decrease of AgCl size in fiber matrix. This work provides a novel and simple way to adjust the AgCl size in electrospinning cellulose matrix which can be applied as functional biomaterials.

Improving the degradation behavior and in vitro biological property of nano-hydroxyapatite surface- grafted with the assist of citric acid.

To obtain ideal nano-hydroxyapatite(n-HA) filler for poly(lactide-co-glycolide) (PLGA), a new surface-grafting with the assist of citric acid for nano-hydroxyapatite (n-HA) was designed, and the effect of n-HA surface-grafted with or without citric acid on in vitro degradation behavior and cells viability was studied by the experiments of soaking in simulated body fluid (SBF) and incubating with human osteoblast-like cells (MG-63). The change of pH value, tensile strength reduction, the surface deposits, cells attachment and proliferation of samples during the soaking and incubation were investigated by means of pH meter, electromechanical universal tester, scanning electron microscope (SEM) coupled with energy-dispersive spectro-scopy (EDS), fluorescence microscope and MTT method. The results showed that the introduction of citric acid not only delayed the strength reduction during the degradation by inhibiting the detachment of n-HA from PLGA, but also endowed it better cell attachment and proliferation, suggesting that the n-HA surface-grafted with the assist of citric acid was an important bioactive ceramic fillers for PLGA used as bone materials.

An efficient calcium phosphate nanoparticle-based nonviral vector for gene delivery.

BACKGROUND: Smaller nanoparticles facilitate the delivery of DNA into cells through endocytosis and improve transfection efficiency. The aim of this study was to determine whether protamine sulfate-coated calcium phosphate (PS-CaP) could stabilize particle size and enhance transfection efficiency. METHODS: pEGFP-C1 green fluorescence protein was employed as an indicator of transfection efficiency. Atomic force microscopy was used to evaluate the morphology and the size of the particles, and an MTT assay was introduced to detect cell viability and inhibition. The classical calcium phosphate method was used as the control. RESULTS: Atomic force microscopy images showed that the PS-CaP were much smaller than classical calcium phosphate particles. In 293 FT, HEK 293, and NIH 3T3 cells, the transfection efficiency of PS-CaP was higher than for the classical calcium phosphate particles. The difference in efficiencies implies that the smaller nanoparticles may promote the delivery of DNA into cells through endocytosis and could improve transfection efficiency. In addition, PS-CaP could be used to transfect HEK 293 cells after one week of storage at 4°C with a lesser extent of efficiency loss compared with classical calcium phosphate, indicating that protamine sulfate may increase the stability of calcium phosphate nanoparticles. The cell viability inhibition assay indicated that both nanoparticles show similar low cell toxicity. CONCLUSION: PS-CaP can be used as a better nonviral transfection vector compared with classical calcium phosphate.

Self-stratified films obtained from poly(methyl methacrylate/n-butyl acrylate) colloidal dispersions containing poly(vinyl alcohol): a spectroscopic study.

These studies focus on the role of poly(vinyl alcohol) (pVOH) during colloidal synthesis of poly(methyl methacrylate/n-butyl acrylate) (pMMA/nBA) and its effect on particle coalescence. Using 2D photoacoustic FT-IR spectroscopy and internal reflection IR imaging, we showed that the presence of pVOH creates competing environments between the copolymer particle surfaces, aqueous phases, and dispersing agents which results in migration and self-induced stratification occurring during coalescence. pMMA/nBA/pVOH films stratify to form sodium dodecyl sulfate rich film-air interfaces, and the -SO3- moieties exhibit preferential parallel orientation with respect to the surface. At the same time, the bulk of the film is dominated by intramolecular hydrogen bonding between the pVOH phase and the copolymer matrix. This behavior is attributed to significant interactions between pVOH and pMMA/nBA, resulting in limited mobility of pVOH.

Simultaneous determination of water-soluble and fat-soluble synthetic colorants in foodstuff by high-performance liquid chromatography-diode array detection-electrospray mass spectrometry.

An accurate method was developed for the simultaneous determination of water-Tartrazine, Amaranth, Ponceau 4R, Sunset Yellow FCF, and fat-Sudan (I-IV), synthetic soluble colorants in foodstuff. This method uses dimethylsulfoxide (DMSO) as the extraction solvent in the sample preparation process and high performance liquid chromatography (HPLC)-diode array detector (DAD)-electrospray mass spectrometry (ESI-MS), applying selected ion recording in positive/negative alternate mode to acquire mass spectral data, as the analytical technique. Linearity of around three orders in the magnitude of concentration was generally obtained. Detection and quantification limits of the investigated dyes, which were evaluated at signal to noise ratio of 3 for detection limit and 10 for quantification limit, were in the ranges of 0.01-4 and 0.03-11.2 ng, respectively. The recoveries of the eight synthetic colorants in four matrices ranged from 93.2 to 108.3%. Relative standard deviations of less than 8.2% were also achieved. This method has been applied successfully in the determination of water-soluble colorants in the soft drink and the delicious ginger, and fat-soluble dyes in chilli powders and chilli spices.