Balancing mechanical property and swelling behavior of bacterial cellulose film by in-situ adding chitosan oligosaccharide and covalent crosslinking with γ-PGA.

Bacterial cellulose (BC) is an ideal candidate material for drug delivery, but the disbalance between the swelling behavior and mechanical properties limits its application. In this work, covalent crosslinking of γ-polyglutamic acid (γ-PGA) with the chitosan oligosaccharide (COS) embedded in BC was designed to remove the limitation. As a result, the dosage, time, and batch of COS addition significantly affected the mechanical properties and the yield of bacterial cellulose complex film (BCCF). The addition of 2.25 % COS at the incubation time of 0.5, 1.5, and 2 d increased the Young's modulus and the yield by 5.65 and 1.42 times, respectively, but decreased the swelling behavior to 1774 %, 46 % of that of native BC. Covalent γ-PGA transformed the dendritic structure of BCCF into a spider network, decreasing the porosity and increasing the swelling behavior by 3.46 times. The strategy balanced the swelling behavior and mechanical properties through tunning hydrogen bond, electrostatic interaction, and amido bond. The modified BCCF exhibited a desired behavior of benzalkonium chlorides transport, competent for drug delivery. Thereby, the strategy will be a competent candidate to modify BC for such potential applications as wound dressing, artificial skin, scar-inhibiting patch, and so on.

A facile synthesis of highly efficient In2S3 photocatalysts for the removal of cationic dyes with size-dependent photocatalysis.

In this study, a 3D thornball-like hierarchical ß-In2S3, displaying extremely rapid photodegradation of cationic dyes, was synthesized by a facile method. The formation of a uniform thornball-like structure depended on the microwave reaction method and citric acid as the pH regulator. The size of In2S3 was easily adjusted by changing the microwave irradiation time from 5 min to 15 min. The morphology, structure, composition, energy level, charge separation, and surface properties of different-sized In2S3 were characterized. The results showed that In2S3 synthesized in 10 min (In2S3-10) displayed optimal interface property for the electron-hole separation, maximum hydrophilia with most surface negative charges for the surface adsorption, contributing to the complete photodegradation of rhodamine B (RhB) in just 25 minutes of visible light illumination. The photodegradation path of RhB was speculated with four possible paths, including the processes of de-ethylation, open-ring of xanthene, and rupture of carbon-carbon bonds up to the decomposition into small molecules. Finally, the reusability of In2S3-10 was tested, obtaining nearly 96% photodegradation efficiency after sequential 5 cycles.

ß-Alanine enhancing the crosslink of chitosan/poly-(γ-glutamic acid) hydrogel for a potential alkaline-adapted wound dressing.

Tiny crosslink in chitosan (CS)/poly-(γ-glutamic acid) (γ-PGA) hydrogel leads to some disadvantages including low mechanical strength and high swelling. To enhance the crosslink of CS/γ-PGA hydrogel, amino acid (AA) was introduced to remove the drawbacks. The results indicated that AA can dramatically increase the crosslink and mechanical properties of CS/γ-PGA hydrogel, and AA chain length and concentration have a drastic effect on them. Particularly, 0.5 % ß-Alanine (ß-Ala) decreased the hydrogel by 70 % in porosity, 52 % in water solubility, and 30 % in swelling, but increased by 2.2-fold in elastic modulus, 2.08-fold in stress, and 1.53-fold in water retention. The porosity of the hydrogel correlates positively with the elastic modulus but negatively with the crosslinking degree. The effect of pH on CS/ß-Ala/γ-PGA hydrogel was investigated in the load and release of benzalkonium chlorides (BAC). ß-Ala strengthened pH response of the hydrogel in BAC load and release. The loading capacity increased with pH value, and 0.5 % ß-Ala increased the hydrogel by 1.25-fold in the release capacity in alkaline environment, suggesting a good buffering effect of ß-Ala on pH variation to accelerate the transportation of BAC. CS/ß-Ala/γ-PGA hydrogel will be competently applied as a potential material for wound dressing in alkaline environment.

Dendrobium officinale Enzyme Changing the Structure and Behaviors of Chitosan/γ-poly(glutamic acid) Hydrogel for Potential Skin Care.

Hydrogels have been widespreadly used in various fields. But weak toughness has limited their further applications. In this study, Dendrobium officinale enzyme (DOE) was explored to improve chitosan/γ-poly(glutamic acid) (CS/γ-PGA) hydrogel in the structure and properties. The results indicated that DOE with various sizes of ingredients can make multiple noncovalent crosslinks with the skeleton network of CS/γ-PGA, significantly changing the self-assembly of CS/γ-PGA/DOE hydrogel to form regular protuberance nanostructures, which exhibits stronger toughness and better behaviors for skin care. Particularly, 4% DOE enhanced the toughness of CS/γ-PGA/DOE hydrogel, increasing it by 116%. Meanwhile, water absorption, antioxygenation, antibacterial behavior and air permeability were increased by 39%, 97%, 27% and 52%.

Preparation of pH-sensitive carboxymethyl cellulose/chitosan/alginate hydrogel beads with reticulated shell structure to deliver Bacillus subtilis natto.

pH-sensitive hydrogels have been applied in delivering probiotics and drugs. However, pH sensitivity has been found to be contradictory with structural stability in hydrogel preparation. In this work, a novel strategy based on two systems of sodium carboxymethyl cellulose (CMC)/chitosan (CS) and sodium alginate (SA)/calcium chloride was designed to construct a reticulated shell structure stable for 3 h in simulated gastric fluid (pH 1.2) but began to break up at 2 h in simulated intestinal fluid (pH 6.8), exhibiting obvious pH sensitivity. The embedding rate of Bacillus subtilis natto reached to 67.3%, and the sustained release lasted for more than 10 h. It is implicated that the reticulated shell structure has harmoniously balanced the two incompatible properties of pH sensitivity and sustained release of CMC/CS/SA beads.

Harnessing digital imaging to detect the transmittance coupled with the uniformity of transparent optical materials.

A digital image (DI) method is reported to determine the transmittance and the uniformity of transparent optical materials (TOMs) at the same time, in which an objective image (OI) with a two dimensional (2D) entropy of 3.45 is scanned using a scanner with a black background. The OI pictures covered without and with a TOM went through gamma correction and color correction. The two corrected pictures were transformed into two matrixes, between which the transparency ratio and the correlation coefficient refer to the transmittance and the uniformity of TOMs. As a result, a p-value of 0.97 and an r value of 0.92 were achieved from the paired T-test between the DI method and the ultraviolet spectrometry (UVS) method, indicating a similar accuracy in determining the transmittance of TOMs between them. In addition, the DI method is a simple and rapid method to evaluate the uniformity of TOMs and to reveal the correlation among transmittance, uniformity and thickness of TOMs, particularly applicable for inhomogeneous TOMs.

A rapid and rapid method to quantify poly (γ-glutamic acid) content via copper ion complexation.

Presently, there have been some limitations in most of methods to determine poly (γ-glutamic acid) (γ-PGA) content because of many impurities in test specimens. It is necessary to establish a rapid and accurate method to quantify γ-PGA content. In this work, γ-PGA and some impurities commonly seen in fermented broth like glucose, glutamic acid and proteins were used to complex with copper ions. The results show that only γ-PGA can make copper ion precipitated, which content linearly correlates with the precipitate amount. From the study on the validity of the method, it is found that the accuracy and precision are 95.82% and 99.29%, much higher than the ones of method UV and weighing. Therefore, the method via the complexation of copper ion will be popularized to determine γ-PGA content in crude biological samples.

Co-Production of Nattokinase and Poly (γ-Glutamic Acid) Under Solid-State Fermentation Using Soybean and Rice Husk

ABSTRACTThe aim of this work was to study the co-production of nattokinase and poly (γ-glutamic acid) by Bacillus subtilis natto with soybean and rice husk under solid-state fermentation (SSF). The results showed that the size of soybean particle and rice husk significantly improved the co-production of nattokinase and poly (γ-glutamic acid), yielding 2503.4 IU/gs and 320 mg/gs, respectively in the improved culture medium composed of 16.7% soybean flour and 13.3% rice husk with 70% water content. The yields increased by approximate 7- and 2-fold factor relative to their original ones. Thus, the co-production of nattokinase and poly (γ-glutamic acid) under SSF could be considered as an efficient method to exploit agro-residues for economical production of some higher-value products.

Influence of Photoactive Layer Structure on Device Performance of Poly(2-methoxy-5-(2-ethylhexyloxy)- 1,4-phenylene vinylene)-CuInS2/ZnO Solar Cells.

This paper reported ternary MEH-PPV-CuInS2/ZnO solar cells, which were fabricated with the mixture of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and CuInS2 quantum dots (QDs) as photovoltaic layer and ZnO nanorod arrays (ZnO-NAs) as electron acceptor. The effects of photoactive layer structure (e.g., the change of spinning rate, thermal annealing temperature, annealing order and annealing method) on device performance are observed, and devices are measured by steady current-voltage (J-V) curve under the monochromic illumination at 470 nm. Results showed that the spinning rate of photoactive layer at 2000 rpm obtained the optimum thickness, moreover, solvent annealing firstly then the deposition of the positive electrode, finally thermal annealing at 140 degrees C contributing to the better reorganization for polymer and CuInS2 QDs to form the more stable phase-segregated state in the photovoltaic layer in the MEH-PPV-CuInS2/ZnO-NAs solar cells, obtaining the maximum power conversion efficiency of 2.54% under the monochromic illumination at 470 nm.

Tunable Device Parameters of Polymer/CulnS2 Solar Cells Depending on CulnS2 Quantum Dot Size.

This paper reports tunable device parameters of polymer/CuInS2 solar cells depending on CulnS2 quantum dot size, for the first time. The CuInS2 quantum dots (CuInS2-QDs) of tunable sizes displayed size-dependent band gaps, following by the size-dependent morphologies and optical properties in MEH-PPV-CuInS2 composites. Polymer/CulnS2 solar cells with poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) as polymer exhibited tunable device parameters depending on CuInS2-QDs size, resulting in a maximum power conversion efficiency of ca. 0.12% under the monochromic illumination at 470 nm in the device with the small-sized CuInS2-QDs. The origins for size-dependent performance in the solar cells are elucidated, which suggests that the higher short circuit current (Jsc) in the MEH-PPV/CuInS2 device with the small-sized QDs may due to the increased MEH-PPV/CuInS2 interface areas, while the higher open circuit voltage (Voc) may result from the higher energy difference between the conduction band position (Ec) of CuInS2-QDs and the highest occupied molecular orbital (HOMO) of the polymer. In particular, it is found that the device Voc is linearly dependent on the energy difference between Ec of CuInS2-QDs and HOMO of the polymer.

Solution-processed solar cells based on inorganic bulk heterojunctions with evident hole contribution to photocurrent generation.

To develop solution-processed and novel device structures is of great importance for achieving advanced and low-cost solar cells. In this paper, we report the solution-processed solar cells based on inorganic bulk heterojunctions (BHJs) featuring a bulk crystalline Sb2S3 absorbing layer interdigitated with a TiO2 nanoarray as an electron transporter. A solution-processed amorphous-to-crystalline transformation strategy is used for the preparation of Sb2S3/TiO2-BHJs. Steady-state and dynamic results demonstrate that the crystalline structure in the Sb2S3 absorbing layer is crucial for efficient devices, and a better Sb2S3 crystallization favors a higher device performance by increasing the charge collection efficiency for a higher short-circuit current, due to reduced interfacial and bulk charge recombinations, and enhancing the open-circuit voltage and fill factor with the reduced defect states in the Sb2S3 layer as well. Moreover, an evident contribution to photocurrent generation from the photogenerated holes in the Sb2S3 layer is revealed by experimental and simulated dynamic data. These results imply a kind of potential non-excitonic BHJ for energy conversion.

[Preparation and spectral analysis of coordination compounds of chitosan with Ce(III), Zr(IV), Pb(II) and Cd(II)].

Coordination compounds of chistosan (CTS) with Ce(III), Zr(IV), Pb(II) and Cd(II) (M-CTS) were prepared, which were synthesized by the reaction of CTS with cerium nitrate, zirconium nitrate, cadmium sulfate, and lead nitrate in acid systems. The coordination compounds were characterized by infrared spectrum (IR), X-ray diffraction spectrum (XRD) and X-ray photoelectron spectrum (XPS). The results showed that the N atom in amidogen of CTS coordinates with Cd in the coordination compounds of Cd-CTS, while in the coordination compounds of Ce-CTS, Zr-CTS and Pb-CTS, the N atom in amidogen and O atom in hydroxyl of CTS participate in the coordination reaction. It is suggested that the coordination bonds are different with the change of heavy metal ions.

Effects of amino acids on crystal growth of CaC2O4 in reverse microemulsion.

Crystal growth of calcium oxalate (CaC2O4) in bulk aqueous solution, reverse microemulsion of p-octyl polyethylene glycol phenylether (OP)/iso-octyl alcohol (IOA)/cydohexane/water and above microemulsions containing different kinds of amino acids, such as aspartic acid (Asp), tyrosine (Tyr) and tryptophan (Trp) were studied. The results indicated that different crystallization types of the crystals, which were calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD) and calcium oxalate trihydrate (COT), existed in bulk aqueous solution. But CaC2O4 growth mainly paralleled with (1 01) plane of COM in reverse microemulsion because of the induction of surfactant at water/oil interface. After adding amino acids into microemulsions, the growth of CaC2O4 crystals mainly influenced by the varieties of amino acids and the pH values of the amino acid aqueous solution. When pH values of the solutions was higher than isoelectric points of amino acids, CaC2O4 crystal paralleled with (1 01) plane of COM more easily with the addition of Trp, Tyr, Asp in turn; however, when pH of the solutions was lower than isoelectric points of Trp, CaC2O4 crystal growth paralleled with (020) face of COM. It is obviously that amino acids, pH values of the solutions and surfactant played important roles in the process of crystal growth of CaC2O4 in the microemulsions. The formation mechanism of CaC2O4 was also discussed in different microemulsions at last.