Hu Tang

A facile and efficient strategy for the fabrication of porous linseed gum/cellulose superabsorbent hydrogels for water conservation

The linseed gum/cellulose composite hydrogels were successfully fabricated by mixing cellulose and linseed gum solutions dissolved in the NaOH/urea aqueous system and cross-linked with epichlorohydrin. The morphology and structure of the composite hydrogels were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD) and thermogravimetric analysis (TGA). The swelling ratio and water retention properties were investigated. The results revealed that linseed gum mainly contributed to water adsorption, whereas the cellulose acted as a backbone to strengthen the porous structure. This work provided a simple way to prepare cellulose-based superabsorbent hydrogels, which could be potentially applied as an effective water conservation material in agriculture.

Removal of methyl orange from aqueous solutions by adsorption on cellulose hydrogel assisted with Fe2O3 nanoparticles

Cellulose hydrogel, fabricated from cellulose solution in an LiOH/urea aqueous system at low temperature, was successfully applied for in situ synthesis of Fe2O3 nanoparticles to obtain hybrid magnetic nanomaterials. The microporous structure of cellulose hydrogel at wet state provided reaction chambers to synthesize the Fe2O3 nanoparticles. The structure and properties of the magnetic cellulose/Fe2O3 hydrogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, magnetic detection, thermal analysis, etc. The results revealed that the magnetic cellulose/Fe2O3 hydrogels exhibited efficient adsorption of methyl orange in the aqueous solution as a result of the microporous structure, large surface area, and affinity for organic dyes. The equilibrium process was described well by the Langmuir isotherm model, showing a monolayer adsorption. From kinetic experiments, the adsorption process followed the pseudo-second-order kinetic model, indicating that the overall rate of dye uptake could be controlled by external mass transfer at the beginning of adsorption, while intra-particle diffusion controlled the overall rate of adsorption at a later stage. This work provided an attractive adsorbent for removing hazardous materials from wastewater.

Cellulose Anionic Hydrogels Based on Cellulose Nanofibers As Natural Stimulants for Seed Germination and Seedling Growth

Cellulose anionic hydrogels were successfully prepared by dissolving TEMPO-oxidized cellulose nanofibers in NaOH/urea aqueous solution and being cross-linked with epichlorohydrin. The hydrogels exhibited microporous structure and high hydrophilicity, which contribute to the excellent water absorption property. The growth indexes, including the germination rate, root length, shoot length, fresh weight, and dry weight of the seedlings, were investigated. The results showed that cellulose anionic hydrogels with suitable carboxylate contents as plant growth regulators could be beneficial for seed germination and growth. Moreover, they presented preferable antifungal activity during the breeding and growth of the sesame seed breeding. Thus, the cellulose anionic hydrogels with suitable carboxylate contents could be applied as soilless culture mediums for plant growth. This research provided a simple and effective method for the fabrication of cellulose anionic hydrogel and evaluated its application in agriculture.

A novel candidate for wound dressing: Transparent porous maghemite/cellulose nanocomposite membranes with controlled release of doxorubicin from a simple approach

The aim of this study is to develop transparent maghemite/cellulose nanocomposite membranes with high porosity, high adsorption capacity and controlled release of doxorubicin to be used as a candidate for wound dressing. The membranes were fabricated by a tape casting method through blending a homogeneous dispersion of citrate coated maghemite nanoparticles and cellulose in the NaOH/urea aqueous solution system. The prepared membranes were characterized by Light transmittance measurements, Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray Diffractometry (XRD), Differential scanning calorimetry (DSC), Tensile tests and Vibrating sample magnetometer (VSM). Furthermore, porosity, swelling behavior, water loss ratio and Bovine serum albumin adsorption capacity were evaluated. Drug loading and release was investigated using doxorubicin hydrochloride as a model drug. In vitro cytotoxicity and cells morphology assays of cells growth and proliferation were also studied. This study served as a demonstration of the feasibility of maghemite/cellulose nanocomposite membranes for loading and release of bioactive compounds as a candidate for wound dressing.

Fabrication of cellulose nanowhiskers reinforced chitosan-xylan nanocomposite films with antibacterial and antioxidant activities

Antibacterial and antioxidant chitosan-xylan/cellulose nanowhiskers (CNW) nanocomposite films were successfully prepared using CNW as nanofillers. The structure and morphology of the nanocomposite films were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The optical transmittance, thermal stability, mechanical property, and swelling property of the nanocomposite films were also evaluated. These results revealed the microstructure of the films and confirmed the good miscibility between chitosan-xylan and CNW. The improvements of tensile strength and elongation at break of the nanocomposite films confirmed the reinforcement effects of CNW. Moreover, the inhibitory effects against S. aureus and E. coli and the ABTS+ scavenging activity indicated antibacterial and antioxidant functions of the nanocomposite films. In this work, the prepared chitosan-xylan/CNW nanocomposite films, combined the antibacterial property of chitosan, the antioxidant property of xylan, and good mechanical property of CNW, could be potentially applied in food and health-related areas.

Cellulose-Based Composite Macrogels from Cellulose Fiber and Cellulose Nanofiber as Intestine Delivery Vehicles for Probiotics

Cellulose-based composite macrogels made by cellulose fiber/cellulose nanofiber (CCNM) were used as an intestine delivery vehicle for probiotics. Cellulose nanofiber (CNF) was prepared by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation system, and the carboxyl groups in CNF acted as pore size and pH responsibility regulators in CCNMs to regulate the probiotics loading and controlled release property. The macrogel presented a porosity of 92.68% with a CNF content of 90%, and the corresponding released viable Lactobacillus plantarum (L. plantarum) was up to 2.68 × 108 cfu/mL. The porous structure and high porosity benefited L. plantarum cells to infiltrate into the core of macrogels. In addition, the macrogels made with high contents of CNF showed sustainable release of L. plantarum cells and delivered enough viable cells to the desired region of intestine tracts. The porous cellulose macrogels prepared by a green and environmental friendly method show potential in the application of fabricating targeted delivery vehicles of bioactive agents.

Development of poly (lactic acid) microspheres and their potential application in Pickering emulsions stabilization

The aim of the present work was to study the feasibility of fabricating poly (lactic acid) (PLA) microspheres stabilized Pickering emulsions. For this purpose, the PLA microspheres were first prepared by oil-water emulsion solvent evaporation method. The effects of preparation conditions such as hydrophilic-lipophilic balance (HLB) value, emulsifier concentration, oil-water ratio and preparation temperature were evaluated by using optical microscopy. Besides, orthogonal experiments were designed to investigate the influence of preparation parameters on average diameter and uniformity, include stirring time, stirring speed, and PLA and polyvinyl alcohol (PVA) concentrations. Based on the analysis of orthogonal experimental results, an optimal level of parameters was defined for the fabrication of PLA microspheres. Furthermore, these microspheres were applied to the stabilization of Pickering emulsions, and the optimal Pickering emulsion with uniform microstructure was obtained through the adjustment of PLA microspheres concentrations. This study opens up a promising way for producing PLA microspheres stabilized Pickering emulsions.

A cationic conjugated polymer and graphene oxide: Application to amplified fluorescence detection of sinapine

An amplified fluorescence strategy is described for the detection of sinapine (SP) by using a cationic conjugated polymer (PFP) and graphene oxide (GO). It is observed that the fluorescein (FAM)-labeled single-stranded DNA (FAM-DNA) is absorbed on the surface of GO if SP is absent. This causes that fluorescence resonance energy transfer (FRET) from PFP to FAM is inefficient when adding PFP into FAM-DNA/GO complex. If SP is added to FAM-DNA/GO complex, FAM-DNA is desorbed from GO surface due to the competitive binding of SP and FAM-DNA toward GO. In this case, FAM-DNA is close to PFP in the presence of PFP through strong electrostatic interaction, leading to the occurrence of efficient FRET. Based on the above phenomenon, we demonstrate a method to amplify fluorescence signal of traditional GO-based SP assay by introducing PFP. In comparison to the use of single GO, the combination of PFP with GO-based strategy displays high turn-on ratio and enhanced sensitivity with a limit of detection as low as 7.3 ng mL-1 for SP detection. Satisfactory results in practical samples are also obtained by the recovery experiments, demonstrating the potential application of cationic conjugated polymer in plant-derived small molecule.

Novel amphiphilic polyvinylpyrrolidone functionalized silicone particles as carrier for low-cost lipase immobilization

The high catalytic activity, specificity and stability of immobilized lipase have been attracting great interest. How to reduce the cost of support materials has always been a hot topic in this field. Herein, for the development of low-cost immobilized lipase, we demonstrate an amphiphilic polyvinylpyrrolidone (PVP) grafted on silicone particle (SP) surface materials (SP-PVP) with a rational design based on interfacial activation and solution polymerization. Meanwhile, hydrophilic pristine SP and hydrophobic polystyrene-corded silicone particles (SP-Pst) were also prepared for lipase immobilization. SP-PVP was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermogravimetry. Our results indicated that the lipase loading amount on the SP-PVP composites was about 215 mg of protein per gram. In the activity assay, the immobilized lipase SP-PVP@CRL exhibited higher catalysis activity and better thermostability and reusability than SP@CRL and SP-Pst@CRL. The immobilized lipase retained more than 54% of its initial activity after 10 times of re-use and approximately trended to a steady rate in the following cycles. By introducing the interesting amphiphilic polymer to this cheap and easily obtained SP surface, the relative performance of the immobilized lipase can be significantly improved, facilitating interactions between the low-cost support materials and lipase.

Candida rugosa lipase covalently immobilized on facilely-synthesized carbon nitride nanosheets as a novel biocatalyst

The immobilization of lipase on solid supports provides a significant improvement to the stability and reusability of lipase. During immobilization, the restricted surface area and inferior separation capacity of matrix materials are crucial for obtaining high-quality immobilized lipase. Carbon nitride nanosheets (C3N4-NS) as a type of two-dimensional nanomaterial have attracted various attentions for their prominent 2D planar nanostructure, characteristic surface area, thermostability and biocompatibility. Herein, we report a rational design and fabrication of immobilized Candida rugosa lipase based on carbon nitride nanosheets (C3N4-NS) as the matrix. The synthetic C3N4-NS are characterized by transmission electron microscopy, Brunauer–Emmett–Teller gas sorptometry measurement, X-ray powder diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. These results show that C3N4-NS possess an as-expected two-dimensional nanostructure with a large surface area of 74.374 m2 g−1. In addition, we chose glutaraldehyde-assisted covalent attachment to combine C3N4-NS and Candida rugosa lipase (CRL) via amino groups at the margins of C3N4-NS. The as-constructed immobilized lipase (C3N4-NS@CRL) exhibits satisfactory enzyme-loading (44.76 mg g−1), pH-flexibility, thermostability (after 180 min at 50 °C, 67% of the initial activity remained) and recyclability (after 10 runs, 72% of the initial activity remained). When compared with the free CRL, all experimental data indicate that C3N4-NS@CRL exhibited improved stability and enhanced practicability. To our knowledge, this is the first report of the application of carbon nitride nanosheets to enzyme immobilization.