Lingyun Chen

Construction of PANI–cellulose composite fibers with good antistatic properties

For the first time, novel polyaniline (PANI)–cellulose filament fibers have been successfully spun from hydrophobic PANI and hydrophilic cellulose complex solution dissolved in aqueous containing 7 wt% NaOH/12 wt% urea as the solvent by wet-spinning. The composite fibers had a circular cross-section and homogenous surface structure, as a result of good miscibility between PANI and cellulose associated through hydrogen bonds. Moreover, at low PANI content, the composite fibers realized a transition from an insulator to a semiconductor. This work has provided a simple and eco-friendly avenue for the production of PANI composite fibers that have great potential applications in the antistatic textile and military industries.

Fabrication and characterization of novel assembled prolamin protein nanofabrics with improved stability, mechanical property and release profiles

In spite of the numerous advantages of natural polymer nanofibers as biomedical materials, they are suffering due to their poor water resistance and tensile strength which largely restrict their applications. Here, we present a novel assembled protein nanofabric prepared by incorporating compact zein nanoparticles into electrospun hordein networks. The effects of zein content on the structure, morphology and properties of assembled protein fibers were investigated in detail. The results revealed that zein particles were well dispersed in hordein networks while maintaining their compact structures, which in one aspect acted as the plasticizer to decrease the strong hydrogen bonding interactions among extended hordein molecules, leading to the accelerated continuous electrospinning and narrowed diameter distribution of composite fibers. In another, hydrophobic zein nanoparticles also acted as the reinforcing filler in the flexible hordein matrix. The fibers with a zein content of 30 wt% exhibited the stable assembled network structure and significantly improved tensile strength and wet stability in both water and ethanol. The release experiment indicated that such fibers with a 3D porous structure could serve as the carrier for controlled release of incorporated bioactive compounds into phosphate-buffered saline (PBS). In addition, they were stable in simulated gastric fluid and pepsin resistant, whereas they could be digested in a simulated intestinal environment to gradually release the incorporated compounds where they are normally absorbed. These fibers also demonstrated low toxicity in both human colon carcinoma (Caco-2) and primary epidermal keratinocyte (NHEK) cell cultures. Therefore, the novel assembled fabrics showed promise as a three-dimensional delivery vehicle of bioactive compounds for wound healing and food industry applications.

Wood cellulose-based polyelectrolyte complex nanoparticles as protein carriers

Novel wood cellulose-based polyelectrolyte complex nanoparticles were prepared by mixing negatively charged carboxymethyl cellulose (CMC) and positively charged quaternized cellulose (QC) in aqueous medium. As observed by transmission electron microscopy (TEM), the CMC–QC nanoparticles were approximately spherical and dispersed homogeneously. The impacts of CMC and QC concentration, as well as encapsulation of bovine serum albumin (BSA), on nanoparticle size, surface charge and cytotoxicity, were investigated. CMC–QC nanoparticles displayed high encapsulation efficiency for BSA, and their particle size and zeta potential could be modulated by adjusting either CMC or QC concentration. BSA-encapsulated CMC–QC nanoparticles had significantly decreased particle size and surface charge in comparison to BSA-free nanoparticles. Even at a relatively high concentration, the optimized CMC–QC nanoparticles exhibited low cytotoxicity as well as significant BSA cellular uptake in Caco-2 cells. The encapsulated BSA could be steadily released from CMC–QC nanoparticles within the first 8 h. The novel CMC–QC nanoparticles show promise as protein delivery systems.

Hydrogel particles and other novel protein-based methods for food ingredient and nutraceutical delivery systems

Abstract: Biopolymer hydrogels have gained considerable attention in recent years as one of the most promising delivery systems for food ingredients and nutraceuticals. In this chapter, an attempt is made to review the state of the art of food grade polysaccharide- and protein-based hydrogels over past decades. Several approaches have been used in the way to prepare and engineer the hydrogel matrix, which can be classified in two major groups of physical and chemical crosslinking. Regardless of the type of biopolymer composed, the release mechanism of the loaded compounds from hydrogels is complex, while mainly resulting from three vectors: via diffusion, swelling followed by diffusion, and degradation. Various stimuli-responsive hydrogels developed from polysaccharides, proteins and their derivatives are also introduced, which can deform quickly and reversibly under environmental stimuli. Finally, the applications of biopolymer hydrogels in food science, i.e. delivery of antioxidants, bioactive peptides and probiotics, are highlighted.

Fabrication of flexible self-standing all-cellulose nanofibrous composite membranes for virus removal

All-cellulose nanocomposite membranes with excellent performance were successfully fabricated as novel filtration system to remove nanoparticles and virus from aqueous medium. These membranes were composed of two combined layers: an electrospun cellulose nanofabric layer treated by hot-pressing to provide mechanical support and a coating of regenerated cellulose gel with tiny inter-connected pores as barrier. Hot-pressing did not affect the fiber shape of electrospun nanofabrics, but significantly improved their mechanical properties due to increased hydrogen bonds. The regenerated cellulose gel formed a porous coating that tightly attached to electrospun nanofabrics, and its pore size varied depending on cellulose source, solution concentration, and drying process. By assembling these two layers together, the nanocomposite membranes showed the notable retention of negatively charged 100 nm latex beads (99.30%). Moreover, the electronegative nature of cellulose membranes imparted the rejection ratio of 100% and (98.68 ± 0.71)% against positively charged 50 nm latex beads and Hepatitis C Virus, respectively.

Highly specific capacitance materials constructed via in situ synthesis of polyaniline in a cellulose matrix for supercapacitors

On the basis of the requirements for both biobased economy and energy storage materials, we are interested in using cellulose-based microporous film as a template for in situ synthesis of polyaniline (PANI). Multifunctional carbon nanotube (CNT)/cellulose composite films were also prepared from a CNT/cellulose suspension in a NaOH/urea aqueous system. Subsequently, PANI was synthesized in situ in the pores of cellulose and CNT/cellulose substrates to construct PANI/cellulose (PC) films and PANI/CNT/cellulose (PCC) films, respectively. Both PC and PCC films were flexible and exhibited a highly specific capacitance and good cycle stability. With the addition of CNTs, the specific capacitance of the PCC films as supercapacitor materials was significantly improved. Moreover, a homogeneous structure intertwined with the cellulose, CNTs and PANI appeared in the composite films, indicating good miscibility. This work has provided a new approach to the fabrication of flexible, lightweight, highly effective, and low-cost energy storage materials, broadening the applications of cellulose.

Enhanced emulsifying properties of wood-based cellulose nanocrystals as Pickering emulsion stabilizer

Cellulose nanocrystals are hydrophilic nanomaterials, which limits their applications as interfacial compounds. Herein, we propose using modified wood-based cellulose nanocrystals as Pickering emulsion stabilizer. Wood cellulose was consecutively oxidized and modified with phenyltrimethylammonium chloride to create hydrophobic domains comprised of phenyl groups. These modified oxidized cellulose nanocrystals (m-O-CNCs) were homogeneous/electrostatically stable in water and they can stabilize O/W Pickering emulsions. The dispersed phase volume fraction (DPVF) of the Pickering emulsion was 0.7 at around 1.5g/L, whereas the tween-20 control needed a 13-fold greater concentration to have a similar DPVR. In addition, these m-O-CNC stabilized Pickering emulsions also showed good mechanical and thermal stability against centrifugation and heat, as well as size controllability. In terms of stability, size controllability, surfactant-free status, these m-O-CNCs possess superior and enhanced emulsifying properties. Future research for these new interfacial materials have potential in applications, for personal care, cosmetic and pharmaceutic industries.

Cellulose-based polyelectrolyte complex nanoparticles for DNA vaccine delivery

Cellulose-based nanoparticles were prepared from oppositely charged carboxymethyl cellulose (CMC) and quaternized cellulose (QC) in an aqueous medium. The DNA complexing capacity of CMC-QC nanoparticles and the transfection efficiency of the DNA-loaded nanoparticles in COS-7 cells were first investigated using pEGFP-N1-a plasmid DNA encoding the enhanced green fluorescent protein (EGFP)-as a model, and then with a candidate DNA vaccine, pMASIA-tPAs-tE2.2, that has been developed against infection with bovine viral diarrhea virus (BVDV). The results revealed that CMC-QC nanoparticles could bind DNA efficiently, and the optimized DNA-loaded nanoparticles mediated very effective transfection in COS-7 cells, which was comparable to that achieved with Lipofectamine 2000. The novel CMC-QC nanoparticles show promise as a delivery system for DNA vaccines.

Fabrication of ultrathin conductive protein-based fibrous films and their thermal sensing properties

For the first time, ultrathin polypyrrole/protein fibrous films have been successfully fabricated by polymerizing pyrrole onto three-dimensional electrospun hordein network surfaces at a low temperature. The nanostructured polypyrrole is rooted on the surface of protein microfibers like “taste buds”. Such modification not only eliminated the issue of protein shrinkage in the liquid medium, but also significantly improved the films mechanical strength and wettability. The ultrathin fibrous films exhibited a “metallic” character, and could effectively respond to temperature changes, and thus have potential to be used as flexible materials for sensors and electronic devices.

Rapid dissolution of spruce cellulose in H2SO4 aqueous solution at low temperature

Dissolution of cellulose is the key challenge in its applications. It has been discovered that spruce cellulose with high molecular weight (4.10xa0×xa0105xa0gxa0mol−1) can be dissolved in 64xa0wt% H2SO4 aqueous solution at low temperature within 2xa0min, and the cellulose concentration in solution can reach as high as 5xa0% (w/v). FT-IR spectra and XRD spectra proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The cold H2SO4 aqueous solution broke the hydrogen bonds among cellulose molecules and the low temperature dramatically slowed down the hydrolysis, which led to the dissolution of cellulose. The resultant cellulose solution was relatively stable, and the molecular weight of cellulose only slightly decreased after storage at −20xa0°C for 1xa0h. Due to the high molecular weight of cellulose, cellulose solution could form regenerated films with good mechanical properties and transparency at low concentration (2xa0% w/v). This work has not only provided the new evidence of cellulose dissolution which facilitated the development of cellulose solvent, but also suggested a convenient way to directly transfer cellulose with high molecular weight into materials without structure modifications.