TiO2/rectorite-trapped cellulose composite nanofibrous mats for multiple heavy metal adsorption.

The anthropogenic release of highly toxic heavy metals into the environment presents a huge challenge for ecosystems and human society. Recoverable and efficient adsorption materials could be obtained by trapping inorganic adsorbents (e.g., TiO2 nanoparticles and rectorite (REC)), in a natural polymer matrix. In this study, a series of cellulose-TiO2/REC composite nanofibrous mats were fabricated via electrospinning. The interactions between inorganic adsorbents and cellulose molecules improved the thermal stability, surface area, tensile strength and adsorption capacity of the mats. We focused on the adsorption of Pb2+, Cu2+ and Cd2+ from acidic solutions onto cellulose-TiO2/REC composite nanofibrous mats in multiple systems because the magnitudes of heavy metal concentrations in wastewater typically varied. The maximum total adsorption capacity of 69.81 mg/g was obtained by Cellulose-TiO2/REC2:1 nanofibrous mats. The composite nanofibrous mats successfully trapped TiO2 nanoparticles, and the obtained cellulose-TiO2/REC nanofibrous mats could be used to remove heavy metals from acidic wastewater.

Chitosan/silk fibroin modified nanofibrous patches with mesenchymal stem cells prevent heart remodeling post-myocardial infarction in rats.

Poor functional survival of the engrafted stem cells limits the therapeutic efficacy of stem-cell-based therapy for myocardial infarction (MI). Cardiac patch-based system for cardiac repair has emerged as a potential regenerative strategy for MI. This study aimed to design a cardiac patch to improve the retention of the engrafted stem cells and provide mechanical scaffold for preventing the ventricular remodeling post-MI. The patches were fabricated with electrospinning cellulose nanofibers modified with chitosan/silk fibroin (CS/SF) multilayers via layer-by-layer (LBL) coating technology. The patches engineered with adipose tissue-derived mesenchymal stem cells (AD-MSCs) (cell nano-patch) were adhered to the epicardium of the infarcted region in rat hearts. Bioluminescence imaging (BLI) revealed higher cell viability in the cell nano-patch group compared with the intra-myocardial injection group. Echocardiography demonstrated less ventricular remodeling in cell nano-patch group, with a decrease in the left ventricular end-diastolic volume and left ventricular end-systolic volume compared with the control group. Additionally, left ventricular ejection fraction and fractional shortening were elevated after cell nano-patch treatment compared with the control group. Histopathological staining demonstrated that cardiac fibrosis and apoptosis were attenuated, while local neovascularization was promoted in the cell nano-patch group. Western blot analysis illustrated that the expression of biomarkers for myocardial fibrosis (TGF-ß1, P-smad3 and Smad3) and ventricular remodeling (BNP, ß-MHC: α-MHC ratio) were decreased in cell nano patch-treated hearts. This study suggests that CS/SF-modified nanofibrous patches promote the functional survival of engrafted AD-MSCs and restrain ventricular remodeling post-MI through attenuating myocardial fibrosis. STATEMENT OF SIGNIFICANCE: First, the nanofibrous patches fabricated from the electrospun cellulose nanofibers could mimic the natural extracellular matrix (ECM) of hearts to improve the microenvironment post-MI and provide three dimensional (3D) scaffolds for the engrafted AD-MSCs. Second, CS and SF which have exhibited excellent properties in previous tissue engineering research, such as nontoxicity, biodegradability, anti-inflammatory, strong hydrophilic nature, high cohesive strength, and intrinsic antibacterial properties further optimized the biocompatibility of the nanofibrous patches via LBL modification. Finally, the study revealed that beneficial microenvironment and biomimetic ECM improve the retention and viability of the engrafted AD-MSCs and the mechanical action of the cell nano-patches for the expanding ventricular post-MI leads to suppression of HF progression by inhibition of ventricular remodeling.

Polyethylenimine/silk fibroin multilayers deposited nanofibrics for cell culture.

Scaffold with good three-dimensional (3D) structure and appropriate surface modification is essential to tissue regeneration in the treatment of tissue or organ failure. Silk fibroin (SF) is a promising scaffolding material with high biocompatibility, cytocompatibility, biodegradability and flexibility. In this study, positively charged polyethylenimine (PEI) and negatively charged SF assembled alternately onto cellulose nanofibrous substrates hydrolyzed from electrospun cellulose acetate nanofibrous mats. The obtained nanofibrous membranes modified with multiple layers of PEI/SF were characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. L929 cells were applied to examine the cytocompatibility of PEI/SF coated membranes. The results demonstrated that the nanofibrous membranes after modification with multiple layers of PEI/SF maintained 3D nanofibrous structure, and cells cultured on them showed good adherence and spreading on them as well, which indicated that PEI/SF coated membranes had potential application in tissue engineering.

Controllable immobilization of naringinase on electrospun cellulose acetate nanofibers and their application to juice debittering.

Electrospinning is a facile method to fabricate nanofibers, in terms of their high specific surface area and porous structure. Electrospun nanofibrous mats are excellent candidates for immobilization of enzymes. In this study, a simple route based on electrospinning and layer-by-layer (LBL) self-assembly processes has been developed to prepared naringinase/alginate multilayer coated electrospun cellulose acetate nanofibers. The content of immobilized naringinase could be tuned by adjusting the number of multilayers. XPS results indicated that naringinase was successfully immobilized on cellulose acetate nanofibers. SEM images showed the nanofibers maintain their sharp but became rougher after multilayer coating. Besides, the surface area of electrospun cellulose acetate nanofibers decreased and mesopores reduced. The major bitter components of grapefruit juice are naringin and limonin, naringin could be slightly removed by hydrolysis with naringinase and limonin might be removed by adsorption with cellulose acetate nanofibers.

Production of thick uniform-coating films containing rectorite on nanofibers through the use of an automated coating machine.

When an efficient automated coating machine is used to process layer-by-layer (LBL) deposited nanofibrous mats, it causes an obvious planar effect on the surface of the mats, which can be eliminated through ultimate immersion. During this process, chitosan (CS) - rectorite (REC) intercalated composite films are built on the surface of cellulose acetate (CA) nanofibrous mats by a coating machine. Then, the immersion process is utilized to allow positively charged CS or CS-REC intercalated composites to uniformly assemble on the surface of negatively charged CA nanofibers. An investigation into the morphology of the resultant scaffolds confirms that the uniquely small pore size, high specific surface area and typically three-dimensional (3D) structure of nanofibrous mats remain present. The results of Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) indicate that it is feasible to assemble nanofibrous mats using a coating machine. The intercalated structure of CS-REC is confirmed by the results of small-angle X-ray diffraction (SAXRD) and wide-angle X-ray diffraction (WAXRD). The results of the cell experiment and antibacterial test demonstrate that the addition of REC not only has little impact on the cytocompatibility of the mats but also enhances their ability to inhibit bacteria.

Regulating the gaps between folds on the surface of silk fibroin membranes via LBL deposition for improving their biomedical properties.

Silk fibroin (SF) has become a promising biomaterial in guided bone regeneration (GBR). In an attempt to modify the size of the gaps on the surface of SF barrier membrane and improve its antibacterial activity, biological and mechanical properties, positively charged Lysozyme (LY)-Collagen Type-I (COL) composites and negatively charged SF were introduced to the negatively charged surface of SF substrates utilizing the electrostatic layer-by-layer (LBL) self-assembly technique. The morphology, chemical structures and element content of the LBL structured membranes were investigated. The results suggested that LY and COL were successfully assembled and the gaps between the folds on the surface of the membranes became smaller gradually with the increase of coated film numbers. Besides, the content of ß-sheets of the membranes increased after deposition, which indicated the improvement of their mechanical properties. Moreover, the results of the measurement of immobilized LY and antibacterial assay not only revealed that the enzymatic catalysis and antibacterial activity of the samples enhanced with the increase of coated bilayer numbers but also implied that LBL modified membranes had better antibacterial activity when LY-COL was on the outermost layer. Furthermore, CCK-8 assay certified both SF membrane and LBL structured membranes could facilitate cell growth and proliferation, and the introduction of COL could further promote this ability. Finally, cell attachment and morphology examination provided intuitional evidence that SF membrane and LBL modified membranes have excellent biocompatibility.

Pectin/lysozyme bilayers layer-by-layer deposited cellulose nanofibrous mats for antibacterial application.

Positively charged lysozyme (LZ) and negatively charged pectin, were alternately deposited on the surface of the cellulose nanofibrous mats by layer-by-layer (LBL) self-assembly technique. Scanning electron microscopy images showed that the nanofibers were orderly and compactly arrayed after LBL. Besides, as the number of LZ/pectin bilayers increased, the average diameter of nanofibers increased. LZ has assembled on the cellulose mats successfully, which was confirmed by X-ray photoelectron spectroscopy analysis. Thermal gravimetric analysis results showed that the thermal properties of LZ/pectin films coated mats was better than that of the unmodified cellulose mats. Importantly, the results of the bacterial inhibition test for LBL structured mats and cellulose mats indicated that the nanofibrous mats coated by 10.5 LZ/pectin bilayers (with LZ on the outmost layer) possessed the strongest inhibitory effect against both Escherichia coli and Staphylococcus aureus.

Plasma treated polyethylene terephthalate/polypropylene films assembled with chitosan and various preservatives for antimicrobial food packaging.

In this study, polyethylene terephthalate/polypropylene (PET/PP) films were treated via atmospheric pressure plasma, assembled with chitosan and various preservatives and applied for antimicrobial food packaging. Surface properties of these obtained films were studied by contact angle measurement, atomic force microscopy (ATM), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR) and dynamic laser scattering (DLS). The above results showed that the surface hydrophilicity and roughness of the films increased after the plasma treatment. Besides, chitosan and the preservatives were successfully assembled onto the surface of the films. In addition, the antimicrobial activities of the films against three kinds of microorganisms (Staphylococcus aureus, Bacillus subtilis and Escherichia coli) were investigated and the results indicated that the inhibition ratios against B. subtilis and E. coli reached almost 100% while the inhibition ratios against S. aureus were lower than 85%. Moreover, the accumulative release profiles of the antimicrobial substances migrating from the assembled films into the release solutions revealed that their release speed increased with the increment of temperature and acidity, but decreased with enhancing the ionic strength regulated by sodium chloride or with lowering the ionic mobility regulated by sucrose.

Layer-by-layer immobilized catalase on electrospun nanofibrous mats protects against oxidative stress induced by hydrogen peroxide.

Catalase, a kind of redox enzyme and generally recognized as an efficient agent for protecting cells against hydrogen peroxide (H2O2)-induced cytotoxicity. The immobilization of catalase was accomplished by depositing the positively charged chitosan and the negatively charged catalase on electrospun cellulose nanofibrous mats through electrospining and layer-by-layer (LBL) techniques. The morphology obtained from Field emission scanning electron microscopy (FE-SEM) indicated that more orderly arranged three-dimension (3D) structure and roughness formed with increasing the number of coating bilayers. Besides, the enzyme-immobilized nanofibrous mats were found with high enzyme loading and activity, moreover, X-ray photoelectron spectroscopy (XPS) results further demonstrated the successful immobilization of chitosan and catalase on cellulose nanofibers support. Furthermore, we evaluated the cytotoxicity induced by hydrogen peroxide in the Human umbilical vascular endothelial cells with or without pretreatment of nanofibrous mats by MTT assay, LDH activity and Flow cytometric evaluation, and confirmed the pronounced hydrogen peroxide-induced toxicity, but pretreatment of immobilized catalase reduced the cytotoxicity and protected cells against hydrogen peroxide-induced cytotoxic effects which were further demonstrated by scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM) images. The data pointed toward a role of catalase-immobilized nanofibrous mats in protecting cells against hydrogen peroxide-induced cellular damage and their potential application in biomedical field.