The green, ultrafine cellulose-based porous nanofibrous membranes for efficient heavy metal ion removal through incorporation of chitosan by various electrospinning ways

The rapid global industrialization worsens the contamination of heavy metals in aquatic ecosystems on the earth. In this study, the green, ultrafine cellulose-based porous nanofibrous membranes for efficient heavy metal removal through incorporation of chitosan by the conventional and core-shell electrospinning ways were firstly obtained. The relations among parameters of electrospun solution, micro-morphology and porosity for nanofibers, the variation of chemical active sites and adsorption performance of biocomposite nanofibrous membranes for conventional and core-shell electrospinning as well as the adsorption effect factors of copper ions including initial concentration, pH of solution and interaction time were comprehensively investigated. The results show that the average diameter for conventional and core-shell ultrafine nanofibers at 50% chitosan and 30% chitosan loading can achieve 56.22 nm and 37.28 nm, respectively. The core-shell cellulose acetate/chitosan (CA/CS) biocomposite nanofibrous membranes induced the surface aggregation of copper ions to impede the further adsorption. The more uniform distribution for chemical adsorption sites can be obtained by the conventional single-nozzle electrospinning than by the core-shell one, which promotes the adsorption performance of copper ions and decreases the surface shrinkage of nanofibrous membranes during adsorption. The 30% CS conventional nanofibrous membranes at the pH=5 aqueous solution showed the optimum adsorption capacity of copper ions (86.4 mg/g). The smart combination of renewable biomass with effective chemical adsorptive sites, the electrospinning technology with interwoven porous structure and the adsorption method with low cost and facile operation shows a promising prospect for water treatment.

Electrospun Nanofibrous Membranes Based on Citric Acid-Functionalized Chitosan Containing rGO-TEPA with Potential Application in Wound Dressings

The present research work is focused on the design and investigation of electrospun composite membranes based on citric acid-functionalized chitosan (CsA) containing reduced graphene oxide-tetraethylene pentamine (CsA/rGO-TEPA) as materials with opportune bio-properties for applications in wound dressings. The covalent functionalization of chitosan (CS) with citric acid (CA) was achieved through the EDC/NHS coupling system and was checked by 1H-NMR spectroscopy and FTIR spectrometry. The mixtures to be electrospun were formulated by adding three concentrations of rGO-TEPA into the 1/1 (w/w) CsA/poly (ethylene oxide) (PEO) solution. The effect of rGO-TEPA concentration on the morphology, wettability, thermal stability, cytocompatibility, cytotoxicity, and anti-biofilm activity of the nanofibrous membranes was extensively investigated. FTIR and Raman results confirmed the covalent and non-covalent interactions that appeared between the system’s compounds, and the exfoliation of rGO-TEPA sheets within the CsA in the presence of PEO (CsA/P) polymer matrix, respectively. SEM analysis emphasized the nanofibrous architecture of membranes and the presence of rGO-TEPA sheets entrapped into the CsA nanofiber structure. The MTT cellular viability assay showed a good cytocompatibility with the highest level of cell development and proliferation registered for the CsA/P composite nanofibrous membrane with 0.250 wt.% rGO-TEPA. The designed nanofibrous membranes could have potential applications in wound dressings, given that they showed a good anti-biofilm activity against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacterial strains.

Electrospun Polycaprolactone (PCL)-Amnion Nanofibrous Membrane Promotes Nerve Repair after Neurolysis

Peripheral nerve adhesion after neurolysis leads to nerve dysfunction, limiting nerve regeneration and functional recovery. We previously developed an electrospun polycaprolactone (PCL)-amnion nanofibrous membrane for preventing adhesion formation. In this study, we investigated the effect of protective nerve wrapping and promoting nerve regeneration in a rat sciatic nerve compression model. A total of 96 SD rats after sciatic nerve chronic compression were randomly divided into three groups: the PCL-amniotic group, in which nerves were wrapped with a PCL-amniotic membrane for treatment; the chitosan group, in which nerves were wrapped with a clinically used chitosan hydrogel; the control group, which involved neurolysis alone without treatment. Twelve weeks postoperatively, the nerve regeneration was evaluated by general and ultrastructure observation, as well as the expressions of neuronal regeneration and inflammatory reaction biomarkers. The nerve functions were assessed with gastrocnemius muscle measurement, hot-plate test, and walking track analysis. Compared with the chitosan hydrogel, the PCL-amnion nanofibrous membrane significantly reduced peripheral nerve adhesion and promoted nerve regeneration. The morphological properties of axons in the nerve wrap group were preserved. Intraneural macrophage invasion, as assessed by the number of CD68-positive cells, was less severe in the PCL-amnion group than in the other groups. Additionally, the gastrocnemius muscle weight and muscle bundle area were significantly higher in the PCL-amnion group than those in the chitosan group. The abilities of sense and movement of the rats in the PCL-amnion group were significantly improved compared to the other groups. In summary, electrospun PCL-amnion nanofibrous membranes effectively prevented post-neurolysis peripheral nerves from developing adhesion, whereas promoted nerve repair and regeneration, which make PCL-amnion nanofibrous membranes a promising biomaterial for clinical application.