Preparation of Nanocellulose Reinforced Chitosan Films, Cross-Linked by Adipic Acid.

Adipic acid, an abundant and nontoxic compound, was used to dissolve and cross-link chitosan. After the preparation of chitosan films through casting technique, the in situ amidation reaction was performed at 80-100 °C as verified by Fourier transform infrared (FT-IR). The reaction was accompanied by the release of water which was employed to investigate the reaction kinetics. Accordingly, the reaction rate followed the first-order model and Arrhenius equation, and the activation energy was calculated to be 18 kJ/mol. Furthermore, the mechanical properties of the chitosan films were comprehensively studied. First, optimal curing conditions (84 °C, 93 min) were introduced through a central composite design. In order to evaluate the effects of adipic acid, the mechanical properties of physically cross-linked (uncured), chemically cross-linked (cured), and uncross-linked (prepared by acetic acid) films were compared. The use of adipic acid improved the tensile strength of uncured and chemically cross-linked films more than 60% and 113%, respectively. Finally, the effect of cellulose nanofibrils (CNFs) on the mechanical performance of cured films, in the presence of glycerol as a plasticizer, was investigated. The plasticized chitosan films reinforced by 5 wt % CNFs showed superior properties as a promising material for the development of chitosan-based biomaterials.

Synthesis and Characterization of Novel Magnetic Nano-Biocomposite Hydrogels Based on Starch-g-poly(acrylic acid) Reinforced by Cellulose Nanofibers for Cu2+ Ion Removal.

One of the crucial challenges of the adsorption process is to recapture the adsorbent from the solution, especially for adsorbents in powder form. This study synthesized a novel magnetic nano-biocomposite hydrogel adsorbent to successfully remove Cu2+ ions, followed by convenient recovery and reusability of the adsorbent. The Cu2+ adsorption capacity of starch-g-poly(acrylic acid)/cellulose nanofibers (St-g-PAA/CNFs) composite hydrogel and magnetic composite hydrogel (M-St-g-PAA/CNFs) was investigated and compared in both bulk and powder forms. Results showed that Cu2+ removal kinetics and swelling rate were improved by grinding the bulk hydrogel into powder form. The kinetic data and adsorption isotherm were best correlated with the pseudo-second-order and Langmuir models, respectively. The maximum monolayer adsorption capacity values of M-St-g-PAA/CNFs hydrogels loaded with 2 and 8 wt % Fe3O4 nanoparticles in 600 mg/L Cu2+ solution were found to be 333.33 and 555.56 mg/g, respectively, compared to 322.58 mg/g for the St-g-PAA/CNFs hydrogel. Vibrating sample magnetometry (VSM) results demonstrate that the magnetic hydrogel that included 2 and 8 wt % magnetic nanoparticles exhibited paramagnetic behavior with the magnetization of 0.6-0.66 and 1-1.04 emu/g at the plateau, respectively, which showed a proper magnetic property and good magnetic attraction in the magnetic field for separating the adsorbent from the solution. Also, the synthesized compounds were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). Finally, the magnetic bioadsorbent was successfully regenerated and reused for four treatment cycles.

Osteogenic potential of PHB-lignin/cellulose nanofiber electrospun scaffold as a novel bone regeneration construct.

The electrospun scaffolds could mimic the highly hierarchical structure of extracellular matrix (ECM). Modern tissue engineering focuses on the properties of these microstructures, influencing the biological responses. This research investigates the variation of morphology, crystallinity, bioactivity, mechanical properties, contact angle, mass loss rate, roughness, cell behavior, biomineralization, and the efficacy of polyhydroxybutyrate (PHB)-based nanocomposite. Hence, 6 wt% lignin and 3 wt% cellulose nanofiber were added to the 9 wt% of PHB to prepare a novel electrospun nanocomposite structure (PLC). The outputs indicated more symmetrical circular fibers for PLC mat, higher surface roughness (326 to 389 nm), better hydrophilicity (120 to 60°), smaller crystal size (24 to 16 nm), and more reasonable biodegradability compared to PHB. These changes lead to the improvement of mechanical properties (toughness factor from 300 to 1100), cell behavior (viability from 60 to 100 %), bioactivity (from Ca/P ratio of 0.77 and 1.67), and higher level of alizarin red, and ALP enzyme secretion. Eventually, the osteopontin and alkaline phosphatase expression was also enhanced from ≃2.35 ± 0.15 and 2.1 ± 0.1 folds on the 1st day to ≃12.05 ± 0.35 and 7.95 ± 0.35 folds on 2nd week in PLCs. Accordingly, this newly developed structure could enhance biological responses and promote osteogenesis compared to PHB.

Plasma surface modification of electrospun polyhydroxybutyrate (PHB) nanofibers to investigate their performance in bone tissue engineering.

Polyhydroxybutyrate (PHB) is a natural-source biopolymer of the polyhydroxyalkanoate (PHA) family. Nanofibrous scaffolds prepared from this biological macromolecule have piqued the interest of researchers in recent years due to their unique properties. Nonetheless, these nanofibers continue to have problems such as low surface roughness and high hydrophobicity. In this research, PHB nanofibers were produced by the electrospinning method. Following that, the surface of nanofibers was modified by atmospheric plasma. Scanning electron microscopy (SEM), water contact angle (WCA), atomic force microscopy (AFM), tensile test, and cell behavior analyses were performed on mats to investigate the performance of treated and untreated samples. The achieved results showed a lower water contact angle (from ≃120° to 43°), appropriate degradation rate (up to ≃20 % weight loss in four months), and outstanding biomineralization (Ca/P ratio of ≃1.86) for the modified sample compared to the neat PHB. Finally, not only the MTT test show better viability of MG63 osteoblast cells, but also Alizarin staining, ALP, and SEM results likewise showed better cell proliferation in the presence of modified mats. These findings back up the claim that plasma surface modification is a quick, environmentally friendly, and low-cost way to improve the performance of nanofibers in bone tissue engineering.

Optimization and characterization of polyhydroxybutyrate/lignin electro-spun scaffolds for tissue engineering applications.

The tissue engineering scaffolds requires efficient combination of materials, appropriate method of preparation, and precise characterization of final product. In this study, the optimal electrospinning process conditions of polyhydroxybutyrate (PHB) were investigated by Taguchi design. Then, the initial PHB solution characteristics in the presence of lignin were optimized and then electro-spun. In this regard, the uniformity of electro-spun nanofibers, observed by SEM, confirmed that 9 w/v % is the optimum concentration of PHB in Trifluoro acetic acid. Addition of 6 wt% of lignin to PHB, could alleviate both the brittleness and hydrophobicity of PHB, as DSC, XRD, and WCA results indicated decrement in crystallinity (from 46 to 39 %), crystal size (from 21.8 to 15.2 nm), and WCA (from 118 to 73°). On the other hand, FESEM results represented diameter reduction from 1318 ± 202.07 to 442 ± 111.04 nm, and transformation of nanofiber physical structure from ribbon-like to cylindrical fiber by adding lignin. In addition, the mechanical properties of PHB including elongation at break, toughness, young modulus, and tensile strength were also improved (up to twice) by adding lignin. Ultimately, reviewing the outputs of degradation, bioactivity, MG63 cell viability, proliferation, mineralization, and antioxidant activity confirm that PHB/lignin electrospun scaffold has potential application in tissue engineering.

Effect of cellulose nanofibers on polyhydroxybutyrate electrospun scaffold for bone tissue engineering applications.

The choice of materials and preparation methods are the most important factors affecting the final characteristics of the scaffolds. In this study, cellulose nanofibers (CNFs) as a nano-additive reinforcer were selected to prepare a polyhydroxybutyrate (PHB) based nanocomposite mat. The PHB/CNF (PC) scaffold properties, created via the electrospinning method, were investigated and compared with pure PHB. The obtained results, in addition to a slight increment of crystallinity (from ≃46 to 53 %), showed better water contact angle (from ≃120 to 96°), appropriate degradation rate (up to ≃25 % weight loss in two months), prominent biomineralization (Ca/P ratio about 1.50), and ≃89 % increment in toughness factor of PC compare to the neat PHB. Moreover, the surface roughness as an affecting parameter on cell behavior was also increased up to ≃43 % in the presence of CNFs. Eventually, not only the MTT assay revealed better human osteoblast MG63 cell viability on PC samples, but also DAPI staining and SEM results confirmed the more plausible cell spreading in the presence of cellulose nano-additive. These improvements, along with the appropriate results of ALP and Alizarin red, authenticate that the newly PC nanocomposite composition has the required efficiency in the field of bone tissue engineering.

Development of a continuous fixed-bed column to eliminate cadmium(II) ions by starch-g-poly(acrylic acid)/cellulose nanofiber bio-nanocomposite hydrogel.

This paper presents an experimental study on continuous adsorptive removal of Cd2+ from the water body using a bio-nanocomposite hydrogel within a fixed-bed column (FBC) system. The bio-nanocomposite hydrogel was synthesized based on starch grafted poly(acrylic acid) (St-g-PAA) reinforced by cellulose nanofibers (CNFs). The effects of processing conditions including pH, flow rate, and initial concentration of Cd2+ on adsorption efficiency were examined. Based on the results, the highest removal efficiency was achieved to be 82.5% at pH of 5, initial concentration of 10 mg L-1, and flow rate of 5 mL min-1. Furthermore, by applying isotherm models, it was uncovered that the Langmuir isotherm model was the most appropriate one, and the maximum adsorption capacity was 40.65 mg g-1. Also, an adsorption process was carried out using the FBC system, and the outcome data were processed using Thomas and Yoon-Nelson models to find the characteristics of the column. In this study, the recovering capacity of the exhausted hydrogel was evaluated. Desorption process efficiencies of batch and continuous operations were obtained to be 91.9% and 90%, respectively.

Extraction and characterization of fungal chitin nanofibers from Mucor indicus cultured in optimized medium conditions.

Chitin nanofibers (ChNFs) were extracted from Mucor indicus by a purification method followed by a mechanical treatment, cultivated under obtained optimum culture medium conditions to improve fungal chitin production rate. A semi synthetic media containing 50 g/l glucose was used for cultivation of the fungus in shake flasks. The cell wall analysis showed that N-acetyl glucosamine (GlcNAc) content, which is an indication of chitin content, was maximum in presence of 2.5 g/l H3PO4, 2.5 g/l of NaOH, 1 g/l of yeast extract, 1 mg/l of plant hormones, and 1 ml/l of trace metals. The chemical characterizations demonstrated that the isolated fibers had a degree of deacetylation lower than of 10%, and were phosphate free. The FTIR results revealed successful removal of different materials during the purification step. The FE-SEM of fibrillated chitin illustrated an average diameter of 28 nm. Finally, X-ray diffraction results showed that the crystallinity index of nanofibers was 82%.

Facile strategy for improvement properties of whey protein isolate/walnut oil bio-packaging films: Using modified cellulose nanofibers.

This work aims to explore the addition impact of surface modified cellulose nanofibers (CNF) with poly (methyl methacrylate) (PMMA), CNF-g-PMMA, on the required properties of whey protein isolate (WPI)/walnut oil (WNO) films for packaging applications. WPI/WNO films containing 15 wt% WNO were selected for CNF incorporation. The addition effects of different quantities of unmodified and modified CNF (CNF and MCNF) on mechanical strength, fracture surface morphology, hydrophobicity, water vapor permeability (WVP), water uptake, and transparency of bionanocomposite films were studied. Fracture surface was observed by Scanning electron microscopy (SEM). The maximum ultimate tensile strength (UTS) was obtained to be 9 ±â€¯0.11 and 10.38 ±â€¯0.16 MPa, respectively, at 7.5 wt% of both CNF and MCNF. Compared with WPI/WNO unfilled films, while CNF increased the hydrophilicity of the films, MCNF resulted in more hydrophobic films. In addition, 51% and 64% improvement in water vapor barrier features of CNF and MCNF-loaded films was observed, respectively. The similar trend was occurred for the water uptake behavior. In the case of film transparency, MCNF-loaded films were opaque with 18.12% light transmittance (600 nm wavelength). Generally, WPI films including 15 wt% of WNO and 7.5 wt% MCNF shows promising potential as bio-packaging films.

Development of electrospun poly (vinyl alcohol)-based bionanocomposite scaffolds for bone tissue engineering.

The article is focused on the role of nanohydroxy apatite (nHAp) and cellulose nanofibers (CNFs) as fillers in the electrospun poly (vinyl alcohol) (ES-PVA) nanofibers for bone tissue engineering (TE). Fibrous scaffolds of PVA, PVA/nHAp (10 wt.%), and PVA/nHAp(10 wt.%)/CNF(3 wt.%) were successfully fabricated and characterized. Tensile test on electrospun PVA/nHAp10 and PVA/nHAp10/CNF3 revealed a three-fold and seven-fold increase in modulus compared with pure ES-PVA (45.45 ± 4.77). Although, nanofiller loading slightly reduced the porosity percentage, all scaffolds had porosity higher than 70%. In addition, contact angle test proved the great hydrophilicity of scaffolds. The presence of fillers reduced in vitro biodegradation rate in PBS while accelerates biomineralization in simulated body fluid (SBF). Furthermore, cell viability, cell attachment, and functional activity of osteoblast MG-63 cells were studied on scaffolds showing higher cellular activity for scaffolds with nanofillers. Generally, the obtained results confirm that the 3-componemnt fibrous scaffold of PVA/nHAp/CNF has promising potential in hard TE. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1111-1120, 2018.

Porous starch/cellulose nanofibers composite prepared by salt leaching technique for tissue engineering.

Starch/cellulose nanofibers composites with proper porosity pore size, mechanical strength, and biodegradability for cartilage tissue engineering have been reported in this study. The porous thermoplastic starch-based composites were prepared by combining film casting, salt leaching, and freeze drying methods. The diameter of 70% nanofibers was in the range of 40-90 nm. All samples had interconnected porous morphology; however an increase in pore interconnectivity was observed when the sodium chloride ratio was increased in the salt leaching. Scaffolds with the total porogen content of 70 wt% exhibited adequate mechanical properties for cartilage tissue engineering applications. The water uptake ratio of nanocomposites was remarkably enhanced by adding 10% cellulose nanofibers. The scaffolds were partially destroyed due to low in vitro degradation rate after more than 20 weeks. Cultivation of isolated rabbit chondrocytes on the fabricated scaffold proved that the incorporation of nanofibers in starch structure improves cell attachment and proliferation.

Parameter estimation and characterization of a single-chamber microbial fuel cell for dairy wastewater treatment.

In this study, for the first time, the conduction-based model is extended, and then combined with Genetic Algorithm to estimate the design parameters of a MFC treating dairy wastewater. The optimized parameters are, then, validated. The estimated half-saturation potential of -0.13 V (vs. SHE) is in good agreement while the biofilm conductivity of 8.76×10(-4) mS cm(-1) is three orders of magnitude lower than that previously-reported for pure-culture biofilm. Simulations show that the ohmic and concentration overpotentials contribute almost equally in dropping cell voltage in which the concentration film and biofilm conductivity comprise the main resistances, respectively. Thus, polarization analysis and determining the controlling steps will be possible through that developed extension. This study introduces a reliable method to estimate the design parameters of a particular MFC and to characterize it.

Single chamber microbial fuel cell with spiral anode for dairy wastewater treatment.

This study reports on the fabrication of a novel annular single chamber microbial fuel cell (ASCMFC) with spiral anode. The stainless steel mesh anode with graphite coating was used as anode. Dairy wastewater, containing complex organic matter, was used as substrate. ASCMFC had been operated for 450 h and results indicated a high open circuit voltage (about 810 mV) compared with previously published results. The maximum power density of 20.2 W/m(3) obtained in this study is significantly greater than the power densities reported in previous studies. Besides, a maximum coulombic efficiency of 26.87% with 91% COD removal was achieved. Good bacterial adhesion on the spiral anode is clearly shown in SEM micrographs. High power density and a successful performance in wastewater treatment in ASCMFC suggest it as a promising alternative to conventional MFCs for power generation and wastewater treatment. ASCMFC performance as a power generator was characterized based on polarization behavior and cell potentials.