Chitin Whiskers Research Articles

Enzymatic Degradation of Nanosized Chitin Whiskers with Different Degrees of Deacetylation.

In order to study the relationship between the degree of deacetylation of chitin whiskers (CHWs) and their enzymatic degradation properties, in this paper, CHWs were first deacetylated to different degrees by alkali treatment, and the CHWs with the degrees of deacetylation of 17.84, 67.76, and 82.54% was obtained, respectively. Moreover, the partially deacetylated CHWs still maintained good crystallinity and nanoneedle-like morphology. Next, the in vitro degradation behavior of CHWs with different degrees of deacetylation was further studied under the single or synergistic action of lysozyme and lipase (37 °C, pH = 7.4). The results showed that the morphology change of CHWs was more obvious as the degree of deacetylation increased. The mass loss, the crystallinity index at the (110) crystal plane, and the concentration of reducing sugar of the CHWs also increased with the degree of deacetylation. Moreover, the synergistic effect of the two enzymes was more conducive to the degradation process of CHWs than single lysozyme or lipase. The difference in the rate of enzymatic degradation provides an idea for the regulation of the degradation rate of the CHWs.

Effect of exfoliating agent on rheological behavior of β-chitin fibrils in aqueous suspensions and on mechanical properties of poly(acrylic acid)/β-chitin composites

Chitin whiskers are promising reinforcing filler for composites due to their mechanical properties, renewable nature and low cost. A new method for preparation of β-chitin fibrils from squid pens in ascorbic acid aqueous solutions (AscA) was developed. Stirring of the solution with 2 g/l AscA for 2 h disperses the swollen chitin to individualized fibrils with an aspect ratio > 250. The optimal conditions of β-chitin exfoliation in acrylic acid (AcrA) aqueous solution were found (0.75–2 g/l, 3–4 h). TEMPO-oxidized β-chitin fibrils were chosen as a reference sample for comparison of different methods. 0.1% chitin suspensions exfoliated in AscA and AcrA solutions show similar gel-like behavior with a storage modulus (G′) of 98 ± 23 and 34 ± 12 Pa, respectively, whereas G′ of 0.1% dispersion of the TEMPO-oxidized β-chitin fibrils was 0.015 ± 0.005 Pa only. Composites based on poly(acrylic acid) comprising 1–3 wt% of β-chitin fibrils were fabricated by polymerization filling. Mechanical properties of the composites were investigated in dry state in the temperature range of 25–250 °C and at controlled relative humidity in the range from 53.6% to 100%. It was revealed that the maximum reinforcing effect is achieved at high temperature (>120 °C) and high relative humidity (≥75.3%RH).

Morphological, barrier and mechanical properties of films from poly (butylene succinate) reinforced with nanocrystalline cellulose and chitin whiskers using melt extrusion

Nanocomposites from biodegradable poly (butylene succinate) (PBS), blended with nanofillers chitin whiskers (CHW, 1–5%) and nanocrystalline cellulose (NCC, 1–5%), were synthesized using melt extrusion. Morphological studies using transmission electron microscopy showed the dispersion of nanofillers in the polymer matrix. The nanofillers restricted the mobility of polymer chains, and promoted nucleation and recrystallization of polymer as reflected by increase in degree of crystallinity (Xc) from 65.9 to 75.6%. Addition of NCC and CHW increased the tensile strength of PBS based films from 23.2 MPa to 32.9 MPa and 43.6 MPa, respectively. Decrease in oxygen transmission rate of PBS films from 737.7 to 280 cc/m2/day was observed by adding 3% NCC, which further reduced to 23.8 cc/m2/day by adding compatibilizer methylene diphenyl diisocyanate (MDI, 4%). Water vapor transmission rate of PBS films reduced from 83.8 to 49.4 g/m2/day with 3% NCC addition and addition of 4% MDI further reduced it to 30.8 g/m2/day. This research suggested potential of NCC and CHW as nanofillers for enhancement of mechanical and barrier properties of PBS based films used in biodegradable food packaging applications.

Synergistic effect of functionalized poly(l-lactide) with surface-modified MgO and chitin whiskers on osteogenesis in vivo and in vitro

Favorable cytocompatibility and osteogenesis potential are critical for the development of a bone repair material. In this study, two types of surface-modified whiskers, grafted magnesia and chitin (g-MgO and g-CHN) whiskers, were synthesized and introduced into a poly(l-lactide) (PLLA) matrix singly or together to prepare PLLA/g-MgO/g-CHN composite films and bone nails via injection molding. On the account of the synergetic contribution of g-MgO and g-CHN whiskers, the enhanced cell adhesion, spreading, proliferation of mouse embryo osteoblast precursor (MC3T3-E1) cells, as well as the alteration of cell-cycle and inhibition of cell apoptosis, were observed on PLLA/g-MgO/g-CHN film as compared to pure PLLA, PLLA/g-MgO and PLLA/g-CHN films. More importantly, the highest level of the secretion of ALP and the formation of calcium deposition, accompanied with expression of osteogenesis genes (ALP, Runx-2, COL I, OCN) in vitro were obtained for the PLLA/g-MgO/g-CHN film among all of the material groups. Additionally, the PLLA and PLLA composite bone nails were implanted in rabbits' femurs and new bone formation was detected on PLLA/g-MgO/g-CHN group after 16 weeks of implantation by 3D reconstruction of micro-CT and histological analyses. Besides, the bending strength of defected bone repaired by PLLA/g-MgO/g-CHN bone nail was high to 48 MPa, which was far stronger than other bone nail groups. Overall, this study demonstrated the addition of g-MgO and g-CHN whiskers together in PLLA matrix played a synergistic promoting role in cell affinity and osteogenic differentiation, and the developed PLLA/g-MgO/g-CHN composites hold great potential in fields of bone repair.

Investigation of Carmine Dye Removal by Green Chitin Nanowhiskers Adsorbent

A green adsorbent was evaluated to remove the carmine dye. Chitin nanowhiskers were synthesized via acid hydrolyzed method. The diameter of the synthesized chitin whiskers was about 20 nm and had 200 to 400 nm length. The morphology and chemical structure of the synthesized adsorbent were investigated by Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FT-IR), X- Ray Diffraction (XRD). The adsorption process parameters of the carmine dye removal were optimized as follow: adsorption time (3 h), initial carmine dye solution concentration (100 ppm), mass loaded of the chitin whiskers suspension 1% weight of chitin nanowhiskers, as an adsorbent (1.4 g). The removal efficiency of the carmine dye adsorption was about 85% which is modified 15% better than the previous researches. The results indicated that carmine dye molecules were absorbed by hydrogen bonding mechanism due to the N-H bond in the chitin nanowhiskers structure.

Synergistic Effect of Surface-Modified MgO and Chitin Whiskers on the Hydrolytic Degradation Behavior of Injection Molding Poly(l-lactic acid).

To regulate the degradation behavior of poly(l-lactic acid) (PLLA) for its use as a bone internal fixation material, surface grafted magnesium oxide and chitin whiskers (g-MgOs and g-CHNs) were added to PLLA in combination or separately via injection molding in this study. The as-prepared binary or ternary composites were degraded in vitro in PBS solution with a pH value of 7.4 at 37.5 °C. The variations in mass, pH value, surface morphology, crystallization performance, melting behavior, and mechanical properties of the samples during the degradation course were systemically considered. The results revealed that the g-MgOs accelerated the early degradation of the composite, while the g-CHNs played a regulatory role in the later degradation of the composite. Simultaneously adding g-MgOs and g-CHNs can maintain the mechanical properties of the composite at an early stage but promote the degradation of the composite at a later stage, which suggests that the degradation behavior of the PLLA matrix could be regulated to some extent. This tunable degradation behavior of the g-MgOs/g-CHNs/PLLA composite is conducive to its application as a bone internal fixation implant.

Well-ordered chitin whiskers layer with high stability on the surface of poly(d,l-lactide) film for enhancing mechanical and osteogenic properties

In order to better utilize and combine the advantages of poly(d,l-lactide) (PDLLA) matrix and natural polysaccharide chitin whiskers (CHWs), needle-like CHWs with chiral nematic liquid crystal characteristics and remarkable moduli were chosen to surface modify PDLLA film. By a vertical coating method, a stable and well-ordered CHWs coating was formed on the surface of the PDLLA film through a polydopamine (PDA) interlayer. The high stability of the well-ordered CHWs coating on the surface of the PDLLA film was confirmed by PBS soaking experiment in terms of the changes of weight and surface morphology of the film. The surface microstructure and composition of the resulting PDLLA-PDA-CHWs film were characterized by field emission scanning electron microscopy (FESEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), and the thickness of the PDLLA, PDA and CHWs layers was determined using FESEM, too. Comparing with traditional PDLLA/CHWs film, prepared by solution blending with optimal content of 5 wt% CHWs, the hydrophilicity and mechanical properties of the PDLLA-PDA-CHWs film were significantly improved owing to the immobilization of a highly ordered CHWs coating. Furthermore, in vitro cell culture showed that the well-ordered CHWs coating had a more significant effect on promoting the adhesion, spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells. All these results showed that the resulting PDLLA-PDA-CHWs film with well-ordered CHWs coating designed through simple and effective approach has promising application in bone repair material field.

The liquid crystalline order, rheology and their correlation in chitin whiskers suspensions

To explore the concentration range of chitin whiskers (CHWs) aqueous suspensions with the liquid crystalline state, and the correlation between liquid crystalline characteristic and rheology of CHWs suspensions, the CHWs aqueous suspensions with different CHWs concentration, pH value, ionic strength and temperature were prepared. The liquid crystalline characteristic and rheological properties of the obtained suspensions were investigated by polarizing microscope and rotational rheometer. The results showed that the liquid crystalline state of the suspensions appeared at the CHWs concentration of 3.5 wt% and disappeared at 22.5 wt%. Increasing the CHWs concentration, pH value and ionic strength, the values of elastic modulus (Gʹ) and viscous modulus (Gʺ) increased, and the liquid crystal texture basically became more and more regular and obvious. Moreover, the value of Gʺ/Gʹ was always less than 1, suggesting the elastic behavior of CHWs aqueous suspension. Besides, the effect caused by heating on the elastic modulus was irreversible.

Adsorption Mechanism of Composite Whisker on Copper Ions and Lead Ions

A new kind of inorganic composite adsorbent based on chitin whiskers(CHW) and potassium tetratitanate whiskers(PTW) was synthesized via the thermal deposition to remove Cu2+ and Pb2+ from wastewater. CHW could be successfully coated on the surface of PTW when thermal treated 8 times. The adsorption process was better fitted with the Langmuir and Freundlich models. The adsorption process was more conformed to the Pseudo-second-order model. The results from XPS(X-ray photoelectron spectrum) further show that the adsorption mechanism between CHW-PTW and Cu2+, Pb2+ are both ion exchange and chemical adsorption. Thermodynamic parameters suggest that the adsorption processes are nonspontaneous. The adsorption of Cu2+ and Pb2+ is endothermic and exothermic, respectively.

Preparation of Chitin Whisker and Effect to Crystallization of Polylactide

The aim of this study was to investigate the effect of chitin whisker (CW) to the crystallization of polylactide (PLA) nanocomposite films. CW which obtained from acidolysis reaction was compounded with PLA pellets into nanocomposite films by cast film extrusion. The morphology and crystallinity of CW were observed by TEM and XRD, illustrated that the dimension of whisker was affected by hydrolysis time. Increasing of hydrolysis time, the length of whisker was more regular with narrower distribution. Moreover, the crystallinity of whisker was obviously increased after acid hydrolysis. The nanocomposite film showed rough surface compared to pure PLA film due to some agglomeration of nanoparticles. However, CW and PLA were well-mixed with no phase separation. The introduction of 0.1 phr of CW decrease cold-crystallization temperature (Tcc) from about 121 °C to 118 °C and also increase the degree of crystallinity around 10%. There was no difference of thermal transition temperature between pure PLA and nanocomposite films with the addition of CW more than 0.1 phr which inspected by DSC. Despite the transition temperature express insignificantly different, the degree of crystallinity of nanocomposite was increase, indicating that chitin whisker would induce the crystallinity of PLA.

Mechanical Behavior Optimization of Chitosan Extracted from Shrimp Shells as a Sustainable Material for Shopping Bags.

The use of biodegradable materials for shopping bag production, and other products made from plastics, has recently been an object of intense research—with the aim of reducing the environmental burdens given by conventional materials. Chitosan is a potential material because of its biocompatibility, degradability, and non-toxicity. It is a semi-natural biopolymeric material produced by the deacetylation of chitin, which is the second most abundant natural biopolymer (after cellulose). Chitin is found in the exoskeleton of insects, marine crustaceans, and the cell walls of certain fungi and algae. The raw materials most abundantly available are the shells of crab, shrimp, and prawn. Hence, in this study chitosan was selected as one of the main components of biodegradable materials used for shopping bag production. Firstly, chitin was extracted from shrimp shell waste and then converted to chitosan. The chitosan was next ground to a powder. Although, currently, polyethylene bags are prepared by blown extrusion, in this preliminary research the chitosan powder was dissolved in a solvent and the films were cast. Composite films with several fillers were used as a reinforcement at different dosages to optimize mechanical properties, which have been assessed using tensile tests. These results were compared with those of conventional polyethylene bags used in Egypt. Overall, the chitosan films were found to have a lower ductility but appeared to be strong enough to fulfill shopping bag functions. The addition of fillers, such as chitin whiskers and rice straw, enhanced the mechanical properties of chitosan films, while the addition of chitin worsened overall mechanical behavior.

Deformation of microfibrillated chitin film and composites

Composites of poly(acrylic acid) (PAA) and chitin whiskers were prepared using evaporation method. The weight fraction of chitin whiskers (CHW) was varied from 73 to 23%. Raman was utilised for the first time to monitor the deformation of chitin film and chitin-reinforced PAA composites. The Raman band located at 1622 cm−1 was monitored for deformation. On application of tensile force, the Raman band initially found at 1622 cm−1 corresponding to the single H-bonded amide one spectrum shifted towards a lower wavenumber. Raman band shift rates of − 1.85 cm−1/% for chitin film and − 0.25, − 0.59 and − 0.59 cm−1/% for 23, 43 and 73 wt% CHW whiskers, respectively, were obtained. The Young modulus of composites materials and whiskers were 37, 16 and 115 GPa, respectively, for a two-dimensional in-plane distribution of CHW. CHW within PAA did not show any preferential alignment. At high volume or weight of PAA or low weight CHW (3, 11% chitin) monitoring of the Raman peak shift was difficult.

Reinforcement of thermoplastic chitosan hydrogel using chitin whiskers optimized with response surface methodology

To strengthen the mechanical strength of thermo-sensitive hydroxybutyl chitosan (HBC) hydrogel, chitin whiskers were used as sticker to fabricate reinforced HBC (HBCW) hydrogel by using response surface methodology. Unlike the intrinsic network of HBC hydrogel, HBCW hydrogel showed a laminar shape with firm structure. The preparation condition was optimized by three-factor-three-level Box-Behnken design. The maximum mechanical strength (1011.11 Pa) was achieved at 50 °C, when the concentrations of HBC and chitin whiskers were 5.1 wt% and 2.0 wt%, respectively. The effects of temperature, pH value and NaCl concentration on mechanical strength of HBCW hydrogels were investigated via the oscillatory stress sweeps. The results showed that HBCW hydrogel could reach the maximum stiffness (∼1126 Pa) at 37 °C pH 12.0. Low pH and high salty ions could decrease the stability of hydrogel, while chitin whiskers could increase the stress tolerance and related ruptured strain of HBCW hydrogels.

Production and characterization of a nanocomposite of highly crystalline nanowhiskers from biologically extracted chitin in enzymatic poly(ε-caprolactone)

A nano-composite from biologically obtained chitin nanofillers homogenously dispersed in a poly(ε-caprolactone) matrix was successfully achieved by an ultrasonication-assisted non-toxic and non-aqueous methodology. For this purpose, biological chitin was obtained from lactic acid fermentation of shrimp wastes and converted into chitin whiskers by acidic hydrolysis in a novel process at low temperature (4°C) that enhanced the distribution and yield. Additionally, the polyester matrix was enzymatically produced in a non-toxic compressed fluid (1,1,1,2-tetrafluoroethane at 25bar and 65°C) medium. The homogeneous distribution of the nanofiller in the matrix was corroborated by confocal and atomic force microscopies. Films of the nanocomposite were physicochemically characterized to assess its adequate properties. Additionally, the qualitative viability of human fibroblasts and osteoblasts cells was studied on the produced nanocomposite films showing good biocompatibility.

Enhanced mechanical properties and gelling ability of gelatin hydrogels reinforced with chitin whiskers

Gelatin is widely used in the food industry because of its biocompatibility, nonimmunogenicity, and biodegradability. The small diameter, renewability, and low cost of chitin whiskers (CHWs), in addition to good biocompatibility and high stiffness, make them a very promising reinforcing nanofiller for composite materials. In this work, gelatin/CHW nanocomposite hydrogels containing various concentrations of CHWs (0.25–1.0%, w/v) were successfully fabricated. The gelling temperature, dynamic viscoelasticity, compression behavior, pH, and NaCl sensitivity of gelatin hydrogels were determined using dynamically rheological experiments and compression tests. The addition of the CHWs remarkably enhanced the mechanical properties and gelling ability of the gelatin. Scanning electronic microscope images revealed that the pores of the nanocomposite hydrogels containing CHWs were smaller than those of the pure gelatin hydrogels. Moreover, the gelatin nanocomposite hydrogels showed excellent resistance under conditions of strong alkalinity/acidity and high ionic strength. The results suggest that biocompatible gelatin/CHW nanocomposite hydrogels have potential applications in the food industries.

Characterisation of alpha-chitin/poly(acrylic acid) blend films

Chitin whiskers reinforced Poly(acrylicacid) films were prepared by casting. Films were characterised for mechanical and thermal properties. Raman and XRD spectrum and SEM morphology were examined. The tensile strength increased as chitin increases up to 11.39% and gradually decreases. The % strain gradually reduces as whiskers increases. Thermal stability of films improved from those of the pure PAA as the Tg increases at higher whiskers content. The strongest interaction between the carboxylic (CO) group of PAA and the amide (NH3+) of chitin at the amorphous phase occurs at 3.23% whiskers. The particle size of chitin was reduced as revealed by XRD.

Monitoring cell substrate interactions in exopolysaccharide-based films reinforced with chitin whiskers and starch nanoparticles used as cell substrates

ABSTRACTExopolysaccharides (EPS) extracted from Nostoc commune cyanobacteria were used to prepare low-adhesion cell substrates for tumor-selective cell growth. The substrates were reinforced with chitin whiskers and starch nanoparticles and characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and tensile tests. Two anchorage independent cells, green fluorescent protein-modified HeLa and THP-1 cells were seeded on the samples to assess their interaction with the composites. The results confirmed the cell–surface interaction of EPS-based composites. The mechanical properties of these films can be tailored by controlling the type and concentration of the reinforcement, which can be used in the design of different types of biomaterials.

Sericin-binded-deprotenized natural rubber film containing chitin whiskers as elasto-gel dressing

Here, we aims to demonstrate a simple concept in biomaterials design by using natural resources solely as raw materials to fabricate elastic wound care dressing. Elasto-gel films comprise of silk sericin (SRC), natural rubber (NR), and chitin whisker (CTW) were developed. A glue-like protein SRC found in silk cocoons is beneficial for the treatment of wounds due to its superior skin moisturizing ability. However, the pure SRC film is generally difficult to be fabricated because of its weak structural feature. This limitation was overcome by using NR as a binder which consecutively rendered elasticity and strength of the films. CTW was chosen as another component to promote ability of the films for tissue restoration. Before the film formation, protein in the natural rubber latex (NRL) was removed to avoid allergic and cytotoxic problems. The enzyme-treated NR/SRC (ETNR/SRC) films having different blend compositions were fabricated by solution casting technique. The highest amount of the SRC to gain an easy to handle ETNR/SRC film was 30%. The ETNR/SRC/CTW films having 20% SRC were fabricated and studied in comparison. Essential properties of the films as elastic wound care dressings were investigated and effect of the materials chemistry on the observed properties were discussed.

Separation of Lead with a Novel Ion Separating Agent Prepared by Clothing a Chitin Whisker on a Potassium Tetratitanate Whisker.

Separation of Pb2+ from Cu2+-Pb2+ mixed solution by a newly-developed ion separating agent was examined, which was obtained by clothing chitin whiskers (ChW) on the surface of potassium tetratitanate whiskers (PTW). The separation capability and mechanism of the ion separating agent (ChW-PTW) was determined, based on the difference of the adsorption isotherm pattern and the adsorption kinetics model between ChW and PTW on Cu2+ and Pb2+, respectively. The results showed that the adsorption process of ChW could be described by Freundlish isotherm. The adsorption affinity of Cu2+ (kF = 0.085·g−1) on ChW was greater than Pb2+ (kF = 0.077 g−1). The adsorption pattern of PTW was inclined to the Langmuir isotherm, and Pb2+ (kL = 310.59 L·mmol−1) could be obviously more easily adsorbed on PTW than Cu2+ (kL = 25.85 L·mmol−1). The experimental data both fitted well with the pseudo-second order kinetics. The reaction rate of Pb2+ (k2 = 4.442 for ChW and k2 = 0.846 for PTW) was greater than that of Cu2+ on both ChW and PTW, while the diffusion rate of intra-particles of PTW was much higher than ChW. The adsorption model of ChW and PTW could illustrate well the separation mechanism of ChW-PTW and allowed for relevant results.

Stable chitin whisker/Ag3PO4 composite photocatalyst with enhanced visible light induced photocatalytic activity

One-dimentional chitin whisker (ChW) was prepared by reflux method. Then, a novel composite material (ChW/Ag3PO4) was obtained by attaching Ag3PO4 nanoparticles on the surface of the ChW by simple chemical deposition. The photocatalytic activity and stability of the ChW/Ag3PO4 composite material for degradation of rhodamine B (RhB) showed obvious enhancement compared with that of pure Ag3PO4, attributing to the enhancement of visible-light absorption, the increase of active sites, the more effective separation between the photogenerated electrons and holes, and the faster transfer of photogenerated carriers.