Homogeneous Chitosan Research Articles

A comprehensive characterization of Hermetia illucens derived chitosan produced through homogeneous deacetylation

The increasing demand for chitin and chitosan is driving research to explore alternative sources to crustaceans. Insects, particularly bioconverters as Hermetia illucens, are promising substitutes as they process food industry waste into valuable molecules, including chitin. Chitosan can be produced by chitin deacetylation: hot deacetylation to obtain a heterogeneous chitosan, the commonly produced, and cold deacetylation to obtain a homogeneous chitosan, not widely available. The two different treatments lead to a different arrangement of the amine and acetyl groups in the chitosan structure, affecting its molecular weight, deacetylation degree, and biological activity. This is the first report on the production and chemical-physical and biological characterization of homogenous chitosan derived from H. illucens larvae, pupal exuviae, and adults. This work, in addition to the report on heterogeneous chitosan by our research group, completes the overview of H. illucens chitosan. The yield values obtained for homogeneous chitosan from pupal exuviae (3 and 7 %) are in the range of insect (2–8 %) and crustaceans (4–15 %) chitosan. The evaluation of the antioxidant activity and antimicrobial properties against Gram-negative (Escherichia coli) and Gram-positive (Micrococcus flavus) bacteria confirmed the great versatility of H. illucens chitosan for biomedical and industrial applications and its suitability as an alternative source to crustaceans.

Development of films based on chitosan, gelatin and collagen extracted from bocachico scales (Prochilodus magdalenae)

Biodegradable biopolymers from species of the animal kingdom or their byproducts are sustainable as ecological materials due to their abundant supply and compatibility with the environment. The research aims to obtain a biodegradable active material from chitosan, gelatin, and collagen from bocachico scales (Prochilodus magdalenae). Regarding the methodology, films were developed from gelatin, chitosan, and collagen from bocachico scales (Prochilodus magdalenae) at different concentrations using glycerol as a plasticizer and citric acid as a cross-linker. The films were obtained with the hydrated mass processed by compression molding and characterized according to humidity, water solubility, contact angle, mechanical properties, and structural properties. The results of the films showed a hydrophobic characteristic. First, the chitosan-collagen (CS/CO) films showed a yellowish color, while the gelatin-collagen (Gel/CO) films were transparent and less soluble than the gelatin-collagen (Gel/CO) films. Concerning mechanical properties, gelatin films showed higher stiffness and tensile strength than chitosan films. Furthermore, in the morphological analysis, more homogeneous chitosan films were obtained by increasing the concentration of citric acid. In general, chitosan, gelatin, and collagen extracted from the scales of the bocachico (Prochilodus magdalenae) are an alternative in the application of films in the food industry.

Antimicrobial and wound healing potential of naphthoquinones encapsulated in nanochitosan.

Introduction: The use of chitosan in pharmaceutical formulations is an advantageous approach due to this compound intrinsic biodegradability and biocompatibility, as well as ready availability and low polymer cost. Methods: Herein, the naphthoquinones 3- chloromethylene-menadione (NQ1) and 2,3-dichloro-1,4-naphthoquinone (NQ2) were nanoencapsulated into chitosan (CNP) by the ionotropic gelatinization technique and characterized by DLS, FTIR, SEM, TGA and DSC, and their release profiles evaluated. The antimicrobial and wound healing activities were investigated. Results and Discussion: Homogeneous chitosan nanocapsulses of about 193nm and Z potential ranging from +30.6 to +33.1mV loaded with NQ1 (CNP-NQ1) or NQ2 (CNPQNQ2). With nanoencapsulation efficiencies of ≥ 96%, the solubility of naphthoquinones in aqueous environments was improved, making them suitable for biological system applications. The encapsulated naphthoquinones displayed a controlled release of approximately 80% for CNP-NQ1 and 90% for CNP-NQ2 over an 8h period at 36°C. Both CNP-NQ1 and CNP-NQ2 retained the already established free naphthoquinone antimicrobial activity against two Staphylococcus aureus strains, Staphylococcus epidermidis, Streptococcus pyogenes and Pseudomonas aeruginosa. Although presenting low toxicity to healthy human cells, only CNP-NQ1 displayed therapeutic indices above 100 for S. aureus and S. epidermidis and above 27 for S. pyogenes and P. aeruginosa, allowing for safe use in human tissues. Furthermore, CNP-NQ1 did not impair the migration of human fibroblast cells in scratch assays, adding promising wound healing properties to this formulation. These findings emphasize that CNP-NQ1 may be useful in protecting injured skin tissue from bacterial contamination, avoiding skin infections not only by reducing bacterial loads but also by accelerating the healing process until complete dermal tissue recovery.

Preliminary investigation on the effect of insect-based chitosan on preservation of coated fresh cherry tomatoes

Chitosan was produced from Hermetia illucens pupal exuviae by heterogeneous and homogeneous deacetylation. Tomato fruits (Solanum lycopersicum), that are one of the most grown and consumed food throughout the world, were coated with 0.5 and 1% chitosan, applied by dipping or spraying, and stored at room temperature or 4 °C, for a storage period of 30 days. Statistical analysis give different results depending on the analysed parameters: heterogeneous chitosan, indeed, had a better effect than the homogenous one in maintaining more stable physico-chemical parameters, while the homogenous chitosan improved the total phenols, flavonoids and antioxidant activity. Chitosan coatings applied by spraying were more effective in all the analyses. Chitosan derived from H. illucens always performed similarly to the commercial chitosan. However, a general better performance of insect-derived chitosan on the concentration of phenolics and flavonoids, and the antioxidant activity was observed as compared to the commercial one. Chitosan coating has already been successfully used for preservation of fresh fruits, as alternative to synthetic polymers, but this is the first investigation of chitosan produced from an insect for this application. These preliminary results are encouraging regarding the validation of the insect H. illucens as a source of chitosan.

Effects of shell-thickness on the powder morphology, magnetic behavior and stability of the chitosan-coated Fe3O4 nanoparticles

Chitosan-coated Fe3O4 nanoparticles were prepared by coprecipitation followed by reaction with chitosan and different volumes of glutaraldehyde. Coating was modified by varying the volume of glutaraldehyde and reaction time. XRD pattern shows maxima compatible Fe3O4 structure. FTIR spectroscopía confirms the presence of chitosan, more evident in samples with higher chitosan content, as denoted by TGA. TEM images of samples with low glutaraldehyde content reveal particles coated with a homogeneous chitosan shell. Meanwhile, those prepared with high glutaraldehyde volume show nanoparticles dispersed in an organic matrix. Samples present almost superparamagnetic behavior with magnetization saturation values that are reduced as the content of organic matter increases. Regarding the stability of these samples in solution, the presence of a homogeneous coating improves the initial suspension, although it does not prevent its subsequent aggregation over time. However, this aggregation process is reduced for sample synthesized with 1mL of glutaraldehyde after 6h of reaction.

Chitosan-GPTMS-Silica Hybrid Mesoporous Aerogels for Bone Tissue Engineering.

This study introduces a new synthesis route for obtaining homogeneous chitosan (CS)-silica hybrid aerogels with CS contents up to 10 wt%, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as coupling agent, for tissue engineering applications. Aerogels were obtained using the sol-gel process followed by CO2 supercritical drying, resulting in samples with bulk densities ranging from 0.17 g/cm3 to 0.38 g/cm3. The textural analysis by N2-physisorption revealed an interconnected mesopore network with decreasing specific surface areas (1230–700 m2/g) and pore sizes (11.1–8.7 nm) by increasing GPTMS content (2–4 molar ratio GPTMS:CS monomer). In addition, samples exhibited extremely fast swelling by spontaneous capillary imbibition in PBS solution, presenting swelling capacities from 1.75 to 3.75. The formation of a covalent crosslinked hybrid structure was suggested by FTIR and confirmed by an increase of four hundred fold or more in the compressive strength up to 96 MPa. Instead, samples synthesized without GPTMS fractured at only 0.10–0.26 MPa, revealing a week structure consisted in interpenetrated polymer networks. The aerogels presented bioactivity in simulated body fluid (SBF), as confirmed by the in vitro formation of hydroxyapatite (HAp) layer with crystal size of approximately 2 µm size in diameter. In vitro studies revealed also non cytotoxic effect on HOB® osteoblasts and also a mechanosensitive response. Additionally, control cells grown on glass developed scarce or no stress fibers, while cells grown on hybrid samples showed a significant (p < 0.05) increase in well-developed stress fibers and mature focal adhesion complexes.

A Novel and Inexpensive Method Based on Modified Ionic Gelation for pH-responsive Controlled Drug Release of Homogeneously Distributed Chitosan Nanoparticles with a High Encapsulation Efficiency

Homogeneous chitosan nanoparticles utilizing EPR effect and pH-sensitive properties have an immense potential for loading and delivery of anticancer drugs. The aim of this study was preparing doxorubicin-loaded homogeneously distributed chitosan nanoparticles by using a simple and mild method, modified ionic gelation, with a very high encapsulation efficiency for controlled and pH-sensitive release. FESEM image revealed that the synthesized chitosan nanoparticles had a uniform spherical morphology with the size range 20–35 nm. The parameters of drug stirring duration, drug amount and nanoparticles formation time were changed to achieve maximum encapsulation efficiency as well as the effect of each parameter on the encapsulation efficiency was studied. The encapsulation efficiency toward doxorubicin under optimal conditions was 81.6±0.8 % (n=5±SD) that was higher than those previously published in literature. The investigations of doxorubicin release from chitosan nanoparticles in four media with different pH values showed a pH-sensitive release with a higher release rate in an acidic environment. The drug release mechanism at all pH values was also evaluated by zero-order, first-order, Higuchi and Korsmeyer-Peppas models. The most consistent model for release curve at four pHs was Korsmeyer-Peppas model. Therefore, we presented a method for the preparation of homogeneous doxorubicin-loaded chitosan nanoparticles with small size that can be industrialized because they were made based on a very simple and green method without the use of a complex system and expensive materials as well as due to their high encapsulation efficiency.

Effect of chitin and chitosan hexamers on growth and photosynthetic characteristics of wheat seedlings

In this study, two homogeneous chitin and chitosan hexamers and one partially acetylated chitosan hexamer were used to investigate the degree of acetylation (DA) effects of chitooligosaccharides on the growth and photosynthesis of wheat seedlings. Both chitin and chitosan hexamers showed a significant promoting effect on the growth and photosynthesis of wheat seedlings but the positive effect depended on their DA. The homogeneous chitosan hexamers [(GlcN)6] exhibited the optimal activity compared to other samples. Seven days after (GlcN)6 treatment, the growth parameters of wheat seedlings were all significantly enhanced including fresh mass, dry mass, and length of both shoots and roots, and the contents of soluble sugar were increased by 22.8%. Additionally, (GlcN)6 could significantly promote (by 90.0%) the photosynthetic rate of wheat seedlings. Both Rubisco and fructose-1,6-bisphosphatase activity of photosynthetic carbon metabolism was also found to be significantly improved by (GlcN)6 treatment.

Novel application of chitosan: ameliorative effect of homogeneous and floccular chitosan on the interfacial property of carbon fiber/epoxy resin composites

A novel homogeneous floccular chitosan was directly grafted onto carbon fiber surface by a simple and controllable method. Scanning electron microscopy (SEM), single fiber strengths and interlaminar shear strength (ILSS) have been applied to characterize the fiber and the interface bonding. Compared with raw carbon fibers, the chitosan-treated ones demonstrate significant increases in the surface roughness and wettability. Particularly, about 21.21% increase in the mechanical properties of composites was obtained, which is attributed to good adhesion between functional carbon fiber and resin matrix in the interlaminar regions, as revealed by fracture surfaces.

Electrophoretic Deposition of Chitosan Films Doped with Nd2Ti2O7Nanoparticles as Protective Coatings against Corrosion in Saline Solutions

In this study, the electrophoretic deposition of chitosan films doped with Nd2Ti2O7nanoparticles was carried out as corrosion protection systems for exposed materials in aqueous environments rich in chlorides. Completely crystalline Nd2Ti2O7nanoparticles with an average size of 100-200 nm were obtained. Electrophoretic deposition of chitosan films with Nd2Ti2O7nanoparticles was possible. With a working voltage of 5 V and 20 minutes of deposition, homogenous chitosan films with a thickness of 4 microns were obtained. According to the FT-IR (Fourier transform infrared spectroscopy), Raman, and XRD (X-ray diffraction) analyses, it was observed that the presence of the nanoparticles modified the properties of the chitosan films, that is, their crystallinity was increased and their moisture absorption capacity was reduced. These modifications caused a better performance against the corrosion of chitosan films deposited on 1018 carbon steel. Its electrochemical evaluation showed that the chitosan films perform as cathodic coatings by affecting the oxygen reduction reaction. This was possible due to the barrier effect of the Nd2Ti2O7nanoparticles, by blocking the effective area for the diffusion of the aggressive electrolyte species.

Nanocomposite chitosan hydrogels based on PLGA nanoparticles as potential biomedical materials

We report on the preparation and characterization of nanocomposite chitosan hydrogels with embedded poly (lactic-co-glycolic acid) (PLGA) nanoparticles employed for encapsulation of an enriched flavonoid fraction of Cecropia glaziovii Snethl. As a first step, the experimental conditions to obtain homogeneous chitosan hydrogels at 37 °C through gelation with NaHCO3 were optimized. Then, nanocomposite chitosan hydrogels were prepared through direct incorporation of nanoparticlesat different concentrations ranging from 1 to 10% w/w to gelling aqueous chitosan solutions. The resulting hydrogels were characterized through Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), oscillatory rheological experiments and cytotoxicity tests. FT-IR spectra confirmed the PLGA nanoparticles presence within the chitosan matrix through the absorption peak located at 1750 cm−1. The presence of the PLGA nanoparticles decreased the thermal stability of the nanocomposite chitosan hydrogels compared to the pure chitosan hydrogel. SEM images allowed observing porous matrixes where nanoparticles appeared to be homogeneously dispersed. The elastic moduli found for nanocomposite chitosan hydrogels varied with the PLGA nanoparticles concentration with a maximum at 3% nanoparticles concentration. Cytotoxicity tests revealed that after 48 h, neither thepure hydrogel nor the nanocomposite chitosan hydrogels with 10% nanoparticles concentration showed toxicity on VERO cells.

PERFORMANCE OF MEMBRANES CROSSLINKED WITH GLUTARALDEHYDE IN PERVAPORATION SEPARATION

Chitosan membranes crosslinked with glutaraldehyde (GA) were prepared through a solution method, where the dry homogeneous chitosan membranes were immersed into the reaction solutions containing 1.25 x 10-3 wt. % of glutaraldehyde (GA). The extent of the crosslinking was controlled by varying the crosslinking time from 1 to 5 minutes. The prepared crosslinked membranes were used for pervaporation dehydration of isopropanol-water mixtures. The influence of feed composition on the separation characteristics has been investigated. The 2-minute-crosslinked-membrane yields the highest water concentrations in the permeate with moderate flux at 50 wt. % of isopropanol in the feed solution. The overall pervaporation results for the homogeneous and crosslinked membranes are compared in term of pervaporation separation index (PSI). The crosslinked membranes showed higher pervaporation separation index (PSI) than that of uncrosslinked membranes especially for isopropanol in feed solution below 78 wt. %.

Enzymatic gelation to prepare chitosan gels: Study of gelation kinetics and identification of limiting parameters for controlled gel morphology

Chitosan gels with well-controlled morphology were prepared by an enzymatic chitosan gelation process using in-situ production of ammonia through the urea enzymatic hydrolysis by urease. The reaction kinetics were studied by four complementary methods (rheological, colorimetric, flowing and pH-metric measurements) to define an advanced gelation pH (and the corresponding advanced gelation time) enabling to obtain homogeneous chitosan gels with well-controlled morphology and strong enough to be suitable for a future membrane preparation. A comparative study of chitosan gelation kinetics in water and aqueous chitosan solution highlighted differences mainly related to ammonia consumption when chitosan was present. The key parameters evidenced for the control of the gelation kinetics were the temperature and the urease concentration. The operating parameters required to elaborate gels with sufficient mechanical resistance to be handled from 2.5% w/v chitosan concentration were defined: a 3.5umL−1 urease concentration, a 75mM urea concentration and a temperature of 5°C.

Biocompatible Ceramic-Biopolymer Coatings Obtained by Electrophoretic Deposition on Electron Beam Structured Titanium Alloy Surfaces

An area of major interest in biomedical engineering is currently the development of improved materials for medical implants. Research efforts are being focused on the investigation of surface modification methods for metallic prostheses due to the fundamental bioinert character of these materials and the possible ion release from their surfaces, which could potentially induce the interfacial loosening of devices after implantation. Electron beam (EB) structuring is a novel technique to control the surface topography in metals. Electrophoretic deposition (EPD) offers the feasibility to deposit at room temperature a variety of materials on conductive substrates from colloidal suspensions under electric fields. In this work single layers of chitosan composite coatings containing titania nanoparticles (n-TiO2) were deposit by EPD on electron beam (EB) structured Ti6Al4V titanium alloy. Surface structures were designed following different criteria in order to develop specific topography on the Ti6Al4V substrate. n-TiO2 particles were used as a model particle in order to demonstrate the versatility of the proposed technique for achieving homogenous chitosan based coatings on structured surfaces. A linear relation between EPD time and deposition yield on different patterned Ti6Al4V surfaces was determined under constant voltage conditions, obtaining homogeneous EPD coatings which replicate the 3D structure (pattern) of the substrate surface. The present results show that a combination of both techniques can be considered a promising surface modification approach for metallic implants, which should lead to improved interaction between the implant surface and the biological environment for orthopaedic applications.

VAPOUR PERMEATION STUDY OF WATER AND ETHANOL THROUGH CROSSLINKED CHITOSAN AND ALGINATE MEMBRANES

A vapour permeation of water and ethanol through homogenous chitosan and alginate membranes was investigated. The influence of the polymer matrix and crosslinking agents, and measurement protocol on the transport properties were discussed. The conducted experiments showed the greater separation factor, better stability and resistant to solvents for chemically crosslinked membranes. On the other hand, stronger association of the matrix, than the physical, caused decrease of vapour fluxes.

Chitosan nanoparticles produced with the gradual temperature decrease technique for sustained gene delivery

Different techniques have been employed to produce chitosan nanoparticles; thus, suitable alternatives and easy-handling production methods are highly desired. We used a tank reactor with baffles and mechanical stirring with Cowles impellers that can feasibly be up-scaled and allows for the production of homogenous chitosan nanoparticles. First, we explored the effects of temperature on the production of chitosan (CHI)/pentasodium tripolyphosphate (TPP) nanoparticles. We compared the effect of gradual temperature decrease between 40 to 55°C with the effect of isothermal processes (25, 45 and 55°C). CHI/TPP nanoparticles produced by the gradual temperature decrease technique had polydispersity indices (PDIs) that were significantly smaller than the nanoparticles produced by isothermal processes. To further control the production process, we employed an experimental design to determine the effects of CHI and TPP concentrations and CHI/TPP mass ratios in the gradual temperature decrease technique. Under all conditions, the sizes of the CHI/TPP nanoparticles were on the nanoscale. Gene delivery capacities of the nanoparticles were evaluated; the plasmid pEGFP-N1 was incorporated (10 and 40% of the chitosan weight) into the nanoparticles and incubated with 293A cells. The in vitro transfection efficiencies were evaluated over 120h and indicated sustained gene delivery at 10% pDNA. The polyplexes demonstrated some cytotoxicity after 120h. These findings will contribute to the development of processes for generating CHI/TPP nanoparticles for gene delivery applications.

Carbon Nanotube Nanocomposites with Highly Enhanced Strength and Conductivity for Flexible Electric Circuits.

Carbon nanotubes (CNTs) have an important role in nanotechnology due to their unique properties, retaining the inherent material flexibility, superior strength, and electrical conductivity, unless the bottleneck of CNTs persists and the aggregated structure is overcome. Here, we report on the highly enhanced mechanical and electrical properties of the CNT-chitosan nanocomposites through homogeneous dispersion of CNTs into chitosan solution using a high-pressure homogenizer. The optimal condition is a 50% (w/w) chitosan-CNT film, providing about 7 nm thickness of homogeneous chitosan layer on CNTs, a good tensile strength of 51 MPa, high electrical conductivity under 16 Ω/sq, and a stable bending and folding performance. This CNT-chitosan nanocomposite with highly enhanced properties is an amenable material to fabricate structures of various shapes such as films, sensors, and circuits and also enables a simple and cost-effective approach to improve the performance of a device that presents the first flexible and soft electric circuits yet reported using only CNT-chitosan as the conductor.

Chitosan surface modification of fully interconnected 3D porous poly(ε-caprolactone) by the LbL approach

In this study, the deposition of a homogeneous chitosan layer on the surface of a 3D interconnected porous network of poly(ε-caprolactone) (PCL), prepared from a co-continuous polymer blend of PCL/PEO (poly(ethylene oxide)), was achieved. A Layer-by-Layer (LbL) self-assembly of polyelectrolytes (PDADMAC as polycation and PSS as polyanion) followed by chitosan deposition was compared with a traditional dip-coating strategy of chitosan on pure PCL surfaces. According to gravimetric measurements for the LBL technique, few layer depositions lead to an interpenetration of polyelectrolyte molecule chains, however upon increasing the number of layers, more well defined layers are formed. The oxygen/carbon, nitrogen/carbon and sulfur/carbon ratios determined by X-ray photoelectron spectroscopy (XPS) on 2D solid discs clearly showed that the PSS molecule dominated the surface as the last deposited layer at higher number of depositions (n = 8). The further addition of chitosan by LbL was demonstrated to be superior as compared to the dip-coating technique since uniform local deposition of chitosan on the LbL coating was observed in both 2D solid discs and 3D porous cubes at various depths within the scaffolds. SEM imaging shows the multilayer assembly ranges in thickness from 550 to 700 nm. These data demonstrate that the LbL technique of polyelectrolyte deposition followed by chitosan addition provides a route towards stable and homogeneous surface modification and has the potential to transform a classic fully interconnected porous synthetic polymer material to one with essentially complete chitosan-like surface characteristics.

Internal plasticization of chitosan with oligo(dl-lactic acid) branches

To enhance the mechanical properties of chitosan without impairing its biological properties and rendering it a more flexible and pliable material, oligo(lactic acid) branches were inserted in a systematic way onto the polymer's backbone. Six grafted copolymers were prepared and thoroughly characterized using chemical means, Dynamical Mechanical Thermal Analysis (DMTA), and Solid State Nuclear Magnetic Resonance (SSNMR, CPMAS and SPMAS). The degree of insertion and the length of the pendant groups were determined. The resulting morphology and mechanical properties demonstrated that the branching introduced strong modifications on the dynamic behavior of the pristine chitosan, and consequently on the mechanical properties of the composite materials a whole. The method described makes it possible to design homogeneous chitosan based materials with good mechanical properties, including a desired degree of flexibility. The results demonstrated that the degree of plasticization of chitosan can be achieved by proper control of the oligo(dl-lactic acid) branching.

Design and Fabrication of a Silicone Rubber-based Mediatorless Bioelectrode for Oxygen Reduction

Abstract In this work, a mediatorless bioelectrode has been constructed for the first time on a flexible silicone rubber sheet coated with homogeneous chitosan–carbon nanotubes composites. Bilirubin oxidase was employed as a model biocatalyst to reduce O2 to H2O. These novel fabricated electrodes showed good electrochemical properties and exhibited comparatively high operational stability even after 5 days of continuous operation. The results obtained here demonstrated the potential of silicone rubber-based materials as a promising platform for flexible bioelectronics in medical devices.