Polyelectrolyte complexes of gum kondagogu and chitosan,as diclofenac carriers

Polyelectrolyte complexes (PEC) of gum kondagogu (GKG) and chitosan were prepared by mixing polymeric solutions of different concentrations (0.02–0.18% w/v). The complex formed were loaded with diclofenac sodium, and the release of the drug was measured in vitro and in vivo, along with the measurement of particle size, zeta potential, complex formation, flow properties, and loading efficiency. Maximum yield of PEC was observed at gum kondagogu concentrations above 80%. The PEC showed lower release of diclofenac sodium in 0.1 N HCl as compared to phosphate buffer (pH 6.8). Increasing the concentration of gum kondagogu in PEC led to an increase in drug release. However, PEC 1:3 (gum kondagogu: chitosan) with higher concentration of chitosan showed 98% release with in 4.5 h, owing to the fact that chitosan has a higher degree of swelling in acidic medium. PEC 5:1 and 3:1 showed a 5.3- and 5.8-fold increase in relative bioavailability compared to the free drug when administered orally to the rats.     

Preparation and pharmacodynamics of low-molecular-weight chitosan nanoparticles containing insulin

Low-molecular-weight chitosan (LMWC) was obtained by enzymatic degradation and ultrafiltration separation. LMWC nanoparticles with LMWC having 20 kDa weight average molecular weight (M_w) were then prepared by solvent evaporation method. The resultant nanoparticles were spherical with a narrow particle size distribution. LMWC nanoparticles loaded with insulin as a model drug were prepared. The average entrapment efficiency of insulin could reach up to 95.54%. The in vitro drug release profiles from the nanoparticles showed an initial burst of release in the first 2 h, followed by zero order release kinetics. In vivo pharmacodynamics of chitosan nanoparticles containing insulin showed that the nanoparticles showed some hypoglycemic activity. Compared with an insulin solution, a relative bioavailability of 0.737 was observed for four times the dosage of insulin in the chitosan nanoparticles after pulmonary administration.     

Upgrading the preparation of high-quality chitosan from Procambarus clarkii wastes over the traditional isolation of shrimp chitosan

Crustacean waste is one of the most severe issues, posing significant environmental and health risks. This study aims to improve managing marine waste by isolating chitosan from Procambarus clarkii by devising a new methodology, incorporating technical steps, e.g., washing, decolorization and deacetylation under a reflexive condenser and dialysis purification. A comparison was made between the prepared P. clarkii chitosan and four types of shrimp chitosans: commercial, high, low, and nano. The obtained chitosan has a low molecular weight and viscosity compared to the commercial shrimp chitosan used in various applications. P. clarkii chitosan was prepared in high quality from a cheap source, as its color and quality were better than those of the commercial shrimp chitosan. The new methodology has successfully extracted chitosan from P. clarkii in a good quality and high purity, achieving 89% deacetylation, high solubility, high purity, and medium molecular weight. Analysis of the different chitosan samples with Fourier transform infrared spectroscopy (FTIR), atomic force microscopy, Raman spectrum referred indicated high similarity between the chitosan different types, regardless of its source. The 3D image of P. clarkii showed the distance between the highest and most profound points of extracted chitosan is 728.94 nm, revealing homogeneous, smooth surfaces, apparently free of pores and cracks. FTIR and Raman spectrum of P. clarkii indicated various functional groups, e.g., alcohol, amines, amides, and phenols. These active groups are responsible for about 60% of the antioxidant activity of that product. Evaluating the quality traits indicated the excellence of the chitosan prepared from P. clarkii, especially in color, viscosity, and antioxidant activity, nominating it for different food applications.     

Exenatide-loaded PLGA microspheres with improved glycemic control: In vitro bioactivity and in vivo pharmacokinetic profiles after subcutaneous administration to SD rats

A subcutaneous exenatide delivery system was developed and characterized in vitro and in vivo. The results clearly showed that the exenatide loaded PLGA microspheres prepared by using a non-aqueous processing medium had low burst release and high drug encapsulation efficiency. Exenatide loaded in the microspheres preserved its bioactivity. The pharmacokinetics parameters were determined after subcutaneous administration of microspheres to SD rats. The plasma concentration of the single dose of the sustained-release microspheres attained C_max of 108.19 ± 14.92 ng/ml at t_max of 1.33 ± 0.58 h and the t_1/2 was 120.65 ± 44.18 h. There was a linear correlation between the in vitro and in vivo release behavior (R² = 0.888). Exenatide loaded microspheres may prove to have great potential for clinical use.     

Synthesis,characterization and antifungal activity of quaternary derivatives of chitosan on Aspergillus flavus

Two series of new chitosan derivatives were synthesized by reaction of deacetylated chitosan (CH) with propyl (CH-Propyl) and pentyl (CH-Pentyl) trimethylammonium bromides to obtain derivatives with increasing degrees of substitution (DS). The derivatives were characterized by ¹H NMR and potentiometric titration techniques and their antifungal activities on the mycelial growth of Aspergillus flavus were investigated in vitro. The antifungal activities increase with DS and the more substituted derivatives of both series, CH-Propyl and CH-Pentyl, exhibited antifungal activities respectively three and six times higher than those obtained with commercial and deacetylated chitosan. The minimum inhibitory concentrations (MIC) were evaluated at 24, 48 and 72 h by varying the polymer concentration from 0.5 to 16 g/L and the results showed that the quaternary derivatives inhibited the fungus growth at polymer concentrations four times lower than that obtained with deacetylated chitosan (CH). The chitosans modified with pentyltrimethylammonium bromide exhibited higher activity and results are discussed taking into account the degree of substitution (DS).     

Preparation and characterization of novel chitosan/gelatin membranes using chitosan hydrogel

Chitin and chitosan are novel biomaterials. The novel chitosan/gelatin membranes were prepared using the suspension of chitosan hydrogel mixed with gelatin. The prepared chitosan/gelatin membranes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical, swelling, and thermal studies. The morphology of these chitosan/gelatin membranes was found to be very smooth and homogeneous. The XRD studies showed that the chitosan/gelatin membranes have good compatibility and interaction between the chitosan and gelatin. The stress and elongation of chitosan/gelatin membranes on wet condition showed excellent when the mixture ratio of gelatin was 0.50. The prepared chitosan/gelatin membranes showed good swelling, mechanical and thermal properties. Cell adhesion studies were also carried out using human MG-63 osteoblast-like cells. The cells incubated with chitosan/gelatin membranes for 24 h were capable of forming cell adhesion. Thus the prepared chitosan/gelatin membranes are bioactive and are suitable for cell adhesion suggesting that these membranes can be used for tissue-engineering applications. Therefore, these novel chitosan/gelatin membranes are useful for biomedical applications.     

Cross-linking chitosan into UV-irradiated cellulose fibers for the preparation of antimicrobial-finished textiles

Chitosan cross-linked cellulose fibers were prepared using non-toxic procedures in order to confer antimicrobial properties to cellulose fibers. Citric acid was used as the cross-linker and NaH₂PO₄ as catalyst in previously UV-irradiated cellulose fibers. Further heat dried-cure process and washing with detergent, water and acetic acid (0.1 M) gave a maximum incorporation of chitosan of 27 mg per gram of functionalized textile. The thermogravimetric analysis of the material with the highest chitosan content showed an increased thermal stability compared to cellulose and chitosan. The UV-irradiation induced morphological changes, such as less entangled cellulose fibers, as observed by scanning electron microscopy, which was prompted to enhance the chitosan incorporation. The biomass and spore germination percentage of Penicillium chrysogenum and colony forming units per millilitre for Escherichia coli decreased significantly on the composed materials as compared to raw cellulose fiber and it was similar to that obtained with a commercial antimicrobial cellulose fiber.     

Physicochemical characterization of chitin and chitosan from crab shells

Crab chitosan was prepared by alkaline N-deacetylation of crab chitin for 60, 90 and 120 min and the yields were 30.0-32.2% with that of chitosan C120 being the highest. The degree of N-deacetylation of chitosans (83.3–93.3%) increased but the average molecular weight (483–526 kDa) decreased with the prolonged reaction time. Crab chitosans showed lower lightness and WI values than purified chitin, chitosans CC and CS but higher than crude chitin. With the prolonged reaction time, the nitrogen (8.9–9.5%), carbon (42.2–45.2%) and hydrogen contents (7.9–8.6%) in chitosans prepared consistently increased whereas N/C ratios remained the same (0.21). Crab chitosans prepared showed a melting endothermic peak at 152.3–159.2 °C. Three chitosans showed similar microfibrillar crystalline structure and two crystalline reflections at 2θ = 8.8–9.0° and 18.9–19.1°. Overall, the characteristics of three crab chitosans were unique and differed from those of chitosan CC and CS as evidenced by the element analysis, differential scanning calorimetry, scanning electron microscopy and X-ray diffraction patterns.     

Polydimethylsiloxane modified chitosan. Part III: Preparation and characterization of hybrid membranes

The paper deals with the synthesis of organic–inorganic hybrid membranes, Hy, obtained by simultaneous grafting and crosslinking of chitosan with epoxy-terminated polydimethylsiloxane and γ-glycidoxypropyltrimethoxysilane. Porous membranes, HyP, were also obtained by acid decomposition, at different temperatures (25 and 50 °C), of calcium carbonate porogenic agent trapped inside the material. As proved by electron and atomic force microscopy, the non-porous membrane is a phase segregated material with spherical domains (10–40 μm) of silica core covered by hydrophobic siloxane in a hydrophilic chitosan matrix. The porous membranes showed different morphologies with irregular circular pores of 10–30 μm diameters for the membranes obtained at lower temperature, while the membranes prepared at 50 °C tend to adopt a plan-parallel porosity. The water contact angles of hybrid membranes (78°) and pure chitosan membranes (72°) indicated a lower hydrophilic character of modified chitosan. As a result of the crosslinking and of increased hydrophobicity, the hybrid membranes were characterized by a smaller water swelling degree (about 30%) as compared to pure chitosan membrane (700%). However, the presence of the pores in HyP membranes determined an increase of the water adsorption (maximum swelling degree, about 100%). The hybrid membranes possess a slightly higher thermal stability as compared to chitosan (first initial decomposition temperature, 147 and 175 °C for chitosan and hybrid membranes, respectively), but a lower one as compared to pure polydimethylsiloxane. The high storage modulus of chitosan (about 5.1 × 10⁹ Pa at 20 °C) is decreased by about one order of magnitude by the introduction of the highly flexible polysiloxane and the hybrid membranes are more flexible.     

Methylated N-(4-N,N-dimethylaminobenzyl) chitosan as effective gene carriers: Effect of degree of substitution

The objective of this study was to investigate the transfection efficiency of quaternized N-(4-N,N-dimethylaminobenzyl) chitosan; TM-Bz-CS, using the plasmid DNA encoding green fluorescent protein (pEGFP-C2) on human hepatoma cell lines (Huh7 cells). The factors affecting the transfection efficiency e.g. degree of quaternization (DQ), the degree of dimethylaminobenzyl substitution (DS) and polymer/DNA weight ratio, have been evaluated. The results revealed that all TM-Bz-CS derivatives were able to condense with DNA. Illustrated by agarose gel electrophoresis, complete complexes of TM₅₇-Bz₄₂-CS/DNA were formed at weight ratio of above 0.5, whereas those of TM₄₇-Bz₄₂-CS/DNA and TM₅₇- Bz₁₇-CS/DNA were above 1. The rank of transfection efficiency of the chitosan derivatives were TM₅₇-Bz₄₂-CS > TM₄₇-Bz₄₂-CS > TM₅₇-Bz₁₈-CS. The pH of culture medium did not affect the transfection efficiency of TM₅₇-Bz₄₂-CS/DNA complex, whereas it affected the transfection efficiency of chitosan/DNA complex. The results indicated that the improved gene transfection was due to the hydrophobic group (N,N-dimethylaminobenzyl) substitution on chitosan which promoted the interaction and condensation with DNA as well as N-quaternization which increased chitosan water solubility and enhance gene expression. For cytotoxicity studies, TM-Bz-CS was safe at the concentration of the highest transfection. In conclusion, this novel chitosan derivative, TM₅₇-Bz₄₂-CS showed elevated potential as gene carrier by efficient DNA condensation and mediated highest level of gene transfection with negligible cytotoxicity in Huh7 cells.     

Rapid harvesting of freshwater microalgae using chitosan

In this study, chitosan was used as a flocculant to harvest freshwater microalgae Chlorella vulgaris. The recovery efficiency of C. vulgaris was tested at various chitosan concentrations. 120 mg/L of chitosan showed the highest efficiency (92 ± 0.4%) within 3 min. The maximum concentration factor of 10 was also achieved at this dose of chitosan. The harvesting efficiency was pH dependent. pH 6.0 showed the highest harvesting efficiency (99 ± 0.5%). Measurement of zeta-potential confirmed that the flocculation was induced by charge neutralization. This study showed that a biopolymer, chitosan, can be a promising flocculant due to its high efficacy, low dose requirements, and short settling time.     

Immobilizing cholesterol oxidase in chitosan–alginic acid network

Proton conducting biopolymer networks have potential use for bio-sensors. The cost-effective, non-hazardous and environmentally safe biopolymer, such as chitosan, is an attractive feature for bio-sensors. Cholesterol oxidase was immobilized in conducting network via complexation of chitosan with alginic acid. A method for the preparation of the complex along with characterization by elemental analysis, FTIR spectroscopy, TGA and DSC were reported. The proton conductivity chitosan–alginic acid network was studied via impedance spectroscopy under humidified condition. The complex polymer electrolyte with x = 1 exhibited maximum proton conductivity of 1.4 × 10^?3 S/cm at RT, RH ～ 50%. The potential use of this network in enzyme immobilization was studied by manufacturing cholesterol oxidase entrapped polymer networks. Additionally, the maximum reaction rate (V_max) and Michaelis–Menten constant (K_m) were investigated for the immobilized cholesterol oxidase. Also, temperature and pH optimization studies were performed, and operational stability and shelf life of the polymer network were examined.     

Preparation and characterization of cellulose/chitosan blend films

Cellulose and chitosan were mixed in N-methylmorpholine-N-oxide (NMMO) and heated to 100 °C, and then were processed under a pressure of 70 kg/cm² exerted by a compression molding machine at 100 °C for 8 min. As a result, transparent orange viscose films were obtained. After rinsing with deionized water and drying transparent yellowish blend films were obtained. Scanning electron microscope (SEM) indicated that when the chitosan content in the blend increased up to 3% the surface structure became smoother, but the film containing 5% (w/w) chitosan, became coarse again probably due to phase separation. Tensile strength test results were consistant with this. Antibacterial assessment proved that addition of chitosan to the films results in slight antibacterial properties. The halo zone test confirmed that the blend films made in this research have non-diffusible antibacterial properties.     

Substituted polyaniline/chitosan composites: Synthesis and characterization

Substituted polyaniline/chitosan(PANIs/Ch) composites were chemically synthesized by using ammonium peroxydisulfate as oxidant and characterized by measurements of conductivity, FTIR, UV–vis, SEM and TGA techniques. FTIR spectra of the composites revealed that there is a strong interaction between substituted polyanilines and chitosan. Among the substituted polyaniline/chitosan composites synthesized, poly(N-ethylaniline)/chitosan PNEANI/Ch has the highest conductivity with a value of 1.68 × 10^?4 S/cm. The P2EANI/Ch composite exhibited higher thermal stability than the other composites. SEM images of the composites showed an agglomerated granular morphology of substituted polyaniline particles coated on the surface of chitosan.     

Antifungal potentiality of mycogenic silver nanoparticles capped with chitosan produced by endophytic Amesia atrobrunnea

This research reports the fabrication of silver nanoparticles (AgNPs) from endophytic fungus, Amesia atrobrunnea isolated from Ziziphus spina-christi (L.). Influencing factors for instance, thermal degree of incubation, media, pH, and silver nitrate (AgNO₃) molarity were optimized. Then, the AgNPs were encapsulated with chitosan (Ch-AgNPs) under microwave heating at 650 W for 90 s. Characterization of nanoparticles was performed via UV–visible (UV–vis) spectrophotometer, Fourier-transform infrared spectrophotometer (FTIR), zeta potential using dynamic-light scattering (DLS), and field-emission-scanning electron microscope (FE-SEM). Anti-fungal activity of Ch-AgNPs at (50, 25, 12.5, 6.25 mg/L) was tested against Fusarium oxysporum, Curvularia lunata, and Aspergillus niger using the mycelial growth inhibition method (MGI). Results indicated that Czapek-dox broth (CDB) with 1 mM AgNO₃, an acidic pH, and a temperature of 25–30 °C were the optimum for AgNPs synthesis. (UV–vis) showed the highest peak at 435 nm, whereas Ch-AgNPs showed one peak for AgNPs at 405 nm and another peak for chitosan at 230 nm. FTIR analysis confirmed that the capping agent chitosan was successfully incorporated and interacted with the AgNPs through amide functionalities. Z-potential was −19.7 mV for AgNPs and 38.9 mV for Ch-AgNPs, which confirmed the significant stability enhancement after capping. FES-SEM showed spherical AgNPs and a reduction in the nanoparticle size to 44.65 nm after capping with chitosan. The highest mycelial growth reduction using fabricated Ch-AgNPs was 93% for C. lunata followed by 77% for A. niger and 66% F. oxysporum at (50 mg/L). Biosynthesis of AgNPs using A. atrobrunnea cell-free extract was successful. Capping with chitosan exhibited antifungal activity against fungal pathogens.     

Efficient digestion of chitosan using chitosanase immobilized on silica-gel for the production of multisize chitooligosaccharides

Chitosanase-coated silica-gels were prepared via cross-linking of the chitosanase onto silica-gels for the efficient production of multisize chitooligosaccharides (MCOs) in a continuous process. The kinetic aspects of immobilized chitosanase (IMMCTase) were investigated based on the reaction time, production of MCOs, and MALDI-TOF mass analyses to achieve maximum bioconversion of high molecular weight chitosan (HMWC) to MCOs. IMMCTase revealed a negligible loss of chitosanase activity after multi uses in continuous digestion of HMWC. The optimal temperature of IMMCTase was 37 °C, and kinetic parameters toward HMWC were determined to be K_m = 1.45 mM and V_max = 360 μmole/μg/min, respectively. Under optimal conditions, the recovery of enzyme activity of IMMCTase was determined to be 82.3%, thus indicating that it can still be reused few more times. In conclusion, use of IMMCTase resulted in rapid and efficient digestions of HMWC with consistent results to produce MCOs.     

Measuring core body temperature with a non-invasive sensor

In various occupations, workers may be exposed to extreme environmental conditions and physical activities. Under these conditions the ability to follow the workers' body temperature may protect them from overheating that may lead to heat related injuries. The "Dräger" Double Sensor (DS) is a novel device for assessing body-core temperature (T_c). The purpose of this study was to evaluate the accuracy of the DS in measuring T_c under heat stress. Seventeen male participants performed a three stage protocol: 30 min rest in a thermal comfort environment (20–22 °C, 50% relative humidity), followed by an exposure to a hot environment of 40 °C, 40% relative humidity −30 min at rest and 60 min of exercise (walking on a treadmill at 5 km/h and 2% elevation). Simultaneously temperatures measured by the DS (T_DS) and by rectal temperature (T_re) (YSI-401 thermistor) were recorded and then compared. During the three stages of the study the average temperature obtained by the DS was within±0.3 °C of rectal measurement. The correlation between T_DS and T_re was significantly better during the heat exposures phases than during resting under comfort conditions. These preliminary results are promising for potential use of the DS by workers under field conditions and especially under environmental heat stress or when dressed in protective garments. For this goal, further investigations are required to validate the accuracy of the DS under various levels of heat stress, clothing and working levels.     

Synthesis and characterization of hydrogels based on grafted chitosan for the controlled drug release

Temperature and pH-responsive hydrogels based on chitosan grafted with poly acrylic acid (PAAc), poly hydroxy propyl methacrylate (PHPMA), poly (vinyl alcohol) (PVA) and gelatin were prepared for controlled drug delivery. These stimuli-responsive hydrogels were synthesized by gamma irradiation technique. The degree of gelation was over 90% and increased as chitosan, AAc and PVA content increased, while the degree of gelation decrease with the increase of gelatin content. The equilibrium swelling studies of hydrogels prepared in various conditions were carried out in an aqueous solution, and the pH sensitivity in the range of 2–9 was investigated. An increase of swelling degree with an increase in the pH was noticed and showed the highest value at pH 9. Also antibiotic drug Oxttetracycline was loaded into the hydrogels and the release studies were carried out at different pH and temperature. The in vitro release profiles of the drug showed that, the release of the drug increased as the time, temperature and pH increased and reached to maximum after 48 h at pH 9. The prepared hydrogels were characterized by using SEM, FTIR, and DSC.     

Improved reproducibility in the determination of the molecular weight of chitosan by analytical size exclusion chromatography

The reproducibility of the determination of the molecular weight of chitosans in the 90–210 kDa range (M_n) by analytical size exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) was improved by reducing the salt concentration in the mobile phase from (0.3 M acetic acid, 0.2 M sodium acetate, and 0.8 mM sodium azide) to (0.15 M acetic acid, 0.1 M sodium acetate, and 0.4 mM sodium azide) using Tosoh TSKgel G6000PW_XL and G5000PW_XL columns in series. The variability of measured molecular weight was significantly reduced by lowering the acetate concentration in the mobile phase, while the average molecular weight did not change significantly. The coefficient of variation of the number-average molecular weight, CV(M_n), decreased from 7–12% to 3–6% upon mobile phase dilution. This reduced variability in molecular weight of chitosans obtained from SEC is a significant improvement when precise values of chitosan molecular weight are required, for example in stability studies where viscosity changes in concentrated chitosan solutions are assessed, and in gene delivery applications.     

Selective and stable production of physiologically active chitosan oligosaccharides using an enzymatic membrane bioreactor

We investigated the production of chitosan oligosaccharides by continuous hydrolysis of chitosan in an enzyme membrane bioreactor, with the goal of improving the yield of physiologically active oligosaccharides (pentamers and hexamers) and achieving operational stability. The bioreactor was a continuous-flow stirred-tank reactor equipped with an ultrafiltration membrane with a molecular weight cut-off of 2000 Da, and the hydrolysis was accomplished with chitosanase from Bacillus pumilus. After optimization of the reaction parameters, such as the amount of enzyme, the yield of the target oligosaccharides produced in the membrane bioreactor with free chitosanase reached 52% on the basis of the fed concentration of chitosan. An immobilized chitosanase prepared by the multipoint attachment method was used to improve the operational stability of the membrane bioreactor. Under the optimized conditions, pentameric and hexameric chitosan oligosaccharides were steadily produced at 2.3 g/L (46% yield) for a month. The half-life of the productivity of the reactor was estimated to be 50 d under the conditions examined.