Molecular Weight Chitosan Research Articles

Molecular weight and pH effects of aminoethyl modified chitosan on antibacterial activity in vitro

Aminoethyl modified chitosan derivatives (AEMCSs) with different molecular weight (Mw) were synthesized by grafting aminoethyl group on different molecular weight chitosans and chitooligosaccharide. FTIR, 1H NMR, 13C NMR, elemental analysis and potentiometric titration results showed that branched polyethylimine chitosan was synthesized. Clinical Laboratory Standard Institute (CLSI) protocols were used to determine MIC for Gram-negative strain of Escherichia coli under different pH. The antibacterial activity of the derivatives was significantly improved compared with original chitosans, with MIC values against E. coli varying from 4 to 64μg/mL depending on different Mw and pH. High molecular weight seems to be in favor of stronger antibacterial activity. At pH 7.4, derivatives with Mw above 27kDa exhibited equivalent antibacterial activity (16μg/mL), while oligosaccharide chitosan derivative with lower Mw (∼1.4kDa) showed decreased MIC of 64μg/mL. The effect of pH on antibacterial activity is more complicated. An optimal pH for HAEMCS was found around 6.5 to give MIC as low as 4μg/mL, while higher or lower pH compromised the activity. Cell integrity assay and SEM images showed evident cell disruption, indicating membrane disruption may be one possible mechanism for antibacterial activity.

Development of encapsulation technique for curcumin loaded O/W emulsion using chitosan based cryotropic gelation

Cryogel based encapsulation of curcumin, an herbal extract, was successfully carried out with a ternary system of colloidal chitosan, κ-carrageenan, and carboxymethylcellulose sodium salt. The effects of chitosan concentration, κ-carrageenan/CMC ratio of the polymer suspension and molecular weight of chitosan on the sol–gel formation were investigated. The effects of cooling rate during freeze-drying and oil phase composition on the encapsulation yield and the release behavior of curcumin from the hydrogel were determined. And so were the effects of pH of the phosphate-buffered media and oil phase composition on the swelling of the specimens. The microstructure of the resulting specimens revealed core-shell nanoparticles (i.e. oil droplet for core and cryogel membrane for shell) entrapped in the cryogel matrix. The encapsulation yield for two types of suspensions was in a range of 83.9 to 99.6% when a high-MW chitosan was used. Controlled release of the encapsulated curcumin in an aqueous system could be maintained for 4days, and the releasable amount of curcumin was in a range of 41.1 to 59.9%. The encapsulation yield as well as the released pattern and releasable amount of curcumin were significantly influenced by the cooling protocol used during freezing. Irrespective of the introduced oil phase composition, controlled release of curcumin was achievable when the cooling rate was sufficiently high at −2.0°C/min and, interestingly, either a burst release or a first order release could simply be achieved by changing the freezing condition.

Study on Effect and Mechanism of Chitosan Coagulation Aid in Flocculation Treatment of Water Supply

The aim of this work is to remove residual turbidity and index of Potassium permanganate of the drinking water by PAC/Chitosan coagulation treatment. The experiments were performd the efficiency of coagulation by PAC/Chitosan at different chitosan dosages , molecular weight and pH value. Zeta potential instrument and Nikon electron microscope were used to test Zeta potential and observe flocs morphology. It turn out that Chitosan enhance the flocculation treatment of the surface water of raw water of Yellow River by polymeric aluminum chloride (PAC)when PAC dosage is 35 mg•l-1 and Chitosan is 0.15 mg•l-1 and infer coagulation aid mechanism was interpartical bridging rather than the electrical neutralization. Microscope and image analysis system of flocs morphology show that fractal dimension of morphology of PAC and PAC/Chitosan were 1.294,1.385, respectively.

Assessment of the effect of chitosan of different molecular weights in controlling Rhizopus rots in tomato fruits

The effect of chitosan was evaluated in three isolates of Rhizopus stolonifer from infected tomatoes that were harvested in different regions of the state of Morelos, México. Changes in the membrane integrity of spores, modifications in pH media and the proteins released were analysed in each isolate against three different molecular weights of chitosan at three fixed concentrations. There was an observed decline in the integrity of spores in the presence of chitosan at all the concentrations evaluated. The protein released was different depending on the isolate, kind of chitosan and used concentration. There was a significant difference in the pH changes on the growth media for all the tested isolates. Chitosan of high molecular weight showed the best results to inhibit the infection caused by R. stolonifer on the tomato fruits. The severity of symptoms of soft rot was not related with the molecular weight of chitosan.

Low molecular weight chitosan conjugated with folate for siRNA delivery in vitro: optimization studies

The low transfection efficiency of chitosan is one of its drawbacks as a gene delivery carrier. Low molecular weight chitosan may help to form small-sized polymer-DNA or small interfering RNA (siRNA) complexes. Folate conjugation may improve gene transfection efficiency because of the promoted uptake of folate receptor-bearing cells. In the present study, chitosan was conjugated with folate and investigated for its efficacy as a delivery vector for siRNA in vitro. We demonstrate that the molecular weight of chitosan has a major influence on its biological and physicochemical properties, and very low molecular weight chitosan (below 10 kDa) has difficulty in forming stable complexes with siRNA. In this study, chitosan 25 kDa and 50 kDa completely absorbed siRNA and formed nanoparticles (≤220 nm) at a chitosan to siRNA weight ratio of 50:1. The introduction of a folate ligand onto chitosan decreased nanoparticle toxicity. Compared with chitosan-siRNA, folate-chitosan-siRNA nanoparticles improved gene silencing transfection efficiency. Therefore, folate-chitosan shows potential as a viable candidate vector for safe and efficient siRNA delivery.

Preparation of water-soluble chitosan derivatives by modification of the polymer in vapors of monobasic acids

Sorption of vapors of monobasic acids and of vapors over their solutions of various concentrations by high-molecular-weight chitosan was studied. The dependence of the degree of the vapor sorption by the polymer on the acid solution concentration, chitosan molecular weight, and sorption temperature was determined. Watersoluble chitosan derivatives were obtained. The hydrodynamic properties of aqueous solutions of the modified samples were examined.

Low molecular weight chitosan nanoparticulate system at low N:P ratio for nontoxic polynucleotide delivery

Chitosan, a natural polymer, is a promising system for the therapeutic delivery of both plasmid DNA and synthetic small interfering RNA. Reports attempting to identify the optimal parameters of chitosan for synthetic small interfering RNA delivery were inconclusive with high molecular weight at high amine-to-phosphate (N:P) ratios apparently required for efficient transfection. Here we show, for the first time, that low molecular weight chitosan (LMW-CS) formulations at low N:P ratios are suitable for the in vitro delivery of small interfering RNA. LMW-CS nanoparticles at low N:P ratios were positively charged (ζ-potential ~20 mV) with an average size below 100 nm as demonstrated by dynamic light scattering and environmental scanning electron microscopy, respectively. Nanoparticles were spherical, a shape promoting decreased cytotoxicity and enhanced cellular uptake. Nanoparticle stability was effective for at least 20 hours at N:P ratios above two in a slightly acidic pH of 6.5. At a higher basic pH of 8, these nanoparticles were unravelled due to chitosan neutralization, exposing their polynucleotide cargo. Cellular uptake ranged from 50% to 95% in six different cell lines as measured by cytometry. Increasing chitosan molecular weight improved nanoparticle stability as well as the ability of nanoparticles to protect the oligonucleotide cargo from nucleases at supraphysiological concentrations. The highest knockdown efficiency was obtained with the specific formulation 92-10-5 that combines sufficient nuclease protection with effective intracellular release. This system attained >70% knockdown of the messenger RNA, similar to commercially available lipoplexes, without apparent cytotoxicity. Contrary to previous reports, our data demonstrate that LMW-CS at low N:P ratios are efficient and nontoxic polynucleotide delivery systems capable of transfecting a plethora of cell lines.

Influence of Drying Techniques on the Characteristics of Chitosan and the Quality of Biopolymer Films

In this work, spouted bed and tray-drying techniques were employed at different drying air temperatures to produce dried chitosan, and the chitosan powder was used to produce biofilms. The products obtained from each drying technique were compared in relation to quality aspects (molecular weight, lightness, and hue angle). The results found for chitosan in spouted bed drying (90°C) showed lower alteration and best quality aspects in relation to the chitosan powder. However, in tray drying under the best condition (60°C) the chitosan molecular weight increased about 50% in relation to the initial value and browning was observed. The biofilms produced from chitosan dried in the spouted bed showed the best mechanical properties (tensile strength of 42 MPa and elongation of 29%) and lower water vapor permeability (3.95 g mm m−2 kPa−1 day−1).

Preparation and Characterisation of Highly Loaded Fluorescent Chitosan Nanoparticles

Chitosan (CS) nanoparticles have been developed as a versatile drug delivery system to transport drugs, genes, proteins, and peptides into target sites. Demands on fluorescent nanoparticles have increased recently due to various applications in medical and stem-cell-based researches. In this study, fluorescent CS nanoparticles were prepared by a mild method, namely, complex coacervation. Entrapment efficiency of sulforhodamine (SR101) loaded into CS nanoparticles was investigated to evaluate their capacity in incorporating fluorescent molecule. Particle size of produced fluorescent nanoparticles was in the range of 600–700 nm, and their particle size was highly dependent on the CS molecular weight as well as concentration. A high entrapment efficiency of SR101 into CS nanoparticles could also be obtained when it was dissolved in methanol. In conclusion, highly loaded fluorescent CS nanoparticles could be easily prepared using complex coacervation method and therefore can be applied in various medical researches.

Novel hyaluronic acid–chitosan nanoparticles as non-viral gene delivery vectors targeting osteoarthritis

Gene therapy is a promising new treatment strategy for common joint-disorders such as osteoarthritis. The development of safe, effective, targeted non-viral gene carriers is important for the clinical success of gene therapy. The present work describes the use of hybrid hyaluronic acid (HA)/chitosan (CS) nanoparticles as novel non-viral gene delivery vectors capable of transferring exogenous genes into primary chondrocytes for the treatment of joint diseases. HA/CS plasmid–DNA nanoparticles were synthesized through the complex coacervation of the cationic polymers with pEGFP. Particle size and zeta potential were related to the weight ratio of CS to HA, where increases in nanoparticle size and decreases in surface charge were observed as HA content increased. The particle size and the zeta potential varied according to pH. Transfection of primary chondrocytes was performed under different conditions to examine variations in the pH of the transfection medium, different N/P ratios, different plasmid concentrations, and different molecular weights of chitosan. Transfection efficiency was maximized for a medium pH of approximately 6.8, an N/P ratio of 5, plasmid concentration of 4 μg/ml, and a chitosan molecular weight of 50 kDa. The transfection efficiency of HA/CS-plasmid nanoparticles was significantly higher than that of CS-plasmid nanoparticles under the same conditions. The average viability of cells transfected with HA/CS-plasmid nanoparticles was over 90%. These results suggest that HA/CS-plasmid nanoparticles could be an effective non-viral vector suitable for gene delivery to chondrocytes.

Crosslinking Properties on Oxidized Cotton Cellulose and Chitosan with Low Molecular Weight

For exploiting green ecological cotton fiber products with the multifunction, a new cotton fiber crosslinked with chitosan of low molecular weight (CCCF) was prepared through the sodium periodate oxidation method. The reaction between amino groups of chitosan and aldehyde groups in the oxidized cotton cellulose occurred to obtain the CCCF in aqueous acetic acid solutions. The aldehyde group content in oxidized cotton cellulose increased markedly with the sodium periodate concentration, and the maximum weight gain of chitosan introduced on cotton fiber was 11.63% of the weight of cotton fibers. Furthermore, the crosslinking properties were respectively investigated by measurements of FT-IR and XPS spectra, the analysis indicated that the chitosan molecule was crosslinked on the surface of cotton fiber by the C=N covalent bond. This resulting CCCF is a novel ecological fiber and has more abilities of potential modification, which suggested useful information in planning applications for these modified cotton fibers.

Influence of some factors affecting antibacterial activity of PVA/Chitosan based hydrogels synthesized by gamma irradiation

Poly (vinyl alcohol) hydrogels containing different concentrations of chitosan with molecular weight of 471 and 101 kDa were crosslinked by gamma irradiation at a dose of 25 kGy. The swelling behavior, gel content and morphological structure of the blend were investigated. The antibacterial effect, as a function of chitosan content and molecular weight in the hydrogel, was investigated against Escherichia coli and Bacillus subtilis. With increasing chitosan content the equilibrium degree of swelling of the blend increased and the gel fraction decreased. Results of antibacterial activity of chitosan revealed that chitosan was more effective in inhibiting growth of gram positive bacteria than that of gram negative ones. It was observed that, the chitosan content as well as its molecular weight has a direct influence on bacteria growth inhibition. The higher the chitosan content in the blend and the higher its initial molecular weight, the larger was the inhibition zone diameter. The bacteria growth inhibition was attributed to the diffusion of entrapped chitosan from the hydrogel blend to the culture medium.

Chitosan- graft-(PEI-β-cyclodextrin) copolymers and their supramolecular PEGylation for DNA and siRNA delivery

Two water-soluble chitosan- graft-(polyethylenimine-β-cyclodextrin) (CPC) cationic copolymers were synthesized via reductive amination between oxidized chitosan (CTS) and low molecular weight polyethylenimine-modified β-cyclodextrin (β-CD-PEI). The two polycations, termed as CPC1 and CPC2, were characterized by proton nuclear magnetic resonance spectroscopy, gel permeation chromatography, and elemental analysis. These polycations exhibited good ability to condense both plasmid DNA (pDNA) and small interfering RNA (siRNA) into compact and spherical nanoparticles. Gene transfection activity of both polymers showed improved performance in comparison with native CTS in HEK293, L929, and COS7 cell lines. Further investigation of the gene transfection mediated by CPC2/DNA complexes showed both time-dependent and dose-dependent in the tested cell lines, where the polymer showed higher level luciferase expression than commercially available branched PEI (25 kDa) under the condition of high dose or extended time. Gene silencing activity mediated by CPC2/siRNA against luciferase expression showed superior knockdown effect in HEK293 and L929 cell lines. In addition, both polymers exhibited much lower cytotoxicity than PEI (25 kDa) in HEK293, L929, and COS7 cell lines. More interestingly, the pendent β-CD moieties of CPC copolymers allowed the supramolecular PEGylation though self-assembly of adamantyl-modified poly(ethylene glycol) with the β-CD moieties. The supramolecular PEGylation of the polyplexes significantly improved their stability under physiological conditions. The supramolecular PEGylated polyplexes of CPC with pDNA showed decreased transfection efficiency in all tested cell lines. However, remarkably, the supramolecular PEGylated polyplexes with siRNA exhibited even higher silencing efficiency in HEK293 and L929 cells (up to 84%), comparable to commercial DharmaFECT. The interesting mechanism for the enhanced silencing efficiency was discussed. With the pendent β-CD moieties on CTS chains, the system is expected to be further modified via inclusion complexation between β-CD unit and guest molecules to serve as a multifunctional delivery system.

Physicochemical and structural characteristics of chitosan nanopowders prepared by ultrafine milling

Two different molecular weights of chitosan were pulverized to nanopowders by ultrafine milling. The nanopowders were characterized by viscometry small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), FT-IR spectroscopy and UV-vis spectroscopy. Our results showed that ultrafine milling effectively reduced the particle size of chitosan to a nanoscale. The viscosity average molecular weight (Mv) of chitosan was decreased by the milling treatment. The crystalline structure of chitosan was destroyed by the milling since the nanopowder exhibited an amorphous XRD pattern. In addition, thermal stability of the low molecular weight chitosan was decreased after the milling treatment. FT-IR and UV-vis spectra showed that the milling process did not cause significant changes in the chemical structure of chitosan.

Coaxial electrospun poly(lactic acid)/chitosan (core/shell) composite nanofibers and their antibacterial activity

Biodegradable non-woven mats of poly(lactic acid) (PLA) and chitosan (CS) were fabricated by the coaxial electrospinning process. These non-woven mats are composed of PLA/CS core/shell composite nanofibers, in which PLA and CS form the core and shell layers, respectively. CS of high molecular weight could not be electrospun on its own because of its high viscosity in solution and its polycationic possession. The coaxial electrospinning method was able to facilitate the fabrication of double-layer PLA/CS composite nanofibers by employing a PLA layer in the core and a CS layer in the shell part. Transmission electron microscopy (TEM) studies and contact-angle measurements indicated the core/shell structure of the composite nanofibers fabricated with shell and core feed rates of 5μL/min and less than 2μL/min, respectively. The PLA/CS core/shell composite nanofibers showed antibacterial activity against Escherichia coli; hence it can be used as antibacterial materials in fields such as biomedical and filtration areas.

Formulation and physicochemical characterization of chitosan/Acyclovir co-crystals

In the current study, the influence of chitosan on the dissolution rate and bioavailability of acyclovir has been illustrated through the preparation of co-crystals by simple solvent change method. Chitosan was precipitated on acyclovir crystals using sodium citrate as the salting out agent. The pure drug and the prepared co-crystals using different concentrations and molecular weights of chitosan were characterized in terms of drug content, particle size, thermal behavior, IR analysis, surface morphology, in vitro drug release and physical stability. The results obtained showed that the practical yield of the prepared co-crystals was found to be inversely proportional to chitosan concentration. The drug content of the co-crystals was uniform among the different batches. The prepared co-crystals showed a slower drug release when compared to that of pure drug. The considerable change in the dissolution rate of acyclovir from optimized crystal formulation was attributed to the wetting effect of chitosan, the reduction in drug crystallinity and the altered surface morphology. The thermograms showed a decrease in the melting enthalpy of acyclovir indicating a disorder in the crystalline content whereas IR spectroscopy studies revealed an interaction between acyclovir and chitosan. The optimized co-crystals were stable for three months at 40°C and 75 ± 5% RH.

Improved postharvest quality in patagonian squash ( Cucurbita moschata) coated with radiation depolymerized chitosan

Different molecular weight chitosans were evaluated on the decay of coated Anquito squashes ( Cucurbita moschata) as well as the maintenance of the fruit quality along five storage months. The original chitosan (Mw=391 kDa, 83% DD), was depolymerized by gamma radiation. Apart from chain scission, other chemical changes were not detected by FTIR or UV–vis analyses. The molecular weight characterization of chitosans was done by size exclusion chromatography with dual light scattering and concentration detection (SEC-MALLS-RI). The coating effectiveness was evaluated on the following parameters: fungal decay incidence, weight loss, firmness, total reducing sugar, soluble solid, flesh color, carotene content, pH and titratable acidity. No sign of fungal decay was observed in squashes coated with 122 and 56 kDa chitosans, which were also the most effective treatments in reducing the weight loss. The chitosan with Mw=122 kDa was also the best treatment considering firmness, internal aspect, sugar and carotene content. Then, radiation degraded chitosan was better in C. moschata preservation than the original chitosan.

Chitosan as a flocculant for pre-hydrolysis liquor of kraft-based dissolving pulp production process

In this work, the flocculation concept was employed to recover the dissolved lignocellulosic materials of industrially produced pre-hydrolysis liquor (PHL) using two different molecular weights of chitosan. The analysis revealed the maximum turbidity of 1000NTU or 1900NTU via adding 2.2mg/g low molecular weight (LMW) or 1.7mg/g high molecular weight (HMW) chitosan to the PHL, respectively. Also, the maximum furfural removal of 55% or 50% was obtained by adding 0.7mg/g or 0.5mg/g LMW or HMW chitosan to the PHL, respectively. The maximum recovery of oligomeric sugars was 20% or 25% by adding 1.5 or 0.5mg/g LMW or HMW chitosan, while that of lignin was 40% or 35% by applying 2.2mg/g or 1.7mg/g LMW or HMW chitosan to the PHL, respectively. The removal of monomeric sugars and acetic acid was rather limited. The particle size and nitrogen analyses were also hired to characterize the properties of the formed complexes.

Study of Flocs Morphology of Chitosan Coagulation Aid Treatment and Fractal Dimensions

Flocculation water treatment is one of the important aspects of water treatment .The aim of this work is to use PFS for treating Yellow River surface water and different molecular weights of chitosan as coagulant aid. Electron microscope was used to observe flocs morphology and study CTS coagulation aid morphological change, floc image with microscope camera system analysis, calculation of floc fractal dimension. The results show that the different molecular weights of CTS in dealing with surface raw water to play a good coagulation aid effect. Microscope and image analysis system of flocs morphology show that fractal dimension of morphology of PFS / CTS were significantly higher ,Among them，high molecular weight of CTS as coagulant aid，and fractal dimension of morphology of PFS/ CTS were 1.1026,1.5593 , low molecular weight of CTS as coagulant aid，and fractal dimension of morphology of PFS/ CTS were 1.0904,1.5440 respectively. Floc fractal dimension changes to better reflect the flocculation level and treatment effect for the establishment of floc fractal dimension number of changes in the coagulation control is provided for reference.

Effects of chitosan molecular weight and degree of deacetylation on the properties of gelatine-based films

The effect of chitosan molecular weight (MW) and degree of deacetylation (DD) on the physicochemical properties of gelatine-based films was studied with the goal of improving the films. Determination of the dynamic viscoelastic properties (elastic modulus G′ and viscous modulus G″) of the film-forming solutions revealed that the interactions between gelatine and chitosan were stronger in the blends made with chitosan of higher molecular weights or higher degrees of deacetylation than the blends made with lower molecular weights or degrees of deacetylation. Fish gelatine films modified with chitosan of higher molecular weights or higher degrees of deacetylation had higher tensile strengths (TS, 72.4 MPa for 550 kDa vs. 62.2 MPa for 200 kDa; 63.2 MPa for 93.6% DD vs. 38.0 MPa for 76.5% DD) and higher glass transition temperatures ( T g, 130 °C for 550 kDa vs. 108 °C for 200 kDa; 108 °C for 93.6% DD vs. 103 °C for 76.5% DD). Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) studies indicated that gelatine and chitosan interactions determined the properties of the film. Thus, combining gelatine and chitosan may be a method for improving the physicochemical properties of gelatine films, especially when using chitosan of higher molecular weights and higher degrees of deacetylation.