Medium Molecular Weight Chitosan Research Articles

Protein adsorption through Chitosan-Alginate membranes for potential applications.

BackgroundChitosan and Alginate were used as biopolymers to prepare membranes for protein adsorption. The network requires a cross-linker able to form bridges between polymeric chains. Viscopearl-mini® (VM) was used as a support to synthesize them. Six different types of membranes were prepared using the main compounds of the matrix: VM, Chitosan of low and medium molecular weight, and Alginate.ResultsExperiments were carried out to analyze the interactions within the matrix and improvements were found against porous cellulose beads. SEM characterization showed dispersion in the compounds. According to TGA, thermal behaviour remains similar for all compounds. Mechanical tests demonstrate the modulus of the composites increases for all samples, with major impact on materials containing VM. The adsorption capacity results showed that with the removal of globular protein, as the adsorbed amount increased, the adsorption percentage of Myoglobin from Horse Heart (MHH) decreased. Molecular electrostatic potential studies of Chitosan–Alginate have been performed by density functional theory (DFT) and ONIOM calculations (Our own N-layered integrated molecular orbital and molecular mechanics) which model large molecules by defining two or three layers within the structure that are treated at different levels of accuracy, at B3LYP/6-31G(d) and PM6/6-31G(d) level of theory, using PCM (polarizable continuum model) solvation model.ConclusionsFinally, Viscopearl-mini® acts as a suitable support on the matrix for the synthesis of Chitosan–Alginate membranes instead of cross-linkers usage. Therefore, it suggests that it is a promise material for potential applications, such as: biomedical, wastewater treatment, among others.Graphical abstractChitosan, Alginate, and Cellulose beads-based membranes for protein adsorption. Special attention was given for preparation, charaterization, adsorption capacity, and molecular electrostatic potential studies calculation. Viscopearl-mini® gives support on the matrix of Chitosan–Alginate membranes instead of cross-linkers usage

Effect of chitosan molecular weight as micro and nanoparticles on antibacterial activity against some soft rot pathogenic bacteria

This study evaluates the in vitro antibacterial activity of three molecular weights of chitosan in the form of micro (CS) as well as nanoparticles (CSNPs). CSNPs were prepared using low (LWC), medium molecular weight (MWC) and middle-viscous crab shells chitosan (MVC). The antibacterial activities were evaluated through determination of IC50, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Pseudomonas fluorescens, Erwinia carotovora and Escherichia coli. Experimental results showed that the antibacterial activity was significantly enhanced in the CSNPs comparison to CS microparticles, especially so for MVC nanoparticles (MVCN) in that the MIC values against all tested bacteria were ca. 50% those of the microparticles. Moreover, MWC and LWC nanoparticles showed lower MIC values compared with related microparticles only for P. fluorescens and E. coli, respectively. In addition, atomic force microscopy (AFM) of CSNPs-treated cultures of selected bacteria species revealed structural changes in the bacterial cell wall. The present study indicates that the antibacterial activity of CS varied depending on the molecular weight of CS micro and nanoparticles forms as well as on the particular bacterium. The selection of CS's molecular weight could be thought to be more dependent on its application.

In Vitro Investigation of Influences of Chitosan Nanoparticles on Fluorescein Permeation into Alveolar Macrophages.

Pulmonary infection namely tuberculosis is characterized by alveolar macrophages harboring a large microbe population. The chitosan nanoparticles exhibit fast extracellular drug release in aqueous biological milieu. This study investigated the matrix effects of chitosan nanoparticles on extracellular drug diffusion into macrophages. Oligo, low, medium and high molecular weight chitosan nanoparticles were prepared by nanospray drying technique. These nanoparticles were incubated with alveolar macrophages in vitro and had model drug sodium fluorescein added into the same cell culture. The diffusion characteristics of sodium fluorescein and nanoparticle behavior were investigated using fluorescence microscopy, scanning electron microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy techniques. The oligochitosan nanoparticles enabled macrophage membrane fluidization with the extent of sodium fluorescein entry into macrophages being directly governed by the nanoparticle loading. Using nanoparticles made of higher molecular weight chitosan, sodium fluorescein permeation into macrophages was delayed due to viscous chitosan diffusion barrier at membrane boundary. Macrophage-chitosan nanoparticle interaction at membrane interface dictates drug migration into cellular domains.

Chitosan:PEGDA hybrid-gel scaffolds printed by stereolithography

Event Abstract Back to Event Chitosan:PEGDA hybrid-gel scaffolds printed by stereolithography Siddharth N1, Viola B. Morris1, Mousa Younesi1 and Ozan Akkus1 1 Case Western Reserve University, Department of Mechanical and Aerospace Engineering, United States Introduction: 3D biofabrication strategies enable the development of tissue engineering scaffolds with complex heterogeneous architectures[1]. The hybridization of natural and synthetic polymer offers the advantages of enabling cell adhesion and adjustment of mechanical properties[2]. In the present work we have developed a hybrid resin of natural polymer chitosan and synthetic polymer polytheylene glycol diacrylate (PEGDA) with Irgacure 819 as photoinitiator for photo-printing by stereolithography. Due to rigid crystalline structure of chitosan polymer, its solubility is restricted in dilute acids and it becomes an obstacle to formulate chitosan with other photocurable synthetic polymers, as the protonated amines will quench the newly formed free radicals by the photoinitiators[3]. We have developed a novel and simplified approach to address this issue by dialyzing chitosan in salt solution. Materials and Method: High molecular weight (η=800-2000 cP) chitosan solution (18mg/ml) was prepared in 1% acetic acid and dialyzed in 0.1N CH3COONa for 24h. Photocurable resins were prepared by mixing varying feed ratios of Chitosan to PEGDA (MW=575 Da) such as 1:5, 1:10, 1:20 and 1:25 with Irgacure 819 in N-vinyl-2-pyrolidinone (100 mg/ml) as photoinitiator. Scaffolds were designed in SolidWorks. 3D printing was performed by Form 1+ High Resolution printer (Formlab) and layer by layer using 405 nm laser via galvanometric mirrors. Young’s modulus of scaffolds was calculated from the slope of stress-strain curves in the range of 20-40% strain using a compression test device. Cell viability was measured at day 1 using calcein AM/ethidium homodimer 1 LIVE/DEAD assay. Results and Discussion: To deprotonate the primary amines we have dialyzed chitosan in 0.1N sodium acetate solution that enabled photocuring of Chitosan:PEGDA hybrid gels. Chitosan increased the viscosity of resin and decreased the minimum required concentration of PEGDA from 20% to 12.5%[4]. The required concentration of photoinitiator was reduced from 0.0325 to 0.02 % as the feed ratio of Chitosan to PEG increased from 1:5 to 1:25, likely due to the higher concentration of diacrylate functional group. However, higher concentration diacrylate group was responsible for excessing crosslinking at higher ratios and resulted in less precise shapes (Fig 1B). So we have chosen feed ratios of 1:5 to 1:15 for further studies. Hybrid of PEG with chitosan (1:10) has enhanced the modulus (157.5 kPa ± 0.03, n=3) 40 fold higher compared to uncrosslinked chitosan[5] (Fig 1C). The same feed ratio (1:10) was found to be result in higher number of live cells after 24h of incubation as evidenced by Live Dead assay. The lower live cell cell counts of hybrid with 1:5 (~ 10 fold) and 1:15 (~4 fold) compared to 1:10 was assumed to be due to higher concentration of photoinitiator and higher concentration of PEGDA which is less conducive to cell adhesion, respectively (Fig 2A&B). Conclusion: Chitosan:PEGDA hybrid resins were formulated for 3D bioprinting of complex structured scaffold for tissue engineering. Presently we have used only high molecular weight chitosans. However for fabricating more precise 3D structures we plan to use low and medium molecular weight chitosan in our future experiments.

Medium Molecular Weight Chitosan as a Carrier for Delivery of Lincomycin Hydrochloride from Intra-pocket Dental Film: Design, Development, in vitro and ex vivo Characterization

Medium Molecular Weight Chitosan as a Carrier for Delivery of Lincomycin Hydrochloride from Intra-pocket Dental Film: Design, Development, in vitro and ex vivo Characterization

Characterization and evaluation of mechanical properties of injectable porous spherical nano-hydroxyapatite/chitosan particles for craniofacial bone regeneration

Event Abstract Back to Event Characterization and evaluation of mechanical properties of injectable porous spherical nano-hydroxyapatite/chitosan particles for craniofacial bone regeneration Suren Uswatta1 and Ambalangodage C. Jayasuriya2 1 University of Toledo, Bioengineering, United States 2 University of Toledo, Department of Orthopaedic Surgery, United States Introduction: Craniofacial bone surgery and regeneration is a major challenge in regenerative medicine. As a solution injectable microscale particles have been fabricated and characterized since they can be implanted with a minimally invasive surgery[1]. Although craniofacial bone is not a load bearing bone, injectable particles should possess stability towards certain physiologic conditions and retain its mechanical strength at abruptly occurring external loading applications. In this study we have fabricated porous particles using chitosan biopolymer and nano-hydroxyapatite (nHA). We hypothesized that incorporating nHA into chitosan could emulate the mineralized cortical bone structure, thus improve the mechanical strength of the particles. Materials and Methods: Medium molecular weight chitosan, hydroxyapatite nanopowder (nHA, <200nm particle size), sodium tripolyphosphate (TPP, technical grade, 85%) and acetic acid (A.C.S reagent, 99.7%) 2% (w/v) chitosan solution was prepared by dissolving chitosan and 1% (v/v) acetic acid. Then nHA has been added to 2% (w/v) chitosan solution to make 0.5%, 1% and 2% (w/v) nHA/chitosan composite mixtures. These mixtures were dripped into 27.18mM TPP/Deionized water solution using 30 gauge needle and stirred at 600RPM. After 30 minutes TPP cross-linked nHA/chitosan beads filtered out from TPP solution and lyophilized at -52oC temperature and 0.02 mbar pressure for 24 hours. Portion of each batch were treated further by soaking followed by drying and named as Lyophilized Soaked and Dried (LSD) particles. Finally particles were characterized for their morphology, chemical structure, physical structure, cell cytotoxicity and attachment. Finally particles were tested for its ultimate compressive strength (UCS) at dry and wet states using ADMET’s MTESTQuattro universal testing machine using 0.05mm/s cross head movement. Statistical data were analyzed using IBM SPSS Statistics version 21. Figure 1- Scanning electron microscopy images of 2% nHA/Chitosan particle surfaces Results and Discussion: Fabricated lyophilized and LSD particles had a mean diameter of 1.33 and 0.93 mm respectively which is promising for injectability of the particles via needles. SEM images showed porous surface morphology and interconnected pore structures inside the particles. Lyophilized and LSD particles had surface pores with diameters less than 10 and 2 µm respectively (Figure 1.A and 1.B). This highly porous surface morphology improves the osteoconductivity of scaffolds by facilitating osteoblast cell adhesion and proliferation. One-way ANOVA results showed that, there is significant increase in UCS of 1% and 2% nHA compared to 0% nHA lyophilized particles at (p<0.001) significance level (Figure 2.A). Further increase in nHA percentage affects the dripping process due to high clogging factor in the needle and higher viscosity of the solution. Moreover, 2% nHA LSD particles had increased their mean UCS by 120% compared to 2% nHA lyophilized particles at (p<0.005) significance level. In a drawback, all particles have lost their mechanical properties by 95% at (p<0.001) significance level on the 2nd day when fully immersed in phosphate buffered saline (PBS). However, particles preserved its initial shape and showed minimal degradation at the end of 100th day in PBS solution. Additionally live and dead cell assay showed zero cytotoxicity and good osteoblast cell attachment to both lyophilized and LSD particles at the end of 6th day of in vitro studies (Figure 2.B and 2.C). Figure 2- Ultimate compressive strengths of nHA/Chitosan lyophilized particles at different nHA compositions are shown in 2.A. Live and Dead cell assay results are shown in 2.B and 2.C. Live cells proliferation can be seen on 2.B FITC image. Presence of dead cells in the same region is captured using TRITC filter as shown in 2.C Conclusion: Experiments results shows that incorporating nHA can improve the mechanical properties of lyophilized chitosan particles. This result is consistent with a study that HA can improve the mechanical properties of electrospun fibers[2]. No cell cytotoxicity and higher cell attachment shows improved osteoconductivity of the particles. However further modifications on particles is required to improve to wet state mechanical properties. National Institute of Health - Grant account number R01DE023356

Chitosan seed soaking: germination and growth of Coriandrum sativum and Solanum lycopersicum

Chitosan seed soaking: germination and growth of Coriandrum sativum and Solanum lycopersicum

Active Molecular Chitosan (AMC-S1): Preparation and characterization of Antibacterial Activity

The aim of the present study is to prepare the chitosan hydrolysates and characterize their potential antibacterial activity. High molecular weight chitosan (CTSN-H) and medium molecular weight chitosan (MMWC, 2~10-kDa) were further degraded efficiently by using chitosanase from Bacillus subtilis JH-1122. Molecular weight (MW) of the final product was determined by MALDI-TOF MS, showed several peaks ranging from 0.8 to 2.5-kDa. Based on antibacterial activity of the hydrolysates, final products were named as active molecular chitosan (AMC-S1). AMC-S1 was evaluated as IC50 to 12.5 μg/mL of the concentration toward Candida albicans. Our present study demonstrates that AMC-S1 derived from the digestion of CTSN-H and MMWC can be selected as a potent factor affecting on antimicrobial activity against C. albicans for the industry and pharmaceutical applications.

Design, Optimization, and Evaluation of a Novel Metronidazole-Loaded Gastro-Retentive pH-Sensitive Hydrogel.

Floating pH-sensitive chitosan hydrogels containing metronidazole were developed for the eradication of Helicobacter pylori from the stomach. Hydrogels were prepared by crosslinking medium or high molecular weight chitosan in lyophilized solutions containing metronidazole using either citrate or tripolyphosphate (TPP) salts at 1% or 2% concentration. A 23 factorial design was developed to study the influence of formulation parameters on the physical characteristics of the prepared hydrogels. The interaction between hydrogel components was investigated. The morphology of the prepared hydrogels was inspected and their percentage swelling, release pattern, and moisture content were evaluated. The results revealed the absence of interaction between hydrogel components and their highly porous structure. Percentage swelling of the hydrogels was much higher, and drug release was faster in gastric pH compared with intestinal pH. The formula prepared using 2% high molecular weight chitosan and 2% TPP significantly swelled (700%) within the first 4h and released the loaded drug over a period of 24h. Its moisture content was not affected by storage at high relative humidity. Therefore, this formula was selected to be tested in dogs for its gastric retention (using X-ray radiography) and efficacy in the eradication of H. pylori (using histopathological and microbiological examination). The results revealed that the prepared hydrogel formula was retained in dog stomach for at least 48h, and it was more effective against H. pylori than the commercially available oral metronidazole tablets (Flagyl®).

Ruthenium Recovery from Acetic Acid Waste Solution by Using PEI-Coated Biomass-Chitosan Composite Fiber

Polyethylenimine (PEI)-coated biomass-chitosan composite fiber (PBCF) was fabricated to recover Ru from acetic acid waste solution. The present work aimed to understand the effects of molecular weight of chitosan and drying method on stability and sorption performance of the PBCF. For this, the PBCF was prepared by extruding the mixed solutions of chitosan and Corynebacteriumglutamicum to form the composite fibers which were modified with ionic polymer, PEI. The degree of swelling of PBCFs prepared by hot-air, natural, and freeze drying methods were 1.25, 1.34, and 1.07 %, respectively, indicating that the freeze-drying method was the best. Batch biosorption studies showed that the maximum Ru uptake could be achieved with PBCF prepared with medium molecular weight chitosan, and could reach 34.1 mg/g, which was 7.9 times higher than that of the commercial ion exchange resin, LEWATIT® MonoPlus M 500 (4.3 mg/g). Therefore, PBCF can be considered as an alternative sorbent to synthetic resin for recovery of Ru form industrial acetic acid waste solution.

The effects of direct addition of low and medium molecular weight chitosan on the formation of heterocyclic aromatic amines in beef chop

The effects of direct addition of low and medium molecular weight chitosan at different levels (0.25, 0.50, 0.75 and 1%) to beef chops on the formation of heterocyclic aromatic amines (HCAs) were investigated. Chops were cooked at three different temperatures (150, 200 and 250 °C). The use of chitosan had very significant effects on water content, pH and cooking loss values of the samples. Cooking temperature had very significant effects on water content and cooking loss, while it had significant effect on pH value. On the other hand, molecular weight of chitosan had very significant effects on water content and cooking loss. While IQ and MeAαC were not detected, varying amounts of IQx (up to 0.45 ng/g), MeIQx (up to 0.09 ng/g), MeIQ (up to 0.07 ng/g), 7,8-DiMeIQx (up to 0.15 ng/g), 4,8-DiMeIQx (up to 0.05 ng/g), PhIP (up to 2.94 ng/g) and AαC (up to 0.68 ng/g) were detected. While the total HCA content ranged between non-detectable level and 4.21 ng/g, chitosan addition decreased (14.3–100%) the total HCA content.

Nanoparticles incorporating pH-responsive surfactants as a viable approach to improve the intracellular drug delivery.

The pH-responsive delivery systems have brought new advances in the field of functional nanodevices and might allow more accurate and controllable delivery of specific cargoes, which is expected to result in promising applications in different clinical therapies. Here we describe a family of chitosan-TPP (tripolyphosphate) nanoparticles (NPs) for intracellular drug delivery, which were designed using two pH-sensitive amino acid-based surfactants from the family N(α),N(ε)-dioctanoyl lysine as bioactive compounds. Low and medium molecular weight chitosan (LMW-CS and MMW-CS, respectively) were used for NP preparation, and it was observed that the size distribution for NPs with LMW-CS were smaller (~168 nm) than that for NPs prepared with MMW-CS (~310 nm). Hemolysis assay demonstrated the pH-dependent biomembrane disruptional capability of the constructed NPs. The nanostructures incorporating the surfactants cause negligible membrane permeabilization at pH7.4. However, at acidic pH, prevailing in endosomes, membrane-destabilizing activity in an erythrocyte lysis assay became evident. When pH decreased to 6.6 and 5.4, hemolytic capability of chitosan NPs increased along with the raise of concentration. Furthermore, studies with cell culture showed that these pH-responsive NPs displayed low cytotoxic effects against 3T3 fibroblasts. The influence of chitosan molecular weight, chitosan to TPP weight ratio, nanoparticle size and nature of the surfactant counterion on the membrane-disruptive properties of nanoparticles was discussed in detail. Altogether, the results achieved here showed that by inserting the lysine-based amphiphiles into chitosan NPs, pH-sensitive membranolytic and potentially endosomolytic nanocarriers were developed, which, therefore, demonstrated ideal feasibility for intracellular drug delivery.

Biopolymer-Based Thin Film for Sensor Application

Chitosan is one of the most available biopolymers in nature, which is non-toxic, biocompatible and biodegradable. The crosslinked chitosan solution was synthesized by homogeneous reaction of medium molecular weight chitosan in aqueous acetic acid with glutaraldehyde as crosslinking agent. Then the solution was deposited on glass cover slip by spin coater to form a thin film. The functional group and chemical binding of crosslinked chitosan thin film has been confirmed by X-ray photoelectron spectroscopy (XPS). The chemical interaction between copper ion and the crosslinked chitosan thin film has also been analyzed by XPS. XPS revealed that copper ion adsorbed to the crosslinked chitosan thin film and the functional groups involved in the adsorption mechanisms of copper ion on the thin film were determined. This biopolymer thin film can be incorporated with surface plasmon resonance technique to produce a high potential optical sensor for detection of Cu (II) ion in solution.

모링가의 항산화 효과에 미치는 중저분자 키토산의 영향

The aim of this study is to elucidate the antibacterial activity of medium molecular weight chitosan (MMWC) along with keeping antioxidant activity of Moringa oleifera leaves extracts, which has shown the significant antioxidant activity. Antioxidant activity of the extracts as either free or ingredient in edible food was investigated in vitro by radical scavenging assays with 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and 2,4,6-Tris(2-pyridyl)-s-triazine (FRAP). The results showed that extracts has showed high antioxidant activity while added in edible food as like a muk, although when it was added in muk as food additives, its original activity was reduced slightly. In addition, in the presence of MMWC with ranging from 3 to 8-kDa in muk, various improvements including antibacterial effect and stability of structure of muk were observed. Taken together, specified size of chitosan seems to be a good candidate playing a key role to maintain the antioxidant and antibacterial activities in functional foods.

High Resolution X-Ray Photoelectron Spectroscopy Study of the Interaction of Copper Ion with Chitosan Thin Film

In this study, high-resolution X-ray photoelectron spectroscopy (XPS) has been used to study the chemical interaction between copper ion and chitosan thin film. The chitosan solution was synthesized by homogeneous reaction of medium molecular weight chitosan in aqueous acetic acid with glutaraldehyde as crosslinking agent. Then the solution was deposited on glass cover slip by spin coater to form a thin film. The functional group and chemical binding of crosslinked chitosan thin film has been confirmed by XPS. XPS revealed that copper ion adsorbed to the crosslinked chitosan thin film and the functional groups involved in the adsorption mechanisms of copper ion on the thin film were determined.

The influence of chitosan on the structural properties of whey protein and wheat starch composite systems

The structural properties of medium molecular weight chitosan (CHT), whey protein isolate (WPI) and native wheat starch (WS) from low- to intermediate-solid single systems and composite matrices were investigated. Analysis involved monitoring the thermal behavior of these biopolymers during controlled heating from 25 up to 95°C and subsequent cooling to 5°C under small deformation dynamic oscillation in-shear and micro differential scanning calorimetry experiments. Further information regarding the molecular interactions of components and overall network morphology of the systems was revealed through subjecting thermally developed gels to large deformation compression testing, scanning electron microscopy and infrared spectroscopy. Our study found a significant change in the structure of WPI networks upon incorporation of CHT in preparations due to electrostatic forces developing between the two polymeric constituents. In the tertiary system, the presence of low levels of starch contributed to a reduction in the firmness of the gel matrix. However, at higher additions of the polysaccharide, a recovery in the stored energy of composite materials was apparent, as recorded in the thermomechanical protocol.

Coated nickel foam electrode for the implementation of continuous electro‐Fenton treatment

ABSTRACTBACKGROUNDElectro‐Fenton technology has already demonstrated its ability to degrade organic pollutants. In this treatment hydroxyl radicals are formed due to the reaction of the iron catalyst along with in situ electrogenerated H2O2. However, one of the main limitations of this system is the iron released in the treated effluent. Therefore, retention of iron is required, and in this study, the use of a new cathode in which the iron is fixed on nickel foam is proposed as a solution to the electro‐Fenton treatment in continuous processes.RESULTSThe retention of iron was ensured by its fixation on nickel foam using chitosan, an eco‐friendly polymer, as coating agent. Different chitosan coatings were tested to optimize the manufacturing process of the new cathode. It was concluded that the best electrode for the electro‐Fenton treatment of different dyes (Poly R‐478 and Lissamine Green B) was obtained using a half‐coating electrode cover with iron–chitosan of medium molecular weight. Furthermore, its reusability was positively evaluated in successive cycles. Finally, a continuous treatment using a fluidized bed reactor was successfully performed for the treatment of dye Lissamine Green B.CONCLUSIONSummarizing, this new cathode is a suitable alternative for the treatment of coloured wastewater by continuous electro‐Fenton treatment. © 2014 Society of Chemical Industry

Chitosan/corn starch blend films with extract from Brassica oleraceae (red cabbage) as a visual indicator of fish deterioration

Chitosan and Starch are polymers that can be obtained from renewable sources, with good film-forming properties and many applications in food industry, such as active and smart-packaging, which can monitor and inform consumers about food conditions in real-time. Hence, we report here a system for pH monitoring based on Chitosan, Corn Starch and red cabbage extract, all inexpensively obtained from renewable sources. The system was produced from medium molecular weight Chitosan, Corn–Starch and phytochemical extract from Brassica oleracea var. capitata (Red Cabbage). TG-DSC, FT-IR, Water Vapour Transmission Rate, as well as light microscopy were used to characterize the system. The colour variation after activation in different pH range was measured with the CIELab methodology. In order to validate the use of this system as a fish spoilage detection sensor, application tests were conducted with fish fillets. The results show that the system has good optical and morphological properties and is very sensitive to pH variations. During the application test, the system visually indicated pH changes. Thus, the system shows a clear response to pH variation of the samples. Therefore, it has potential to be used as a visual indicator of the storage and consumption conditions of food.

Antimicrobial analysis of films processed from chitosan and N,N,N-trimethylchitosan

Chitosan and its derivatives have been proposed as bactericidal and fungicidal agents against a large numbers of gram-negative and gram-positive bacteria and fungi. Some antimicrobial mechanisms have been proposed for chitosan, with the most widely acceptable being the presence of charged-NH3+ groups in the polymer backbone and its interactions with the bacterial wall constituents. Since this mechanism is based on an electrostatic interaction, it suggests that the greater the number of cationic amines, the higher will be the antimicrobial activity. So, in the present study, the effectiveness of commercial medium molecular weight chitosan and its ionic charged derivative (quaternized N,N,N-trimethylchitosan) were evaluated. Cast films of both materials were assessed against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) as model bacteria by inhibition zone formation. The results show positive activity against the gram-positive microorganism for both materials. The antibacterial effectiveness of the chitosan derivative was dependent on the film polymer concentration. No activity however, was observed against the gram-negative species for either material in film form. The results point to the possibility of considering different antimicrobial mechanisms acting on each type of bacteria.

In situ synthesis of calcium phosphates on chitosan macromolecules in the presence of glutamic and aspartic acids

Calcium hydrogen phosphate dihydrate and amorphous calcium phosphate have been synthesized in an aqueous suspension of medium molecular weight chitosan in the presence of glutamic or aspartic acid. X-ray diffraction and transmission and scanning electron microscopy characterization showed that the morphology of the phases present depended on the nature of the amino acid. The amino acids participate in the protonation of the amino groups of the chitosan and, probably, in the formation of chelate intermediate compounds with calcium ions, which act as calcium phosphate nucleation centers.