Gelatin/carboxymethyl chitosan/aloe juice hydrogels with skin-like endurance and quick recovery: Preparation, characterization, and properties.

Gelatin-based hydrogels have gained considerable attention due to their resemblance to the extracellular matrix and hydrophilic three-dimensional network structure. Apart from providing an air-permeable and moist environment, these hydrogels optimize the inflammatory microenvironment of the wounds. These properties make gelatin-based hydrogels highly competitive in the field of wound dressings. In this study, a series of composite hydrogels were prepared using gelatin (Gel) and carboxymethyl chitosan (CMCh) as primary materials, glutaraldehyde as a crosslinker, and aloe vera juice as an anti-inflammatory component. The properties of the hydrogel, including its rheological properties, microscopic structures, mechanical properties, swelling ratios, thermal stability, antibacterial properties, and biocompatibility, were investigated. The results demonstrate that the gelatin-based hydrogels exhibit good elasticity and rapid self-healing ability. The hydrogels exhibited slight shear behavior, which is advantageous for skin care applications. Furthermore, the inclusion of aloe vera juice into the hydrogel resulted in a dense structure, improved mechanical properties and enhanced swelling ratio. The Gel/CMCh/Aloe hydrogels tolerate a compressive strength similar to that of human skin. Moreover, the hydrogels displayed excellent cytocompatibility with HFF-1 cells, and exhibited antibacterial activity against E. coli and S. aureus. Lomefloxacin was used as a model drug to study the releasing behavior of the Gel/CMCh/aloe hydrogels. The results showed that the drug was released rapidly at the initial stage, and could continue to be released for 12 h, the maximum releasing rate exceeded 20 %. These findings suggest that the gelatin-based hydrogels hold great promise as effective wound dressings.

N-lauric-O-carboxymethyl chitosan: Synthesis, characterization and application as a pH-responsive carrier for curcumin particles.

A pH-responsive amphiphilic chitosan derivative, N-lauric-O-carboxymethyl chitosan (LA-CMCh), is synthesized. Its molecular structures are characterized by FTIR, 1H NMR, and XRD methods. The influencing factors are investigated, including the amount of lauric acid (LA), carboxymethyl chitosan (CMCh), N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC), and N-hydroxysuccinimide (NHS), and their molar ratio, reaction time, and reaction temperature on the substitution. The degrees of substitution (DS) of the lauric groups on the -NH2 groups are calculated based on the integrated data of 1H NMR spectra. The optimum reaction condition is obtained as a reaction time of 6 h, a reaction temperature of 80 °C, and a molar ratio of lauric acid to O-carboxymethyl chitosan to N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride to N-hydroxysuccinimide of 1:3:4.5:4.5, respectively. The crystallinity and initial decomposition temperature of LA-CMCh decrease, but the maximum decomposition temperature increases. The crystallinity is reduced due to the introduction of LA and the degree of hydrogen bonding among LA-CMCh molecules. LA-CMCh could self-aggregate into particles, which size and critical aggregation concentration depend on the degree of substitution and medium pH. LA-CMCh aggregates could load curcumin up to 21.70 %, and continuously release curcumin for >200 min. LA-CMCh shows nontoxicity to fibroblast HFF-1 cells and good antibacterial activity against S. aureus and E. coli, indicating that it could be used as an oil-soluble-drug carrier.

Acyl-protein thioesterase1 alleviates senile osteoporosis by promoting osteoblast differentiation via depalmitoylation of BMPR1a.

Objective: Senile osteoporosis (SOP) is an aging-related disease. The depalmitoylating enzyme Acyl-protein thiesterase1 (APT1) is involved in disease regulation. This study explored the mechanism of APT1 in SOP. Methods: Eight-week-old SAMP6 mice were selected as SOP models and SAMR1 mice were controls, while osteoblasts were isolated from the femoral surface-soft tissues of SOP and control mice as in vitro models. Mouse femur morphological, bone mineral density (BMD), femur maximum elastic stress and maximum load, and APT1 expression were detected by HE staining, X-ray bone densitometer, material testing machine, and RT-qPCR and Western blot (WB). Osteoprotegrin (OPG)-labeled osteoblasts and APT1 localization in bone tissues were detected by immunohistochemical staining. APT1 expression was promoted in SOP mice by tail vein injection of APT1 lentivirus or promoted/silenced in osteoblasts by transfection of pcDNA3.1-APT1 overexpression or si-APT1 plasmids. SOP mouse osteoblast differentiation (OD), OD-related protein levels, osteoblast proliferation, BMPR1a palmitoylation level, and BMP/Smad pathway were detected by alizarin red staining, ALP activity detection, WB, CCK-8, and IP-ABE method. The effects of the pathway inhibitor LDN-193189 on OD were detected. Results: APT1 was under-expressed in osteoblasts of bone tissue in SOP mice and mainly localized in osteoblasts. SOP mice manifested increased bone marrow cavity and bone trabecular space, thinned trabecular bone, decreased BMD, maximum elastic stress, maximum load, and reduced OPG-positive osteoblasts in bone tissues, which were averted by APT1 overexpression, thus alleviating SOP. APT1 overexpression increased osteoblast calcium nodules, ALP activity, OD-related protein levels, and cell proliferation. In mechanism, APT1 overexpression inhibited BMPR1a palmitoylation in SOP mouse osteoblasts and activated the BMP/Smad pathway, thus promoting OD. Conclusion: APT1 activated the BMP/Smad pathway and promoted OD by regulating BMPR1a depalmitoylation, thus alleviating mouse SOP.

Effects of Chitosan and Cellulose Derivatives on Sodium Carboxymethyl Cellulose-Based Films: A Study of Rheological Properties of Film-Forming Solutions.

Bio-based packaging materials and efficient drug delivery systems have garnered attention in recent years. Among the soluble cellulose derivatives, carboxymethyl cellulose (CMC) stands out as a promising candidate due to its biocompatibility, biodegradability, and wide resources. However, CMC-based films have limited mechanical properties, which hinders their widespread application. This paper aims to address this issue by exploring the molecular interactions between CMC and various additives with different molecular structures, using the rheological method. The additives include O-carboxymethylated chitosan (O-CMCh), N-2-hydroxypropyl-3-trimethylammonium-O-carboxymethyl chitosan (HTCMCh), hydroxypropyltrimethyl ammonium chloride chitosan (HACC), cellulose nanocrystals (CNC), and cellulose nanofibers (CNF). By investigating the rheological properties of film-forming solutions, we aimed to elucidate the influencing mechanisms of the additives on CMC-based films at the molecular level. Various factors affecting rheological properties, such as molecular structure, additive concentration, and temperature, were examined. The results revealed that the interactions between CMC and the additives were dependent on the charge of the additives. Electrostatic interactions were observed for HACC and HTCMCh, while O-CMCh, CNC, and CNF primarily interacted through hydrogen bonds. Based on these rheological properties, several systems were selected to prepare the films, which exhibited excellent transparency, wettability, mechanical properties, biodegradability, and absence of cytotoxicity. The desirable characteristics of these selected films demonstrated the strong biocompatibility between CMC and chitosan and cellulose derivatives. This study offers insights into the preparation of CMC-based food packaging materials with specific properties.

Genipin-crosslinked amphiphilic chitosan films for the preservation of strawberry.

As a material for films used to keep fruits fresh, chitosan has attracted extensive interest because of its advantages of degradability, environmental friendliness, and biocompatibility. In this study, two amphiphilic chitosan derivative films were prepared by crosslinking N-2-hydroxypropyl-3-butyl ether-O-carboxymethyl chitosan (HBCC) and N-2-hydroxypropyl-3-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC)) with genipin, an excellent natural cross-linking agent. The microstructures, mechanical properties, water vapor permeability, swelling ratios, light transmittance, wettability, thermal stability, antibacterial properties, and biocompatibility of the crosslinked films were characterized. The results showed that the crosslinked films had compact structures, low moisture permeability, strong water resistance, strong ultraviolet resistance, unaffected visible light transmittance, and good hydrophilicity. Compared with the uncrosslinked films, the tensile strength of the genipin-crosslinked ones was increased by 328.33 % (HBCC) and 397.83 % (H2ECC). More importantly, the crosslinked films had strong antibacterial activity against Staphylococcus aureus and Escherichia coli and were non-toxic to endothelial cells. The crosslinked films could effectively prolong the preservation time of strawberries, inhibit the decay of strawberries, and inhibit the reduction of vitamin C in strawberries. In conclusion, genipin-crosslinked HBCC and H2ECC films are potential fruit preservation materials.

Studies on Intermolecular Interaction of N-Glycidyltrimethyl Ammonium Chloride Modified Chitosan/N,N-Dimethyl-N-dodecyl-N-(2,3-epoxy propyl) Ammonium Chloride and Curcumin Delivery.

Chitosan has potential applications in many fields, due to its biocompatibility, biodegradability and reproducibility. However, the insolubility in water restricts its wide application. In order to expand the application of chitosan in the delivery of oil-soluble drugs and improve the efficacy of oil-soluble drugs, N-Glycidyltrimethyl ammonium chloride-modified chitosan (GTA-m-CS) and N,N-Dimethyl-N-dodecyl-N-(1,2-epoxy propyl) ammonium chloride (DDEAC), a kind of reactive surfactant, were synthesized and characterized by FTIR, NMR and XRD methods. The interactions between GTA-m-CS and DDEAC was studied by surface tension, viscosity, conductivity and fluorescence methods. The parameters, including equilibrium surface tension, critical micelle concentrations of DDEAC with different GTA-m-CS concentration, critical aggregation concentration of DDEAC, the amount of DDEAC adsorbed on GTA-m-CS, pc20 and πcmc were obtained from the surface tension curves. The influence of temperature on the above parameters were evaluated. The degree of counterion binding to micelle and the thermodynamic parameters of the system were calculated from the conductivity curves. According to the change of conductivity with temperature, the thermodynamic parameters of micellar formation were calculated. The aggregation number of DDEAC molecules in GTA-m-CS/DDEAC aggregates were calculated from steady-state fluorescence data. Based on the experimental results, the interaction models between GTA-m-CS and DDEAC were proposed. The GTA-m-CS/DDEAC aggregates could be used as curcumin carries, and achieved sustained release.

Porphyriynes: 18-π-Conjugated Macrocycles Incorporating a Triple Bond.

Tetraphenylporphyriyne (Pyne1), a novel porphyrin analogue with a C≡C bond incorporated into an 18-π-conjugated system, has been created via cleavage of the N-confused pyrrolic ring in Ag(III) N-confused tetraphenylporphyrin. The structure of Pyne1 was confirmed by X-ray crystallography and 1H NMR, IR, and UV-vis spectroscopy. The mechanism of cleavage of the N-confused pyrrolic ring was investigated by theoretical calculations. The successful synthesis of other Pynes indicated the generality of this protocol.

N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride/carboxymethyl cellulose films filled with in-situ crystallized calcium carbonate.

The research and development of substitutes for petroleum-based plastics has become a hot topic. The N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC, 10 wt%)/sodium carboxymethyl cellulose (CMC) films have showed enhanced mechanical properties, which also provide a potential substitute to petroleum-based plastics. In this paper, calcium carbonate was crystallized (cry-CaCO3) in HTCC/CMC film-forming solutions, and the effects of the cry-CaCO3 particles on HTCC/CMC film properties including microstructures, mechanical properties, thermal stability, whiteness, and wettability were characterized. An HTCC/CMC film with commercially available CaCO3 (com-CaCO3) was used as a control. The results showed that the cry-CaCO3 promoted the homogeneous distribution of the HTCC/CMC matrix and significantly improved mechanical properties, but showed little effect on the thermal stability, whiteness and wettability of the films. To reveal the affecting mechanism of cry-CaCO3 on HTCC/CMC film properties, the cry-CaCO3 particles were isolated from film-forming solutions and characterized by scanning electron microscope (SEM), powder X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA) methods. The results showed that the HTCC/CMC matrix modulated spherical CaCO3 particles, and the macromolecules were encapsulated in cry-CaCO3 particles, decreasing their adhesion to the HTCC/CMC matrix while increasing their distribution in the HTCC/CMC matrix. The strong electrostatic, hydrogen bonding and flexible interaction between CMC and cry-CaCO3 particles played a key role in improving the mechanical properties of HTCC/CMC films.

Solution properties of N-(2-allyl-butyl ether)-O-carboxymethyl chitosan and N-(2-allyl-isooctyl ether)-O-carboxymethyl chitosan.

pH-sensitive and amphiphilic chitosan derivatives can be used as hydrophobic drug carriers, and their rheological properties play a key role in their performance. In this paper, two pH-responsive and amphiphilic chitosan derivatives, N-(2-allyl-butyl glycidyl ether)-O-carboxymethyl chitosan (HBCC) and N-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC) were synthesized, and their rheological properties were studied. The influence of parameters including concentrations of HBCC and H2ECC, the degree of substitution, solution pH, and [Ca2+] on the rheological properties were investigated. The results showed that the overlap and entanglement concentration of HBCC and H2ECC was ca. 1.7 wt% and 5 wt%, respectively. The dilute and semidilute solutions showed Newtonian behavior. Above 5 wt%, strong networks formed, and shear-thinning behavior appeared at high shear rates (>10 s-1) for entangled solutions. A high degree of substitution and pH near the isoelectric points of HBCC and H2ECC corresponded to a low viscosity and viscoelasticity. In addition, Ca2+ played a shielding effect on the -COO- groups at low concentrations (<10 mmol/L), whereas it acted as a cross-linker when [Ca2+] ≥ 20 mmol/L. The intermolecular hydrogen bonds were examined by molecular dynamics simulations. The results provide new information related to the application of HBCC and H2ECC for hydrophobic drug packaging and transportation.

Enhancement of a zwitterionic chitosan derivative on mechanical properties and antibacterial activity of carboxymethyl cellulose-based films.

A type of zwitterionic chitosan derivative, N-2-hydroxylpropyl-3-trimethylammonium-O-carboxymethyl chitosan (HTCMCh), was synthesized and introduced into carboxymethyl cellulose (CMC)-based films as a film strength enhancer and antibacterial agent. The influencing factors include degree of substitution (DS) and mHTCMCh/mCMC. Their influences on mechanical properties, thermal stability, antibacterial activities, microstructures, transmittance, and wettability of the CMC-based films were studied. It was found that HTCMCh improves the tensile strength (by 9.0-130.9%), Young's modulus (47.8-351.6%), and elongation at break (90.8-280.8%) of CMC/HTCMCh films simultaneously, depending on the DS and mass content of HTCMCh. However, the HTCMCh shows little influence on microstructure and thermal stability of CMC/HTCMCh films. Satisfactorily, CMC/HTCMCh films show strong antibacterial activities against E. coli and S. aureus and are nontoxic to fibroblast HFF-1 cells. Pork packaging experiments demonstrated that CMC/HTCMCh10%,0,58 film could significantly inhibit bacterial growth, indicating that the HTCMCh-doped CMC films could be used as food packaging materials.

O-Carboxymethyl chitosan-based pH-responsive amphiphilic chitosan derivatives: Characterization, aggregation behavior, and application.

Chitosan has attracted much attention in drug delivery, however, carboxymethyl chitosan (CMC)-based self-aggregated nanocarriers are seldom reported. In this paper, two kinds of CMC-based pH-responsive amphiphilic chitosan derivatives, N-2-hydroxylpropyl-3-butyl ether-O-carboxymethyl chitosan (HBCC) and N-2-hydroxylpropyl-3-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC), have been synthesized by the homogeneous reaction. The molecular structures were characterized by FTIR, 1H NMR and 13C NMR. The optimum reaction condition was obtained based on the data of 1H NMR spectrum: reaction time of 4 h, reaction temperature of 80 °C and nepoxyn-NH2 of 3/1, respectively. The XRD patterns showed the crystallinity of HBCC and H2ECC decreased due to the introduction of hydrophobic segments. The thermostability of HBCC and H2ECC was improved for the formation of heat-resistant stereo-complexed structures. The intermolecular hydrophobic interaction hindered the intermolecular mobility by increasing glass transition temperature of ca. 10 °C. Both HBCC and H2ECC have very low critical aggregation concentrations (HBCC: 0.66-1.56 g/L, H2ECC: 0.57-1.07 g/L) and moderate aggregate particle size, which is advantageous for utilization as a drug carrier. The curcumin loaded HBCC and H2ECC aggregates showed nontoxicity, meanwhile, HBCC and H2ECC showed good antibacterial activity against Staphylococcus aureus and Escherichia coli. As a result of these two favorable properties, HBCC and H2ECC could be used as curcumin nanocarriers as well as antibacterial agents.

Synthesis, structure, and properties of N-2-hydroxylpropyl-3-trimethylammonium-O-carboxymethyl chitosan derivatives.

N-2-hydroxylpropyl-3-trimethylammonium-O-carboxymethyl chitosan (HTCMCh) was synthesized through homogeneous reaction. The effects of different reaction condition on the properties of HTCMCh were characterized by FTIR, NMR, SEM, TEM, DLS, XRD, TGA, and DSC. The results of FTIR spectra, 1H NMR, and 13C NMR proved the successful synthesis of HTCMCh. The DS was dependent upon reaction time and pretreated pH of the starting material, independent of temperature and nepoxy/n-NH2. With increasing reaction time, the crystallinity of HTCMCh decreased, and the intermolecular interactions transformed from hydrogen bonding to strong electrostatic interactions, which enhanced HTCMCh thermal stability. SEM observations showed smooth cross section morphologies of HTCMCh films. With the increase in reaction time, the tensile strength significantly increased. The viscoelasticity transformed from viscous to elastic with aging time, confirming the formation of polyelectrolyte complexes. The optimum reaction conditions: reaction time of 2 h, an initial material pH of 9.47, nepoxy/n-NH2 of 2/1.

Effects of chitosan quaternary ammonium salt on the physicochemical properties of sodium carboxymethyl cellulose-based films.

The effects of N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC) on the physicochemical properties of sodium carboxymethyl cellulose (CMC)-based films were investigated. The prepared HTCC/CMC film-forming solutions (FFSs) with varying mass ratios exhibited shear-thinning behavior and typical pseudo-plasticity. The highest apparent viscosity and lowest crossover frequency was obtained for the HTCC/CMC FFS with a mass ratio of 10%, due to the formation of the strongest intermolecular interactions, which also led to the best mechanical properties. Furthermore, the effects of temperature and degree of substitution of HTCC on the composite film properties were also investigated. Structural property assessment by FTIR, SEM, and DSC showed a clear interaction between HTCC and CMC, leading to the formation of a new composite material with enhanced physicochemical properties. The data demonstrate the importance of HTCC in CMC-based films for food and drug packaging.

Flavobacterium phocarum sp. nov., isolated from soils of a seal habitat in Antarctica.

A Gram-stain-negative, yellow-pigmented, non-flagellated, gliding, rod-shaped, oxidase-negative and catalase-positive bacterium, designated SE14T, was isolated from soil on King George Island, South Shetland Islands, Antarctica. Strain SE14T grew at 4-25 °C (optimum, 20 °C), at pH 6.0-9.0 (optimum, pH 7.0-7.5) and with 0-3.0 % NaCl (optimum, 1.0-1.5 %), and could not produce flexirubin-type pigments. 16S rRNA gene sequence analysis showed the the isolate belonged to the genus Flavobacterium. Strain SE14T had the highest 16S rRNA gene sequence similarity to Flavobacterium antarcticum, F. tegetincola and F. degerlachei with 95.8, 95.5 and 95.2 %, respectively. The strain SE14T consisted of a clade with Flavobacteriumnoncentrifugens (16S rRNA gene sequence similarity 94.9 %) and F. qiangtangense (16S rRNA gene sequence similarity 94.2 %) and simultaneously formed a distinct phyletic lineage in the neighbour-joining phylogenetic tree. Polar lipids of the strain included phosphatidylethanolamine and four unidentified aminolipids. Strain SE14T contained anteiso-C15 : 0, iso-C15 : 0 and a mixture of iso-C15 : 0 2-OH and/or C16 : 1ω7c as the main fatty acids, and the only respiratory quinone was menaquinone-6. The genomic DNA G+C content was 42.3 mol%. The polyphasic taxonomic study revealed that strain SE14T belongs to a novel species within the genus Flavobacterium , and the name Flavobacterium phocarum sp. nov. is proposed. The type strain is SE14T (=CCTCC AB 2017225T=KCTC 52612T).

Flavobacterium ardleyense sp. nov., isolated from Antarctic soil.

A Gram-stain-negative, aerobic, yellow-pigmented, non-flagellated, non-gliding, rod-like, oxidase- and catalase-positive bacterium, designated A2-1T, was isolated from soil on Ardley Island, South Shetland Islands, Antarctica. Strain A2-1T grew at 4-22 °C (optimum, 10 °C), at pH 6.0-8.0 (optimum, pH 6.5) and with 0-1.5 % NaCl (optimum, 0.5 %), but could not produce flexirubin-type pigments. 16S rRNA gene sequence analysis showed that the isolates belonged to the genus Flavobacterium. Strain A2-1T had the highest 16S rRNA gene sequence similarity to Flavobacterium cucumis, F. ahnfeltiae and F. cheniae with 95.7, 95.6 and 95.4 %, respectively. The strain A2-1T consisted of a clade with F. cucumis and F. cheniae and simultaneously formed a distinct phyletic lineage in the neighbour-joining phylogenetic tree. Polar lipids of the strain included phosphatidylethanolamine (PE), four unidentified aminolipids and one unidentified lipid. The strain A2-1T contained anteiso-C15 : 0 (20.2 %), iso-C15 : 0 (16.2 %) and C15 : 1 G (11.0 %) as the main fatty acids and the only respiratory quinone was menaquinone MK-6. The genomic DNA G+C content was 34.0 mol%. The polyphasic taxonomic study revealed that the strain A2-1T belongs to a novel species within the genus Flavobacterium and the name Flavobacterium ardleyense sp. nov. is proposed. The type strain is A2-1T (=CCTCC AB 2017157T=KCTC 52644T).

Rheological properties of N-[(2-hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride.

N-[(2-hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride (HTCC) was synthesized using 1-allyl-3-methylimidazole chloride (AmimCl) as a homogeneous green reaction media. The effects of polymer concentration, temperature, cation valence, anion type and concentration of inorganic salt, and degree of substitution (DS) on the rheological properties of HTCC were investigated. The apparent viscosity indicated that HTCC solution was a typical pseudoplastic fluid, which could be described by Ostwald de Waele and Cross-empirical models. The viscoelastic properties showed the formation of gel-like structures. Temperature showed slight effect on the apparent viscosity of HTCC solution, while the DS of HTCC showed remarkable effect on the apparent viscosity. At a low shear rate, the apparent viscosities of HTCC solution increased firstly with an increase of cNaCl from 0 to 40mmol/L, and then decreased with further increasing cNaCl to 60mmol/L. At a high shear rate, the opposite trends were observed. The variation of HTCC molecular construction under different inorganic salt conditions was confirmed by scanning electron microscopy, meanwhile, the variation mechanism was proposed.

Theoretical study of the reaction of chitosan monomer with 2,3-epoxypropyl-trimethyl quaternary ammonium chloride catalyzed by an imidazolium-based ionic liquid.

The molecular mechanism of the graft reaction of 2,3-epoxypropyl-trimethyl quaternary ammonium chloride with chitosan monomer was investigated by performing density functional theory (DFT) calculations. The calculated results show that the -NH2 group of chitosan monomer is more reactive than its -OH and -CH2OH groups, and the graft reaction on the -NH2 group is calculated to be exothermic by 20.5kcal/mol with a free energy barrier of 42.6kcal/mol. The reaction cannot benefit from the presence of the intruded water molecule, but can be considerably assisted by 1-allyl-3-methylimidazolium chloride ([Amim]Cl) ionic liquid. The reaction catalyzed by the ion-pair is calculated to be exothermic by 36.5kcal/mol and the barrier is reduced to 29.3kcal/mol, which are further corrected to 28.0 and 29.1kcal/mol by considering the solvent effect of [Amim]Cl ionic liquid. Calculated results verified the experimental finding that imidazolium-based ionic liquids can promote the reaction of chitosan with epoxy compounds.

A simple and convenient method to synthesize N-[(2-hydroxyl)-propyl-3-trimethylammonium] chitosan chloride in an ionic liquid.

N-[(2-Hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride (HTCC) was synthesized through nucleophilic substitution of 2,3-epoxypropyltrimethyl ammonium chloride (EPTAC) onto chitosan using ionic liquid of 1-allyl-3-methylimidazole chloride (AmimCl) as a homogeneous and green reaction media. The chemical structure of HTCC was confirmed by FTIR, (1)H NMR and (13)C NMR. The FTIR peak intensity of amino group at 1595 cm(-1) decreased and that of [Formula: see text] at 1475 cm(-1) increased with the increase of reaction time, confirming the substitution of EPTAC on CS. The degree of substitutions (DS) were calculated from the integral area of (1)H NMR, and the optimum reaction condition was obtained, namely, reaction time of 8h, temperature of 80°C and [Formula: see text] of 3/1. The degree of crystallinity and thermal properties of HTCC were characterized by XRD, TG, DSC, and DMA methods. Data from XRD, TG, DSC and DMA show that the degree of crystallinity, thermal stability, as well as glass transition temperature of HTCC decreased with the increase of DS. The reaction mechanism of chitosan with EPTAC in AmimCl was elucidated by performing density functional theory (DFT) calculations.

Effect of amino acids on aggregation behaviour of sodium deoxycholate in solution: a fluorescence study.

The influence of three alkaline amino acids, L-lysine (L-Lys), L-arginine (L-Arg) and L-histidine (L-His), on the aggregation behaviour of sodium deoxycholate (NaDC) in phosphate buffer, pH 7.0, was studied at 25 °C. The fluorescence probe technique based on pyrene was employed to determine accurately the critical aggregation concentration (cac), polarity of the microenvironment and aggregation numbers for the NaDC aggregates. The added amino acids can effectively reduce the cac values and micropolarity of NaDC, indicating that it is easier for NaDC to aggregate in a compact manner in the presence of amino acids. The aggregation numbers of NaDC were increased, indicating that more NaDC molecules connect together to form stable aggregates. The performance of L-Arg is similar to that of L-His, and both have a smaller effect on the above parameters than L-Lys. In view of this, it may be inferred that both electrostatic and hydrophobic interaction are responsible for the interaction between NaDC and amino acids in aqueous solution.

Phase behavior studies of quaternary systems containing N-lauroyl-N-methylglucamide/alcohol/alkane/water.

The three-phase behavior of quaternary systems comprising N-lauroyl-N-methylglucamide (MEGA-12)/alcohol/alkane/water has been studied using epsilon-beta fishlike phase diagrams. From the epsilon-beta fishlike phase diagrams a series of phase inversions Winsor I (2) --> III (3) --> II (2) were observed, and the hydrophilic-lipophilic balanced (HLB) plane equation for the quaternary system was deduced. Some physicochemical parameters, such as the mass fraction of alcohol in the HLB interfacial layer, A S, the coordinates of the start (beta B, epsilon B) and end points (beta E, epsilon E) of the middle-phase microemulsion, the mass fractions of MEGA-12 and alcohol in the total system (C S and C A), and the solubilities of MEGA-12 and alcohol in oil phase (S O and A O), were calculated. The effects of different alcohols, alkanes, and NaCl concentrations in the aqueous phase on the phase behavior and solubilization capacity were investigated, which indicates that alcohol with longer and alkane with shorter hydrocarbon chains have a larger solubilization capacity. NaCl concentration has little influence on the phase behavior.