Synthesis and characterization of some novel antimicrobial thiosemicarbazone O-carboxymethyl chitosan derivatives

Three novel thiosemicarbazone O-carboxymethyl chitosan derivatives were obtained via a condensation reaction of thiosemicarbazide O-carboxymethyl chitosan with o-hydroxybenzaldehyde, p-methoxybenzaldehyde, and p- chlorobenzaldehyde respectively. Their structures were characterized by elemental analysis, FTIR, (13)C NMR and X-ray diffraction. The antimicrobial behaviors of the prepared derivatives against three types of bacteria Staphylococcus aureus (S. aureus, RCMBA 2004), Bacillus subtilis (B. subtilis, RCMBA 6005), and Escherichia coli (E. Coli, RCMBA 5003) and three crops-threatening pathogenic fungi Aspergillus fumigatus (A. fumigatus, RCMBA 06002), Geotrichum candidum (G. candidum, RCMB 05098), and Candida albicans (C. albicans, RCMB 05035) were investigated. The results indicated that the antibacterial and antifungal activities of the investigated derivatives are much higher than those of the parent O-carboxymethyl chitosan. They were more potent in case of Gram-positive bacteria than Gram-negative bacteria. The presence of electron withdrawing chlorine atom on the aryl moiety of the aldehyde portion improved greatly antimicrobial activity to be nearly equivalent to the used standard drugs.

[Preparation and performance characterization of electrospun drug loaded poly (vinyl alcohol)/chitosan nanofibrous membrane]

OBJECTIVE

To prepare nanofibrous membranes of poly (vinyl alcohol)/chitosan (PVA/CS) loaded with varied salvianic acid A sodium (SAS) contents.

METHODS

Ultrafine fiber mats were prepared with PVA/CS as matrix and SAS as model drug. The structure and morphology of the nanofibrous membranes were characterized by FT-IR and SEM. Drug-loading amount and drug release profiles of these membranes were determined by UV VIS spectra, and the degradation of the membranes was also investigated.

RESULTS

Average diameters of PVA/CS/SAS nanofibers with different SAS contents were 280 ≊390 nm. Drug-loading amount of these nanofibrous membranes was high and exhibited sustained and controlled release behavior for SAS.

CONCLUSION

The PVA/CS/SAS nanofibrous membrane prepared in this study loads drug uniformly and has remarkably sustained release behavior, which may offer strategies for the research and development of novel topical drug delivery systems.

Synthesis and characterization of chitosan tripolyphosphate nanoparticles and its encapsulation efficiency containing Russell's viper snake venom

Chitosan Tripolyphosphate (CS/TPP) nanoparticle is a biodegradable and nontoxic polysaccharide, used as a carrier for drug delivery. The morphology and particle-size measurements of the nanoparticles were studied by field emission scanning electron microscopy and Fourier Transform Infrared Spectroscopy (FTIR). This study aims to evaluate the impact of Russell's viper venom encapsulation on various factors and loading capacity, in addition to explore the physicochemical structure of nanoparticles. FTIR confirmed that tripolyphosphoric groups of TPP linked with ammonium groups of CS in the nanoparticles. Our results showed that CS can react with TPP to form stable cationic nanoparticles. The results also showed that encapsulation efficiency of venom at different concentrations of 20, 40, 60, 500, and 1000 µg/mL were achieved for CS/TPP nanoparticles at different concentrations of 1.5, 2, and 3 mg/mL. The cytotoxicity of CS/TPP nanoparticles was evaluated by MTT (-3 (4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, a tetrazole) assay.

[The effects and its mechanism of N-arginine chitosan as transdermal enhancer]

The purpose of this study is to investigate the penetration effects and mechanism of N-arginine chitosan (ACS). This novel transdermal enhancer with a mimetic structure of cell-penetration peptides was synthesized by introducing hydrophilic arginine groups to the amino-group on chitosan's side chain. The structure of ACS was confirmed by FT-IR, 1H NMR and element analysis. In addition, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to study the protein conformation and the water content of stratum corneum, and the result suggested that ACS can change the orderly arrangement of the molecules in the stratum corneum, making the stack structure of keratin become loose. And ACS can increase the water content of the stratum corneurn. Inverted fluorescence microscope and flow cytometry were used to examine penetration effect of ACS on Hacat cell. The result confirmed that the uptake of ACS was enhanced with increased substitution degree of arginine by 4-8 folds compared to chitosan. In vitro penetration studies on three electrical types of drugs were carried out using three model drugs of negatively charged aspirin, positively charged terazosin and neutral drug isosorbide mononitrate by the method of Franz diffusion cells. The results showed that ACS has obviously penetration of the negatively charged drug aspirin, and certain penetration of neutral drug issorbide mononitrate, but inhibition of positively charged terazosin. In vivo imaging technology research results show that the ACS can significantly enhance the fluorescence intensity of morin, which is the auto-fluorescence anionic drug. These obtained results suggested that ACS, as a promising transdermal enhancer, can change the structure of the keratinocytes and analog penetrating peptides promote absorption, but have certain selectivity for the drug.

Facile and green synthesis of silver nanoparticles in quaternized carboxymethyl chitosan solution

A facile and green method to synthesize stable Ag nanoparticles (Ag NPs) with a narrow size distribution in water is reported. Water-soluble quaternized carboxymethyl chitosan (QCMC) with a surfactant-like structure was used as both a reducing and stabilizing agent under microwave irradiation via the modified Tollens reaction. In order to study the preparation mechanism, carboxymethyl chitosan (CMC) and quaternized chitosan (QCS) were compared as both reducing and stabilizing agents. Full characterization was performed using UV-vis, XRD, TEM, AAS, FT-IR, NMR and TGA. The results revealed that the prepared Ag NPs were mostly spherical with a small proportion being cylinders or cuboids; they were stable due to the package of the macromolecules; the diameters were 10.24 ± 3.13 nm. The Tollens reaction followed first order kinetics, and the Ea was 102.4 kJ mol(-1) for QCMC/Ag NP composite. During the growth of the Ag NPs, some quaternary ammonium groups and carboxymethyl groups were respectively oxidized to -CH2COCH3 and -CH3 groups, and the quaternary ammonium groups were more helpful for the growth of Ag NPs than the carboxymethyl groups. In addition, QCMC/Ag NP composite had much higher thermal stability than QCMC.

Eudragit® L100/N-trimethylchitosan chloride microspheres for oral insulin delivery

Effective oral delivery of protein and peptide drugs remains an active topic in scientific research. In this study, matrix type microspheres were prepared with Eudragit^® L100 containing N-trimethylchitosan chloride to improve the permeation of insulin across the intestinal epithelium via the paracellular pathway. Insulin loaded microspheres were initially formulated in accordance with a factorial design (2³) and manufactured by means of a single water-in-oil emulsification/evaporation method. Based on external and internal morphology two microsphere formulations were selected from the initial formulations for further investigation in terms of particle size, dissolution behaviour and in vitro insulin transport across excised rat intestinal tissue. The initial eight microsphere formulations exhibited drug loading capacities ranging from 27.9–52.4% with different shapes and internal structures. The two selected microsphere formulations had average particle sizes of 157.3 ± 31.74 µm and 135.7 ± 41.05 µm, respectively, and mean dissolution time values for insulin release of 34.47 and 42.63 min, respectively. In vitro transport of insulin across excised rat intestinal tissue from the two selected microsphere formulations was 10.67–fold and 9.68–fold higher than the control group (insulin alone). The microsphere delivery system prepared from Eudragit^® L100 containing N-trimethylchitosan chloride is therefore a promising candidate for effective oral insulin delivery.

One-step biofunctionalization of quantum dots with chitosan and N-palmitoyl chitosan for potential biomedical applications

Carbohydrates and derivatives (such as glycolipids, glycoproteins) are of critical importance for cell structure, metabolism and functions. The effects of carbohydrate and lipid metabolic imbalances most often cause health disorders and diseases. In this study, new carbohydrate-based nanobioconjugates were designed and synthesized at room temperature using a single-step aqueous route combining chitosan and acyl-modified chitosan with fluorescent inorganic nanoparticles. N-palmitoyl chitosan (C-Pal) was prepared aiming at altering the lipophilic behavior of chitosan (CHI), but also retaining its reasonable water solubility for potential biomedical applications. CHI and C-Pal were used for producing biofunctionalized CdS quantum dots (QDs) as colloidal water dispersions. Fourier transform infrared spectroscopy (FTIR), thermal analysis (TG/DSC), surface contact angle (SCA), and degree of swelling (DS) in phosphate buffer were used to characterize the carbohydrates. Additionally, UV-Visible spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), dynamic light scattering (DLS), scanning and transmission electron microscopy (SEM/TEM) were used to evaluate the precursors and nanobioconjugates produced. The FTIR spectra associated with the thermal analysis results have undoubtedly indicated the presence of N-palmitoyl groups "grafted" to the chitosan chain (C-Pal) which significantly altered its behavior towards water swelling and surface contact angle as compared to the unmodified chitosan. Furthermore, the results have evidenced that both CHI and C-Pal performed as capping ligands on nucleating and stabilizing colloidal CdS QDs with estimated average size below 3.5 nm and fluorescent activity in the visible range of the spectra. Therefore, an innovative "one-step" process was developed via room temperature aqueous colloidal chemistry for producing biofunctionalized quantum dots using water soluble carbohydrates tailored with amphiphilic behavior offering potential applications as fluorescent biomarkers in the investigation of glycoconjugates for the nutrition, biology, pharmaceutical, and medicine fields.

Synthesis, characterization, and antibacterial activity of cross-linked chitosan-glutaraldehyde

This present study deals with synthesis, characterization and antibacterial activity of cross-linked chitosan-glutaraldehyde. Results from this study indicated that cross-linked chitosan-glutaraldehyde markedly inhibited the growth of antibiotic-resistant Burkholderia cepacia complex regardless of bacterial species and incubation time while bacterial growth was unaffected by solid chitosan. Furthermore, high temperature treated cross-linked chitosan-glutaraldehyde showed strong antibacterial activity against the selected strain 0901 although the inhibitory effects varied with different temperatures. In addition, physical-chemical and structural characterization revealed that the cross-linking of chitosan with glutaraldehyde resulted in a rougher surface morphology, a characteristic Fourier transform infrared (FTIR) band at 1559 cm⁻¹, a specific X-ray diffraction peak centered at 2θ = 15°, a lower contents of carbon, hydrogen and nitrogen, and a higher stability of glucose units compared to chitosan based on scanning electron microscopic observation, FTIR spectra, X-ray diffraction pattern, as well as elemental and thermo gravimetric analysis. Overall, this study indicated that cross-linked chitosan-glutaraldehyde is promising to be developed as a new antibacterial drug.

[Preparation of magnetic quaternary chitosan salt and its adsorption of methyl orange from water]

First, quaternary chitosan salts with different substitution degrees were prepared in glycine hydrochloride ([Gly]Cl) ionic liquid. Nano-sized Fe3O4 powder was obtained through chemical co-precipitation method. And then, magnetic quaternary chitosan particles were prepared through inverse suspension cross-linking using Fe3O4 was the nucleus and glutaraldehyde as the cross-linking agent. The influence of different reaction conditions on adsorption was discussed. Adsorption of methyl orange (MO) by magnetic quaternary chitosan particles was studied through the static adsorption method. The results showed that at pH 3.0 and 25 degrees C the adsorption capacity varied from 37.45 mg x g(-1) to 277.5 mg x g(-1) with the MO concentration ranging from 20 mg x L(-1) to 150 mg x L(-1). The adsorption isotherm was fitted to the Freundlich model and the adsorption kinetics was fitted to the pseudo-second order kinetic isotherms capacity experiment. It was found that after the adsorbent was used for four times, its removal rate still exceeded 90%.

Sulfadiazine modified CS/HA PEC destined to wound dressing

AIM

To present the research results concerning enhanced antimicrobial and release properties of the chitosan derivative with sulfadiazine/hyaluronic acid polyelectrolyte complex (PEC) hydrogel.

MATERIAL AND METHODS

The PECs have been prepared from chitosan of different molecular weight, sulfadiazine chitosan derivative and sodium hyaluronate. The complex structure was assessed by FT-IR spectroscopic method and swelling capacity was followed by weighing measurements.

RESULTS

It has been establish that chitosan derivative influenced both PEC properties and swelling capacity.

CONCLUSIONS

Incorporation in PEC of the sulfadiazine chitosan is a new way to combine bacteriostatic effect of chitosan with that of sulfadiazine, to control properties, antimicrobial activity in the treatment of the wound.

Chitosan/hyaluronic acid polyelectrolyte complex hydrogels in the management of burn wounds

AIM

This paper is a short review on the state-of-the-art of the use of polyelectrolyte complexes containing polysaccharides for wound and burn healing and treatment using the chitosan/hyaluronic acid polyelectrolyte complex (PEC) hydrogel.

RESULTS AND CONCLUSIONS

PEC is suitable for wound healing because a wet treatment can be realized and both components of PEC contribute by their properties to the enhanced antimicrobial activity, promote wound healing and prevent wound damage during treatment.

Synthesis, spectrochemical characterisation and catalytic activity of transition metal complexes derived from Schiff base modified chitosan

Three novel quadridentate Schiff base complexes, [Cu(OIAC)Cl(2)], [Co(OIAC)Cl(2)] and [Ni(OIAC)Cl(2)] [OIAC, a Schiff base ligand: (([2-oxo-1H-indol-3-ylidene]amino)chitosan)] have been synthesized. The molecular structure of the complexes has been characterised by elemental analyses, magnetic measurements, molar conductance studies, vibrational (FT-IR), electronic (UV-Vis) and (1)H NMR spectroscopic techniques. Thermal properties of the complexes have been investigated with TG-DTG analyses. The surface morphological difference of ligand and the complexes has been explored with scanning electron microscopy. The crystallinity of the compounds was analysed by powder X-ray diffraction technique and it was found to be less for the Schiff base (OIAC) and the complexes as compared to the chitosan. The catalytic activities of the complexes have been studied in the oxidation of cyclohexane, using environmental friendly oxidant, hydrogen peroxide. Complex with rough surface has shown higher catalytic activity compared to the other complexes.

Synthesis and evaluation of diethylethylamine-chitosan for gene delivery: composition effects on the in vitro transfection efficiency

Chitosan has been indicated as a safe and promising polycation vector for gene delivery. However its low transfection efficiency has been a challenging obstacle for its application. To address this limitation, we synthesized chitosan derivatives which had increasing amounts of diethylethylamine groups (DEAE) attached to the chitosan main chain. The plasmid DNA VR1412 (pDNA), encoding the ß-galactosidase (ß-gal) reporter gene was used to prepare nanoparticles with the chitosan derivatives, and the transfection studies were performed with HeLa cells. By means of dynamic light scattering and zeta potential measurements, it was shown that diethylethylamine-chitosan derivatives (DEAE(x)-CH) were able to condense DNA into small particles having a surface charge depending on the polymer/DNA ratio (N/P ratio). Nanoparticles prepared with derivatives containing 15 and 25% of DEAE groups (DEAE(15)-CH and DEAE(25)-CH) exhibited transfection efficiencies ten times higher than that observed with deacetylated chitosan (CH). For derivatives with higher degrees of substitution (DS), transfection efficiency decreased. The most effective carriers showed low cytotoxicity and good transfection activities at low charge ratios (N/P). Vectors with low DS were easily degraded in the presence of lysozyme at physiological conditions in vitro and the nontoxicity displayed by these vectors opens up new opportunities in the design of DEAE-chitosan-based nanoparticles for gene delivery.

Functionalization of graphite oxide with magnetic chitosan for the preparation of a nanocomposite dye adsorbent

In the current study, the functionalization of graphite oxide (GO) with magnetic chitosan (Chm) was investigated to prepare a nanocomposite material (GO-Chm) for the adsorption of a reactive dye (Reactive Black 5). The synthesis mechanism was investigated by various techniques (SEM/EDAX, FTIR spectroscopy, XRD, XPS, DTA, DTG, VSM). Characterization results indicated that a significant fraction of the amines of the chitosan (i) were inserted between the GO layers and (ii) reacted with carboxyl and epoxy groups of GO, leading to its reduction and hence the destruction of the layered structure. The concentrations of iron were found to be ∼25% for Chm and ∼12% for GO-Chm. A VSM plot presents the value of 9 emu/g for the saturation magnetization of GO-Chm. The adsorption behavior of the prepared composite was elucidated with a series of experiments. The tests of the effects of pH revealed that the adsorption mechanism dominated (between dye molecules and the GO-Chm matrix) and showed that acidic conditions were the optimum for the adsorption process (pH 3). Kinetic experiments presented the relatively "fast" adsorption phenomenon using pseudo-first-order, pseudo-second-order, and modified pseudo-second-order equations. The equilibrium data were fitted to the Langmuir, Freundlich, and Langmuir-Freundlich (L-F) models, calculating the maximum adsorption capacities at 25, 45, and 65 °C (391, 401, and 425 mg/g, respectively). Thermodynamic analysis was also performed to calculate the changes in free energy (ΔG(0)), enthalpy (ΔH(0)), and entropy (ΔS(0)).

Chitosan-based nanofibrous membranes for antibacterial filter applications

Nanofibrous membranes have drawn considerable interest for filtration applications due to their ability to withstand high fluid flux while removing micro- and nano-sized particulates from solution. The desire to introduce an antibacterial function into water filter applications presents a challenge to widespread application of fibrous membranes because the addition of chemicals or biocides may produce harmful byproducts downstream. Here, we report the development of chitosan-polycaprolactone (PCL) nanofibrous membranes to utilize the natural antibacterial property of chitosan for antibacterial water filtration. Chitosan-PCL fibers with diameters of 200-400 nm and chitosan contents of 25, 50 and 75 wt% were prepared by electrospinning. In a series of bacterial challenge tests, chitosan-PCL fibrous membranes significantly reduced Staphylococcus aureus adhesion compared to PCL fibrous membranes. In water permeability and particulate size removal tests, fibrous membranes with 25% chitosan supported the greatest water flux (∼7000 L/h/m(2)) with 100% removal of 300-nm particulates, while maintaining the membrane integrity. This study demonstrates the potential of chitosan-PCL nanofibrous membranes as pre-filters for water filtration systems that demonstrate combinatorial filtration and intrinsic antibacterial advantages.

Mucoadhesive 4-carboxybenzenesulfonamide-chitosan with antibacterial properties

The mucoadhesive property of chitosan, especially in an acidic (<pH 6.0) environment, was increased by conjugating an aromatic sulfonamide group at the C2-N position of chitosan. Four different feeding ratios of 4-carboxybenzensulfonamide (4-CBS) to chitosan in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride as a coupling agent were investigated. The 0.2:1 (w/w) ratio 4-CBS:chitosan revealed a 20-fold stronger mucoadhesion to mucin type II than the native chitosan in the simulated gastric fluid (SGF; pH 1.2), and a swelling ratio after 1 h in water, SGF and simulated intestinal fluid (pH 7.4) of about 2.9-, 3.0- and 3.4-fold higher than that of chitosan, respectively. In tissue culture, the 4-CBS-chitosan, like chitosan, were found to be non-cytotoxic to the Vero, KB, MCF-7 and NCI-H187 cell lines but showed potential antibacterial activity against Escherichia coli and Staphlyococcus aureus as model gram-negative and gram-positive bacteria, respectively.

Investigation of adsorption capacity of N-carboxymethyl chitosan for Pb(II) ions

N-carboxymethyl chitosan (NCMC) was prepared by reacting chitosan (CTS) with chloroacetic acid and characterized by (13)C-NMR spectroscopy to confirm that carboxymethylation occurred only in the amino groups. The adsorption properties of CTS, NCMC and O-carboxymethyl chitosan (OCMC) towards Pb(II) ions were evaluated and the order of the adsorption capacity was as follows: NCMC > OCMC > CTS. The effects of initial pH value (2.0-5.5) of the solutions and contact time (5-120 min) on adsorption of Pb(II) were investigated and the kinetic data were evaluated using the pseudo-first-order and pseudo-second-order models. Kinetics study showed that the adsorption process followed second-order kinetics rather than the first-order one. Furthermore, the experimental equilibrium data of Pb(II) on the NCMC were analyzed using the Langmuir and Freundlich isotherm models and the results indicated that the Langmuir model gave a better fit than the Freundlich equation and the maximum adsorption capacity obtained from the Langmuir model was 421.9 mg g(-1).

In situ precipitation of amorphous calcium phosphate and ciprofloxacin crystals during the formation of chitosan hydrogels and its application for drug delivery purposes

The immobilization of more than one single substance within the structure of a biocompatible polymer provides multifunctional biomaterials with attractive and enhanced properties. In the context of bone tissue engineering, it could be of great interest to synthesize a biomaterial that simultaneously contains amorphous calcium phosphate (ACP), to favor calcium and phosphate precipitation and promote osteogenesis, and an antibiotic such as ciprofloxacin (CFX) that can, eventually, avoid infections resulting after surgical scaffold implantation. However, the co-immobilization of multiple substances is by no means a trivial issue because of the enhanced number of interactions that can take place. One of the main issues is controlling not only the diverse solid forms that individual substances can eventually adopt, but also the forces responsible for the self-organization of the individual components. The latter determines whether phase-separated structures or conjugated architectures are obtained and, consequently, may dramatically affect their functionality. Herein, we have observed-by SEM, TEM, and solid-state NMR-that enzymatically-assisted coprecipitation of ACP and CFX resulted in phase-separated structures. Thus, CFX crystals showed identical morphology to that obtained in the absence of ACP, but the size was smaller. Neither the size nor the morphology of ACP exhibited significant differences whether precipitated with or without CFX, but, in the former case, ACP was stabilized over a wider range of pH and temperature. Finally, by using this methodology and the ice segregation induced self-assembly process (ISISA), we have successfully co-immobilized ACP and CFX in chitosan-based scaffolds. Interestingly, the presence of ACP exerted significant control on the CFX release from these materials.

Novel high-viscosity polyacrylamidated chitosan for neural tissue engineering: fabrication of anisotropic neurodurable scaffold via molecular disposition of persulfate-mediated polymer slicing and complexation

Macroporous polyacrylamide-grafted-chitosan scaffolds for neural tissue engineering were fabricated with varied synthetic and viscosity profiles. A novel approach and mechanism was utilized for polyacrylamide grafting onto chitosan using potassium persulfate (KPS) mediated degradation of both polymers under a thermally controlled environment. Commercially available high molecular mass polyacrylamide was used instead of the acrylamide monomer for graft copolymerization. This grafting strategy yielded an enhanced grafting efficiency (GE = 92%), grafting ratio (GR = 263%), intrinsic viscosity (IV = 5.231 dL/g) and viscometric average molecular mass (MW = 1.63 × 10⁶ Da) compared with known acrylamide that has a GE = 83%, GR = 178%, IV = 3.901 dL/g and MW = 1.22 × 10⁶ Da. Image processing analysis of SEM images of the newly grafted neurodurable scaffold was undertaken based on the polymer-pore threshold. Attenuated Total Reflectance-FTIR spectral analyses in conjugation with DSC were used for the characterization and comparison of the newly grafted copolymers. Static Lattice Atomistic Simulations were employed to investigate and elucidate the copolymeric assembly and reaction mechanism by exploring the spatial disposition of chitosan and polyacrylamide with respect to the reactional profile of potassium persulfate. Interestingly, potassium persulfate, a peroxide, was found to play a dual role initially degrading the polymers—“polymer slicing”—thereby initiating the formation of free radicals and subsequently leading to synthesis of the high molecular mass polyacrylamide-grafted-chitosan (PAAm-g-CHT)—“polymer complexation”. Furthermore, the applicability of the uniquely grafted scaffold for neural tissue engineering was evaluated via PC12 neuronal cell seeding. The novel PAAm-g-CHT exhibited superior neurocompatibility in terms of cell infiltration owing to the anisotropic porous architecture, high molecular mass mediated robustness, superior hydrophilicity as well as surface charge due to the acrylic chains. Additionally, these results suggested that the porous PAAm-g-CHT scaffold may act as a potential neural cell carrier.

Self-assembled nanoparticles of modified-chitosan conjugates for the sustained release of DL-α-tocopherol

Synthetic O6-succinylated chitosan and commercial glycol chitosan were covalently linked to dl-α-tocopheryl monoesters for controlled release of vitamin E. These conjugates formed self-assembled nanoparticles in aqueous solution with 254-496 nm mean diameters and dl-α-tocopherol contents between 27 and 39% (w/w). The particles appeared as 40-75 nm almost spherical nanoparticles when studied by scanning and transmission electron microscopy upon drying. Drug linking to chitosan matrix was confirmed by FTIR spectroscopy and proton NMR. Conjugates were also characterized by differential scanning calorimetry and wide-angle X-ray diffraction. In vitro tocopherol release studies performed in water at acid pH indicated a drug release dependence on drug content, hydrated particle sizes and employed chitosan derivative. Almost constant release rates were observed the first 7h. The obtained nanoparticles exhibited radical scavenging activity in DPPH essay. The potential of these nanoparticles was also demonstrated by the enhancement of HMVEC cell proliferation.

Novel quantum dots-carboxymethyl chitosan nanocomposite nitric oxide donors capable of detecting release of nitric oxide in situ

Nitric oxide (NO) donor compounds are primarily monofunctional in that they release NO under the requisite conditions. To detect the amount and duration of NO released, subsequent analysis methods are required. It would be advantageous if a NO donor compound could both release and detect NO at the same time. This would eliminate potential errors in the analysis. In this paper, novel cadmium telluride quantum dots (CdTe QD)-carboxymethyl chitosan (CMCS) nanocomposite NO donors, including both diazeniumdiolates and fluorescence probes, were fabricated by first synthesizing CdTe QD in CMCS aqueous solution and then reacting NO as well as ethyl bromide with the resultant CdTe QD-CMCS nanocomposites. Transmission electron microscopy, scanning electron microscopy and particle size analysis were used to examine the morphology and size distribution of the CdTe QD-CMCS nanocomposite NO donors. The donors are nanospheres with CdTe QD encapsulated and have dimensions of ~300 nm. Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and contact angle tests were employed to characterize the chemical structure of the donors, and the results also show that CdTe QD are well incorporated into CMCS, and many of them are close to the surface of the donors. The precursors of the donors exhibit a fluorescent effect, and the fluorescence can be quenched by NO. The donors can release NO spontaneously in a phosphate-buffered saline solution similar to a physiological environment, and can quantitatively detect the release of NO in situ based on fluorescence quenching of the donors by the NO.

Synthesis, characterization and stability of chitosan and poly(methyl methacrylate) grafted carbon nanotubes

The single walled carbon nanotubes (CNTs) were effectively functionalized through grafting with chitosan (CTS) and poly(methyl methacrylate) (PMMA). Prior to grafting reaction, the carboxylated SWNCTs (SWNCTs-COOH) were obtained by treating pristine CNTs with a mixture of 3:1 (v/v) H(2)SO(4) and HNO(3), and the successive treatment of SWNCTs-COOH with SOCl(2) yielded the acylated CNTs (CNTs-COCl). The functionalized derivatives of CNTs were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Both CTS and PMMA grafted CNTs showed better dispersability in acetic acid and tetrahydrofuran, in addition to higher stability in solution.

A new supramolecular gel via host-guest complexation with cucurbit[8]uril and N-(4-diethylaminobenzyl)chitosan

A novel supramolecular gel has been prepared via host-guest interaction between cucurbit[8]uril (Q[8]) and N-(4-diethylaminobenzyl)chitosan (EBCS). The structure of supramolecular gel has been characterized. The spectrum of (1)H NMR demonstrated the benzene ring of EBCS is reside inside the hydrophobic cavity of Q[8] and the host-guest interaction between Q[8] and EBCS was the main driving force for the formation of the supramolecular gel. The network structure of the xerogel of Q[8]/EBCS gel was observed by SEM. The Q[8]/EBCS gel system showed thermosensitive and pH-sensitive properties. The physical characterization by SEM, DSC, TG demonstrated the distinguished characters, which proved the formation of supramolecular gel instead of physical blending. The in vitro release study of the 5-fluorouracil-loaded supramolecular gel showed that sustained release profile in acidic condition, suggesting that Q[8]/EBCS gel could be a potential carrier for pH-sensitive drug controlled release system.

Synthesis of organosoluble chitosan derivatives with polyphenolic side chains

A one-pot synthesis was used to produce chitosan derivatives with polyphenolic side chains via a regioselective phenolic coupling reaction. Under Mannich reaction conditions, treatment of chitosan with formaldehyde and methyl 2,4-dihydroxybenzoate gave N-(2,6-dihydroxy-3-methoxycarbonylphenyl)methylated chitosan in good yield (87%). Formation of a CC bond occurred regioselectively at the C(3) position of methyl 2,4-dihydroxybenzoate. Chitosan derivatives having various phenolic compounds as a side chain were easily synthesized in a similar manner. The chitosan derivatives showed good biodegradability and improved their solubility in methanol (9.8mg mL(-1)) and 2-methoxyethanol (> 10mg mL(-1)). The UV protection provided by the derivatives with phenolic benzophenone side chain was evaluated using UV spectra of polyethylene terephthalate and poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) films coated with the derivatives and the derivatives absorbed effectively in the UV-A region (<60%). Self-aggregation of the chitosan derivatives with the phenolic side chain was observed by using a fluorescent probe in aqueous solution.

[Preparation of alpha-tricalcium phosphate/HA whisker/carboxymethyl chitosan-gelatin composite porous bone cement]

In order to investigate the effects of HA whisker and carboxymethyl chitosan-gelatin(CMC-Gel) on the mechanical properties of porous calcium phosphate cement, a series of alpha-tricalcium phosphate (alpha-TCP), HA whisker and L-sodium glutamate porogen with different mass fractions were mixed, and setting liquid was added to them to prepare alpha-TCP/HA whisker composite porous bone cement. Then, the cement was immersed in a series of CMC-Gel solutions which had different weight ratios of CMC to Gel to prepare alpha-TCP/HA whisker/CMC-Gel composite porous bone cement. The compressive strengths and microstructure of cement were characterized by mechanical testing machine and SEM. The results showed that when the mass fraction of HA whisker is 4%, the compressive strength of alpha-TCP/HA whisker composite porous bone cement reaches 2.57MPa, which is 1.81 times that of alpha-TCP bone cement. When the weight ratio of CMC to Gel is 50:50, the compressive strength of alpha-TCP/HA whisker/CMC-Gel composite porous bone cement is 3. 34MPa, which is 2.35 times that of alpha-TCP bone cement, and the toughness of the composite cement is greatly improved as well.