Evaluation of the mucoadhesive properties of N-trimethyl chitosan chloride

Previous studies have established that N-trimethyl chitosan chloride (TMC) is a potent absorption enhancer for peptides and large hydrophilic compounds across mucosal surfaces, especially in neutral and basic environments where chitosan is ineffective as an absorption enhancer. The degree of quaternization of TMC plays an important role on its absorption-enhancing properties. Several TMC polymers with different degrees of quaternization were synthesized and the molecular mass of the polymers was determined by SEC/MALLS. The mucoadhesive properties of the TMC polymers were measured with a modified tensiometer based on the Willhelmy plate method. The effect of the TMC polymers on the surface tension of a mixture of polymer and mucus was measured with a Du Noüy tensiometer. The degrees of quaternization of the synthesized TMC polymers were between 22.1% and 48.8% and the molecular mass was above 100,000 g/mole for all the polymers. A decrease in mucoadhesivity with an increase in the degree of quaternization of the TMC polymers was found. Surface-tension analysis of a mixture of polymer and mucus showed the effect of excessive polymer hydration on mucoadhesion. The results show that the degree of quaternization of TMC had a pronounced effect on the mucoadhesive properties of this polymer. Although the mucoadhesive profiles for the TMC polymers were lower than the original chitosan, they still retained sufficient mucoadhesive properties for successful inclusion into mucoadhesive dosage forms.     

N-trimethyl chitosan chloride: optimum degree of quaternization for drug absorption enhancement across epithelial cells

N-trimethyl chitosan chloride (TMC) is a polycation that enhances drug transport across epithelia by opening tight junctions. The degree of quaternization of TMC determines the number of positive charges available on the molecule for interactions with the negatively charged sites on the epithelial membrane and thereby influences its drug absorption-enhancing properties. The effects of six different TMC polymers (degree of quarternization between 12% and 59%) on the transepithelial electrical resistance (TEER) of Caco-2 cell monolayers and on the transport of hydrophilic and macromolecular model compounds across Caco-2 cells were determined. All the TMC polymers were able to decrease the TEER markedly in a slightly acidic environment (pH 6.2). However, only TMC polymers with higher degrees of quaternization (> 22%) were able to reduce the TEER in a neutral environment (pH 7.4). The maximum reduction in TEER (47.34 +/- 6.0% at a concentration of 0.5% w/v and pH 7.4) was reached with TMC with a degree of quaternization of 48%, and this effect did not increase further with higher degrees of quaternization of TMC. In agreement with the TEER results, the transport of model compounds across Caco-2 cell monolayers increased with an increase in the degree of quaternization of TMC. However, the transport reached a maximum for TMC with a degree of quaternization of 48% (25.3% of the initial dose for [14C]mannitol and 15.2% of the initial dose for [14C]PEG 4000), and this effect did not increase further with higher degrees of quaternization of TMC. Therefore, the increase in the effects of TMC on intestinal epithelia did not directly correlate up to the maximum quaternization degree of this polymer, but reached an optimum value already at an intermediate degree of quaternization (ca. 48%).     

Synthesis and characterization of lower size,laurylamine protected palladium nanoparticles

A procedure to synthesize lower size mono dispersed palladium nanoparticles is described. The nanoparticles are stabilized by lauryl amine and are isolable as dispersible solids. The particles are characterized by UV–Vis, FT-IR, XRD, STM and TEM techniques.     

Cross-linked cationic polymer microparticles: effect of N-trimethyl chitosan chloride on the release and permeation of ibuprofen

Microparticles made by cross-linking hydrophilic polymers, such as chitosan, have been used to modify the release rate of a loaded drug. In this study a polymer with fixed positive charges, N-trimethyl chitosan chloride (TMC), was used in combination with chitosan to formulate microparticles to investigate its effects on drug release rate and transport across intestinal epithelial cells. The microparticles were prepared by cross-linking these cationic polymer(s) using sodium citrate as the ionic cross-linker. This process was done under homogenization and ultrasonication to control the size of the particles. The addition of TMC to the chitosan microparticles resulted in an increase in particle size of the microparticles and an increase in ibuprofen release rate as compared to the microparticles containing chitosan alone. Permeation of ibuprofen across Caco-2 cell monolayers, after administration of a suspension of the microparticles to the apical side, was not significantly different for the microparticles containing TMC as compared to those consisting of chitosan alone. It was concluded that release of TMC molecules from the microparticles was probably not sufficient to interact with the intestinal epithelial cells in order to change the permeation of the released drug.     

Synthesis,characterization and antibacterial activity of superparamagnetic nanoparticles modified with glycol chitosan

Abstract

Iron oxide nanoparticles (IONPs) were synthesized by coprecipitation of iron salts in alkali media followed by coating with glycol chitosan (GC-coated IONPs). Both bare and GC-coated IONPs were subsequently characterized and evaluated for their antibacterial activity. Comparison of Fourier transform infrared spectra and thermogravimetric data of bare and GC-coated IONPs confirmed the presence of GC coating on IONPs. Magnetization curves showed that both bare and GC-coated IONPs are superparamagnetic and have saturation magnetizations of 70.3 and 59.8 emu g^?1, respectively. The IONP size was measured as ～8–9 nm by transmission electron microscopy, and their crystal structure was assigned to magnetite from x-ray diffraction patterns. Both bare and GC-coated IONPs inhibited the growths of Escherichia coli ATCC 8739 and Salmonella enteritidis SE 01 bacteria better than the antibiotics linezolid and cefaclor, as evaluated by the agar dilution assay. GC-coated IONPs showed higher potency against E. coli O157:H7 and Staphylococcus aureus ATCC 10832 than bare IONPs. Given their biocompatibility and antibacterial properties, GC-coated IONPs are a potential nanomaterial for in vivo applications.     

Synthesis,characterization and antibacterial activity of superparamagnetic nanoparticles modified with glycol chitosan

Iron oxide nanoparticles (IONPs) were synthesized by coprecipitation of iron salts in alkali media followed by coating with glycol chitosan (GC-coated IONPs). Both bare and GC-coated IONPs were subsequently characterized and evaluated for their antibacterial activity. Comparison of Fourier transform infrared spectra and thermogravimetric data of bare and GC-coated IONPs confirmed the presence of GC coating on IONPs. Magnetization curves showed that both bare and GC-coated IONPs are superparamagnetic and have saturation magnetizations of 70.3 and 59.8 emu g⁻¹, respectively. The IONP size was measured as ∼8–9 nm by transmission electron microscopy, and their crystal structure was assigned to magnetite from x-ray diffraction patterns. Both bare and GC-coated IONPs inhibited the growths of Escherichia coli ATCC 8739 and Salmonella enteritidis SE 01 bacteria better than the antibiotics linezolid and cefaclor, as evaluated by the agar dilution assay. GC-coated IONPs showed higher potency against E. coli O157:H7 and Staphylococcus aureus ATCC 10832 than bare IONPs. Given their biocompatibility and antibacterial properties, GC-coated IONPs are a potential nanomaterial for in vivo applications.     

聚合物保护纳米镍粉的制备与表征

采用改进的多元醇液相还原工艺,用 1,2 丙二醇作还原剂,在聚乙烯吡咯烷酮(PVP)稳定剂保护下,通过调整反应条件,在均相成核条件下,合成了粒径 25nm,具有面心立方晶体结构的纳米镍粉,运用XRD、TEM、SAED、FTIR 等微观分析手段,研究了NaOH浓度、PVP加入量等因素对制备纳米镍粉的影响。研究发现NaOH可以提高成核速率,调节颗粒生长溶质浓度,是形成粒径均匀纳米颗粒的重要条件。适量的聚合物保护剂,可以阻止成核颗粒生长,减小粒径,防止颗粒团聚,FTIR分析显示PVP分子与纳米颗粒之间存在化学作用。     

Deposition of metallic nanoparticles on carbon nanotubes via a fast evaporation process

A new technique was developed for the deposition of colloidal metal nanoparticles on carbon nanotubes. It involves fast evaporation of a suspension containing sonochemically functionalized carbon nanotubes and colloidal nanoparticles. It was demonstrated that metallic nanoparticles with different sizes and concentrations can be deposited on the carbon nanotubes with only a few agglomerates. The technique does not seem to be limited by what the nanoparticles are, and therefore would be applicable to the deposition of other nanoparticles on carbon nanotubes. PtPd and CoPt(3) alloy nanoparticles were used to demonstrate the deposition process. It was found that the surfactants used to disperse the nanoparticles can hinder the nanoparticle deposition. When the nanoparticles were washed with ethanol, they could be well deposited on the carbon nanotubes. The obtained carbon nanotube supported metal nanoparticles were characterized by transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and cyclic voltammetry.     

Self-assembled nanoparticles for cellular delivery of peptide nucleic acid using amphiphilic N,N,N-trimethyl-O-alkyl chitosan derivatives

Peptide nucleic acid (PNA) holds enormous potentials as antisense/antigenic drug due to its specific binding ability and biostability with DNA or RNA. However, the poor cellular delivery is the key obstacle in development of PNA therapy. To overcome this difficulty, we developed self-assembled nanoparticles (NPs) for delivery of PNA to living cells using amphiphilic CS derivatives. A series of N,N,N-trimethyl-O-alkyl chitosans (TMACs) with different lengths of alkyl chains were synthesized. The structures of these synthesized chemicals were characterized with FT-IR and ¹H NMR. We found that the TMACs were all able to self-assemble in aqueous condition to form nano-size NPs. These nano-size NPs are spherical shape with a size range of around 100?nm and a zeta potential above +30?mV. PNA was easily encapsulated into chitosan derivative NPs by an ultrasonic method with entrapment efficiency up to 75%. The PNA-loaded TMAC NPs released the drug in a sustained manner in PBS (pH 7.4) at 37?°C. N,N,N-trimethyl-O-cetyl chitosan (TMCC) showed the best in vitro hemocompatibility and cell viability. These TMCC based NPs were able to dramatically increase the cellular uptake of PNA, specifically, 66-fold higher compared to without using these nanoparticles. The results suggest that the designed TMCC NPs might be a promising solution for improving cellular delivery of PNA.

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Synthesis of nickel nanoparticles with uniform size via a modified hydrazine reduction route

Well dispersed nickel nanoparticles with uniform size were synthesized via a modified hydrazine reduction route without any surfactant introduced. Ethanol was used as solvent and played the complementary reducing role. The as-prepared samples were characterized by XRD, FESEM, TEM and TG. Pure metallic Ni could be easily obtained when ethanol instead of water was used as solvent. The particle surface was much improved when ethanol was involved in the reduction process at high temperature. The resultant particles have smooth surface and uniform size of about 50 nm. The nickel powders have an oxidization temperature of about 200 °C. The formation process was discussed based on the experimental results.     

壳聚糖修饰氧化铁磁性纳米颗粒的制备和性能研究

通过共沉淀法制备氧化铁磁性纳米颗粒,用壳聚糖对其表面进行修饰得到样品(CS@MNPs);表征其形貌结构、尺寸、表面基团、表面电荷、磁学性质和在不同介质中的稳定性等。实验结果表明,CS@MNPs具有典型的立方反尖晶石晶体结构;粒径为16.5nm;在生理(pH值7.4)条件下拥有较高的正电荷(10mV);呈现超顺磁性,对驰豫时间T1、T2,尤其是T2*具有很强的响应;在双蒸馏水和含10%新生牛血清的RPMI 1640培养液中具有良好的稳定性,具有作为磁共振造影剂的潜力。     

Synthesis of TbMnO3 nanoparticles via a polyacrylamide gel route

We report here the synthesis of TbMnO₃ nanoparticles via an acrylamide gel route. XRD, TG analysis, DSC analysis, and FTIR spectroscopy are combinatively used to investigate the thermal decomposition process of precursor xerogels and the formation of TbMnO₃ phase. It is demonstrated that high-phase-purity TbMnO₃ nanoparticles can be prepared by using different chelating agents at a sintering temperature of 800 °C. SEM observation and XRD analysis reveal that the particle size and morphology of the products have a dependence on the chelating agent. The particles prepared using citric acid as the chelating agent appear to be regularly spherical in shape and highly uniform in size with a diameter of ～67 nm, while the sample prepared by using the chelating agent EDTA mainly consists of sphere-, ellipsoid-, and rod-like particles and exhibits a relatively broad particle size distribution with an average particle size centered around 115 nm. The use of a combination of citric acid and EDTA generally results in sphere- and ellipsoid-like particles with an average particle size between those of the samples prepared separately by using the two chelating agents.     

Synthesis of barium titanate nanoparticles via a novel electrochemical route

An electrochemical route from Ti metal plate in KOH and Ba(OH)₂ electrolyte at room temperature is first established for the synthesis of BaTiO₃ nanoparticles. Anodic sparks play a key role, and KOH concentration is one of the most significant factors which affect the appearance of anodic sparks in this method. XRD patterns show that the powder obtained in our study is a pure perovskite phase BaTiO₃ with a cubic structure, whose size and morphology are subsequently studied by TEM. The mean diameter of the particles is 13.8 nm and the standard deviation (S.D.) fitted is 6.26 nm. It is also found that the mean size of the obtained nanoparticles increase from 13.8 nm to 168.0 nm, when 60 vol.% absolute ethanol is replaced by distilled water as the solvent of the electrolyte.     

Synthesis of Cu nanoparticles with self-assembled monolayers via inert-gas condensation

Cu nanoparticles with vaporized self-assembled monolayers (SAMs) for the prevention of oxidation were synthesized via inert-gas condensation (IGC). When processing the nanoparticles, the convection in the vacuum chamber was controlled using carrier gases such as Ar and He. Cu shots (2-8 mm) were used as raw materials and were evaporated via resistance heating. Octanethiol (CH3(CH2)7SH) was used for the SAMs and was introduced with the carrier gases during the process. The prepared samples were examined via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to determine the particle sizes, the coating thicknesses of the SAMs, and the particle distribution states. The ingredients were confirmed via X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy (EDS). The particle size and morphology were controlled by introducing various combinations of carrier gases, such as He, Ar and H2. Finally, stabilized Cu nanoparticles stably coated with octanethiol were successfully fabricated.     

Synthesis of silver nanoparticles using N 1, N 2-diphenylbenzamidine by microwave irradiation method

Silver nanoparticles have been prepared under microwave irradiation from a solution of silver nitrate in the presence of N ¹,N ²-diphenylbenzamidine (DPBA) or simply amidine without any stabilizing agent. Different morphologies of silver colloids with charming colors could be obtained using N ¹,N ²-diphenylbenzamidine (DPBA). The structures of silver colloids were determined by TEM. UV-Vis spectroscopy was used to follow the reaction process and to characterize the optical properties of the resultant silver colloids. The influence of unconventional reducing agent on the morphology of silver was investigated.     

Synthesis and characterization of CuInSe2 nanoparticles via a solution method

Pure CuInSe₂ nanoparticles have been successfully synthesized via a solution method in the solvent of oleylamine. Anhydrous InCl₃, CuCl, and Se powder were used as the starting materials. The CuInSe₂ samples were characterized by XRD, TEM, and XPS techniques. It was found that tetragonal chalcopyrite structured CuInSe₂ nanoparticles were obtained with temperature above 230 °C. Sample prepared at 200 °C possesses triangular morphology and a minute amount of In₂Se₃ coexists as intermediate. CuInSe₂ nanoparticles with size of 20.2 ± 0.4 nm were prepared at 230 °C and the narrow size distribution was ascribed to the employment of hot injection, which was better for homogeneous nucleation. Stable “ink” can be formed when the as-synthesized CuInSe₂ nanoparticles were dispersed in organic solvents such as hexane and tolune, and such “ink” might have a practical application in CuInSe₂-based solar cells.     

pH-insensitive fabrication of gold nanoparticles with high concentration by ultrasound-assisted electrochemical process via aid of chitosan

In this work, we report a new pathway to prepare pure gold nanoparticles with high concentrations in acid solutions via the aid of chitosan without the addition of other stabilizers and reductants based on electrochemical methods. Interestingly, this fabrication of gold nanoparticles with high concentrations in solutions is pH-insensitive. The characteristics of prepared gold nanoparticles were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (HRXPS) measurements. Experimental results indicate the concentration and the particle size of Au nanoparticles prepared in 0.1N HCl are ca. 50 ppm and 12 nm in diameter, respectively. Similar experiment performed in 0.1N NaCl with the aid of chitosan shows that the corresponding concentration of prepared Au nanoparticles is ca. 100 ppm. Further similar experiments performed in 0.1N HCl and 0.1N NaCl without the aid of chitosan show that the corresponding concentrations of prepared Au nanoparticles are ca. 1 and 60 ppm, respectively.     

液相还原法制备纳米银颗粒

以聚丙烯酸铵为保护剂,利用液相化学还原法成功的制备了纳米银颗粒.利用透射电子显微镜(TEM),X射线衍射(XRD)对样品的形貌和结构进行了分析,并讨论了聚丙烯酸铵的加入量对纳米银粒径的影响.利用紫外分光光度计(UV光谱)对纳米银溶胶的粒径分布及其稳定性进行了分析.研究结果表明,聚丙烯酸铵的加入量对纳米银的粒径和形貌有重要的影响.同时,所制备的纳米银溶胶的稳定性较好.     

Synthesis and characterisation of cross-linked chitosan composites functionalised with silver and gold nanoparticles for antimicrobial applications

Abstract

We present a study of a range of cross-linked chitosan composites with potential antimicrobial applications. They were formed by cross-linking chitosan and siloxane networks and by introducing silver and gold nanoparticles (NPs). The aim was to investigate whether adding the metal NPs to the chitosan-siloxane composite would lead to a material with enhanced antimicrobial ability as compared to chitosan itself. The composites were synthesised in hydrogel form with the metal NPs embedded in the cross-linked chitosan network. Spectroscopic and microscopic techniques were employed to investigate the structural properties of the composite and the tensile strength of the structures was measured. It was found that the addition of metal NPs did not influence the mechanical strength of the composite. A crystal violet attachment assay results displayed a significant reduction in the attachment of E. coli to the cross-linked chitosan surfaces. Release profile tests suggest that the metal NPs do not contribute to the overall antimicrobial activity under neutral conditions. The contribution to the mechanical and antimicrobial properties from cross-linking with siloxane is significant, giving rise to a versatile, durable, antimicrobial material suitable for thin film formation, wound dressings or the coating of various surfaces where robustness and antimicrobial control are required.