Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction.

The Baylis-Hillman reaction of aldehydes with alpha,beta-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at -78 degrees C using catalytic amounts of quaternary ammonium salts (R4N+X-, X = Cl, Br, I) as Lewis bases, in the presence of titanium(IV) chloride, the chlorinated aldol adduct 1 was obtained as the major product. Quaternary ammonium bromides and iodides (R4N+X-, X = Br, I) have higher catalytic activity than corresponding chlorides (R4N+Cl-). Quaternary ammonium fluorides (R4N+F-) do not have activity at all. The amounts of Lewis acid and quaternary ammonium salts used affect the reaction rate and product. A plausible reaction mechanism is proposed. If the reaction was carried out at room temperature (about 20 degrees C) in the presence of titanium(IV) chloride and quaternary ammonium salts (R4N+X-, X = Cl, Br, I), the elimination product 3, derived from 1, was formed as the major product.     

Engineering quaternized chitosan in the 3D bacterial cellulose structure for antibacterial wound dressings

Balancing antibacterial properties with biocompatibility is of paramount importance for wound dressings loaded with antibacterial agents. In this work, a water soluble antibacterial agent, quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan, HACC) with an appropriate degree of substitution was introduced into the bacterial cellulose (BC) network by adding it into the BC culture medium. Results indicated that the addition of HACC could affect the yield of BC, porous structure, thermal stability, water absorption and antibacterial properties. HBC-1 with a low content of HACC (13.65 ± 0.30%) cannot inhibit the biofilm formation of bacteria, while HBC-3 with a high content of HACC (62.05 ± 0.90%) has a low yield of BC and confused structure. HBC-2 with an optimum concentration of HACC (37.33 ± 0.80%) possessed a typical porous structure, acceptable thermal stability, good water absorption and favorable antibacterial properties against Staphylococcus aureus (S. aureus, ATCC 25923) and methicillin-resistant S. aureus (ATCC 43300). Most importantly, none of the HACC/BC films exhibited cytotoxicity to NIH3T3 cells. We believe that obtained HACC/BC films with favorable bactericidal properties and biocompatibility could be potential candidates for wound dressings in clinical applications.     

Quaternary ammonium chitosan derivative dynamic coating for the separation of veterinary sulfonamide residues by CE with field-amplified sample injection

A quaternary ammonium chitosan, 2-hydroxypropyltrimethylammonium chloride chitosan (HACC), has been developed for the dynamic coating material in CE for the first time. It presented many advantages such as favorable water solubility, satisfactory coating efficiency, and EOF toward the anode at pH >7.0. Using the modified fused-silica capillary, sulfonamides (SAs), an important group of veterinary drugs, were separated and detected by CE combined with field-amplified sample injection (FASI). The LODs of sulfonamides with UV detection were less than 0.5 ng/mL. The proposed method has been applied to the determination of veterinary sulfonamide residues in samples such as chicken, beef, and honey with fast separation (15 sulfonamides within 20 min), low LODs (0.1-0.5 ng/mL), and good reliability compared to the criteria of China (GB/T 18932.17-2003).     

高效抗菌Cu~(2+)-壳聚糖季铵盐/丙烯酸复合物的制备

以过硫酸铵为引发剂,在壳聚糖季铵盐(HACC)上接枝丙烯酸(AAc)并络合Cu~(2+),制备了具有高效抗菌性能的HACC-g-PAAc-Cu~(2+)复合物.采用红外光谱(FTIR)和核磁共振波谱(~1H NMR)表征了壳聚糖季铵盐接枝改性前后的化学结构变化;利用紫外-可见吸收光谱(UV-Vis)、Cu~(2+)选择电极和热失重分析(TGA)表征了壳聚糖季铵盐接枝前后负载Cu~(2+)的能力;测定了HACC-Cu~(2+)和HACC-g-PAAc-Cu~(2+)对金黄色葡萄球菌及大肠杆菌的最小抑菌浓度,并对小鼠经口摄入毒性和兔皮肤敷涂刺激性进行了考察.研究结果表明,在壳聚糖季铵盐上负载Cu~(2+)能够有效提高其抗菌性;接枝丙烯酸能提高HACC负载Cu~(2+)的能力和抗菌性,Cu/HACC结构单元的摩尔比由接枝前的3∶7提高到接枝后的1∶1;对金黄色葡萄球菌的最小抑菌浓度由60 mg/L下降到9.2 mg/L,对大肠杆菌的最小抑菌浓度由37 mg/L下降到6.3 mg/L,无摄入毒性和皮肤刺激性.     

Synthesis, Structure and Properties of Novel Quaternized Carboxymethyl Chitosan with Drug Loading Capacity

A modified approach to prepare novel amphipathic octadecyl-quaternized carboxymethyl chitosan (QACMC) was reported, in which carboxymethyl chitosan (CMC), prepared from chitosan, was made to react with glycidyl octadecyl dimethylammonium chloride; thus, the octadecyl quaternary ammonium group was introduced into CMC. The structure and thermal properties of these derivatives were characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The crystalline properties of QACMC were perfect, and it had a high degree of crystallinity. All the chitosan derivatives had good thermal stability when the temperature was lower than 200 °C. The moisture-absorption and retention abilities of QACMC were lower than that of hyaluronic acid (HA) and CMC. The carboxymethyl and quaternary ammonium groups did not show a synergistic effect, and the effects of both the molar mass and the hydrophobic side chains of long alkyl moieties were important. Minocycline hydrochloride was successfully incorporated into QACMC polymeric micelles with a remarkably high efficiency (10.9%, mass fraction). QACMC promises to be a high-potential delivery vector for lipophilic drugs.     

新型载药壳聚糖季铵盐的合成、结构与性能

通过羧甲基壳聚糖接枝二甲基十八烷基环氧丙基氯化铵, 制备了一系列不同取代度和分子量的羧甲基壳聚糖十八烷基季铵盐(QACMC). 用傅立叶变换红外(FTIR)光谱、核磁共振谱(1H-NMR)、X射线衍射(XRD)谱、差式扫描量热法(DSC)等对其分子结构、结晶和热性能进行研究, 同时研究QACMC的吸湿保湿性能, 并与透明质酸(HA)、壳聚糖(chitosan)和羧甲基壳聚糖(CMC)进行比较. 结果表明, QACMC具有较好的结晶性和热稳定性, 结晶度可达72.3%; 其吸湿保湿性低于透明质酸(HA)和羧甲基壳聚糖, 而受季铵基团取代度和QACMC分子量的影响, 羧酸盐和季铵盐两种亲水基团对QACMC吸湿性的影响不具有协同作用; QACMC对亲脂性药物盐酸米诺环素的载药率可达10.9%(质量分数), 远高于壳聚糖和羧甲基壳聚糖.     

Novel 2-Hydroxypropyltrimethyl Ammonium Chitosan Derivatives: Synthesis,Characterization, Moisture Absorption and Retention Properties

Recent years have seen a steady increase in interest and demand for the use of humectants based on biodegradable natural polymers in many fields. The aim of this paper is to investigate the moisture absorption and retention properties of 2-hydroxypropyltrimethyl ammonium chitosan derivatives which were modified by anionic compounds via ion exchange. FTIR, ¹H NMR, and ¹³C NMR spectroscopy were used to demonstrate the specific structures of chitosan derivatives. The degrees of substitution for objective products were calculated by the integral ratio of hydrogen atoms according to ¹H NMR spectroscopy. Meanwhile, moisture absorption of specimens was assayed in a desiccator at different relative humidity (RH: 43% and 81%), and all target products exhibited enhanced moisture absorption. Furthermore, moisture retention measurement at different relative humidity (RH: 43%, 81%, and drier silica gel) was estimated, and all target products possessed obviously improved moisture retention property. Specifically, after 48 h later, the moisture retention property of HACBA at 81% RH was 372.34%, which was much higher than HA (180.04%). The present study provided a novel method to synthesize chitosan derivatives with significantly improved moisture absorption and retention properties that would serve as potential humectants in biomedical, food, medicine, and cosmetics fields.     

Balance of disinfection and cytotoxicity of hydroxypropyltrimethyl ammonium chloride chitosan with polyhexamethylene biguanide at low concentrations

Any microorganisms killing molecules have some cytotoxicity more or less. The effective way of reducing cytotoxicity mainly included two approaches: One was reducing the concentration of antiseptic, while this would lead to the decreased antimicrobial efficiency; the other way was choosing suitable antiseptics and then combining of them, which can balance the disinfection and cytotoxicity. In this paper, hydroxypropyltrimethyl ammonium chloride chitosan (HACC), a cationic natural macromolecular, as the first antiseptic, incorporated with polyhexamethylene biguanide (PHMB), a smaller molecular weight cationic antiseptic polymer, as the second antiseptic, their disinfection effect and cell cytotoxicity in borate buffer solution were investigated at fairly low contents. When HACC/PHMB weight ratios were 100/1 and 150/1, the disinfection solutions produced >1-log reductions against C. albicans and >3-log reductions against S. aureus and P. aeruginosa. HACC/PHMB disinfection solution at weight ratio of 150/1 even showed a highest antimicrobial efficiency and the cell proliferation rates were approximately 100% in MTT assays. Meanwhile, the research of micromorphology and fluorescence spectra indicated that bigger aggregation state of HACC-PHMB were helpful to improve antimicrobial ability. These results showed that the HACC-PHMB combination might be a promising candidate for novel antimicrobial group for biomedical applications.     

交联结构对水不溶性聚季铵盐类杀菌性能的影响

Ron等 [1 ]报道了以聚苯乙烯或交联聚苯乙烯的氯甲基化物等为反应载体 ,通过载体上的氯甲基与含有长链烷基的不同叔胺进行季铵化反应 ,制得水不溶性聚季铵盐或聚双季铵盐杀菌剂 .Hiroki等 [2 ]报道了以聚苯乙烯的氯甲苯化物或苯乙烯、二乙烯苯交联共聚物的氯甲基化物为反应载体 ,通过载体上的氯甲基与叔二胺的季铵化或与带有长链烷基的联吡啶　的　化反应 ,制得了含铵盐官能团和联吡啶　官能团的水不溶性聚合物杀菌剂 .陈拥军等 [3]以聚苯乙烯或交联聚苯乙烯的氯甲基化物为反应载体制备了含氮和磷的水不溶性杀菌剂 .但迄今为止 ,对不溶性聚…     

水溶性壳聚糖降血脂作用的化学机理(Ⅰ)--水溶性壳聚糖及其衍生物对胆酸盐的结合能力研究

通过壳聚糖氧化裂解,制备了分子量为8000的水溶性壳聚糖,并通过烷基化反应合成了二乙氨乙基壳聚糖、二甲氨基(1-甲基)乙基壳聚糖及二乙基甲基铵乙基壳聚糖.在体外测定了水溶性壳聚糖及其衍生物对胆酸盐(牛磺胆酸钠和甘氨胆酸钠)的结合能力及其影响因素.结果表明,水溶性壳聚糖结合胆酸盐的能力主要取决于其阳离子化程度.修饰后的壳聚糖结合胆酸盐的能力增强,说明引入更多的胺基或铵基有利于对胆酸盐的结合.