Effect of Molecular Weight and Structure on Antitumor Activity of Oxidized Chitosan

Various low molecular weight chitosans were prepared by oxidative degradation with H2O2, and characterized by IR,13C-NMR and gel permeation chromatography. Their carboxylic contents increased with decrease in molecular weight (M w ). The antitumor test of the samples against sarcoma 180 tumors suggested that the water-soluble chitosan with higherM w have higher inhibitory ratioin vivo. The introduction of carboxylic group is advantage to water-solubility of chitosan, but more acidic groups might decrease the function of amino groups of chitosan against sarcoma 180 tumor.

Researches on the Internal Molecular Weight Uniformity of Chitosan Biomaterials

Uniform molecular weight(Mw)chitosan(CS)is highly demanded in medical biomaterial industry.This present article described heterogeneous degradation of CS in aqueous HCl/ethanol solution,in which progress uniform Mw CS was successfully prepared.The Mw distribution of CS was measured by gel permeation chromatography(GPC)analysis.Moreover,the structure and properties of degraded CS were characterized by Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance spectroscopy(^1H NMR),X-ray diffraction(XRD)and thermogravimetric(TG)analysis.In addition,the biocompatibility of degraded CS was also assessed by hemolysis rate(HR)measurement.The Mw of CS dramatically decreased from 246 KDa to 76 k Da at the initial 30 min,and stabilized at 18 kDa after 24 h.GPC analysis results showed that the degraded CS molecular become homogenization.FT-IR and 1 H NMR analysis confirmed the basic structure of CS molecular backbone was not destroyed during this progress.Besides,the water solubility of CS was not significantly influenced by this reaction.Moreover,the XRD analysis revealed that crystallinity of degraded CS increased from 70.32% to 99.25%with time.The TG analysis showed improved thermal stability of degraded CS.HR measurement demonstrated the degraded CS possessed excellent biocompatibility.This simple and efficient heterogeneous degradation would open up a new route to produce uniform Mw CS.

LOW MOLECULAR WEIGHT O-CARBOXYMETHYLATED CHITOSANS DERIVED FROM IRRADIATED CHITOSAN AND THEIR ANTIBACTERIAL ACTIVITY

Original chitosan with M-v of 2.7 x 10(5) was degraded by irradiation with gamma-rays and a series of low molecular weight O-carboxymethylated chitosans (O-CMCh) were prepared based on the irradiated chitosan. A kinetic model of the irradiation of chitosan was put forward. Results show that the irradiation degradation of chitosan obeys the rule of random degradation and the degree of deacetylation of irradiated chitosan is slightly raised. The antibacterial activity of O-CMCh is significantly influenced by its MW, and a suppositional antibacterial peak appears when M-v is equal to 2 x 10(5).

不同分子质量水溶性壳聚糖在纸质文献加固中的应用研究

本研究采用乙酸酐制备了不同分子质量的水溶性壳聚糖(WSC-3、WSC-10、WSC-20、WSC-30和WSC-60)并用作修复液,探究其对纸质文献加固及耐老化的效果。结果表明,与未经加固处理的纸张(原纸)相比,采用不同分子质量的水溶性壳聚糖加固处理后,纸张的强度性能有所提升,白度下降幅度较小,色差变化较小,pH值和碱储量均增加。纸张加速老化后,与原纸相比,加固处理后纸张的强度性能下降幅度明显较小,其中WSC-30加固处理后纸张的抗张指数、撕裂指数、零距抗张强度的保留率分别提升了9.7、7.4、4.5个百分点,外观形貌、白度和色差等相差较小。

儿茶酚化/季铵化双重改性高分子量壳聚糖基复合银纳米粒子

银纳米粒子比表面积大,抗菌效力强,被广泛应用于生物医学领域,但浓度过高时存在毒性。通过双重化学改性,水相中实现高分子量壳聚糖的溶解分散,并利用邻苯二酚结构的还原稳定作用制得一种儿茶酚化/季铵化双重改性壳聚糖基复合银纳米粒子(CQCS-AgNPs),有望发挥季铵化壳聚糖和银的协同抗菌效应。核磁共振氢谱法(1H NMR)和X射线衍射(XRD)表征证实CQCS的成功合成,季铵化度为10%,CQCS1的儿茶酚化度为15%,水中溶解度达21.5 mg/mL。透射电子显微镜(TEM)、动态光散射仪(DLS)、分光光度仪(UV)证实CQCS-AgNPs的成功制备,并具有良好的分散性和稳定性,粒径范围为3~25 nm。溶液共培养抗菌试验、抑菌圈试验和CCK-8体外细胞毒性试验证明银浓度仅为0.0197μg/mL时的CQCS-AgNPs对革兰氏阳性菌金黄色葡萄球菌和革兰氏阴性菌大肠杆菌具有优异的抗菌性能,同时对NIH3T3细胞的毒性较小。CQCS-AgNPs有效减少99.8%的银使用量,从而降低银的毒性,可用作广谱高效低毒抗菌剂。

INFLUENCE OF MOLECULAR WEIGHT OF CHITIN AND ITS THREE DERIVATIVES ON CRITICAL CONCENTRATION OF LYOTROPIC LIQUID CRYSTALLINE PHASE TRANSITION

The critical concentration of lyotropic liquid crystalline phase transition for chitin derivatives was determined using a polarization microscope. The influence of molecular weight on critical concentration of liquid crystalline solution for chitin, chitosan, cyanoethyl chitosan and propionyl chitin successively increases as the chain rigidity decreases. Therefore it can be used as an indicator of the chain rigidity.

Solid-Phase Preparation and Characterization of Chitosan

Chitosan was prepared with stressing method by blending chitin and solid alkali in a single-screw extruder at given temperature and characterized by potentiometric titration, gel permeation chromatography (GPC), infrared spectrum (IR) and carbon-13 magnetic resonance sperctroscopy ( 13 C NMR) . Chitosan with a deacetylation degree (DD) of 76.1% was obtained at a mass ratio 0.2∶1∶1 for H_ 2 O/chitin/NaOH at 160 ℃ for 12 min. Compared to conventional solution method(usually 1∶10 for chitin/NaOH), the alkali assumption greatly decreased. Molecular weight of chitosan obtained by solid-phase method(S3,M_w1.54×10 5 ) was lower than that obtained by suspension method(Y2,M_w3.34×10 5 ). During deacetylation, molecular weight decreased with high reaction temperature and long reaction time but remained same at different initial ratios of NaOH/chitin. It might be concluded that degradation of chitosan was caused by breakout of the main chain of the oxidized chitosan catalyzed by alkali during the deactylation. IR and 13 C NMR showed that structures of chitosans prepared by solid-phase method were not changed.

Efficacy of Over-the-Counter (OTC) Medical Device Products as a Tool in Clinical Weight Management

Background: Obesity is a significant public health challenge. Its prevalence is increasing at an alarming rate globally. Numerous slimming products crowd the market, with each offering a proprietary formulation with statements of alleged efficacy. Within the EU, one such class is Medical Device, featuring a range of marine- and vegetal-based fibers as the functional ingredient. Methods: An analysis was performed to investigate and compare the lipid binding performance of three medical devices consisting of: 1) a polyglucosamine;2) a vegetal opuntia extract;and 3) a vegetal opuntia extract with vitamins using an industry-standard, validated test method. 0.5 gr of material from each product was studied. Results: The polyglucosamine exhibited a lipid binding capacity (691.7 g/g) more than 20 times the vegetal opuntia extracts. A significantly higher standard deviation (±12.1) was reported for the polyglucosamine medical device vs. the vegetal opuntia extracts (±1.3 - 4.8). However, the standard deviation reported for the former is approximately 1.7% of the mean value obtained from double determination, significantly smaller than that 2.5% - 15% observed for the extracts. Conclusions: Analysis of lipid binding indicated the polyglucosamine exhibited a substantially higher capacity than the vegetal opuntia samples. Further studies are needed to validate these in vitro results.

Preparation and Characterization of AlginateHyaluronic Acid-chitosan based Composite Gel Beads

The aim of this study was to fabricate composite gel beads based on natural polysaccharides. Hyaluronic acid（HA） and Chitosan（CS） were successfully admixed with Ca^2＋/alginate（SA） gel system to produce SA/HA/CS gel beads by dual crosslinking： the ionic gelation and the polyelectrolyte complexation. The preparation procedure was that the weight ratio of SA（2%, m/v） to HA（2%, m/v） was kept at 2：1, then the mixture was dripped into the Ca^2＋ solution for ion-crosslinking, and finally polyelectrolyte crosslinked with 2% low molecular weight CS（LMW-CS） for 1.5 hours. The optimal formulation was achieved by adjusting the concentration and the weight ratio of SA, HA and LMW-CS. Due to the incorporation of HA and LMWCS, the swelling ratio of the beads at pH 7.4 was increased up to 120, and the time for the maximum swelling degree was prolonged to 7.5 h. The swelling behavior was obviously improved compared to the pure SA/Ca^2＋ system. The preliminary results clearly suggest that the SA/HA/CS gel beads may be a potential candidate for biomedical delivery vehicles.

In vivo biodistribution of topical low molecular weight heparin-taurocholate in a neovascularized mouse cornea

AIM： To investigate the ocular biodistribution and clearance of topically administered 7-taurocholic acid conjugated low-molecular weight heparin（LHT7） in a neovascularized mouse cornea using an in vivo optical imaging system. METHODS： A total of 10 eyes of 6 to 8-week-old BALB/c mice were analyzed. Corneal neovascularization（CoNV） was induced in the inferior cornea（IC） of each animal by penetrating the stroma with two interrupted sutures. The development of CoNV was verified after one week and the area of each neovascularized region was measured. A near-infrared fluorescent probe of 20 μmol/L Cy5.5 labeled LHT7（LHT7-Cy5.5） in 0.02 mL solution was topically instilled onto the cornea in the experimental group（n=5）. Free-Cy5.5 of 20 μmol/L in 0.02 mL was instilled in the control group（n=5）. In vivo optical images were obtained before instillation and 5 min, 2, 4, and 6 h after instillation. The intensities were separately measured at the superior cornea（SC） and the IC. RESULTS： The mean CoNV areas were 1.97±0.17 mm^2 and 1.92±0.96 mm^2 in the experimental and control groups, respectively（P=0.832）. The SC remained normal in all 10 subject animals. The IC intensity of the LHT7-Cy5.5 was greater than the SC intensity at 5 min（P=0.038）, 2 h（P=0.041）, and 4 h（P=0.041） after application. The IC intensity fell to less than half of its initial value（42.9%±8.6%） at 6 h in the experimental group. In the control mice, here were no significant differences in the free-Cy5.5 intensity between the IC and SC. CONCLUSION： Topically administered LHT7 shows a high biodistribution in CoNV areas for 4 h and should be reapplied accordingly to maintain its effects. In vivo optical imaging can be a useful tool for evaluating the ocular biodistribution of a drug in an animal model.

THE STUDIES ON DEGRADATIVE KINETIC OF MEDICAL CHITOSAN

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Complex Coacervation composed of Polyelectrolytes Alginate and Chitosan

Alginate sodium(ALG)and chitosan(CHI)can form fiber,films,microspheres,hydrogels and all with a wide range of biomedical applications.Few works have been done as a result of the easily flocculation of chitosan in negatively charged matrix.Complex coacervation composed of polyelectrolytes alginate and chitosan were successfully fabricated.The results showed that the lower molecular weights of the chitosan is better for the fabricated of the complex coacervation.

不同特性壳聚糖对法兰克福香肠品质的影响

为获得一种具有优良性能和健康功效的新型乳化类肉制品,本研究评价了不同分子量(3.2~676 kDa)和不同脱乙酰度(70%~90%)的壳聚糖对法兰克福香肠品质特性的影响。结果表明,分子量670 kDa、脱乙酰度90%的壳聚糖具有最好的增稠能力,在HMHD添加量为1.0%时可显著提高香肠的a^(*)值、硬度、内聚力和pH值,同时可以降低蒸煮损失率(P<0.05)。因此,分子量670 k Da、脱乙酰度90%的壳聚糖可以更好地改善香肠的品质。本研究可为获得具有优良性能和健康功效的新型功能性肉制品提供理论支持。

不同分子质量虾源壳寡糖的抗菌抗氧化活性差异研究

为明确虾源壳寡糖的抗菌抗氧化活性与其数均分子质量之间的相关性,该研究采用乙醇分级沉淀法分离虾源壳聚糖酶解物,得到4种不同分子质量的壳寡糖产品(COS50、COS60、COS70、COS70 s),数均分子质量分别为2365、2807、3105、1390 Da。比较4种壳寡糖产品的抑菌抗氧化活性,发现COS50(数均分子质量为2362 Da)对大肠杆菌、枯草杆菌、金黄色葡萄球菌、假单胞菌和希瓦氏菌均有较强的抑菌效果,对上述各种菌的最低抑菌浓度(minimal inhibitory concentration,MIC)值分别为2.50、1.25、1.25、0.62、0.16 mg/mL;壳寡糖的抗氧化能力整体上随着数均分子质量的增加而减弱,COS50清除DPPH自由基的能力最强,清除自由基一半所需浓度(IC 50)为0.90 mg/mL,COS70 s的总还原力最强(每克相当于9.87 mg抗坏血酸的还原力),COS50次之。综合考虑抗菌抗氧化活性,COS50(数均分子质量为2362 Da)为具备抗菌抗氧化性能的最优壳寡糖。该研究为虾源壳寡糖的开发应用提供理论参考。

不同分子量壳聚糖涂膜对采后西番莲果实贮藏品质的影响

为研究不同分子量壳聚糖涂膜对采后西番莲的保鲜效果,本文以“钦蜜9号”西番莲果实为试材,分别采用30、50、100、150和200 kDa分子量的壳聚糖(1.5%,w/v)进行涂膜,以明确不同分子量壳聚糖涂膜对西番莲果实品质的影响。结果表明,不同分子量壳聚糖涂膜均能延缓西番莲果实的皱缩和果皮转黄,降低果实的失重率和抑制果实腐烂。其中,分子量越大的壳聚糖越有利于减轻西番莲果实成熟衰老、皱缩和腐烂,200 kDa涂膜果实的失重率在贮藏末期较同期30 kDa涂膜果实低近10%,并且150和200 kDa涂膜的果实在贮藏末期均未发生腐烂;较低分子量(30和50 kDa)和较高分子量(150 kDa)的壳聚糖涂膜则更有助于减缓果实贮藏期间失重、可溶性固形物和可溶性糖代谢以及维持果实可滴定酸、类黄酮和总酚含量,而150 kDa的壳聚糖涂膜在保持维生素C含量方面效果最好,在贮藏末期其含量是同期对照组的1.12倍。综上所述,不同分子量壳聚糖涂膜均有助于延缓西番莲果实衰老,减缓果实失水皱缩,保持果实品质,但具体效果在不同分子量间差别较大,综合而言,150 kDa壳聚糖更适合保持西番莲果实品质。

凝胶渗透色谱-激光光散射联用法检测医用壳聚糖类产品稳定性

选取作为Ⅲ类医疗器械管理的4种医用壳聚糖类产品,当其有效期内在自然条件下存放于货架时,利用凝胶渗透色谱-激光光散射联用法跟踪检测其相对分子质量及其分布,以此来评价其产品的稳定性。以0.1 mol/L NaNO_(3)(含质量分数为2×10^(-4) NaN_(3))为流动相,选择Shodex SB806、SB805、SB804与保护柱串联进行分析。三种产品医用几丁糖、外科手术用防粘连冲洗液、医用防粘连改性壳聚糖(膜)的相对分子质量变化均小于38%,相对重均分子质量均维持在1.0×10~5及以上,壳聚糖基可吸收止血非织布相对分子质量降至9.3×10~4,减小90%以上。

壳聚糖酶解的研究

低聚水溶性壳聚糖具有许多独特的生理活性。本文对壳聚糖酶解制备低聚水溶性壳聚糖的研究进展进行了介绍 。

低聚壳聚糖及其金属配合物的抗O_2^(·-)活性研究

以 NBT/VB2 /蛋氨酸为 O· - 2 产生、检测体系 ,对自制低聚壳聚糖及其金属配合物进行了抗 O· - 2 活性研究 ,结果显示低聚壳聚糖及其金属配合物对 O· - 2 均具有明显的清除活性 .质量浓度为 0 .5× 1 0 - 2 g/m L时 ,壳聚糖对 O· - 2 的清除率达 80 .3 % ,其与氯化镧、醋酸铜、醋酸钴的配合物对 O· - 2 的清除率分别为98.9%、84.1 %、78.4% ;相同条件下 ,高分子壳聚糖和单糖对 O· - 2 没有明显的清除作用 ,清除率仅为 1 3 %、9.5 % .随着样品质量浓度降低 。