植物凝胶和蔗糖对橡胶树体胚植株再生的影响

为了筛选巴西橡胶体胚植株最为适合的植物凝胶和蔗糖用量,该研究以巴西橡胶树无性系热研7-33-97成熟体细胞双子叶次生胚状体为材料,以添加0.23μmol·L~(-1)KT,0.11μmol·L~(-1)IAA和8.7μmol·L~(-1)GA3的MS培养基为植株再生培养基,研究了添加不同用量的植物凝胶和蔗糖对巴西橡胶树体胚植株再生和生长的影响。结果表明:在橡胶树体细胞胚植株再生培养基中,不同用量的植物凝胶对植株再生频率和植株生长状况有显著影响,较低浓度(0~1 g·L~(-1))时,随着用量增加,植株再生频率提高,但较高浓度(1~4 g·L~(-1))时,随着用量增加,植株生长受到抑制。植物凝胶添加1 g·L~(-1)时植株生长最好,植株再生率为(86.4±5.7)%,株高5 cm以上的占(53±9.4)%,带叶植株为(81.7±3)%;而蔗糖对植株再生频率影响不显著,但对再生植株生长的影响显著,低蔗糖(20~30 g·L~(-1))时促进植株抽叶但抑制茎干伸长,高蔗糖(70~80 g·L~(-1))时显著抑制抽叶但促进茎干伸长。蔗糖添加50 g·L~(-1)时植株生长最好,株高5 cm以上的占(57.6±5.4)%,株高5 cm以上带叶植株占(46.3±12.3)%,均为最高且从外观来看,在50 g·L~(-1)时植株茎干和根都较为粗壮。因此,在橡胶树体细胞胚植株再生培养基中,植物凝胶和蔗糖最佳用量分别为1 g·L~(-1)和50 g·L~(-1)。     

叶下珠组培快繁体系研究

以叶下珠Phyllanthus urinaria带节茎段为外植体,研究生长调节剂浓度、培养基对茎段诱导芽的影响,再以叶下珠无菌芽为材料,开展丛生芽增殖培养、生根培养和炼苗移栽技术研究。结果表明,适合叶下珠茎段诱导芽的培养基为1/2MS+6-BA 2.0 mg·L~(-1)+IBA 0.2 mg·L~(-1)+琼脂7.5 g·L~(-1)+蔗糖30 g·L~(-1)+活性炭0.5 g·L~(-1)(pH 5.8~6.0),诱导率达100%;适合叶下珠芽增殖的培养基为1/2MS+6-BA 1.0 mg·L~(-1)+IBA 0.2 mg·L~(-1)+琼脂7.5 g·L~(-1)+蔗糖30 g·L~(-1)(pH 5.8~6.0),平均增殖倍数为3.8;生根适宜培养基为1/2MS+IBA 0.5 mg·L~(-1)+琼脂7.5 g·L~(-1)+蔗糖20 g·L~(-1)(pH 5.8~6.0),生根率达100%;最佳炼苗时间为闭盖2 d后开盖3 d,移栽成活率86.6%。     

壬基酚对金鱼（Carassiusauratus ）胚胎发育毒性的初步研究

目的:观察环境激素壬基酚(Nonylphenol,NP)对金鱼胚胎发育的毒性效应。方法:在繁殖季节选取雌雄健康成年金鱼,采用人工受精的方法获取金鱼受精卵于23℃培养箱孵育。将正常发育的囊胚早期金鱼胚胎(50枚胚胎/培养皿)分别暴露在1μmol·L~(-1)、4μmol·L~(-1)、8μmol·L~(-1)、12μmol·L~(-1)和16μmol·L~(-1)的NP实验液中,设空白对照。通过显微成像技术观察NP暴露对金鱼胚胎发育形态、不同发育阶段胚胎死亡率、受精后72小时(72 hpf)孵化率及畸形率的影响。从原肠期开始每隔12 h观察一次。结果:低浓度NP主要影响金鱼胚胎晚期发育,使其尾部脊索弯曲上翘;高浓度NP可导致金鱼胚胎卵凝结、发育延迟、组织坏死、尾部卷曲、体轴缩短并出现血栓。各发育阶段胚胎死亡率和72 hpf畸形率随NP浓度升高而增加,72 hpf孵化率则随NP浓度升高而降低;NP对金鱼胚胎24 h、48 h、72 h的半数致死浓度(LC50)分别为:16.28μmol·L~(-1)、8.27μmol·L~(-1)和6.52μmol·L~(-1)。结论:NP对金鱼胚胎具有明显发育毒性,金鱼胚胎对低浓度NP也具有较高敏感性,在评价环境激素胚胎发育毒性方面具有潜在应用价值。     

负载噬菌体内溶素Lys84水凝胶的制备及性能表征

探究聚(N-异丙基丙烯酰胺)[poly(N-isopropylacrylamide)]基互穿网络(interpenetrating polymer network)温敏水凝胶(记作:IPNT)作为噬菌体内溶素Lys84递送载体的可行性,及载药水凝胶作为抗菌材料的应用潜力。以海藻酸钠和N-异丙基丙烯酰胺为原材料,通过自由基聚合的方法制备互穿网络温敏水凝胶,采用干态浸泡法负载金黄色葡萄球菌(Staphylococcus aureus)噬菌体内溶素Lys84获得载药水凝胶(IPNT-Lys84)。通过红外光谱仪、扫描电子显微镜(scanning electron microscopy,SEM)、差示扫描量热仪(differential scanning calorimetry,DSC)对水凝胶载药前后的物理性能进行表征,并研究水凝胶溶胀、退溶胀以及内溶素Lys84释放情况、在不同温度及不同浓度药液浸泡的抗菌性能。结果表明,IPNT-Lys84水凝胶孔洞均匀,低临界溶解温度(lower critical solution temperature,LCST)为32°C;水凝胶平衡溶胀度为30 g/g,退溶胀时失水率为88%;在37°C时内溶素释放率在6 h内达到70%以上;IPNT-Lys84水凝胶杀菌率达99.9%以上。研究表明,采用IPNT递送内溶素Lys84具有可行性,IPNT-Lys84水凝胶有望成为针对多重耐药金黄色葡萄球菌的有效抗菌材料。     

氢溴酸樟柳碱对离体大鼠颈总动脉的作用及机制研究

目的观察氢溴酸樟柳碱对离体大鼠颈总动脉的作用及相关机制。方法麻醉大鼠后,分离得到大鼠颈总动脉并制成血管环,采用离体血管环实验,观察氢溴酸樟柳碱在1×10~(-4)～5×10~(-3)mol·L~(-1)浓度范围内对KCl、苯肾上腺素(PHE)预收缩的内皮完整及去内皮血管环的作用;并观察预孵一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(L-NAME)、不同的钾离子通道抑制剂格列本脲(Gly)、4-氨基吡啶(4-AP)、四乙基氯化铵(TEA)、BaCl_2对氢溴酸樟柳碱舒张血管环作用的影响;以2×10~(-3)mol·L~(-1)氢溴酸樟柳碱预孵血管环,观察其对以细胞内、外钙为收缩剂的血管收缩的作用,并探讨其舒张血管的机制。结果氢溴酸樟柳碱在体外1×10~(-4)～5×10~(-3)mol·L~(-1)浓度范围内能浓度依赖性舒张KCl和PHE预收缩的血管环,对KCl预收缩的血管环最大舒张幅度(Emax)为33. 97%±11. 53%,并在低浓度(1×10~(-4)～1×10~(-3)mol·L~(-1))收缩血管(P 0. 01,P 0. 05),对PHE预收缩的血管环的半数有效浓度为5. 61(3. 88,8. 10) mmol·L~(-1),Emax=47. 93%±18. 63%;对PHE预收缩的去内皮血管环,氢溴酸樟柳碱舒张血管的Emax无明显变化;而L-NAME、Gly、4-AP、TEA、BaCl_2对氢溴酸樟柳碱舒张PHE预收缩的血管环均无明显作用;在无Ca~(2+)溶液中,2×10~(-3)mol·L~(-1)氢溴酸樟柳碱可以显著增强PHE引起的血管环短暂收缩(P 0. 01)。结论氢溴酸樟柳碱能够在低浓度收缩离体大鼠颈总动脉环,并能浓度依赖性地舒张离体大鼠颈总动脉环,对血管的张力具有双向作用,且其机制与非内皮依赖途径及促肌浆网内钙释放相关。     

水稻幼苗根对羧基化多壁碳纳米管复合镉胁迫的生长生理响应

为了探究羧基化多壁碳纳米管(MWCNTs-COOH)复合镉(Cd)胁迫对植物生长生理的影响,采用液体培养方法,以水稻(Oryza sativa L.)为受试作物,测定了0～12.0 mg·L~(-1)MWCNTs-COOH、10μmol·L~(-1)Cd单一和复合处理水稻幼苗21天后根生长、氧化损伤、抗氧化酶活性及根中Cd含量的变化。结果表明:(1)MWCNTs-COOH单一处理,根长、根鲜重均低于对照,并表现出先升高后降低的趋势,当其浓度达到12.0 mg·L~(-1)时,较对照分别下降了9.3%和15.2%,且低于10μmol·L~(-1)Cd单一处理;而复合处理组水稻幼苗根长、根鲜重、干重皆低于对应的单一处理;(2)MWCNTs-COOH单一胁迫下,水稻根的超氧自由基(O_2~(-·))明显积累,并伴随着超氧化物歧化酶(SOD)及过氧化物酶(POD)活性升高,3.0和6.0mg·L~(-1)MWCNTs-COOH处理下,SOD、POD活性最高;(3)MWCNTs-COOH复合Cd胁迫下,水稻根的SOD、POD活性大均低于单一处理组,而丙二醛(MDA)及羰基化蛋白含量均显著高于单一处理;(4)MWCNTs-COOH复合Cd后,水稻幼苗根尖细胞死亡加剧,其中,10μmol·L~(-1)Cd与12.0 mg·L~(-1)MWCNTs-COOH复合处理的根尖根冠区细胞伊文斯蓝染色最深;(5)1.5～6.0 mg·L~(-1)MWCNTs-COOH复合Cd处理水稻幼苗后,其根中Cd含量呈上升趋势,且在6.0 mg·L~(-1)浓度处理时达到最大值303.30μg·g~(-1);高浓度MWCNTs-COOH及其与Cd的复合均对水稻根产生毒性效应。     

怀牛膝细胞悬浮培养条件的优化

为进一步优化怀牛膝(Achyranthes bidentata)细胞悬浮培养条件,对接种量、继代周期、pH、光照及Cu~(2+)等多种影响因子的作用效果进行了研究,以提高怀牛膝细胞生长量及牛膝多糖含量。结果显示,接种量50 g·L~(–1)、继代周期14天,pH5–6和光照培养可以使细胞保持良好的生长状态及多糖合成能力;添加50μmol·L~(–1 )Cu~(2+),细胞的干重最大,可达44.63 g·L~(–1),多糖含量也最高,为4.02 mg·g~(–1)。     

白花泡桐优树组织培养及产业化快繁技术

以自选育的白花泡桐优树茎段为外植体,进行种苗组培快繁技术研究。结果表明:其最佳的外植体灭菌方法是以0.1%升汞处理7 min;合适的初代诱导培养基为MS+6-BA 2.0 mg·L~(-1)+IBA 0.2 mg·L~(-1)+糖30 g·L~(-1)+琼脂3.5 g·L~(-1)(pH 5.8),培养30 d,芽诱导率70%;合适的继代增殖方法为在高浓度植物生长物质培养基MS+6-BA 4.0 mg·L~(-1)+IBA 0.4 mg·L~(-1)+蔗糖30 g·L~(-1)+琼脂3.5 g·L~(-1)(pH 5.8)和低浓度植物生长物质培养基MS+6-BA 0.4 mg·L~(-1)+IBA 0.04 mg·L~(-1)+蔗糖30 g·L~(-1)+琼脂3.5 g·L~(-1)(pH 5.8)中交替培养,获得的丛生芽长势良好,玻璃化率低于5%,增殖系数大于6.0/25 d;最适的生根培养基为1/2MS+NAA0.2 mg·L~(-1)+蔗糖20 g·L~(-1)+卡拉胶3.4 g·L~(-1)(pH 5.8),培养14 d,得到白花泡桐生根苗,每株长根5~10条,根长3~5 cm,生根率98%,根系洁白、根毛少而短,易于清洗。将生根苗按照常规方法炼苗后移栽于温室大棚中,50 d后即可出圃,此时平均苗高1.0 m、地径1.0~2.0 cm,成活率在90%以上。     

稀土元素铈对斑马鱼肝脏的遗传毒性

以稀土元素中丰度最大的铈(Ce)为代表污染物,以斑马鱼(Danio rerio)为受试生物,采用RAPD-PCR和MSAP-PCR技术研究Ce对斑马鱼基因组DNA损伤及DNA甲基化的影响。结果表明,不同浓度Ce~(3+)(0、5、10和20μmol·L~(-1))胁迫斑马鱼28天后,Ce~(3+)主要在斑马鱼肝脏中富集(BCF:5.49~9.33),其次为腮(BCF:3.58~4.49)和肌肉(BCF:0.13~0.25);RAPD-PCR分析显示,Ce~(3+)(10μmol·L~(-1))胁迫能够诱导斑马鱼肝脏DNA的损伤;MSAP-PCR分析显示,Ce~(3+)胁迫引起的斑马鱼肝脏基因组DNA甲基化总变化率分别为8.93%(CK)、9.12%(5μmol·L~(-1))、15.56%(10μmol·L~(-1))和28.83%(20μmol·L~(-1)),其中低浓度胁迫下,斑马鱼肝脏基因组DNA去甲基化(D)型显著增加,高浓度下,甲基化(M)型显著增加,DNA甲基化多态性亦随胁迫浓度的增大而变大;测序分析结果显示,这些特异性甲基化条带与zinc finger protein STZ/ZAT10、ABC transporter 1、cell cycle control phosphatase superfamily protein等基因具有较高的同源性;与RAPD标记相比,DNA甲基化标记对Ce~(3+)的胁迫响应具有高敏感性。研究结果深化了对稀土元素生物学效应的认识。     

禾本科芦苇属植物纤维的再生及性能测定

以禾本科植物芦苇为纤维素原料,利用纤维素在绿色溶液KOH/硫脲、尿素/水体系中的低温溶胶,高温凝胶的特性,通过化学法提取再生芦苇植物纤维素。并利用超级旋转流变仪、粘度测定仪、扫描电镜、比表面及孔径分析仪、热分析仪、傅里叶红外光谱、X射线衍射等测试手段着重研究了芦苇纤维素在该溶液体系中凝胶化再生的最佳浓度范围、以及芦苇纤维素再生前后结构和性能的变化。结果发现:芦苇纤维素溶解再生后,具有凝胶型的均匀多孔网络结构,孔容在0.77~0.62 cm~3·g~(-1),平均孔径分布在9.9~8.8 nm,比表面积达到345~320m~3·g~(-1),凝胶化再生纤维素质量浓度范围为3%~8%,结果表明芦苇纤维素化学结构再生前后没有改变,结晶度较再生前降低,并具有较再生前更好的调湿性能。     

Characterization and in vitro evaluation of starch based hydrogels as carriers for colon specific drug delivery systems

A series of starch/methacrylic acid (MAAc) copolymer hydrogels of different compositions were synthesized using γ-rays induced polymerization and crosslinking. The effects of the preparation conditions such as the feed solution concentration, feed solution composition and irradiation dose on the gelation process of the synthesized copolymer were investigated. The swelling behavior of the starch/methacrylic acid (MAAc) copolymer hydrogels was characterized by studying the effect of the hydrogel composition on the time- and pH-dependent swelling. Swelling kinetics showed that the synthesized hydrogels possessed Fickian diffusion behavior at pH 1 and non-Fickian diffusion at pH 7 which recommend them as good candidate for colon specific drug delivery systems. The synthesized hydrogels were loaded with ketoprofen as a model drug to investigate the release behavior of the synthesized hydrogels. The results showed the ability of the hydrogels to keep the loaded drug at pH 1 and release it at pH 7. The data also showed that the release rate can be controlled by controlling the preparation conditions such as comonomer concentration and composition and irradiation dose.     

Preparation and properties of a pH/temperature-responsive carboxymethyl chitosan/poly(N-isopropylacrylamide)semi-IPN hydrogel for oral delivery of drugs

Thermo- and pH-responsive semi-IPN polyampholyte hydrogels were prepared by using carboxymethylchitosan and poly(N-isopropylacrylamide) with N,N'-methylenebisacrylamide (BIS) as the crosslinking agent. The swelling characteristics of these hydrogels at distinct compositions as a function of pH and temperature were investigated. It was found that the semi-IPN hydrogels demonstrated the pH- and temperature-responsive nature of the materials, and it also showed good reversibility. The study on the release of coenzyme A (CoA) showed that within 24h the cumulative release ratio of CoA was 22.6% in pH 2.1 solution and 89.1% in pH 7.4 solution at 37 degrees C, respectively. The release rate of CoA was higher at 37 degrees C than 25 degrees C in a pH 7.4 buffer solution. An increased release rate of CoA was observed with the content of carboxymethylchitosan increasing in the hydrogel at 25 degrees C in pH 7.4 solution. These results show that semi-IPN hydrogel seems to be of great promise in pH-temperature oral drug delivery systems.     

New route for synthesizing poly(ethylene glycol)-acrylic acid hydrogels using γ-irradiation for drug delivery carriers

Biocompatible and pH-responsive poly(ethylene glycol) (PEG)-acrylic acid (AAc) hydrogels were prepared by new technique using γ-irradiation for controlled oral drug delivery. The gel fraction was over 80% and the equal amounts of PEG and AAc blended hydrogel had efficient insulin loading using equilibrium swelling. These hydrogels exhibited unique pH-responsive characteristics in which interpolymer complexes were formed in acidic media and dissociated in neutral or basic environments. The insulin release from the gel was significantly retarded in acidic media while rapid release occurred under neutral/basic conditions. At the high pH solution, the gels swelled rapidly and over 70% of the insulin loaded was released over a period of 10 h. Within 2 h of administration of the insulin-containing gels, significant blood glucose reduction effects were observed in diabetic rats. The blood glucose reduction lasted for up to 10 h following administration.     

One-step synthesis of interpenetrating network hydrogels: Environment sensitivities and drug delivery properties

A novel interpenetrating network hydrogel for drug controlled release, composed of modified poly(aspartic acid) (KPAsp) and carboxymethyl chitosan (CMCTS), was prepared in aqueous system. The surface morphology and composition of hydrogels were characterized by SEM and FTIR. The swelling properties of KPAsp, KPAsp/CMCTS semi-IPN and KPAsp/CMCTS IPN hydrogels were investigated and the swelling dynamics of the hydrogels was analyzed based on the Fickian equation. The pH, temperature and salt sensitivities of hydrogels were further studied, and the prepared hydrogels showed extremely sensitive properties to pH, temperature, the ionic salts kinds and concentration. The results of controlled drug release behaviors of the hydrogels revealed that the introduction of IPN observably improved the drug release properties of hydrogels, the release rate of drug from hydrogels can be controlled by the structure of the hydrogels and pH value of the external environment, a relative large amount of drug released was preferred under simulated intestinal fluid. These results illustrated high potential of the KPAsp/CMCTS IPN hydrogels for application as drug carriers.     

Novel complex hydrogels based on N-carboxyethyl chitosan and quaternized chitosan and their controlled in vitro protein release property

A novel pH-responsive hydrogel (CHC) composed of N-carboxyethyl chitosan (CEC) and N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) was synthesized by the redox polymerization technique. Turbidimetric titrations were used to determine the stoichiometric ratio of these two chitosan derivatives. The hydrogel was characterized by FT-IR, thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The dynamic transport of water showed that the hydrogel reached equilibrium within 48 h. The swelling ratio of CHC hydrogel depended significantly on the pH of the buffer solution. The performance of the CHC as a matrix for the controlled release of BSA was investigated. It was found that the release behavior was determined by pH value of the medium as well as the intermolecular interaction between BSA and the hydrogels.     

Synthesis and characterization of hydrogels based on grafted chitosan for the controlled drug release

Temperature and pH-responsive hydrogels based on chitosan grafted with poly acrylic acid (PAAc), poly hydroxy propyl methacrylate (PHPMA), poly (vinyl alcohol) (PVA) and gelatin were prepared for controlled drug delivery. These stimuli-responsive hydrogels were synthesized by gamma irradiation technique. The degree of gelation was over 90% and increased as chitosan, AAc and PVA content increased, while the degree of gelation decrease with the increase of gelatin content. The equilibrium swelling studies of hydrogels prepared in various conditions were carried out in an aqueous solution, and the pH sensitivity in the range of 2–9 was investigated. An increase of swelling degree with an increase in the pH was noticed and showed the highest value at pH 9. Also antibiotic drug Oxttetracycline was loaded into the hydrogels and the release studies were carried out at different pH and temperature. The in vitro release profiles of the drug showed that, the release of the drug increased as the time, temperature and pH increased and reached to maximum after 48 h at pH 9. The prepared hydrogels were characterized by using SEM, FTIR, and DSC.     

Polymer multilayers with pH-triggered release of antibacterial agents

We report on the layer-by-layer design principles of poly(methacrylic acid) (PMAA) ultrathin hydrogel coatings that release antimicrobial agents (AmAs) in response to pH variations. The studied AmAs include gentamicin and an antibacterial cationic peptide L5. Adipic acid dihydrazide (AADH) is a cross-linker which, relative to ethylenediamine (EDA), increases the hydrogel hydrophobicity and introduces centers for hydrogen bonding to AmAs. AmA retention in AADH-cross-linked hydrogels in high-salt solutions was enhanced while AmA release at low pH was suppressed. L5 retains its antibacterial activity toward planktonic Staphylococcus epidermidis after release from PMAA hydrogels in response to pH decreases in the surrounding medium due to bacterial growth. Staphylococcus epidermidis adhesion and colonization was almost completely inhibited by L5 loading of hydrogels. The AmA-releasing and AmA-retaining properties of these hydrogel coatings provide new opportunities to study the fundamental mechanisms of AmA-coating-bacteria interactions and develop a new class of clinically relevant antibacterial coatings for medical devices.     

The influence of the copolymer composition on the diltiazem hydrochloride release from a series of pH-sensitive poly[(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide)-<Emphasis Type="Italic">co</Emphasis>-(methacrylic acid)] hydrogels

A series of poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (P[(N-iPAAm)-co-(MAA)]) hydrogels was investigated to determine the composition that exhibits a better pH-modulated release of diltiazem hydrochloride (DIL.HCl). For this purpose hydrogel slabs were loaded with DIL.HCl by the immersion method, and its release under acidic medium (0.1N HCl, pH 1.2) and in phosphate buffer pH 7.2, using United States Pharmacopeia (USP) 24 Apparatus 1, was investigated. According to the results from the slabs, copolymers with 85% mol N-iPAAm content were selected to prepare tablets with different particle size. The effect of pH and particle size changes on DIL.HCl release from these last hydrogel tablets was investigated by a stepwise pH variation of the dissolution medium. The amount of DIL.HCl released from high N-iPAAm content copolymer slabs under acidic pH medium was not only very low but it was also released at a slow rate. In the 85% N-iPAAm tablets, significant differences between and within release profiles were found as a function of particle size and pH, respectively. A relationship between particle size and release rate has been found. The lower DIL.HCl release at acidic pH from enriched N-iPAAm copolymers is interpreted by a cooperative thermal- and pH-collapse. Although for the whole range of copolymer composition a dependence of the equilibrium of swelling on the pH was found, DIL.HCl release experiments indicated that hydrogels with 85% mol N-iPAAm are the more adequate to be used for modulated drug delivery systems. Additionally, the particle size of the tablet can be used to tailor the release rate.     

Synthesis and characterization of pH-sensitive hydrogel composed of carboxymethyl chitosan for colon targeted delivery of ornidazole

In the present study, carboxymethyl chitosan was prepared from chitosan, crosslinked with glutaraldehyde and evaluated in vitro as a potential carrier for colon targeted drug delivery of ornidazole. Ornidazole was incorporated at the time of crosslinking of carboxymethyl chitosan. The chitosan was evaluated for its degree of deacetylation (DD) and average molecular weight; which were found to be 84.6% and 3.5×10(4) Da, respectively. The degree of substitution on prepared carboxymethyl chitosan was found to be 0.68. All hydrogel formulations showed more than 85% and 74% yield and drug loading, respectively. The swelling behaviour of prepared hydrogels checked in different pH values, 1.2, 6.8 and 7.4, indicated pH responsive swelling characteristic with very less swelling at pH 1.2 and quick swelling at pH 6.8 followed by linear swelling at pH 7.4 with slight increase. In vitro release profile was carried out at the same conditions as in swelling and drug release was found to be dependant on swelling of hydrogels and showed biphasic release pattern with non-fickian diffusion kinetics at higher pH. The carboxymethylation of chitosan, entrapment of drug and its interaction in prepared hydrogels were checked by FTIR, (1)H NMR, DSC and p-XRD studies, which confirmed formation of carboxymethyl chitosan from chitosan and absence of any significant chemical change in ornidazole after being entrapped in crosslinked hydrogel formulations. The surface morphology of formulation S6 checked before and after dissolution, revealed open channel like pores formation after dissolution.     

β‐Cyclodextrin hydrogels containing naphthaleneacetic acid for pH‐sensitive release

β‐Cyclodextrin (β‐CD) hydrogel was prepared in a strong alkali condition using epichlorohydrin (EPI) as a cross‐linker, where the molar ratios of EPI to β‐CD were 8:1, 10:1, and 15:1. In order to endow a pH sensitivity to the hydrogel, naphthaleneacetic acid (NAA) was loaded in the hydrogel by taking advantage of its hydrophobic interaction with the cavities of β‐CD. The releases of blue dextran (a water‐soluble dye) from the hydrogels were promoted, as the pHs of the media increased. When the molar ratio of EPI to β‐CD was lower, the degrees of release were higher, and the pH dependency of the release became more prominent. In fact, the swelling ratio of the hydrogels having a lower molar ratio of EPI to β‐CD was higher. The higher swelling ratio would account for the higher degree of release and the marked pH sensitivity. Biotechnol. Bioeng. 2010;106: 295–302. © 2010 Wiley Periodicals, Inc.