Kinetic evaluation of the size-dependent decomposition performance of solvent-free microcellular polylactic acid foams

A thermal gravimetric method is described for evaluating the kinetics of cell size-dependent decomposition and lifetime estima- tion for microcellular tissue engineering scaffolds made of biodegradable polylactic acid(PLA)foams.PLA foam cell sizes from 550 to 20?m were fabricated experimentally using a solvent-free solid-state foaming technique under saturation pressures from 1 to 5 MPa.The thermal properties of the PLA foams with respect to the cell sizes were measured using thermal gravimetric analy- sis in a nitrogen atmosphere and the activation energy and pre-exponential factor were derived to evaluate the decomposition ki- netics and estimate lifetime.It was found that small cell sizes can be achieved under high saturation pressures and that the thermal stability of PLA decreases after the fabrication process.The cell size-dependent thermal stability and degradation rate indicate that a PLA foam of larger cell sizes has a shorter degradation time,a few tenths that of the PLA raw material,at a temperature of 37°C. The results suggest that it is feasible to optimize fabrication parameters to obtain appropriate cell sizes and lifetimes that satisfy the application requirements for various organs.This study provides the basis for precise scaffold design and quantitative analysis of PLA foams in tissue engineering applications.     

FTIR assessment of the secondary structure of proteins in human breast benign and malignant tissues

The compositions of the secondary structures of protein in the human breast normal, hyperplasia, fibroadenoma and invasive ductal carcinoma tissues have been estimated from the Fourier self deconvolved spectra, the second derivative spectra and the curve-fitting analysis of the amide I bands in their spectra. Some parameters of the secondary structures of proteins in these 4 types of tissues are significantly different and located in separate ranges. Fibroadenoma tissue demonstrates the most remarkable difference in the compositions of α-helical and atypical helical structures. The carcinoma tissue has the highest ratio of the intermolecular β-sheet content and the intramolecular β-sheet content. This noticeable difference in the secondary structure may have important implications for analyzing the properties and types of human breast disease.     

堇叶碎米荠组织培养研究

堇叶碎米荠(Cardamine violifolia)是在我国富硒地区发现的一种富集硒植物,具有很高的科学研究价值。研究以堇叶碎米荠的幼叶为外植体,进行组织培养研究,结果表明:诱导愈伤组织的最佳培养基为MS+6-BA1.0mg/L+2,4-D0.6mg/L,诱导率高达85%,以培养基MS+6-BA1.0mg/L+NAA0.6mg/L诱导不定芽分化效果最好;在生根阶段以培养基MS+NAA1.0mg/L生根效果最好,生根3.2条/株,根系健壮。     

食荚型豌豆组织培养和植株再生研究

以豌豆子叶、茎、真叶为材料进行外植体筛选及组织培养研究,试验结果表明:豌豆带节茎段是最佳试验材料;在MS附加1 mg/L BA和1 mg/L NAA培养基中,愈伤组织诱导率达100%,愈伤组织在分化培养基中未分化出芽;带节茎段在MS附加2～3 mg/L BA和0.1 mg/L NAA培养基中,腋芽和丛生芽产生率达100%,芽增殖系数3以上;不定芽在MS附加3 mg/L NAA上生根率86%;试管苗移栽成活率85%左右.     

丹参嫩茎组织培养及无性系建立的研究

为保护濒危植物丹参,实现人工栽培,以嫩茎为材料,进行了愈伤组织诱导与分化、试管苗生根、继代、移栽和定植研究.结果证明:MS+6-BA0.3 mg.L-1+2,4-D2.0 mg.L-1+NAA0.8 mg.L-1是丹参嫩茎愈伤组织诱导培养和继代培养的理想培养基;1/2MS+AgNO30.2 mg.L-1和1/2MS+AgNO30.2 mg.L-1+6-BA 0.1 mg.L-12种培养基是丹参颗粒状愈伤组织块分化培养的理想培养基;以经过浓度为10mg.L-1的NAA溶液处理3 m in的不定芽为材料、以1/3MS+IAA0.4 mg.L-1为培养基的方法是丹参不定芽生根培养的理想方法.试管苗移栽成活率为92.7%,定植成活率为99.2%.定植的试管苗保持了野生丹参的所有生物性,建立起丹参的无性系.     

香荚兰脱分化过程中大分子物质含量的变化

就香荚兰组织培养过程中外植体脱分化的核酸、蛋白质及淀粉含量的动态变化作了比较分析。研究发现,脱分化过程中DNA含量呈相对下降,RNA含量上升,总核酸含量呈上升趋势,蛋白质呈缓慢上升趋势;淀粉则呈现一个积累、消耗和再积累的过程。     

Monte Carlo方法研究光子在有界肿瘤组织中的分布

目的研究有界肿瘤组织中光子分布特性。方法通过建立光在有界肿瘤组织中传输模型,用蒙特卡罗方法模拟光子在有界生物组织的传输,与半无限大肿瘤组织中光子分布的特性对比,分析光子在有界肿瘤组织中的分布特性。结果肿瘤组织中光子能量密度分布在纵向和横向基本是按负指数规律变化,但沿纵向在入射表面附近有极值点,当取定较小边界范围时,光子能量密度增加,组织内的有效光子数下降。结论有界肿瘤组织光子能量密度沿纵向和横向变化规律与半无限大组织变化规律相似,肿瘤组织边界影响光子在生物组织的能量密度和有效光子数分布。     

角膜组织工程支架壳聚糖-胶原复合膜的性能

制备了壳聚糖-胶原角膜组织工程支架,考察了复合膜支架的光学性能、力学强度、结晶性、吸水率、亲水性、微观形貌及细胞亲和性,发现支架内胶原与壳聚糖两种分子间存在较强的相互作用,且具有良好的相容性,支架表面平滑均一,内部呈现层状有序结构．壳聚糖-胶原复合膜具有优异的透光率和适宜的湿态力学强度．细胞培养实验中,人角膜缘上皮细胞能在支架上较好地粘附和增殖分化,显示复合膜支架具有良好的细胞亲和性．结果表明壳聚糖-胶原复合膜有望成为一种性能良好的角膜组织工程支架．     

植物组织培养中真菌污染防治方法研究

通过对组培接种室空气中真菌的分离和鉴定,发现曲霉(Aspergillus),毛霉(Mucor),青霉(Penicillum),木霉(Trichoderma),根霉(Rhizopus)等常见菌为组培的主要污染真菌.抑菌环实验表明次氯酸钠与制霉菌素抑菌效果较好.50mg/L酮康唑 50mg/L制霉菌素 0.1%次氯酸钠组成的混合杀菌剂,抑菌效果好,对植物伤害小,是良好的防真菌污染添加剂.     

外源激素对防风体细胞胚发生和发育的影响

目的探讨生长素和细胞分裂素对防风体细胞胚发生和发育过程的影响。方法组织培养和石蜡切片。结果0．5mg／L2，4-D是诱导胚性愈伤组织最适宜的生长素浓度，0．5mg／LNAA在胚性愈伤组织的长期继代培养中替代0．5mg／L2，4-D可减少畸形胚的发生，NAA浓度降至0．2mg／L时促进体细胞胚的发生和分化；生长素加一定比例的细胞分裂素(6-BA或KT)可有效促进体细胞胚的发生；通过逐步降低生长素和细胞分裂素的浓度，可促进体细胞胚的分化和生长；体细胞胚在无附加激素或附加激素浓度分别低于0．2mg／LNAA和0．5mg／L6-BA的MS培养基上，均能发育成完整的植株。结论一定浓度的生长素是诱导防风胚性愈伤组织的关键因素，细胞分裂素在体细胞胚的发生和发育过程中起协同作用。