可视化DSC新设备及其在低温冻存研究领域的应用

研制了一套具有可视化功能的差示扫描量热法实验装置(简称可视化DSC),它能在热分析的同时,通过配套使用的显微摄像系统实时观察并记录测试样品的微观结构变化,以同时获得测试样品的热效应数据和微观结构图像数据.利用可视化DSC对低温保护剂1,2-丙二醇和聚乙烯醇(PVA)溶液进行冻结实验,考察PVA对低温保护剂溶液冻结特性的影响,结果表明,在1,2-丙二醇溶液中添加PVA能有效抑制冰晶成核和生长;选择PVA作为冻存液添加剂,利用可视化DSC对脐带血间充质干细胞(MSCs)进行程序冷冻-解冻实验,考察PVA在MSCs低温冻存中的实际效果,结果表明,在冻存液中添加PVA,有助于抑制冰晶形成,降低细胞冷冻损伤,提高细胞在程序慢速冷冻-解冻后的存活率.     

低温保护剂热物性分析与冰晶的显微研究

低温保存过程中,冰晶的形成和生长是造成细胞损伤的主要因素之一。本文研究低温保护剂在降温过程中冰晶的生长规律,方法是应用低温显微镜系统,观察低温保护剂溶液的浓度及不同添加物对于冰晶生长和形状的影响,并利用差示扫描量热法(DSC)研究了溶液的熔融相变过程的变化。低温显微实验表明:低温保护剂溶液结晶形状、大小与溶液的浓度和添加溶质(糖或糖醇)有关,溶液浓度高,形成的冰晶小,对细胞损伤小,添加山梨醇的混合液冰晶形状细小,减轻了冰晶对细胞结构的物理损伤。DSC实验表明:在四种低温保护剂中5%Me2SO与山梨醇混合液(体积比)熔融温度最低,热焓值最小,溶液形成的冰晶最少,因此对细胞的低温损伤最轻。     

冷冻干燥过程中溶液冻结特性的DSC研究

利用差示扫描量热仪(DSC)研究了蔗糖水溶液的冻结特性,分析了溶液浓度和热历史对冻干过程的影响.DSC实验结果表明,过冷度和最大冻结浓缩溶液的玻璃化转变温度Tg'均与热历史有关;降温时溶液中的水分能否充分结晶受浓度和降温速率的共同影响.降温过程中的结晶热可用来确定溶液降温后的冻结水含量以及最大冻结浓缩溶液中的水分含量.     

超声辅助冷冻技术在食品浸渍式冷冻中的研究进展

目的 概述超声辅助冷冻技术在食品浸渍式冷冻中的研究进展,为今后新型技术辅助浸渍式冷冻提供研究方向.方法 研究超声辅助冷冻的成核机理和对冰晶生长的影响,以及超声对溶液性质的影响,并对超声辅助冷冻技术在食品浸渍式冷冻中的应用进行综述.结论 超声辅助浸渍式冷冻技术可以广泛应用在各类食品加工中,有很大的研究和发展空间.超声辅助冷冻技术能够进一步加快食品浸渍式冷冻的冻结速率,减小食品内部冰晶尺寸,较好地改善了冷冻食品的品质和风味,在食品加工中具有广阔的应用前景,可以高效应用于食品工业.     

真空法制备冰浆中冰晶粒径特性的实验研究

为获得真空法制得冰浆中冰晶的平均粒径及粒径分布规律,本文以乙二醇水溶液为制冰溶液,采用真空法制备得到冰浆,并通过显微装置观测冰浆中的冰晶形态。实验分别研究了搅拌速率、乙二醇初始浓度和含冰率(IPF)对冰晶平均粒径的影响,并将实验得到的粒径分布与正态分布、对数正态分布、伽马分布和威尔布分布进行对比。结果表明:不同实验条件下冰浆中冰晶粒径分布均可统一用伽马分布来描述;搅拌速率对冰晶平均粒径几乎无影响;冰晶平均粒径随溶液初始浓度的增大而减小,当乙二醇浓度从1%提高至7%时,冰晶平均粒径从74.8μm降至34.3μm;含冰率达到一定大小时,才会对冰晶平均粒径产生较显著的影响,表现为含冰率越高,平均粒径越大。     

真空冷冻干燥过程参数对玫瑰的冻干过程影响的试验研究

真空冷冻干燥技术是将含水物料在低温状态下冻结,然后在真空条件下,使冰直接升华成水蒸气并排掉脱水物料中的水分使物料干燥.因此真空冷冻干燥产品可以最大限度的保持新鲜物料的原有色、香、味.形和营养成分.本文通过对玫瑰花的真空冷冻干燥实验的分析,对影响真空冻干的过程参数进行了试验研究.试验表明隔板温度、干燥室真空度是很重要的两个参数;冻结速率对总冻干时间没影响.     

接触式超声波辅助平板冷冻对胡萝卜冷冻速率的影响

超声波可以促进晶核形成,缩短冻结时间并且获得较高的冻结品质,但该技术目前多用于液态样品或浸渍冷冻过程,在固体果蔬样品平板冷冻过程中的应用未见报道。本文设计制作了一种接触式超声波辅助冷冻平板,用于固体果蔬的冷冻过程,并进行了三组实验:1)在-1℃施加10 s不同功率(0 W,122.6 W,178.7 W,229.8 W)的超声波;2)在-1℃施加178.7 W超声波,作用0 s,5 s,10 s,15 s;3)在不同阶段(预冷段,相变段,终了段)施加178.7 W的超声波10 s。分别研究了超声波的作用功率、作用时间、作用阶段等参数对胡萝卜冷冻速率的影响,结果表明:在相变阶段作用178.7 W的超声波10 s,能显著降低样品通过最大冰晶生成段的时间tcf和总冻结时间ttf,提高样品的冷冻速率。     

食品的真空冷冻升华干燥

真空冷冻升华干燥技术从最初用于生物、医药制品开始,到现在又拓展应用于食品行业中.着重论述了食品冷冻升华干燥的原理,分别给出了升华速率公式及干操层内水蒸汽迁移速率.在第三部分介绍了升华干燥主要工艺过程及必要的没计数据.最后较详细的介绍了几种食品冷冻升华干燥设备,并进行了比较,给出了设备简图.通过介绍,指出真空冷冻干燥将是干燥食品的发展方向.     

过冷水动态冰晶制取的实验研究

本文提供了一种过冷水动态制取冰晶的实验装置,着重介绍了系统的设计过程以及各部分的技术要求.为保证系统稳定运行,本实验装置采取了一系列措施,包括冰晶消除、过冷解除以及防冻结策略等.实验采用自来水、纯水、6%的乙二醇溶液作为试样,在不同的冷却速率、速度以及壁面条件下进行了对比实验,并给出了定性分析.     

低温医学的一些新问题研究

近年来作者负责承担国家自然科学基金重点项目"临床医学中若干热物理问题的研究".本文报告了此时项目对低温生物医学一些新问题的研究成果.其中包括低温冷冻外科手术治疗的过程控制;溶液冻结过程的显微图象;血管低温断裂及其防止;脂质体药物质的低温冷冻干燥;用于免疫隔离移植的胰岛微胶囊化.     

Development and physico-mechanical characterization of carrageenan and poloxamer-based lyophilized matrix as a potential buccal drug delivery system

Context and objectives: The buccal mucosa presents a unique surface for non-invasive drug delivery and also avoids first-pass metabolism. The objective of this study was the formulation development of polymeric mucoadhesive lyophilized wafers as a matrix for potential buccal drug delivery.

Materials and methods: Differential scanning calorimetry (DSC) was used to develop an optimum freeze-cycle, incorporating an annealing step. The wafers were prepared by lyophilization of gels containing three polymers, κ-carrageenan (CAR 911), poloxamer (P407) and polyethylene glycol 600 (PEG 600). The formulations were characterized using texture analysis (for mechanical and mucoadhesion properties), hydration studies, thermogravimetric analysis (TGA), DSC, X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM).

Results and discussion: DSC showed the eutectic temperature (12.8?°C) of the system where the liquid solution and pure solids both existed at a fixed pressure which helped determine the freeze-annealing cycle at 55?°C for 7?h. Mechanical resistance to compression, hydration and mucoadhesion studies showed that optimized wafers were obtained from aqueous gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600. TGA showed residual water of approximately 1% and SEM showed a porous polymeric network that made ease of hydration possible.

Conclusions: Lyophilized wafers by freeze-drying gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600 with optimum physico-mechanical properties has been achieved.     

聚甲基丙烯酸甲酯包覆十二醇微胶囊的制备及表征

以相变物质正十二醇(DA)为芯材,聚甲基丙烯酸甲酯(PMMA)为壁材,采用悬浮聚合法制备了正十二醇-聚甲基丙烯酸甲酯(DA@PMMA)微胶囊。通过差示扫描量热仪(DSC),扫描电镜(SEM),透射电镜(TEM),傅里叶变换红外光谱仪(FIIR)和热重分析仪(TGA)等仪器对微胶囊进行检测表征。结果表明:当工艺为苯乙烯-马来酸甘钠盐(SMA)加入量占DA质量的7.5%,偶氮二异丁腈(AIBN)加入量占单体甲基丙烯酸甲酯(MMA)质量的7.5%,芯材壁材质量比为2∶1,搅拌速度为1 000r/min时,所制备的微胶囊整体性能最好。DA@PMMA微胶囊为球形,平均粒径26μm,DA@PMMA微胶囊中DA的质量分数为66%。DA@PMMA微胶囊的熔化焓和结晶焓分别是137.6J/g和132.8J/g。TGA和FIIR的分析表明,DA@PMMA微胶囊具有良好的性能。     

Determination of transition temperatures during freezing and melting of interdendritic phases in Ni based superalloys

Abstract

Differential scanning calorimetry (DSC) coupled with microstructural analysis has been used to characterise the freezing and melting response in a typical Ni based superalloy, CMSX10K. Transition temperatures and evolution of fraction solid (or liquid) during freezing and melting are determined from enthalpy considerations. Significant differences in heat capacity (C_P) curves exist between the heating and cooling. It is shown that differences between freezing and melting kinetics occur because of undercooling, which is most significant beyond the solidus temperature up to the onset of eutectic freezing. The correlation of DSC heating and cooling curves to quantitatively characterise directional solidification has been demonstrated.     

甘油对人的红细胞冷冻干燥保存效果的影响

就甘油对人红细胞冷冻干燥保存效果的影响进行了实验研究。实验中先用不同浓度的甘油对红细胞进行处理，用PVP、柠檬酸钠、蔗糖和胎牛血清作为冻干保护剂对红细胞进行冻干保存，冻干后的样品用质量浓度为30g／L的NaCl复水，用血球分析仪和光镜进行检测。实验结果表明；用甘油进行处理后，红细胞的回收率明显高于没有用甘油处理的红细胞组。其中，采用质量浓度为400g／L的甘油处理后，红细胞冻干回收率达到51．4％。     

真空冷冻干燥法制备银纳米粉体的实验研究

以无机盐硝酸银为原料,银氨络合物为前驱体,采用真空冷冻干燥法制备了银纳米粉体。本文在实验中采取了三种冷冻方式:直接冷冻、真空蒸发冷冻和喷雾冷冻。经透射电镜(TEM)、X-射线衍射(XRD)和X射线能谱(EDS)检测,所制备的粉体为颗粒细小、粒度分布狭窄、形状规则、无硬团聚、非晶体的纳米粉体。三种冷冻方式制备的样品的粒径依次为5 nm~40 nm3、nm~10 nm和3 nm~5 nm,粉体煅烧后转变为粒径为10 nm~50 nm的立方晶体。文中给出了银纳米粉体的具体制备过程和化学原理,并根据检测结果,讨论了冷冻方式对所制备粉体品质的影响和真空冷冻干燥法制备粉体物质形态特点的微观机制。     

Inhibiting Au nanoparticle aggregation in freeze-thawing by presence of various additives

After freezing aqueous suspensions of gold nanoparticles (AuNPs) in the presence of various substances, the resulting aggregation of the nanoparticles was evaluated and the anti-aggregation effects of the different additives were compared. Many of the additives exhibited an anti-aggregation effects during freeze-thawing, the extent of which was greater at higher additive concentrations and the effects were 5 ~ 35% less than during the actual freeze-drying. Dextran and polyvinylpyrrolidone highly inhibited the aggregation even at markedly low additive concentrations (2 µg/mL). The use of a combination of a disaccharide (2 mg/mL of sucrose) and a sugar ester (20 µg/mL of sucrose palmitate) successfully preserved the redispersibility of the product after freeze-thawing while using each separately did not. Regarding the influence freezing and thawing conditions, a higher thawing temperature (from 4˚C to 60˚C) resulted in 10 ~ 20% better redispersibility of the AuNPs whereas the freezing temperature had no significant affect. The effect of freezing/thawing cycles of suspensions of AuNPs was also examined. The concentration of additive molecules on the surfaces of the frozen particles was monitored by In-situ Fourier transform IR spectroscopy. The collective findings of this study indicate that the additives essentially exert an anti-aggregation effect by slowing down the movement of the AuNPs.     

7-Ethyl-10-hydroxycamptothecin proliposomes with a novel preparation method: optimized formulation,characterization and in-vivo evaluation

Context:?The proliposomes were used to solve the stability of the ordinary liposomes. Objective: 7-ethyl-10-hydroxycamptothecin (SN-38) proliposomes for intravenous (i.v.) administration were prepared successfully by a new method.

Materials and methods:?SN-38 liposomes solution was reconstituting automatically from proliposomes on contact with the acetic acid buffer solution (0.2 M, pH 2.6). The formulation was optimized by the Box–Behnken design. The physicochemical characteristics of the SN-38 proliposomes were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The stability studies were also carried on. The FLU–HPLC system was served to study the concentration of SN-38 in the plasma of Sprague Dawley (SD) rats.

Results:?The optimized formulation was SN-38: 0.03 g; Soybean phospholipid (SP): 0.6 g; dextrose: 3.00 g. The entrapment efficiency of the optimized formulation was >85% and the mean particle size was about 231 nm. The stability studies showed that SN-38 proliposomes were stable in dark at 20–25°C for 6 months at least. The pharmacokinetic parameters of i.v. administration demonstrated that the half-life of SN-38 loaded in the liposomes was prolonged in vivo.

Discussion and conclusion:?The SN-38 proliposomes was prepared successful by the analysis of TEM, SEM, DSC and XRD, and SN-38 liposomes could be reconstituted on contact with the hydration medium. SN-38 liposomes circulated for a longer time in the blood circulating system than SN-38 solution, which contributed to maintaining the drug action.     

Freeze drying optimization of polymeric nanoparticles for ocular flurbiprofen delivery: effect of protectant agents and critical process parameters on long-term stability

Context: The stabilization of flurbiprofen loaded poly-?-caprolactone nanoparticles (FB-P?CL-NPs) for ocular delivery under accurate freeze-drying (FD) process provides the basis for a large-scale production and its commercial development.

Objective: Optimization of the FD to improve long-term stability of ocular administration’s FB-P?CL-NPs.

Methods: FB-P?CL-NPs were prepared by solvent displacement method with poloxamer 188 (P188) as stabilizer. Freezing and primary drying (PD) were studied and optimized through freeze-thawing test and FD microscopy. Design of experiments was used to accurate secondary drying (SD) conditions and components concentration. Formulations were selected according to desired physicochemical properties. Furthermore, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to study interactions components.

Results: Optimized FB-P?CL-NPs, stabilized with 3.5% (w/w) P188 and protected with 8% (w/w) poly(ethylene glycol), was submitted to precooling at +10?°C for 1?h, freezing at ?50?°C for 4?h, PD at +5?°C and 0.140 mbar for 24?h and a SD at +45?°C during 10?h. These conditions showed 188.4?±?1.3?nm, 0.087?±?0.014, 85.5?±?1.4%, 0.61?±?0.12%, ?16.4?±?0.1?mV and 325?±?7 mOsm/kg of average size, polydispersity index, entrapment efficiency, residual moisture, surface charge and osmolality, respectively. It performed a long-term stability >12 months. DSC and XRD spectra confirmed adequate chemical interaction between formulation components and showed a semi-crystalline state after FD.

Conclusions: An optimal freeze dried ocular formulation was achieved. Evidently, the successful design of this promising colloidal system resulted from rational cooperation between a good formulation and the right conditions in the FD process.     

海藻酸盐基纳米复合气凝胶的制备与性能研究

以海藻酸铵(ALG)、纳米氢氧化铝(ATH)和纳米蒙脱土(MMT)为原料,采用溶液共混法和真空冷冻干燥法制备了海藻酸盐基纳米复合气凝胶。采用扫描电子显微镜、傅里叶红外光谱仪、电子万能实验机、X射线衍射仪、热重分析仪对气凝胶进行了形貌、结构表征,并分析了其力学性能和热稳定性能。结果表明:采用ALG和MMT制备的气凝胶具有典型的三维骨架网络结构,交联反应不影响气凝胶的形貌;气凝胶具有较低的密度和较好的力学性能,密度低至0.12 g/cm³,压缩模量最高可达9.48 MPa;Ca²⁺交联和MMT的加入显著提高了气凝胶的热稳定性,A5MMT5Ca气凝胶的耐热温度高达205℃。     

Interconnected pores on the walls of a polymeric honeycomb monolith structure created by the unidirectional freezing of a binary polymer solution

Interconnected submicron pores were created on the walls of a honeycomb monolith structure by the unidirectional freezing of a binary polymer solution. Agglomerated globules of polyethylene glycol (PEG) in a binary solution of polystyrene (PS) and PEG in 1,4-dioxane solvent were frozen unidirectionally in a liquid nitrogen bath. Removing the frozen solvent and the agglomerated globules of PEG by freeze-drying and leaching, respectively, enabled us to create interconnected pores in the PS walls. The combination of PS and PEG was effective in creating interconnected pores in the walls because PS and PEG are poorly soluble in one another. The higher freezing rate and lower PEG weight fraction of the binary solution effectively reduced the pore size in the microtube walls.