Effect of Cryoprotectant and Freeze-Drying Process on the Stability of W/O/W Emulsions

In order to protect a hydrophilic drug and to prolong its further delivery, the formulation of multiple emulsions could be worthy. However, the double emulsions are not stable, their structure can change, leading to the formation of a single emulsion as the destruction of the system, and the drug can release easily from the globules in liquid state. The freeze-drying technology could be used to produce dry emulsion, the powder form being much more stable. The aim of this work was to study the influence of a cryoprotectant and a freeze-drying process on the stability of W/O/W emulsions. Samples were frozen at two different freezing rate (ν _f  = 0.55°C/min and 1.25°C/min) and successively dried at two different sublimation temperature (T _s  = ? 10°C and ? 20°C). The particle size distributions were measured by granulometer and UV spectrophotometer was performed to investigate the leakage of internal constituent. The glass transition temperature (T _g ) of the double emulsions was analyzed by DSC. The particle sizes became even smaller after freeze drying, except when κ-carrageenan is used as a cryoprotectant. In that case, the particles became aggregated after freeze drying, whatever the process conditions. The mean size is considerably reduced when the globules are diluted at low concentration in glucose and trehalose solution. When the concentration is increased, the size distribution is not significantly affected. The leakage of the internal aqueous phase to the external one during freeze drying was measured as an indicator of the structure stability. It is affected by the nature of the cryoprotectant and the conditions of the freeze-drying process. The leakage of the internal phase was smaller when cycle III (ν _f  = 1.25°C/min, T _s  = ? 10°C) was processed. From our experiments, we suppose that the water transfer from the inner phase to the outer aqueous phase results in the diminution of the globules size in double emulsion. The T _g of the double emulsions diluted with trehalose and glucose were determined at ? 33.8°C and ? 47.1°C. In contrast, the T _g of double emulsion with κ-carrageenan and HES did not appear.     

Effect of the polymeric cryoprotectant dextran on fluid secretion in the isolated rabbit pancreas

Physiological effects of the polymeric cryoprotectant dextran on an ion-transporting epithelium were investigated. In the isolated rabbit pancreas, dextran caused inhibition of fluid secretion and an increase of the concentrations of Na⁺, K⁺ and Cl^? in the secreted fluid. Dextran did not affect the basal or pancreozymin-stimulated enzyme secretion. These effects of dextran can partially be explained by the fact that it is osmotically active and does not permeate through the epithelium. The effect of dextran on water transport can be compensated by lowering the ion concentrations in the solvent of the cryoprotectant. It is concluded that in cryoprotected ion-transporting epithelia the absolute ion concentration values obtained by X-ray microanalysis of frozen-hydrated specimens may not be completely correct, but that valid conclusions about intracellular ion distribution may still be drawn.     

Ice Crystal Growth in Sucrose Solutions Containing Kappa- and Iota-Carrageenans

Measurements of ice recrystallization inhibition (IRI) and thermal hysteresis (TH) activities of kappa (κ)- and iota (ι)-carrageenans were carried out to examine whether they can be novel cryoprotectants or not. IRI measurements indicate that both carrageenans reduce recrystallization in sucrose solution, but that the IRI activity of κ-carregeenan is higher than that of ι-carrageenan. TH measurements indicate that κ- and ι-carrageenans do not exhibit TH activity. TH activity measurements of antifreeze glycoprotein (AFGP) in the presence of κ-carregeenan demonstrate that this carregeenan neither influences the TH activity of AFGP nor the shape of the ice crystals. The round ice crystal shape transformed into an angular and elongated shape in the presence of both carregeenans.     

寄生虫低温保存的研究现状

传统的寄生虫保存方法有体外培养和动物转种,这些方法操作繁琐,成本较高,而且易发生遗传漂变、人为差错或混淆等问题。低温保存寄生虫可克服传统保存方法的弊端,并可保持寄生虫原有的生物学特性。本文就低温保存寄生虫的种类及主要影响因素作一综述,为寄生虫低温保存的研究提供参考。     

Glass Transition of Rainbow Trout and Its Oxidation Stability During Storage

Glass transition of rainbow trout muscle was measured by differential scanning calorimetry (DSC) as ?13°C. Sucrose and sorbitol (2, 2), sucrose and mannitol (2, 2), sucrose and gum arabic (2, 0.15), sucrose and carrageenan (2, 0.15), sorbitol and mannitol (2, 2), sorbitol and gum arabic (2, 0.15), sorbitol and carrageenan (2, 0.15), mannitol and gum arabic (2, 0.15) and mannitol and carrageenan (2, 0.15) were blended with ground rainbow trout as g/100 g fish and stored for 6 months separately at ?9°C, ?13°C and ?18°C. Total volatile basic nitrogen (TVB-N) and Thiobarbituric acid-reactive substances (TBARS) were determined at 1^st, 3^rd and 6^th months of storage periods. Biopolymers blends, storage temperature and storage period had a significant effect (p < 0.05) on the TVB-N and TBARS values.     

Cactus cladode polysaccharide as cryoprotectant in frozen Paneer (Indian Cottage Cheese)

The study investigated the optimisation of freezing conditions for Paneer (Indian cottage cheese) incorporated with cactus cladode polysaccharide as cryoprotectant. The freezing rate of both natural and commercial cryoprotectant‐containing samples varied significantly. The optimised (2% natural cryoprotectant) Paneer sample had about 44% moisture content, 14% protein, 16% carbohydrate and 22% fat. Freezing time of optimised Paneer sample packed in metalised polyester was 40 min. The study concluded that Paneer incorporated with 2% cactus cladode polysaccharide, packaged using metalised polyester and frozen with packaged immersion freezing method, had the least freezing time (40 min) and retained better texture during freezing.     

Freeze-Drying of Liposomes with Cryoprotectants and Its Effect on Retention Rate of Encapsulated Ftorafur and Vitamin A

In this article, the glass transition temperature (T_g) of liposomal suspensions, in which glucose, sucrose, mannitol, and trehalose are used as cryoprotectants, are measured by differential scanning calorimetry (DSC). The protective effect of the cryoprotectants added for liposomes during freeze-drying is investigated. Results show that the T_g of liposomal suspension with trehalose is the highest, while that with glucose is the lowest. Depending on the concentration, the vesicle size of liposomes with trehalose as cryoprotectant varies less, while the vesicle size of liposomes, with glucose as cryoprotectant varies over a wider range during the process of freeze-drying. Water-soluble ftorafur and lipid-soluble vitamin A encapsulated in liposomes were freeze-dried. The retention rates of the encapsulated pharmaceuticals inside the liposomes are measured with high performance liquid chromatography. The results indicate that the retention rate for liposomes with trehalose is the highest, and the leakage of the pharmaceutical material is less than that with glucose used as a cryoprotectant. Through a series of experimental studies, trehalose is identified as a better cryoprotectant. An optimized freeze-drying procedure for liposomes is presented.     

The effect of long-term frozen storage on the quality of frozen and thawed mashed potatoes with added cryoprotectant mixtures

Cryoprotectant mixtures were added to frozen/thawed (F/T) mashed potatoes in the form of amidated low-methoxyl (ALM) pectin and xanthan gum (XG), kappa-carrageenan (κ-C) and XG and sodium caseinate (SC) and XG, and the effect of frozen storage was examined. F/T mashed potatoes without added biopolymers had higher storage modulus G ' after freezing and frozen storage, associated with sponge formation due to amylose retrogradation. Oscillatory measurements indicated weakening of the structure of mashed potatoes without biopolymers and with added κ-C/XG and SC/XG mixtures at the end of storage due to ice recrystallisation, whereas the structure of samples with added ALM/XG mixtures was reinforced by increasing time in storage. Mashed potatoes with added mixtures exhibited water-holding capacity for 1 year. Samples with added κ-C/XG mixtures were more structured, although when both κ-C/XG and SC/XG mixtures were included in mashed potato, very acceptable sensory quality was maintained in usual frozen storage conditions.     

Freeze-Drying of Liposomes with Cryoprotectants and Its Effect on Retention Rate of Encapsulated Ftorafur and Vitamin A

Abstract

In this article, the glass transition temperature (T _g ) of liposomal suspensions, in which glucose, sucrose, mannitol, and trehalose are used as cryoprotectants, are measured by differential scanning calorimetry (DSC). The protective effect of the cryoprotectants added for liposomes during freeze-drying is investigated. Results show that the T _g of liposomal suspension with trehalose is the highest, while that with glucose is the lowest. Depending on the concentration, the vesicle size of liposomes with trehalose as cryoprotectant varies less, while the vesicle size of liposomes, with glucose as cryoprotectant varies over a wider range during the process of freeze-drying. Water-soluble ftorafur and lipid-soluble vitamin A encapsulated in liposomes were freeze-dried. The retention rates of the encapsulated pharmaceuticals inside the liposomes are measured with high performance liquid chromatography. The results indicate that the retention rate for liposomes with trehalose is the highest, and the leakage of the pharmaceutical material is less than that with glucose used as a cryoprotectant. Through a series of experimental studies, trehalose is identified as a better cryoprotectant. An optimized freeze-drying procedure for liposomes is presented.