Nanoencapsulation of a water soluble drug in biocompatible polyesters. Effect of polyesters melting point and glass transition temperature on drug release behavior

2010 ◽  
Vol 41 (5) ◽  
pp. 636-643 ◽  
Author(s):  
Vassilios Karavelidis ◽  
Dimitrios Giliopoulos ◽  
Evangelos Karavas ◽  
Dimitrios Bikiaris
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Drug Release ◽  
Water Soluble ◽  
Release Behavior ◽  
Drug Release Behavior ◽  
Water Soluble Drug

scholarly journals Nanoformulation and Evaluation of Oral Berberine-Loaded Liposomes

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2591
Author(s):  
Thuan Thi Duong ◽  
Antti Isomäki ◽  
Urve Paaver ◽  
Ivo Laidmäe ◽  
Arvo Tõnisoo ◽  
...  
Keyword(s):  
Thin Film ◽  
Drug Release ◽  
Size Distribution ◽  
Water Soluble ◽  
Release Behavior ◽  
Uniform Size ◽  
Ethanol Injection ◽  
Drug Release Behavior ◽  
Poorly Water Soluble

Berberine (BBR) is a poorly water-soluble quaternary isoquinoline alkaloid of plant origin with potential uses in the drug therapy of hypercholesterolemia. To tackle the limitations associated with the oral therapeutic use of BBR (such as a first-pass metabolism and poor absorption), BBR-loaded liposomes were fabricated by ethanol-injection and thin-film hydration methods. The size and size distribution, polydispersity index (PDI), solid-state properties, entrapment efficiency (EE) and in vitro drug release of liposomes were investigated. The BBR-loaded liposomes prepared by ethanol-injection and thin-film hydration methods presented an average liposome size ranging from 50 nm to 244 nm and from 111 nm to 449 nm, respectively. The PDI values for the liposomes were less than 0.3, suggesting a narrow size distribution. The EE of liposomes ranged from 56% to 92%. Poorly water-soluble BBR was found to accumulate in the bi-layered phospholipid membrane of the liposomes prepared by the thin-film hydration method. The BBR-loaded liposomes generated by both nanofabrication methods presented extended drug release behavior in vitro. In conclusion, both ethanol-injection and thin-film hydration nanofabrication methods are feasible for generating BBR-loaded oral liposomes with a uniform size, high EE and modified drug release behavior in vitro.

Elastomer Structures and ‘Cold Crystallization’

1979 ◽  
Vol 52 (1) ◽  
pp. 207-212 ◽  
Author(s):  
M. Bruzzone ◽  
E. Sorta
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Natural Rubber ◽  
Crystallization Rate ◽  
Cold Crystallization ◽  
Structural Defects ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Abstract In a great number of applications an ideal elastomer should satisfy, to a certain extent, both of the following requirements: (1) nearly instantaneous crystallization upon application of strain (strain induced crystallization) and (2) slow or no crystallization when cooled at the temperature of maximum crystallization rate (cold induced crystallization). A noteworthy case of (2) is elastomer crystallization in a strained state. The connection between the points (1) and (2) has not been clearly understood up to now, but it is known that some crystallizable elastomers fulfil the requirements of both (1) and (2) better than others. From an experimental point of view, cold induced crystallization kinetics are substantially easier to measure than those of very fast strain induced crystallization. The phenomenon of cold induced crystallization in natural rubber, NR, has been known since the very beginning of elastomer technology and the tendency of natural rubber to crystallize by cooling has been overcome by crosslinking it with sulphur (vulcanization) without impairing its ability to crystallize by stretching (Goodyear, 1836). The synthesis of cis-polyisoprenes (IR) and cis-polybutadiene (BR) of different microstructural purity (different cis content) gave the possibility of changing the crystallization rate. It has also been reported that the very fast cold crystallization of trans-polypentenamer (TPA) could be reduced by lowering the trans content. The same fact had been observed earlier for trans-polychloroprene. There is a general agreement in postulating that the reduction of the crystallization rate, obtained either by cross-linking or by chain regularity reduction, can be linked with the lowering of the melting point. In both cases the low level of structural defects introduced in the chains does not affect the glass transition temperature in such a way as to vary the crystallization rate. The aim of this paper is to emphasize the importance of the variations of the glass transition temperature and melting point on the elastomeric cold crystallization rate and the way these may be used in planning new elastomer structures.

scholarly journals Predicting the influence of particle size on the glass transition temperature and viscosity of secondary organic material

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Markus Petters ◽  
Sabin Kasparoglu
Keyword(s):  
Particle Size ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Critical Role ◽  
Particle Diameter ◽  
Cloud Formation ◽  
Melting Point Depression ◽  
Wide Range

Abstract Atmospheric aerosols can assume liquid, amorphous semi-solid or glassy, and crystalline phase states. Particle phase state plays a critical role in understanding and predicting aerosol impacts on human health, visibility, cloud formation, and climate. Melting point depression increases with decreasing particle diameter and is predicted by the Gibbs–Thompson relationship. This work reviews existing data on the melting point depression to constrain a simple parameterization of the process. The parameter $$\xi $$ ξ describes the degree to which particle size lowers the melting point and is found to vary between 300 and 1800 K nm for a wide range of particle compositions. The parameterization is used together with existing frameworks for modeling the temperature and RH dependence of viscosity to predict the influence of particle size on the glass transition temperature and viscosity of secondary organic aerosol formed from the oxidation of $$\alpha $$ α -pinene. Literature data are broadly consistent with the predictions. The model predicts a sharp decrease in viscosity for particles less than 100 nm in diameter. It is computationally efficient and suitable for inclusion in models to evaluate the potential influence of the phase change on atmospheric processes. New experimental data of the size-dependence of particle viscosity for atmospheric aerosol mimics are needed to thoroughly validate the predictions.

Thermal Properties of Hyperbranched Polymer/HTPB-PU IPN

2013 ◽  
Vol 575-576 ◽  
pp. 76-80
Author(s):  
Xue Jing Song ◽  
Yun Jun Luo
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Hyperbranched Polymer ◽  
Isophorone Diisocyanate ◽  
Scanning Calorimetry

Hyperbranched polymer/HTPB-PU IPNs were prepared, when HTPB (hydroxyl-terminated polybutadiene) and IPDI (isophorone diisocyanate) were cured into polyurethane (HTPB-PU) at the existence of hyperbranched polymer. Differential scanning calorimetry (DSC) was adopted to study the influence of hyperbranched polymer on thermal properties of HTPB-PU, while IPNs were formed. The result shows that the existance of hyperbranched polymer makes glass transition temperature of HTPB-PU reduces by around 2°C and that HTPB-PU lowers the melting point of hyperbranched polymer. Hyperbranched polymer plays a role of internal plasticization on HTPB-PU, and HTPB-PU influences crystallization of hyperbranched polymer in return.

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