SANS study of colloidal aggregates of silicon tetraethoxide in basic ethanol/water solutions

2004 ◽  
Vol 350 (1-3) ◽  
pp. E905-E908 ◽  
Author(s):  
M.V Avdeev ◽  
V.L Aksenov ◽  
J Kohlbrecher ◽  
L Rosta
Keyword(s):  
Water Solutions ◽  
Colloidal Aggregates

Mechanisms of Drug Solubilization by Polar Lipids in Biorelevant Media

2020 ◽  
Author(s):  
Vladimir Katev ◽  
Zahari Vinarov ◽  
Slavka S. Tcholakova
Keyword(s):  
Chain Length ◽  
Acyl Chain ◽  
Polar Lipids ◽  
Superior Performance ◽  
Head Group ◽  
Formulation Development ◽  
Biorelevant Media ◽  
Drug Solubilization ◽  
Colloidal Aggregates ◽  
Class 1

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. We studied the effect of 26 polar lipids of the fatty acid, phospholipid or monoglyceride type on the solubilization of fenofibrate in a two-stage <i>in vitro</i> GI tract model. The main trends were checked also with progesterone and danazol.<br>Based on their fenofibrate solubilization efficiency, the polar lipids can be grouped in 3 main classes. Class 1 substances (n = 5) provide biggest enhancement of drug solubilization (>10-fold) and are composed only by unsaturated compounds. Class 2 materials (n = 10) have an intermediate effect (3-10 fold increase) and are composed primarily (80 %) of saturated compounds. Class 3 materials (n = 11) have very low or no effect on drug solubilization and are entirely composed of saturated compounds.<br>The observed behaviour of the polar lipids was rationalized by using two classical physicochemical parameters: the acyl chain phase transition temperature (<i>T</i><sub>m</sub>) and the critical micellar concentration (CMC). Hence, the superior performance of class 1 polar lipids was explained by the double bonds in their acyl chains, which: (1) significantly decrease <i>T</i><sub>m</sub>, allowing these C18 lipids to form colloidal aggregates and (2) prevent tight packing of the molecules in the aggregates, resulting in bigger volume available for drug solubilization. Long-chain (C18) saturated polar lipids had no significant effect on drug solubilization because their <i>T</i><sub>m</sub> was much higher than the temperature of the experiment (<i>T</i> = 37 C) and, therefore, their association in colloidal aggregates was limited. On the other end of the spectrum, the short chain octanoic acid manifested a high CMC (50 mM), which had to be exceeded in order to enhance drug solubilization. When these two parameters were satisfied (C > CMC, <i>T</i><sub>m</sub> < <i>T</i><sub>exp</sub>), the increase of the polar lipid chain length increased the drug solubilization capacity (similarly to classical surfactants), due to the decreased CMC and bigger volume available for solubilization.<br>The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order: choline phospholipids > monoglycerides > fatty acids.<br>As both the acyl chain length and the head group type are structural features of the polar lipids, and not of the solubilized drugs, the impact of <i>T</i><sub>m</sub> and CMC on solubilization by polar lipids should hold true for a wide variety of hydrophobic molecules. The obtained mechanistic insights can guide rational drug formulation development and thus support modern drug discovery pipelines.<br>

Mechanisms of Drug Solubilization by Polar Lipids in Biorelevant Media

2020 ◽  
Author(s):  
Vladimir Katev ◽  
Zahari Vinarov ◽  
Slavka S. Tcholakova
Keyword(s):  
Chain Length ◽  
Acyl Chain ◽  
Polar Lipids ◽  
Superior Performance ◽  
Head Group ◽  
Formulation Development ◽  
Biorelevant Media ◽  
Drug Solubilization ◽  
Colloidal Aggregates ◽  
Class 1

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. We studied the effect of 26 polar lipids of the fatty acid, phospholipid or monoglyceride type on the solubilization of fenofibrate in a two-stage <i>in vitro</i> GI tract model. The main trends were checked also with progesterone and danazol.<br>Based on their fenofibrate solubilization efficiency, the polar lipids can be grouped in 3 main classes. Class 1 substances (n = 5) provide biggest enhancement of drug solubilization (>10-fold) and are composed only by unsaturated compounds. Class 2 materials (n = 10) have an intermediate effect (3-10 fold increase) and are composed primarily (80 %) of saturated compounds. Class 3 materials (n = 11) have very low or no effect on drug solubilization and are entirely composed of saturated compounds.<br>The observed behaviour of the polar lipids was rationalized by using two classical physicochemical parameters: the acyl chain phase transition temperature (<i>T</i><sub>m</sub>) and the critical micellar concentration (CMC). Hence, the superior performance of class 1 polar lipids was explained by the double bonds in their acyl chains, which: (1) significantly decrease <i>T</i><sub>m</sub>, allowing these C18 lipids to form colloidal aggregates and (2) prevent tight packing of the molecules in the aggregates, resulting in bigger volume available for drug solubilization. Long-chain (C18) saturated polar lipids had no significant effect on drug solubilization because their <i>T</i><sub>m</sub> was much higher than the temperature of the experiment (<i>T</i> = 37 C) and, therefore, their association in colloidal aggregates was limited. On the other end of the spectrum, the short chain octanoic acid manifested a high CMC (50 mM), which had to be exceeded in order to enhance drug solubilization. When these two parameters were satisfied (C > CMC, <i>T</i><sub>m</sub> < <i>T</i><sub>exp</sub>), the increase of the polar lipid chain length increased the drug solubilization capacity (similarly to classical surfactants), due to the decreased CMC and bigger volume available for solubilization.<br>The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order: choline phospholipids > monoglycerides > fatty acids.<br>As both the acyl chain length and the head group type are structural features of the polar lipids, and not of the solubilized drugs, the impact of <i>T</i><sub>m</sub> and CMC on solubilization by polar lipids should hold true for a wide variety of hydrophobic molecules. The obtained mechanistic insights can guide rational drug formulation development and thus support modern drug discovery pipelines.<br>

DETERMINATION OF LANTHANIDES AND 3D METALS IN ENDOMETALLOFULLERENES WATER SOLUTIONS BY X-RAY FLUORESCENCE SPECTROMETRY

2019 ◽  
Vol 4 (65) ◽  
Author(s):  
V.G Zinovyev. ◽  
V.T. Lebedev ◽  
I.A. Mitropolsky ◽  
G.I. Shulyak ◽  
P.A. Sushkov ◽  
...  
Keyword(s):  
Fluorescence Spectrometry ◽  
X Ray ◽  
Water Solutions ◽  
3D Metals

Surface Nanostructure of Layers from Water Solutions after Sedimentation

2019 ◽  
Vol 11 (4) ◽  
pp. 04012-1-04012-6
Author(s):  
L. A. Bulavin ◽  
◽  
Yu. F. Zabashta ◽  
L. Yu. Vergun ◽  
O. S. Svechnikova ◽  
...  
Keyword(s):  
Water Solutions ◽  
Surface Nanostructure

In pursuit of sustainable water solutions in emerging regions

2013 ◽  
Vol 3 (4) ◽  
pp. 489-499 ◽  
Author(s):  
Laura R. Brunson ◽  
Lowell W. Busenitz ◽  
David A. Sabatini ◽  
Paul Spicer
Keyword(s):  
Drinking Water ◽  
Technology Development ◽  
Market Development ◽  
Safe Drinking Water ◽  
Water Solutions ◽  
Enabling Environment ◽  
Cultural Assessment

While lack of access to consistent safe drinking water is estimated to affect nearly 2 billion people worldwide, many of the efforts to solve this crisis have proven to be unsustainable. This paper discusses some of the reasons for these challenges and suggests interdisciplinary practices that could be integrated from the very beginning of a water intervention to achieve long-term success. Of key importance for sustainable water implementation is an enabling environment that incorporates aspects such as funding, potential for market development, and supportive governance. While this enabling environment is acknowledged, the focus of this work is on the integration of three key areas: (i) social and cultural assessment of behavior and preferences; (ii) market-based implementation approaches that draw on this knowledge; and (iii) technology development for these markets.

Depression of freezing temperature of water and water solutions in porous materials

1989 ◽  
Vol 54 (10) ◽  
pp. 2644-2647 ◽  
Author(s):  
Petr Schneider ◽  
Jiří Rathouský
Keyword(s):  
Water Vapor ◽  
Porous Materials ◽  
Inorganic Salt ◽  
Freezing Point ◽  
Freezing Temperature ◽  
Inorganic Salts ◽  
Freezing Point Depression ◽  
Salt Solutions ◽  
Water Solutions

In porous materials filled with water or water solutions of inorganic salts, water freezes at lower temperatures than under normal conditions; the reason is the decrease of water vapor tension above the convex meniscus of liquid in pores. The freezing point depression is not very significant in pores with radii from 0.05 μm to 10 μm (about 0.01-2.5 K). Only in smaller pores, especially when filled with inorganic salt solutions, this depression is important.

Sorption of Water Soluble Organic Dyes on Magnetic Poly(oxy-2,6-dimethyl-1,4-phenylene)

1995 ◽  
Vol 60 (9) ◽  
pp. 1448-1456 ◽  
Author(s):  
Ivo Šafařík ◽  
Miroslava Šafaříková ◽  
Vlasta Buřičová
Keyword(s):  
Organic Compounds ◽  
Azo Dye ◽  
Organic Dyes ◽  
Water Soluble ◽  
Magnetic Composite ◽  
Water Solutions ◽  
Magnetite Particles

Magnetic composite based on poly(oxy-2,6-dimethyl-1,4-phenylene) (PODMP) was prepared by melting the polymer with ε-caprolactam in a presence of fine magnetite particles. Magnetic PODMP was used for sorption of water soluble organic compounds (dyes belonging to triphenylmethane, heteropolycyclic and azo dye groups) from water solutions. There were considerable differences in the binding of the dyes tested. In general, heteropolycyclic dyes exhibited the lowest sorption.

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