Theory of scattering from colloidal aggregates

2007 ◽  
pp. 161-168 ◽  
Author(s):  
R. Klein ◽  
D. A. Weitz ◽  
M. Y. Lin ◽  
H. M. Lindsay ◽  
R. C. Ball ◽  
...  
Keyword(s):  
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>

Study on Mechanism of Breakage and Coalescence of Colloidal Aggregates at Steady-state under Shear

1999 ◽  
Vol 15 (05) ◽  
pp. 467-470
Author(s):  
Li Jing-Sheng ◽  
◽  
Bian Xuan-Xia
Keyword(s):  
Steady State ◽  
Colloidal Aggregates

Enhancing Polynuclear Aromatic Uptake into Bulk Solution with Amphiphilic Colloidal Aggregates

1992 ◽  
Vol 26 (9-11) ◽  
pp. 2341-2344 ◽  
Author(s):  
D. A. Edwards ◽  
Z. Liu ◽  
R. G. Luthy
Keyword(s):  
Experimental Data ◽  
Partition Coefficients ◽  
Solution Concentration ◽  
Aqueous System ◽  
Bulk Solution ◽  
Similar System ◽  
Colloidal Aggregates ◽  
Total Fraction ◽  
The Relationship ◽  
Amphiphilic Aggregates

Aggregated amphiphiles in an aqueous or solid/aqueous system can substantially enhance the uptake of polynuclear aromatic (PNA)compound into a bulk solution. The extent of PNA compound incorporated in an amphiphilic aggregate solution in the absence of solids is linearly dependent on the bulk solution concentration of the aggregated form of the amphiphile. In a system in which solids are in contact with a solution, however, the relationship is nonlinear as a result of the adherence of both amphiphile and PNA compound to the solids. The formation of amphiphile aggregates in the bulk solution of a system containing solids occurs only after a much greater amount of amphiphile has been added to the system than would be required for a similar system containing only solution. The partitioning of PNA compound between the solid, the colloidal amphiphilic aggregates in bulk solution, and the rest of the bulk solution can be characterized with two different partition coefficients and a number of other parameters, all of which are obtainable from independent experiments. The total fraction of PNA compound incorporated into bulk solution can be estimated with a mathematical model. Model results for the uptake of pyrene into a C8PE9.5 aggregate solution are shown plotted with experimental data. The effect of amphiphile aggregates on PNA compound transport in porous media may in some cases be substantial.

Photocleavable amphiphilic diblock copolymer with an azobenzene linkage

RSC Advances ◽  
2016 ◽  
Vol 6 (62) ◽  
pp. 57227-57231 ◽  
Author(s):  
Jilei Wang ◽  
Yiyun Ouyang ◽  
Shang Li ◽  
Xiaogong Wang ◽  
Yaning He
Keyword(s):  
Diblock Copolymer ◽  
Uv Light ◽  
Light Irradiation ◽  
Amphiphilic Diblock Copolymer ◽  
Colloidal Aggregates ◽  
Uv Light Irradiation

Diblock copolymer with an azobenzene linkage can be efficiently photocleaved upon UV light irradiation. Thus, the colloidal aggregates of this kind of amphiphilic diblock copolymer will be disrupted due to the cleavage of the azobenzene junction.

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

Conformation and dynamics of colloidal aggregates in detergent and copolymer systems

Polymer ◽  
1992 ◽  
Vol 33 (19) ◽  
pp. 4009-4013 ◽  
Author(s):  
Benjamin Chu
Keyword(s):  
Colloidal Aggregates

Comparison of three simulation methods for colloidal aggregates in Stokes flow: Finite elements, lattice Boltzmann and Stokesian dynamics

2013 ◽  
Vol 86 ◽  
pp. 199-209 ◽  
Author(s):  
Eva Schlauch ◽  
Martin Ernst ◽  
Ryohei Seto ◽  
Heiko Briesen ◽  
Martin Sommerfeld ◽  
...  
Keyword(s):  
Finite Elements ◽  
Stokes Flow ◽  
Lattice Boltzmann ◽  
Simulation Methods ◽  
Stokesian Dynamics ◽  
Colloidal Aggregates

Internal structure of colloidal aggregates

2001 ◽  
Vol 64 (4) ◽  
Author(s):  
Alexey Ivanov ◽  
Andrej Zubarev
Keyword(s):  
Internal Structure ◽  
Colloidal Aggregates
Sign in / Sign up

Export Citation Format

Share Document