Release kinetics of pendant substituted bioactive molecules from swellable hydrogels: role of chemical reaction and diffusive transport

1990 ◽  
Vol 51 (1-2) ◽  
pp. 83-104 ◽  
Author(s):  
S.S. Shah ◽  
M.G. Kulkarni ◽  
R.A. Mashelkar
Keyword(s):  
Chemical Reaction ◽  
Release Kinetics ◽  
Bioactive Molecules ◽  
Diffusive Transport ◽  
Kinetics Of

scholarly journals Halloysite nanotubes filled with salicylic acid and sodium diclofenac: effects of vacuum pumping on loading and release properties

2021 ◽  
Author(s):  
Lorenzo Lisuzzo ◽  
Giuseppe Cavallaro ◽  
Stefana Milioto ◽  
Giuseppe Lazzara
Keyword(s):  
Salicylic Acid ◽  
Release Kinetics ◽  
Halloysite Nanotubes ◽  
Drug Molecules ◽  
Sodium Diclofenac ◽  
Tunable Release ◽  
Feature Based ◽  
Kinetics Of ◽  
Filling Mechanism

AbstractIn this work, we investigated the effects of the vacuum pumping on both the loading efficiencies and the release kinetics of halloysite nanotubes filled with drug molecules dissolved in ethanol. As model drugs, salicylic acid and sodium diclofenac were selected. For comparison, the loading of the drug molecules was conducted on platy kaolinite to explore the key role of the hollow tubular morphology on the filling mechanism of halloysite. The effects of the pressure conditions used in the loading protocol were interpreted and discussed on the basis of the thermodynamic results provided by Knudsen thermogravimetry, which demonstrated the ethanol confinement inside the halloysite cavity. Several techniques (TEM, FTIR spectroscopy, DLS and $$\zeta$$ ζ -potential experiments) were employed to characterize the drug filled nanoclays. Besides, release kinetics of the drugs were studied and interpreted according to the loading mechanism. This work represents a further step for the development of nanotubular carriers with tunable release feature based on the loading protocol and drug localization into the carrier. Graphic abstract The filling efficiency of halloysite nanotubes is enhanced by the reduction of the pressure conditions used in the loading protocol.

On the Role of Diffusion in the Oxidation of Fe, Ni, Co and the Fe-Sn Alloy by Calcium and Sodium Sulfates

2006 ◽  
Vol 258-260 ◽  
pp. 63-67
Author(s):  
V.M. Chumarev ◽  
V.P. Maryevich ◽  
V.A. Shashmurin
Keyword(s):  
Co Oxidation ◽  
Chemical Reaction ◽  
Diffusion Processes ◽  
Transport Processes ◽  
Diffusion Transport ◽  
Sodium Sulfates ◽  
Product Forms ◽  
Kinetics Of ◽  
Dominant Part

Diffusion processes play a dominant part in the macro kinetics of Fe, Ni and Co oxidation by calcium and sodium sulfates. Here, the reaction product forms a compact covering which spatially divides the reagents on the surface in the same way as in the oxidation and sulfidization of metals by oxygen and sulfur. Therefore, it is possible to assume in advance that interaction of metals with calcium and sodium sulfates will be determined not by the actual chemical reaction properly but by the diffusion transport processes.

Substituent Effect on Reactivity of Alkyl Thiolacetates

1971 ◽  
Vol 26 (7) ◽  
pp. 703-707
Author(s):  
F. Dutka ◽  
A. F. Márton ◽  
P. Vinkler
Keyword(s):  
Chemical Reaction ◽  
Sulfur Atom ◽  
Substituent Effect ◽  
Linear Structure ◽  
Common Mechanism ◽  
Reaction Site ◽  
Structure Reactivity Relationship ◽  
Kinetics Of

Kinetics of catalyzed acyl group exchange between acetic-1-14C anhydride and alkyl thiolacetates was investigated. The exchange is not accompanied by chemical reaction and demonstrates the full equivalency of anhydride acyl groups in the process. The rate of exchange is lowered by increasing branching rather than lengthening in S-alkyl substituents. The role of catalyst and structures of possible intermediates are interpreted. Upon existing linear structure-reactivity relationship a common mechanism involving sulfur atom as the reaction site seems to be operative.

scholarly journals Investigation of the Role of Cholesterol Superlattice in Release Kinetics of Drugs from Stealth Liposomes

2012 ◽  
Vol 102 (3) ◽  
pp. 83a ◽  
Author(s):  
Nicole Haloupek ◽  
Justin Rafferty ◽  
Kayla Haloupek ◽  
Emmanuel Tejada ◽  
Tamara Mamistvalova ◽  
...  
Keyword(s):  
Release Kinetics ◽  
Stealth Liposomes ◽  
Kinetics Of

The role of microsphere fabrication methods on the stability and release kinetics of ovalbumin encapsulated in polyanhydride microspheres

2006 ◽  
Vol 23 (8) ◽  
pp. 832-843 ◽  
Author(s):  
Amy S. Determan ◽  
Jennifer R. Graham ◽  
Katherine A. Pfeiffer ◽  
Balaji Narasimhan
Keyword(s):  
Release Kinetics ◽  
The Stability ◽  
Kinetics Of

Role of Weathering Layers on the Alteration Kinetics of Medieval Stained Glass in an Atmospheric Medium

2014 ◽  
Vol 1656 ◽  
pp. 175-186
Author(s):  
Aurélie Verney-Carron ◽  
Anne Michelin ◽  
Lucile Gentaz ◽  
Tiziana Lombardo ◽  
Anne Chabas ◽  
...  
Keyword(s):  
Glass Surface ◽  
External Medium ◽  
Protective Role ◽  
Aqueous Environment ◽  
Diffusive Transport ◽  
Stained Glass ◽  
Gel Layer ◽  
Altered Layer ◽  
Kinetics Of

ABSTRACTIn order to model and predict the alteration of medieval potash-containing stained glass, it is necessary to understand the mechanisms of alteration layer formation at the glass surface and its role on the evolution of alteration kinetics. Moreover, the alteration layers observed on stained glasses are particular, as they are often fractured and heterogeneous in terms of thickness, with the appearance of pits and the detachment of scales. Contrary to silicate glasses altered in aqueous environment where the gel layer has a protective role, cracks and scales are harmful to the durability of stained glasses altered in air. In order to address these mechanistic issues, a program of experiments in the laboratory and in the field were performed. The fracturing was shown to be caused by the growth of the alteration layers and amplified by the alternation of humid and dry periods changing the density of hydrated layers. The pitting is initiated by defects at the glass surface and increased in external atmospheric medium as these defects fix the precipitated salts. However, despite fracturing and pitting, the development of an altered layer imposes a diffusive transport of the solution between the external medium and the bulk glass.

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