1. THE STUDY OF THE MICROENCAPSULATED DYE RELEASE FROM SOYBEAN LECITHIN LIPOSOMES
A.L.F.Baptistaa,P.J.G.Coutinhob,M.E.C.D.Real Oliveirab,J.I.N.Rocha Gomesa
aUniversidade do Minho - Departamento de Engenharia Têxtil - Campus de Azurem Guimarães-Portugal
bUniversidade do Minho - Departamento de Física - Campus de Gualtar Braga-Portugal
The objective of our work has been the microencapsulation of dyes with lecithin from soybean, with the formation of liposomes, as a substitute for synthetic auxiliaries so as to improve the quality of the effluent.
Current scenarios promote the disintegration and leakage of the liposomes, such as, changes in temperature, acidity, the use of surfactants, etc. Since dyeing process is a mix of all these parameters, we pretended to study each one separately.
INTRODUCTION
Rhodamine 6G
Equilibrium binding constant of rhodamine in soybean lecithin:
Equilibrium dimerization constant in aqueous media:
Equilibrium dimerization constant in lipid media:
MODELIZATION
Structural parameters
lext=lint=10 Å;
Rext=8000 Å; Rint=7950 Å
Mass balance equation
Conversion factors from bulk to local concentration
Where:
{ } - local concentration
[ ] - bulk concentration
TEMPERATURE AND SURFACTANT EFFECT ON THE CONTROL RELEASE OF THE DYE
TEMPERATURE FITTED PARAMETERS SURFACTANT/TEMPERATUE % DYE RELEASE
pH EFFECT
CONTROL RELEASE OF THE DYE
pH FITTED PARAMETERS % DYE RELEASE
PROTECTION TO MEMBRANE INTERIOR
EXTERNAL pH EXTERNAL pH 3
Carbofluoresceina
CONCLUSIONS
The temperature, the surfactant and pH induce a release of the encapsulated dye resulting in rhodamine dilution and consequently alterations in the dimerization/binding equilibrium.
The amount of dye released induced by temperature changes was greater in the presence of surfactant.
Changes in pH at constant temperature induces a release of dye similar as the one obtained with changes in temperature. In acid conditions we found a very fast initial dye release which doesn’t occur in basic ones.
Using carboxyfluoresceine, as a pH fluorescence probe, we concluded that the liposome membrane doesn’t protect the liposome interior from changes on the external pH although in acid conditions there is a residual protection effect.
ACKNOWLEDGE TO FUNDAÇÃO PARA A CIENCIA E TECNOLOGIA FOR IT SUPPORT TO THIS PROJECT