Encapsulating Function Of Surfactant Micelle And Its Gel For Drug Molecules

This paper studies the encapsulating function of surfactant micelles on two model drugs.One is the poorly water-soluble flavonoid rutin,which is encapsulated by the solubilizing properties of micelles;another is a protease that is easily inactivated in an aqueous environment and is encapsulated in a structured aqueous medium by gelation of worm-like micelles.The encapsulation of these drug molecules is favorable for improving their bioavailability in drug delivery and clinical practice,which is of great importance in many applications,like pharmaceutical,biotechnology,skin care products and food industry etc.The main research content includes the following three parts:1.Study on the encapsulating effect of surfactant on RutinThe UV-vis spectroscopy of Rutin in aqueous surfactant solution was measured to study the solubilization of Rutin in the presence of different surfactants.The results show that the solubilization ability is closely related to the charge properties and charge density of the micellar polar shell.Amphoteric SB3-12 micelles have a stronger ability to dissolve Rutin,reflecting the electrostatic effect of the positive charge carried by SB3-12 and the negatively ionized Rutin（R^-） by,while negatively charged SDS micelles are relatively weak.The spectrum in the mixed SB3-12/SDS system shows that as the mole fraction of SDS increases,the charge density of the mixed micelles changes controllably,which can continuously adjust the solubility of Rutin.The micellization parameters of surfactants in the presence of Rutin were measured by ITC.The encapsulating effect of SB3-12 micelles on Rutin in pure water and PBS（pH 7.0） medium and the effect of adding SDS on encapsulation were further studied.It was found that in aqueous solution of SB3-12,the solubilization of Rutin causes an exothermic interaction,which reduced the cmc of SB3-12.For the SB3-12/SDS mixed micelle system in PBS medium,the electrostatic effect of Rutin is relatively small,which has almost no effect on the mixing cmc and ΔH_mic,but it can cause the concentration range to form stable micelle aggregates（C_f–cmc） becoming significantly wide.In addition,it can be observed from the saturation solubility curve of Rutin that its solubility decreases as the mole fraction of SDS increases.¹H NMR,as a complementary method to UV-Vis spectroscopy and ITC provides the evidence for identifying the interaction sites of Rutin molecules and micelles.Thus through SDS adjusting the net negative charge density on the surface of mixed micelles by SDS,the dissolution in Rutin surfactant becomes controllable.2.Viscoelasticity of gemini surfactant 14-2-14 gel and its encapsulating function for enzymesBy observing the phase behavior of 14-2-14,it was found that there is a stable gel phase region at a concentration higher than 20 mmol·L^–1,which can be used as a carrier for encapsulating enzymes.The rheological study on 14-2-14 gel shows that 14-2-14 at room temperature has the rheological characteristics of typical worm-like micelles and has good elastic behavior.The addition of a small amount of glucoside（Glu） significantly reduces the viscosity of the system and the elasticity of the gel,but the addition of a small amount of maltoside（DM） increases to big extent the viscosity of the system and enhances the resistance to deformation.Therefore 14-2-14 gel containing a small amount of DM is suitiable as the drug carrier encapsulatingα-chymotrypsin.After encapsulatingα-chymotrypsin,the zero-shear viscosity of14-2-14 gel or 14-2-14 gel/DM is reduced,and its elasticity is weakened.This is not only favorable for encapsulatingα-chymotrypsin but also protecting the enzyme activity.3.Phase diagram of 14-2-14/H₂O binary composition to temperature.The phase behavior of 14-2-14/H₂O system was studied by observing phase states with naked eyes and PLM as well as measuring modulus-temperature curves and DSC curves.When the concentration of14-2-14 is<18 mmol·L^–1,there is a white precipitate in the low temperature region,which is a two-phase area（l-p）,and the precipitate phase is the Hexagonal LC phase.When its concentration is≥20 mmol·L^–1,the low-temperature region appears in a white gel phase（white gel）.As the temperature increases,l-p and white gel phases are first transformed into transparent gels,and then into high-viscosity sols.A small amount of adding DM can increase the gel phase area,while the addition ofα-chymotrypsin makes the gel phase area shrink.The modulus-temperature curves were measured by rheology,in which it was observed that the storage modulus（G’）and the loss modulus（G"） decrease with increasing temperature,and there is a sharp drop that occurs between the white gel and gel.Further the intersection of G’ and G" appears at the gel-sol phase transition temperature.DSC results show that the white gel-gel or LC-gel phase transition is accompanied by an endothermic process with a steep change,while the heat capacity between gel-sol trends to be slowly changing.Through the studies on encapsulating function of two kinds of drug carriers（micelle and gel） for two drug molecules,we have a deep understanding of the compatibility and interactions between surfactant aggregates and drug molecules.The development of pharmaceuticals based on it has potential application value and theoretical significance.