The Investigation Of Migration And Extension Of PH Window For Forming Conjugated Linoleic Acid Ufasomes

Fatty acid vesicle(FAV) has a hollow core-shell structure similar to liposomes, and the building block fatty acids are naturally abundant, green and safe, which makes them potential and significant to be applied in embedding/release systems. However FAV is sensitive to p H, and the p H window for forming FAV is narrow and biologically unsuitable. The disadvantages prohibit FAV from being applied in domestic chemicals and exernally applied agents.Conjugated linoleic acid(CLA) was choosed as the template for forming FAV, and its p H window was investigated. Besides CLA has many beneficial physiological functions such as: cancer resistance, resistance to gruel harding, and also it is naturally abundant existing in animals, milk and vegetable oil. In many countries, it has been applied in food, medical and health care products.Besides its benificial physiological functions, it has a low chain-melting temperature, which allows it to form FAV at room temperature. In the meanwhile, the conjugation of double bonds in conjugated unsaturated fatty acids gives a possibility to its self-crosslinking, which makes the FAV can be characterized by transmission electron microscope(TEM) and dynamic light scattering(DLS). A green and safe nonionic surfactant alkyl polyglucoside(APG) and another surfactant for food and medical use Tween 80 were tried in this paper to blend with a model fatty acid conjugated linoleic acid(CLA) to help the later forming FAV in a biologically suitable p H window. Extend and migrate the p H window to improve its sensitive to p H, and make the FAV to be applied in embedding/releade system for domestic chemicals, exernally applied agents and food.In this paper, the main results and conlusions are as follows:(1) CLA vesicles can be self-crosslinked initiated by UV irradiation, and the crosslinkingvesicles can be characterized by the transmission electron microscope to get itsmorphologies photo.(2) A new method to determine the p H window of mixed FAV was developed in this paper.Use Dynamic light scattering to test the scattering intensity of different p H to make ap H-SI curve. We consider the p H at half peak as the limit of the p H window. At themeanwhile, take TEM images of the sample at the p H which is in the range of the p Hwindow of FAV. The results show that the method to determine the p H window of FAVis rational.(3) Investigate the p H window of nonionic surfactant and CLA systems, and the influence ofmigration and extension of the p H window. We choose APG and Tween 80 as the modelsurfactant respectively, for the reason that APG is regarded as a green and safe surfactantfor domestic chemicals, and Tween 80 is a nonionic surfactant used for food additives.The results shows that the p H window of CLA / APG system is 6.0~8.0, while the p Hwindow of pure CLA is 8.0~9.0. The p H window of system of Tween 80 / CLA canmigrate and extend to 2.5~7.5. The reason for the migration and extension of p H windowis that hydroxyl group of APG molecular can form hydrogen bond with the carboxylgroup in CLA, in the meanwhile APG as a surfactant can improve the solubility of CLAvesicles. Tween has polyethylene oxide in its molecular can form hydrogen bond with thecarboxyl group in CLA. This is beneficial for CLA to form vesicles in the acidiccondition so that the p H window can migrate and extend to the acidic direction. Thelower the p H of the system is, the larger the FAV is. This is because that there will be lesscarboxylate ion, and the electrostatic repulse force will reduse which leads to the tightlystacking of the molecular in FAV,and the size of the FAV will be larger.(4) We investigate the effect and mechanism of the anionic surfactant SDS for the p Hwindow of FAV. When SDS was added in the CLA, the p H window of FAV has aexremely migration and extension to p H 7.5~2.5, and improved the p H dependency andsensibility of FAV.,so that the p H window can migrate and extend to the acidic direction.SDS as an anionic surfactant is a strong electrolyte, which makes it possible to ionizatesulfate in the acid aqueous solution. It can form FAV with CLA. The sulfate can make aion dipole interaction with carboxyl in CLA, and the interaction can stabilize the FAV,and the role is smiliar to the carboxylate. SDS can improve the solubility of CLA in theacidic p H, therefore SDS is beneficial to migrate and exend the p H window to the acidicdirection. The more the SDS is, the p H window can migrate to the acidic direction further.When x = 0.5, the p H window is 2.5~7.5, and x = 0.05, the p H window is 6.0~8.8.Dodecanol can migrate and exend the p H window to the alkaline direction to p H 9.2~11.8.There is a hydroxyl group in dodecanol, at alkaline p H, it can reduce the electrostaticrepulsion, so that it will be easier to form FAV, and the hydroxyl group can form iondipole interaction with carboxylate of CLA.(5) The FAV composed of CLA and APG, Tween 80 or SDS was used as a vehicle for drugdelivery, and evaluate its performance. The result shows that the encapsulation efficiencyis higher as the p H of the FAV becoming lower, at the meanwhile, the rate of release isslower. This is identical to the size of FAV. The larger the FAV is, the higer encapsulationefficiency is.(6) By adding surfacrtant to the CLA, we suceeded in migrating and extending the p H to thebiological suitabel p H range and improving the p H sensibility and p H dependant. Wechoose surfactant for domestic chemicals and food additives adding to CLA. The resultsshow that it can achieve the goal to migrate and extend the p H window so that it can suitthe biological p H range. Make FAV possible to act as embedding/release system indomestic chemicals and food.