Preparation And Release Behavior Of Pickering Emulsions Stabilized By Hydrophobically Modified Alginate Nanoparticles

Pickering emulsions stabilized by soild particles instead of traditional surfactants perform good thermodynamic stability and application security on account of irreversible adsorption of particles and free-macromolecule surfactant.Solid particle layer as an emulsifier can also increase the resistance of drug release,which is conducive to sustained release.So Pickering emulsions stabilized by solid particles have a broader application prospects in sustained released field.In this paper,it is proposed that alginic particles with a good biocompatibility and pH sensitivity as an interfacial stabilizer to prepare pH-responsive Pickering emulsion as a drug sustained release carrier.The emulsion is not only highly stable,but also can achieve the purpose of oral drug response and slow release because of the pH sensitivity of alginic particles.Considering that natural sodium alginate contains a large amount of hydrophilic carboxyl groups and hydroxyl groups,it is necessary to hydrophobically modified sodium alginate with diacetone acrylamide by radical polymerization method and then form a modified calcium alginate particles(MCA)by double emulsion method with Ca2+.The MCA is used as a particle emulsifier to adsorb the interface between oil and water to form a functional solid particle layer,which not only stabilizes the emulsion,but also effectively isolates the entrapped material and has pH sensitivity.Compared with the single sodium alginate gel particle carrier,the granular diffusion mass transfer interface is more complex and it can control the diffusion and release of the substance,which effectively avoid the burst release phenomenon in the medicine.The effects of the ratio of modifier and the concentration of crosslinker on the hydrophobicity,particle size and morphology of the particles were investigated.The optimum ratio of alginate to modifier was determined as 1:1.When the concentration of the crosslinking agent was 3%,5%,7% and 10%,respectively,the particle size was 604 nm,316 nm,412 nm and 732 nm,respectively,the contact angles was 73.5°,87.4°,67.2°,76.9°,respectively,and the surface features was porous,porous,dense and dense respectively.Pickering emulsion stabilized by MCA was prepared and the effects of oil-water volume ratio,particle concentration,crosslinker concentration and pH value on emulsion stability,particle size and morphology were investigated.The optimal preparation condition was determined: oil-water volume ratio of 1:1,4% particle concentration,5% crosslinker concentration,dispersed phase pH of 6.5.And the released behaviors of MCA stabilized emulsion were investigated in vitro by using curcumin as drug model.The release profiles showed the release rate was very smallwith 6% in simulate gastric fluid of pH 1.5 while 48% in simulate intestinal fluid in 12 h with gentle process,indicating that MCA-Pickering emulsion showed significantly pH-sensible and sustained release performance with long release cycle.The release kinetics equation demonstated that Fick diffusion and swelling and dissolution of MCA particles are the main release mechanisms of MCA-Pickering emulsions.