Preparation And Application Of Pickering Emulsions Stabilized By Phytosterol/chitosan Complex Particles

Attention has been drawn to the two emulsion formulations of W/O Pickering emulsions and O/W/O Pickering double emulsions(PDEs)due to their huge application prospects in fat substitutes,carriers of active substance transport and controlled release,and platforms of biological catalysis.However,at present,consumers’ demand for “clean label” products in food,cosmetics and drugs is gradually increasing,so there is an urgent need to develop natural,renewable and safe bio-based particles.Phytosterol(PS)is a natural phytochemistry with high nutritional value.Due to its hydrophobic and lipophilic properties,PS particles have potential to be a hydrophobic Pickering stabilizer,but further improvement of PS particles is still needed to enhance the stability of the obtained emulsions.Therefore,it is of great theoretical significance and practical value to develop a new method to make the colloidal particles from the above plants obtain appropriate surface wettability to prepare stable and green W/O Pickering emulsions and O/W/O PDEs.Based on this,a green and simple physical modification method is proposed,which is to prepare PS/CS complex particles with appropriate wettability by using the non-covalent bond between natural PS particles and chitosan(CS).In this paper,the preparation,stabilization mechanism,stability and potential applications of W/O Pickering emulsions and O/W/O PDEs stabilized by PS/CS complex particles were discussed in more detail at a later stage.The detail contents list as follows:(1)Preparation and stabilization mechanism of W/O Pickering emulsions stabilized by PS/CS complex particlesPS/CS complex particles,all-natural colloidal particle,were used as stabilizer to successfully prepare stable W/O Pickering emulsions.Compared with emulsions solely stabilized by PS particles,the stability of W/O Pickering emulsions can be greatly improved by introducing CS into the system.Specifically,CS with positively charge adsorbed on the surface of PS particles with negatively charge through electrostatic interactions,significantly improving the surface wettability and interfacial activity of PS particles.The stability mechanism was further verified by changing the p H value and ionic strength of the aqueous phase and exploring the rheological behavior of the W/O Pickering emulsions.The results showed that the formation of PS/CS complex particles was the key to the preparation of stable W/O Pickering emulsions.(2)Stability and application of W/O Pickering emulsions prepared by PS/CS complex particlesThe stability of W/O Pickering emulsions prepared by PS/CS complex particles and the application prospect of this emulsions system were studied.Specifically,the W/O Pickering emulsions prepared by PS/CS complex particles under the optimal process had extremely high long-term storage stability,and had universality in a wide range of water oil volume ratios and under conditions of different oil phases.Finally,the potential of W/O Pickering emulsions prepared by PS/CS complex particles as a carrier was explored.The results showed that the W/O Pickering emulsions can effectively protect water-soluble active substances from external environment stimulation,and can also control the release of water-soluble substances at different p H and temperature.The in vitro transdermal experiment showed that PS/CS complex particles could penetrate the stratum corneum and deposit in the active epidermis and dermis.The transdermal effect of the W/O Pickering emulsions stabilized by PS/CS complex particles was 3.4 times than the control group,which showed an excellent local delivery ability.(3)O/W/O PDEs prepared by PS/CS complex particles and GT using one-step method:formation mechanism,stability and applicationOn the basis of the W/O Pickering emulsions stabilized by PS/CS complex particles,the O/W/O PDEs can be prepared by one-step method only by introducing gelatin(GT)into the aqueous phase.The formation mechanisms of O/W/O PDEs were explored from two aspects:water phase viscosity and phase inversion.The results indicated that reaching a certain threshold of aqueous viscosity can further drive the formation of O/W/O PDEs through phase inversion.The O/W/O PDEs stabilized by PS/CS complex particles and GT exhibited high anti-coalescence stability.When stored at room temperature and low temperature(4 °C)for 2months,the structure and droplet size of emulsions had no change.In addition,changing the concentration of PS/CS complex particles,volume ratio of water-oil,and types of oil phase can form O/W/O PDEs,similarly.Finally,the O/W/O PDEs can simultaneously load water-soluble and fat-soluble substances and showed excellent protection and local transdermal delivery capabilities,which further provided a new idea for the development of emulsions carriers in the fields of pharmaceuticals and cosmetics.