Factors influencing the stability and type of hydroxyapatite stabilized Pickering emulsion.

Hydroxyapatite (HAp) nanoparticle stabilized Pickering emulsion was fabricated with poly(l-lactic acid) dissolved in dichloromethane (CH2Cl2) solution as oil phase and HAp aqueous dispersion as aqueous phase. Pickering emulsion was cured via in situ solvent evaporation method. Effect of PLLA concentrations, pH value, HAp concentrations, oil-water ratio, emulsification rates and times were studied on emulsion stability and emulsion type, etc. The results indicated emulsion stability increased with the increase of HAp concentration, emulsification rate and time; it is very stable when pH value of aqueous phase was adjusted to 10. Stable W/O and O/W emulsions were fabricated successfully using as-received HAp particles as stabilizer by adjusting the fabricating parameters. The interaction between HAp and PLLA played an important role to stabilize Pickering emulsions. SEM results indicated that both microsphere and porous materials were fabricated using emulsion stabilized by unmodified HAp nanoparticles, implying that both W/O and O/W emulsion type were obtained.