Drying oil-in-water Pickering emulsions to make redispersible powders

Preparation of powdered oil by spray drying the Pickering emulsion stabilized by ovalbumin - Gum Arabic polyelectrolyte complex

The suitability of the perilla seed oil Pickering emulsion stabilized by the ovalbumin (OVA) - gum Arabic (GA) polyelectrolyte complex for spray drying was investigated and the resultant powder was characterized. The OVA - GA complex conferred enhanced stability to the emulsion than OVA, GA, and their mixture. The viscosity of the Pickering emulsion was highly sensitive to stabilizer concentration and that fabricated by 2% OVA - GA complex showed acceptable viscosity and powder yield. The Pickering emulsion was more effective in preventing oil leakage during spray drying than the OVA-stabilized emulsion and the resultant powder possessed an oil content of up to 77.7%. Besides, the spray-dried Pickering emulsion powder showed greater rehydration and better flowability than that of the OVA-stabilized emulsion powder. Hence, the Pickering emulsion stabilized by the OVA - GA polyelectrolyte complex is promising as a novel feed for the production of oil powders by spray drying.

A Novel Solid Nanocrystals Self-Stabilized Pickering Emulsion Prepared by Spray-Drying with Hydroxypropyl-β-cyclodextrin as Carriers

A drug nanocrystals self-stabilized Pickering emulsion (NSSPE) with a unique composition and microstructure has been proven to significantly increase the bioavailability of poorly soluble drugs. This study aimed to develop a new solid NSSPE of puerarin preserving the original microstructure of NSSPE by spray-drying. A series of water-soluble solid carriers were compared and then Box-Behnken design was used to optimize the parameters of spray-drying. The drug release and stability of the optimized solid NSSPE in vitro were also investigated. The results showed that hydroxypropyl-β-cyclodextrin (HP-β-CD), rather than solid carriers commonly used in solidification of traditional Pickering emulsions, was suitable for the solid NSSPE to retain the original appearance and size of emulsion droplets after reconstitution. The amount of HP-β-CD had more influences on the solid NSSPE than the feed rate and the inlet air temperature. Fluorescence microscopy, confocal laser scanning microscopy and scanning electron microscopy showed that the reconstituted emulsion of the solid NSSPE prepared with HP-β-CD had the same core-shell structure with a core of oil and a shell of puerarin nanocrystals as the liquid NSSPE. The particle size of puerarin nanocrystal sand interfacial adsorption rate also did not change significantly. The cumulative amount of released puerarin from the solid NSSPE had no significant difference compared with the liquid NSSPE, which were both significantly higher than that of puerarin crude material. The solid NSSPE was stable for 3 months under the accelerated condition of 75% relative humidity and 40 °C. Thus, it is possible todevelop the solid NSSPE preserving the unique microstructure and the superior properties in vitro of the liquid NSSPE for poorly soluble drugs.

Preparation, Physicochemical Characterisation and DoE Optimisation of a Spray-Dried Dry Emulsion Platform for Delivery of a Poorly Soluble Drug, Simvastatin

In the presented study, insight into the development and optimisation of the dry emulsion formulation and spray drying process is provided. The aim was to facilitate the dissolution of the poorly soluble, highly lipophilic drug, simvastatin, by forming spray-dried dry emulsion particles having adequate powder flow properties, while assuring sufficient drug content. Simvastatin and a mixture of caprylic, capric triglyceride and 1-oleoyl-rac-glycerol were employed as a model drug and solubilising oils, respectively. A matrix of the dry emulsions was composed at a fixed ratio mixture of mannitol and HPMC. Tween 20 was used in low amounts as the primary emulsion stabiliser. To facilitate process optimisation, a DoE surface response design was used to study the influence of formulation and process parameters on the particle size distribution, powder bulk properties, emulsion reconstitution ability, drug stability and process yield of spray-dried products. Two-fluid nozzle geometry was identified, studied and confirmed to be important for most product critical quality attributes. Models obtained after the study showed acceptable coefficients of determination and provided good insight in the relationship governing the process and product characteristics. Five model optimised products showed adequate process yield, suitable particle size distribution, good reconstitution ability and improved dissolution profile, when compared to a non-lipid-based tablet and the pure drug. However, the obtained dry emulsion powders exhibited poor flow character according to the Carr index. The optimised product was further analysed with NMR during lipolysis to gain insight into the species formed during digestion and the kinetics of their formation.

SPI microgels applied to Pickering stabilization of O/W emulsions by ultrasound and high-pressure homogenization: rheology and spray drying

Soybean Protein Isolate (SPI) is a by-product from soybean oil industries with good nutritional and functional properties. Denaturation of hydrated SPI can change its properties, allowing the formation of gel-like particles, which can be used to stabilize emulsions without addition of surfactants. SPI microgel particles were produced by denaturation of hydrated SPI, followed by high pressure homogenization or sonication, with different NaCl or NaF contents, aiming the formation of small particles capable to stabilize O/W emulsions and acting as wall material for microencapsulation of soybean oil by spray drying. The presence of NaF in the suspensions decreased the charge intensity of SPI microgels, leading to formation of significantly bigger SPI microgel particles. Based on Creaming Index (CI), all the emulsions were stable for, at least, 21 days at room temperature. The presence of salt affected minimally the droplet size of the emulsions, though there has been an increase in flocculation. All the emulsions presented shear-thinning behavior and a strong shear rate dependence when salt was present in the system. The microspheres produced by spray drying of the emulsions were spherical and showed few aggregate formation. In addition, they presented high values of oil retention (> 80 wt%) and acceptable values of moisture content (< 4 wt%). SPI microgel particles produced by high-pressure homogenization or sonication may be used to stabilize emulsions with low oil contents. These emulsions can be further spray dried to microencapsulate lipophilic compounds using SPI microgels as wall material.