Surfactant effect on production of monodispersed microspheres by microchannel emulsification method

Abstract

Super-monodispersed oil-in-water (O/W) microspheres (MS) were produced using a microchannel (MC) emulsification technique. To investigate the effect of the surfactant on the behavior of the O/W-MS formation, the MS size and its distribution, various surfactants were used for the MC emulsification process. An MC plate with 8.9 µm equivalent diameter was employed. It was found that the super-monodispersed O/W-MS production depends on the type of surfactant used. When nonionic and anionic surfactants were used, supermonodispersed O/W-MS were produced, and the average droplet diameter was about 30 µm with a standard deviation less than 1 µm. For cationic surfactants, the super-monodispersed O/W-MS production was not successful, especially for the case where hydrophobic surfactant was dissolved in the oil phase. The results indicated that it is very important to maintain the hydrophilicity of the MC surface during the MC emulsification process. It is considered that the hydrophilic group of the anionic and nonionic surfactant was repulsed from the negatively charged MC surface so that the hydrophilicity of the MC surface was maintained. Otherwise, adsorption of the positively charged group of the cationic surfactant occurred on the MC surface which improved wetting of the MC surface and deteriorated the MC emulsification process. The analysis was supported by contact angle measurement.Paper no. S1182 in JSD 3, 285-293 (July 2000). KEY WORDS: Microchannel emulsification, monodispersed microspheres, surfactant effect. Microspheres (MS), which are emulsion cells or solid particles dispersed in a continuous phase, have been utilized in various industries such as foods, cosmetics, and pharmaceuticals. Emulsions are dispersed multiphase systems consisting of two or more almost mutually insoluble liquids, with the dispersed phase present in the form of droplets in a continuous phase (1). Using conventional methods of emulsion production, the emulsion droplets (or MS) are usually polydispersed over a wide range. Formation of MS with a narrow droplet size distribution is highly desirable, but in general is very difficult. Membrane emulsification is a relatively new technique that has the potential of reproducibly forming emulsions with a narrow droplet size (2-4). This method uses the pores of a microporous membrane to disperse the dispersed phase into the continuous phase by applying pressure. Recently Kawakatsu et al. (5) have proposed a novel microchannel (MC) emulsification technique for supermonodispersed MS production. The MC emulsification technique is based on the research of Kikuchi et al. (6 ,7), in which they developed a microscope video system and optically accessible MC formed in a single crystal silicon substrate for the observation of blood rheology and flow behavior of blood cells. For the MC emulsification technique, an MC plate was pressed close to an optically flat glass plate to form uniform-sized channels, and the dispersed phase was pressed through the channels to disperse regularly into the continuous ph...

Emulgieren mit mikrostrukturierten Systemen

“…Höhere Grenzflächenspannungen aufgrund geringerer Emulgatorkonzentrationen bewirken einen hohen ¹break-through pressureª. Die Art des Emulgators und ob er in der kontinuierlichen oder der dispersen Phase gelöst ist, haben ebenfalls einen Einfluss auf diesen Wert [21].…”

Optimizing Delivery Characteristics of Curcumin as a Model Drug via Tailoring Mean Diameter Ranges of Cellulose Beads

“…In contrast, CBs of larger mean diameter were obtained at lower surfactant concentration (<3.0% w/v), as microemulsion droplets tend to coalesce with each other to form larger droplets in order to reduce their surface area or energy. Tong et al [39] reported similar results regarding the effect of surfactant concentration on the mean size of microspheres formed.…”

Modification of interfacial characteristics of monodisperse droplets produced using membrane emulsification by surfactant displacement and/or polyelectrolyte electrostatic deposition

“…-N(CH 3 ) 3 + or -NH 3 + ) on the phospholipid molecules and anionic silanol groups on the SPG membrane [14]. Similar fouling problems have also been reported during the production of oil-in-water emulsions by hydrophilic silicon microchannel plates using cationic or zwitterionic surfactants [15,16]. Consequently, there is a limit to the type of emulsifiers that can currently be used to form stable emulsions with uniformly sized droplets using the SPG membrane method.…”