Preparation Of Microparticles And Core-Shell Nanofibers Via Electrohydrodynamic Technique

Mordern pharmacy has developed accompaning with the progress of material sciences and biomedical technology. However, there is a problem existing in the pharmaceutical research which is the trouble of the inificial burst release of drug. Basing on the reason, many new materials and new processes have been exploited to improve the effect and properties of the drug and obtain ideal controlled release system. This chapter seeks to bring together the conception and application of drug delivery system. Then this article focuses on the study not only of the microsphere and nanofibers but also of their processing technologies that are electrospray and emulsion electrospinning.Firstly, this chapter described the use of electrospray technique to prepare poly[(ethylglycino)-(phenylalanine ethyl ester) phosphazene] (PGPP) microparticles with very low polydispersity. The effects of processing parameters such as solvent, polymer concentration, liquid flow rate, applied voltage and receiving distance on the morphology and size of PGPP particles were investigated systematically. The morphologies of the electrosprayed PGPP microparticles were observed by scanning electron microscope (SEM), and the particle sizes were analyzed by ImageJ basing on SEM photos. It was found that the morphology of PGPP microparitcles depended on polymeric concentration significantly. As PGPP concentration increased from 10 to 30% (w/v), rounder particles could be formed. The particles which used tetrahydrofuran(THF) as the solvent of spraying solution were less agglomerated than that 1,4-dioxane as the solvent, owing to the relatively faster extraction rate of THF. The results exhibited that the liquid flow rate mainly influenced the size of microparticle compared with applied voltage and receiving distance. It indicated that the particle size increased with the increasing flow rate, generally obeying the Scaling law, while with decreasing voltage and increasing distance. Experimental results demonstrated that PGPP microparicles with nearly spherical particles with about 1-2μm could be obtained by electrospraying 25%(w/v) PGPP/THF solution at optimized parameters. In short, as changing the various processing parameters, controllable particle size and shape can be achieved, therefore, electrospray can be used to fabricate drug-loaded PGPP microparticles for further research on the controlled drug release, which may have potential applications in inhaled drug delivery systems.Secondly, amphiphilic block co-polymer poly N-isopropylacryla-mide-b-polycaprolactone nanofibers with the core-shell structure had been prepared by the using of emulsion electrospinning. The effects of electrical field strength and number-average molecular weight of polymer on the morphology and size of the core-shell nanofibers were investigated systematically. The morphologies of the emulsion electrospinning core-shell nanofibers were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Then the sizes of the core-shell nanofibers were analyzed by ImageJ basing on SEM and TEM photos. It was found that the morphology of core-shell nanofibers was influenced by number-average molecular weight of polymer significantly, while was affected little by electrical field strength. As number-average molecular weigh increased from 12000 to 90000, more straight and better long fibers could be formed. And the fiber's diametre decreased slightly with the increasing electrical field strength. The comparison between the emulsion electospinning and classical electospinning has been investigated. The results assumed that the thinner and more straight fibers with much lower polydispersity can be gained by emulsion electospinning. The polymer solution all used trichloromethane(TCM) as the solvent of electrospinning solution. Experimental results also demonstrated that ultrafine fibers with core-shell structure which size are between 150nm and 700nm could be obtained by electrospinning 14%(w/v) BSA/polymer/TCM emulsion at certain parameters. In short, as adjusting the various processing parameters, expected size and straight core-shell nanofibers can be achieved, emulsion electrospinning can be used to fabricate drug-loaded core-shell nanofibers for further research on the controlled drug release, which may have potential applications in sacffolds engineering.