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Title: High intensity ultrasonication-assisted pickering emulsions for the fabrication of monodisperse composite nanoparticles
Authors: Wang, Jiaxin
Degree: M.Phil.
Issue Date: 2018
Abstract: In this study, a method has been developed to improve Pickering emulsions and solvent evaporation using high intensity ultrasonication (HIU) to produce nanoparticles for controlled drug release. By applying the proposed method, fabrication of core-shell structured composite nanospheres composed of biodegradable polymers with a high level of monodispersity based on soft colloid-stabilized Pickering emulsions have been successfully implemented. It overcomes the limitations of methods based on Pickering emulsions, that are, (i) the resulting systems size ranges are normally limited to the micron-scale and (ii) the high dependence of the use of bulky or custom-made auxiliary equipment, such as ceramic membranes or microchannel devices, to achieve high levels of uniformity and monodispersity. Therefore, it can exploit the advantages offered by Pickering emulsions and concurrently produce uniform and monodisperse nano-sized drug delivery systems (DDSs) with controllable size ranges. Moreover, the proposed method can also be further developed to become an alternative drug release strategy due to its ability in enabling a facile fabrication of monodisperse composite DDSs in nanoscale, with no use of molecular surfactants or crosslinkers.
The experimental results demonstrated that the introduction of HIU mainly contributes to two aspects: (i) depolymerization of soft colloidal stabilizers and (ii) well-dispersion of emulsion. With such basis, well-dispersed self-assembled chitosan colloid-stabilized emulsion droplets were resulted and further facilitated the preparation of monodisperse poly(lactic-co-glycolic acid)-chitosan core-shell composite nanospheres (PLGA-CS). Moreover, drug-loaded PLGA core with chitosan as one layer of coating, can be formed simultaneously by polymer precipitation resulting from solvent evaporation at room temperature. The key conditions influencing the proposed fabrication process were also investigated. Particle size of PLGA-CS within the range of 255 nm to 830 nm can be controlled by adjusting the amplitudes of HIU and the initial molecular weight of stabilizers. For instance, a low amplitude of 20% of the total power could be used to control drug-loaded PLGA-CS to an average particle size of 255 nm and a very low level of polydispersity index of 0.078. Results from scanning electron microscopy, Fourier transform infrared spectrometry, zeta potential measurement and drug release study further confirmed the successful implementation of complementary functionalities, such as positive-charged chitosan giving rise to enhanced dispersion in aqueous solution and modulation of in vitro drug release of the PLGA-CS. The requirements of the preparation of biodegradable polymeric DDSs, with regard to tunable sizes, enhanced solubility and potential for controlled release and targeted delivery, were met by applying the proposed method. Investigations on further improving the proposed method, to achieve simultaneous loading of varied therapeutics in single systems with programmed drug release behaviours, are recommended for future studies.
Subjects: Hong Kong Polytechnic University -- Dissertations
Drugs -- Controlled release
Pages: xv, 101 pages : color illustrations
Appears in Collections:Thesis

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