Towards Tuning Microparticle Properties Via Spray Drying Technique:Investigation On Particle Formation Mechanism

Spray drying, one of the most important powder manufacturing methods in both research laboratory and industry, has been widely used in various areas, covering food, pharmaceutical, catalyst, ceramic, chemicals, etc. However, particles fabricated by conventional spray drying technique are often of wide range of size distribution and of non-uniform physicochemical property. The non-uniformity poses a great challenge for the mechanism study of particle formation and for controlling the characteristics and functionalities of microparticles. We have recently introduced a specially-designed micro-fluidic-jet spray dryer(MFJSD) which is capable of producing uniform microparticles and micro-fluidic aerosol nozzle(MFAN) as the atomizer to generate monodisperse droplets. So this provides convenient for mechanism study and controlling particle characteristics(particle size, size distribution, density, morphology, moisture content, etc.) and functionalities(flowability, hygroscopicity, etc.).The research work mainly contains three parts in this thesis. In spray drying granulating theoretical research, a series of drug carrier materials including lysine, whey protein isolate(WPI), sodium alginate, chitosan and starch have been fabricated into uniform microparticles via a micro-fluidic-jet spray dryer. The microparticle morphology can be well controlled by tuning precursor formulation and drying temperature, and the competition between precursor molecule diffusion rate and evaporation rate, which could govern particle formation process, and further result in different particle morphology and size. By the way, a fundamental mechanism for particle formation via spray drying has been proposed. The influences of droplet size and the amount of surface active substance(WPI) in precursor on particle surface composition were studied. Finding WPI was enriched on the surface of particle, however, the degree of enrichment caused by droplet size was not obvious.In spray drying granulating applied research, we used hydroxypropyl methylcellulose phthalate(HPMCP) as carrier materials. Lysine and hydrocortisone were selected as hydrophilic and hydrophobic model drug, respectively. The effects of precursor formulation, including ratio of carrier to drug content and solvent composition, and drying temperature on spray dried particle characteristics and release behaviors have been studied. It is found that a more volatile solvent and a higher drying temperature can result in fast evaporation rates to form microparticles of larger lateral size, more irregular shape, and denser matrix. The nature of the model drugs also plays an important role in determining particle properties. The drug release behaviors of the pharmaceutical microparticles are dependent on their structural properties and the nature of a specific drug, as well as sensitive to the pH value of the release medium. Most importantly, drugs in the microparticles obtained by using a more volatile solvent or a higher drying temperature can be well protected from degradation in harsh simulated gastric fluids due to the dense structures of the microparticles, while they can be fast-released in simulated intestinal fluids through particle dissolution. These pharmaceutical microparticles are potentially useful for site-specific(enteric) delivery of orally-administered drugs.In view of the market demand of mare milk powders, we explored the effect of important processing parameters(homogeneous, sterilization, concentration) and drying conditions(drying temperature) on the mare milk powders quality(appearance, size, density, moisture content, invasive, insoluble coefficient) in laboratory. These works can guide us to improve the quality of mare milk powders.