The study of different properties of Pickering emulsions stabilised with colloidal silicon dioxide particles

Kozmetična in farmacevtska industrija sta področji, na katerih se nenehno in v koraku s tehnološkimi napredki in globalnimi smernicami razvijajo nove kakovostne in učinkovite formulacije. Predvsem kozmetična industrija se je v zadnjih letih usmerila v bolj trajnostne, čiste in naravne izdelke z zmanjšano vsebnostjo pomožnih snovi v topikalnih formulacijah. Nova različica klasičnih emulzij, ki za stabilizacijo ne potrebuje emulgatorjev, temveč le trdne koloidne delce, ki se umestijo na medfazno površino in tako znižajo medfazno napetost, so Pickering emulzije. Slednje manj dražijo kožo v primerjavi s klasičnimi emulzijami, so biokompatibilne, imajo boljšo permeabilnost skozi kožo in z njimi lažje dosegamo nadzorovano sproščanje. Površino delcev spremenimo relativno enostavno, s čimer vplivamo na lastnosti emulzije. V diplomskem delu smo želeli ugotoviti, kateri parametri izdelave so ključni za fizikalno stabilno formulacijo olje v vodi Pickering emulzij, stabiliziranih s koloidnimi delci silicijevega dioksida. Izdelani vzorci so se med seboj razlikovali po deležu vode, olivnega olja in Aerosila 200®, ki je stabiliziral emulzijo. Ob času nič ter po enem mesecu staranja vzorcev, pri različnih temperaturah shranjevanja, smo izmerili indeks smetane, ovrednotili velikost kapljic notranje faze z optičnim mikroskopom ter izmerili viskoznost z Brookfieldovim viskozimetrom. Rezultati so pokazali, da temperatura staranja emulzij nima večje teže pri stabilnosti izdelanih emulzij. Prav tako velikost kapljic emulzij ob času nič ni imelo bistvenega vpliva pri stabilnosti Pickering emulzij, saj so bile nekatere emulzije po enem mesecu shranjevanja bolj stabilne (se niso razplastile po centrifugiranju) in so hkrati imele večje kapljice notranje faze. Najbolj pomembna parametra pri izdelavi sta bila delež stabilizacijskih delcev ter delež vode. Pri merjenju viskoznosti z Brookfieldovim viskozimetrom smo ugotovili, da ima viskoznost formulacij pomemben vpliv na njihovo dolgoročno fizikalno stabilnost, saj so bile bolj viskozne formulacije fizikalno bolj stabilne od nizko viskoznih.The cosmetic and pharmaceutical industries are fields that are continuously trying to take advantage of new technological advances while simultaneously respecting the latest global guidelines in developing quality and effective formulations. The cosmetics industry in particular has in recent years focused on more durable, clean and natural products without using a multitude of ingredients in topical formulations. A new version of classic emulsions, which do not need emulsifiers for stabilization, but merely solid colloidal particles placed on the interfacial surface thus reducing the interfacial tension, are named Pickering emulsions. The latter are less irritating to the skin in comparison to classic emulsions. Pickering emulsions are also biocompatible, have better permeability through the skin, we can easily formulate and control release of active ingredients or active pharmaceutical ingredients and the surface of the particles is easily modified. The aim of this diploma was to experimentally identify the importance of parameters that can influence the physical stability of our Pickering emulsions formulations stabilized with colloidal silica particles. The produced formulations of Pickering emulsions differed in proportions of water, olive oil and Aerosil 200®, which stabilized the emulsion. We evaluated the samples when they were first made and after one month of aging at different storage temperatures. We measured the creaming index, evaluated the droplet size of the inner phase with an optical microscope and measured the viscosity with a Brookfield viscometer. The results showed that the aging temperature of the emulsion does not have a significant impact on the stability of the produced emulsions. In addition, the size of the emulsion droplets at the beginning of the experimental work did not significantly affect the stability of the Pickering emulsions, as some emulsions were more stable after one month while having a much larger droplet size distribution. The two key parameters for emulsion stability were the proportion of stabilizing particles and the proportion of water in the formulation. When measuring the viscosity of the formulations we found that it had a significant effect on the long-term physical stability, as more viscous formulations were physically more stable than low-viscosity ones