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Bolest suhog oka najčešći je oblik kronične bolesti površine oka. Današnje su terapijske opcije ograničene, a lokalni kortikosteroidi, poput loteprednol etabonata, imaju potencijal za učinkovito liječenje blage do umjerene bolesti suhog oka. U posljednje vrijeme ističu se različiti terapijski nanosustavi za sigurnu i poboljšanu terapiju bolesti oka. U/V nanoemulzije niske su toksičnosti i iritacije te velikog kapaciteta za uklapanje lijekova slabo topljivih u vodi. Također, kationske nanoemulzije imaju sposobnost produljenja zadržavanja formulacije na površini oka temeljem interakcije s negativno nabijenim mucinima, a time posljedično i povećanja bioraspoloživosti lijeka. U ovom je diplomskom radu proveden razvoj formulacije oftalmičke kationske nanoemulzije kao inovativni farmaceutski oblik s potencijalom primjene u liječenju bolesti suhog oka. Cilj diplomskog rada bio je razvoj formulacije kationskih U/V nanoemulzija prikladnih za uklapanje loteprednol etabonata. Nanoemulzije su pripravljene visokoenergetskom metodom mikrofluidizacije, a njihova karakterizacija je obuhvaćala određivanje veličine kapljica unutarnje faze, indeksa polidisperznosti i zeta-potencijala. Razvoj je proveden u četiri faze: probir vrste i udjela neionske površinski aktivne tvari, probir vrste lecitina, probir udjela lecitina te ispitivanje utjecaja dodatka kationskog lipida u formulaciji. Uspješno su pripravljene kationske nanoemulzije uljne faze Capryol™ 90 stabilizirane neionskom površinski aktivnom tvari Kolliphorom® EL, lecitinom Lipoidom® S75 te kationskim lipidom cetiltrimetilamonijevim bromidom (CTAB) kao nositeljem pozitivnog naboja. Rezultati pokazuju da visoke pozitivne vrijednosti zeta-potencijala pripravljenih nanoemulzija upućuju na odgovarajuću elektrostatsku stabilizaciju kationskim lipidom CTAB-om; Kolliphor® EL u formulaciji dodatno osigurava steričku stabilizaciju; Lipoid® S75 sadrži smjesu fosfolipida koji su sastavni dio prirodnog suznog filma i pridonose njegovoj stabilnosti. Dry eye disease is the most common form of chronic ocular surface disease. Current therapy is limited, and topical corticosteroids such as loteprednol etabonate have the potential to effectively treat mild to moderate dry eye disease. Recently, various new therapeutic nanosystems have been highlighted for safe and improved treatment of eye diseases. O/W nanoemulsions are nontoxic and nonirritant and have a high capacity to incorporate poorly water-soluble drugs. Moreover, cationic nanoemulsions have the ability to prolong the retention on the surface of the eye due to interaction with negatively charged mucins, and consequently increase the bioavailability of the drug. In this thesis, the development of the formulation of ophthalmic cationic nanoemulsion as an innovative pharmaceutical form with the potential in the treatment of dry eye disease was carried out. The aim of the thesis was the development of the formulation of cationic O/W nanoemulsions suitable for incorporating loteprednol etabonate. Nanoemulsions were prepared by microfluidization, and their characterization included the determination of the internal phase droplet size, polydispersity index and zeta-potential. The development was carried out in four phases: screening of the type and content of non-ionic surfactant, screening of the type of lecithin, screening of the lecithin content and screening of the cationic lipid content. Cationic nanoemulsions of oil phase Capryol™ 90 stabilized with nonionic surfactant Kolliphor® EL, lecithin Lipoid® S75 and cationic lipid cetyltrimethylammonium bromide (CTAB) as a positive charge carrier were successfully prepared. The results show that high positive zeta-potential values of the prepared nanoemulsions indicate adequate electrostatic stabilization by the cationic lipid CTAB; Kolliphor® EL in the formulation additionally provides steric stabilization; Lipoid® S75 contains a mixture of phospholipids that are an integral part of the natural tear film and contribute to its stability.

Bolest suhog oka bolest je površine oka koja je u današnje vrijeme česta pojava. Češće se javlja kod starijih osoba, žena, osoba koje su izložene niskoj vlažnosti zraka, osoba s autoimunim poremećajima, ali i kod mlađih osoba zbog svakodnevne dugotrajne uporabe digitalnih uređaja. Kationske nanoemulzije sa svojstvom mukoadhezivnosti stupaju u kontakt s mucinima na površini oka i namijenjene su liječenju bolesti površine oka zbog duljeg zadržavanja lijeka i veće bioraspoloživosti. U liječenju simptoma blagog oblika bolesti suhog oka dobre rezultate pokazuju kationske nanoemulzije pripravljene od sastavnica sličnih onima koje su fiziološki prisutne na površini oka. U sklopu ovog diplomskog rada uspješno su pripravljene formulacije koje sadrže 2,5% (m/m) polusintetske smjese srednjelančanih triglicerida, 0,05% (m/m) lecitina, 0,25% (m/m) makrogolglicerol ricinoleata 35, 0,05% (m/m) kitozana – polusintetskog kationskog polimera sa svojstvom mukoadhezivnosti, 2,5% (m/m) glicerola – alkohola neutralnog naboja prikladnog za izotonizaciju nanoemulzija i pročišćenu vodu do 100% (m/m). Pripravljenim formulacijama ispitana su fizičko-kemijska svojstva: prosječna veličina, raspodjela veličina te zeta-potencijal kapljica unutarnje faze. Također, ispitano je svojstvo mukoadhezivnosti reološkom metodom te određivanjem veličine kapljica, raspodjele veličina kapljica i zeta-potencijala nanoemulzija nakon miješanja s mucinom. Na temelju provedenih ispitivanja kao formulacija s potencijalom za daljnji razvoj ističe se sekundarna kationska nanoemulzija s oligomerom kitozana pripravljena dodavanjem otopine oligomera kitozana u smjesu prije priprave nanoemulzije procesom mikrofluidizacije. Dry eye disease is an ocular surface disease common in present times, more expressed in certain populations, such as senior citizens, women, people exposed to low humidity, patients with autoimmune diseases as well as younger people due to excessive everyday use of digital devices. Cationic nanoemulsions of mucoadhesive properties interact with mucins on the ocular surface and are intended for treatment of ocular surface diseases due to longer retention time of the drug and consequently its greater bioavailability. In treating symptoms of mild form of dry eye disease, cationic nanoemulsions composed of components similar to those found as constituents of the ocular surface show good results. Formulations prepared for purposes of this diploma thesis are composed of 2.5% (w/w) semisynthetic mixture of middle chain fatty acids, 0.05% (w/w) lecithin, 0.25% (w/w) macrogolglycerol ricinoleate 35, 0.05% (w/w) chitosan – semisynthetic cationic polymer with mucoadhesive properties, 2.5% (w/w) glycerol – neutrally charged alcohol suitable for nanoemulsion isotonisation and purified water to 100% (w/w). Formulations were tested for their physicochemical properties: average size, size distribution as well as zeta-potential of droplets of inner phase of nanoemulsions. In addition, mucoadhesive properties were also tested using rheological method and by measuring droplet size, size distribution and zeta-potential of nanoemulsions after the addition of mucin. Based on all conducted tests, formulation showing the potential for further development is secondary cationic nanoemulsion with chitosan oligosaccharide formed by adding a solution of chitosan oligosaccharide to the mixture before the process of microfluidisation.

Nanoemulzije se ističu kao inovativni farmaceutski oblik s velikim potencijalom u liječenju bolesti suhog oka. Prednosti nanoemulzija temelje se na njihovoj strukturi i sastavu koje imaju učinak nadomještanja i stabilizacije suznog filma te na mogućnosti uklapanja slabo topljivih gluokokoritikoida kao što je loteprednol etabonat, djelatna tvar nedavno odobrena u liječenju blagih do umjerenog oblika bolesti suhog oka. Poseban potencijal imaju kationske nanoemulzije, zbog dobrih svojstava širenja po površini oka pri primjeni te produljenom zadržavanju na površini oka. Cilj ovog diplomskog rada bio je razviti sekundarnu kationsku U/V nanoemulziju s kitozanom pogodnu za uklapanje loteprednol etabonata. Nanoemulzije U/V tipa izrađene su visokoenergetskom metodom mikrofluidizacije. Kao ulja faza odabran je Capryol 90 zbog dobre topljivosti loteprednol etabonata u toj uljnoj fazi. Razvoj nanoemulzije proveden je u tri faze, (i) probir vrste i udjela neionske površinski aktivne tvari, (ii) probir vrste i udjela anionske površinski aktivne tvari te (iii) probir udjela niskomolekulskog kitozana. U svih fazama razvoja provedena je fizičko-kemijska karakterizacija nanoemulzija u vidu određivanja veličine i raspodjele veličina kapljica disperzne faze te zeta-potencijala. Na temelju provedene fizičko-kemijske karakterizacije sekundarna kationska nanoemulzija s 0,05 % (m/m) kitozana, 5 % (m/m) Capryola® 90, 0,25% (m/m) makrogol 15 hidroksistearata i 0,1% (m/m) lecitina Lipoid S75 ističe se kao vodeća formulacija s najvećim potencijalom za uklapanje loteprednol etabonata. Nanoemulsions stand out as an innovative dosage form with great potential in the treatment of dry eye disease. The benefits of nanoemulsions are based on (i) their structure and composition, which have the effect of replacing and stabilizing the tear film; and (ii) the ability to incorporate poorly soluble glucocorticoids such as loteprednol etabonate, an active substance recently approved in the treatment of mild to moderate dry eye disease. Cationic nanoemulsions have a unique potential due to their good spreading properties on the eye surface and prolonged retention on the eye surface. The aim of this thesis was to develop a secondary cationic O/W nanoemulsion with chitosan suitable for the incorporation of loteprednol etabonate. O/W type nanoemulsions are prepared by microfluidization. Capryol® 90 was chosen as the oil phase due to the good solubility of loteprednol etabonate in this oil phase. The development of the nanoemulsion was carried out in three phases, (i) screening of the type and content of nonionic surfactants, (ii) screening of the type and content of anionic surfactants, and (iii) screening of the content of low molecular weight chitosan. In all phases of development, physicochemical characterization of nanoemulsions was performed in the terms of determining the size and size distribution of droplets of the dispersed phase and zeta potential. Based on the performed physicochemical characterization, the secondary cationic nanoemulsion with 0.05% (w/w) chitosan, 5% (w/w) Capryola® 90, 0.25% (w/w) macrogol 15 hydroxystearate and 0.1% (w/w) Lecithin Lipoid® S75 stands out as the leading formulation with the greatest potential for incorporation of loteprednol etabonate.

Bolest suhog oka je multifaktorijalna bolest koju karakterizira nestabilnost i hiperosmolarnost suznog filma te upala površine oka. Kationske nanoemulzije tipa ulje u vodi (U/V) predstavljaju napredak u liječenju bolesti suhog oka služeći kao tehnološka platforma za uklapanje slabo topljivih djelatnih tvari, omogućujući pritom njihovo produljeno zadržavanje na površini oka te istodobnu nadoknadu i stabilizaciju narušenog suznog filma. Cilj ovog doktorskog rada je razvoj funkcionalne kationske nanoemulzije za liječenje bolesti suhog oka. U tu su svrhu pripravljena dva tipa nanoemulzija korištenjem mikrofluidizatora: primarne kationske nanoemulzije sa stearilaminom i sekundarne kationske nanoemulzije s kitozanom. Primarne kationske nanoemulzije s rastućim udjelima stearilamina male su veličine kapljica (< 100 nm), primjerene disperznosti (PDI ≤ 0,25), pozitivnog zeta-potencijala (3,1-25,5 mV), prikladne pH vrijednosti, male viskoznosti i površinske napetosti 31,3-35 mN m-1. Pripravljene nanoemulzije stabilne su tijekom petomjesečne pohrane. Nakon miješanja s disperzijom mucina zapažene su promjene u veličini kapljica i zeta-potencijalu koje ukazuju na interakciju s mucinom. Takve promjene nisu bile izraženije s povećanjem udjela stearilamina na više od 0,05 % (m/m). Vijabilnost 3D HCE-T modela iznosila je najmanje 90 % nakon izlaganja pripravljenim formulacijama. Sekundarne kationske nanoemulzije pripravljene s manjim (NC1: 0,05 %, m/m) i većim (NC2: 0,3 %, m/m) udjelom kitozana veličine su kapljica približno 180 nm, veće homogenosti (PDI < 0,2) i pozitivnog zeta-potencijala (18,7 i 30 mV). Iako je formulacija NC1 pokazala bolju stabilnost, ibuprofen je uspješno uklopljen u obje formulacije (INC1 i INC2). Fizičkokemijska svojstva (pH, viskoznost, osmolarnost i površinska napetost) pripravljenih formulacija unutar su raspona prikladnog za primjenu na oko. Formulacija INC1 stabilnija je od formulacije INC2 nakon jednomjesečne pohrane. Bakteriološka filtracija prikladna je metoda sterilizacije pripravljenih formulacija. Oslobađanje ibuprofena iz pripravljenih formulacija značajno je brže nego iz uljne otopine i suspenzije ibuprofena. Reološka karakterizacija formulacija pomiješanih s disperzijom mucina pokazala je njihov mukoadhezivni karakter koji, ipak, nije izraženiji kod formulacije INC2 s većim udjelom kitozana. Ispitivanja na 3D HCE-T modelu i ex vivo modelu rožnice svinje pokazala su izuzetnu biokompatibilnost INC1 formulacije. Uzimajući u obzir sve rezultate, nanoemulzija s 0,05 % (m/m) stearilamina i INC1 formulacija ističu se kao vodeće formulacije s velikim potencijalom za liječenje bolesti suhog oka. Dry eye disease is a multifactorial disease characterized by tear film instability and hyperosmolarity and ocular surface inflammation. Oil-in-water (O/W) cationic nanoemulsions represent a progress in dry eye disease treatment serving as a technological platform for incorporation of poorly soluble drugs, enabling prolonged residence time at the ocular surface and, at the same time, replenishment and stabilization of compromised tear film. The aim of this doctoral thesis is development of a functional cationic nanoemulsion for dry eye disease treatment. For this purpose two nanoemulsion types were prepared using microfluidizer: primary cationic nanoemulsions with stearylamine and secondary cationic nanoemulsions with chitosan. Primary cationic nanoemulsions with increasing stearylamine weight fraction are characterized with small droplet size (< 100 nm), low PDI (≤ 0.25), positive zeta-potential (3.1-25.5 mV), appropriate pH, low viscosity and surface tension 31.3-35 mN m-1. The nanoemulsions are stable after 5-month storage. Changes in nanoemulsion droplet size and zeta-potential were observed after mixing with mucin dispersion, which indicates interactions with mucin. However, the changes were not more pronounced with the increase in stearylamine weight fraction above 0.05 % (w/w). Viability of 3D HCE-T model was at least 90 % after exposure to the prepared formulations. Secondary cationic nanoemulsions prepared with low (NC1: 0.05 %, w/w) and high (NC2: 0.3 %, w/w) chitosan weight fraction are characterized with droplet size of around 180 nm, greater homogeneity (PDI < 0.2) and positive zeta-potential (18.7 and 30 mV). Although the formulation NC1 showed greater stability, ibuprofen was successfully incorporated in both formulations (INC1 and INC2). The physico-chemical properties (pH, viscosity, osmolarity and surface tension) of the prepared formulations are within the range acceptable for ophthalmic application. The formulation INC1 is more stable than the formulation INC2 after 1-month storage. Filtration is an appropriate sterilization method for the prepared formulations. Ibuprofen release from the prepared formulations is significantly faster than from ibuprofen oil solution and suspension. Rheological characterization of the formulations mixed with mucin dispersion showed their mucoadhesive character which, however, is not more pronounced with the formulation INC2 with higher chitosan weight fraction. The assays performed using 3D HCE-T model and ex vivo porcine cornea model showed remarkable biocompatibility of the formulation INC1. Taking everything into account, the nanoemulsion with 0.05 % (w/w) stearylamine and INC1 formulation point out as the lead formulations holding great potential for the treatment of dry eye disease.