Development of lipid/alginate nanoparticles for nasal delivery of lipophilic drugs

Specifične anatomske, fiziološke i histološke karakteristike nosne šupljine osiguravaju brojne prednosti nazalne primjene lijekova u odnosu na oralnu ili parenteralnu primjenu. Nazalnom primjenom postiže se brz lokalni učinak uz primjenu manjih doza djelatne tvari, a moguća je i direktna dostava lijeka do mozga te sistemski učinak za lijekove nedovoljne oralne bioraspoloživosti. Kako bi se prevladale prepreke nazalnoj apsorpciji, ali i povećala stabilnost, bioraspoloživost i učinkovitost djelatne tvari, razvijaju se novi terapijski sustavi poput nanočestica. Cilj ovog rada bio je razviti lipidno-alginatne nanočestice željene veličine, površinskih svojstava i biokompatibilnosti, prikladne za uklapanje i nazalnu primjenu lipofilnih lijekova, korištenjem metode ionotropnog geliranja. U pripravi lipidno-alginatnih nanočestica, uz natrijev alginat, korišteni su lecitin S45 te kationski lipid dimetil dioktadecil amonijev bromid (DDAB). Svojstva razvijenih nanočestica ovisila su o masenom omjeru kationskog lipida i lecitina S45. Pri izradi lipidnih nanočestica, maseni omjer kationskog lipida i lecitina veći od 3:50 rezultirao je nanočesticama pozitivnog naboja. Indeks polidisperznosti lipidnih nanočestica smanjen je dodatkom DDAB. Lipidno-alginatne nanočestice negativno su nabijene, a one pripravljene s masenim omjerom kationskog lipida i lecitina većim od 3:50 karakterizirane su zeta-potencijalom koji osigurava fizičku stabilnost suspenzije nanočestica (negativniji od -30 mV). Pri istim masenim omjerima uočeno je značajno povećanje veličine lipidno-alginatnih nanočestica u odnosu na same lipidne nanočestice. Povećanje koncentracije natrijevog alginata iznad 200 μg/ml u vodenoj otopini korištenoj u izradi lipidno-alginatnih nanočestica nije utjecalo na svojstva nastalih nanočestica. Nanočestice s najvećim potencijalom za razvoj terapijskog sustava za nazalnu primjenu su one s masenim omjerom kationskog lipida i lecitina od 5:50, 7:50, 8:50 i 9:50; maseni omjer lecitina i alginata iznosio je 10:1. Suspenzije lipidno-alginatnih nanočestica u ispitivanim koncentracijama (50-400 μg/ml) nisu utjecale na vijabilnost Caco-2 stanica. U odabrane nanočestice uspješno je uklopljen lijek loratadin te su im određena fizičko-kemijska svojstva: srednji promjer kretao se od 213,5 do 234,1 nm; indeks polidisperznosti između 0,21 i 0,29; zeta-potencijal od -25,1 do -36,4 mV; uspješnost uklapanja loratadina od 14,1 do 17,9%. Najuspješnije uklapanje postignuto je kod nanočestica s najmanjim omjerom kationskog lipida i lecitina (5:50, m/m).Specific anatomical, physiological and histological characteristics of the nasal cavity provide a lot of advantages of nasal drug delivery, comparing with the oral or parenteral application. Nasal delivery can provide fast local action with lower doses of drugs as well as a direct delivery to the brain and a systemic activity of drugs with poor oral bioavailability. To overcome barriers for nasal absorption, but also to enhance stability, bioavailability and efficacy of the drug, new drug delivery systems such as nanoparticles are being developed. The aim of this work was to develop lipid/alginate nanoparticles of desirable size, surface characteristics and biocompatibility, appropriate for encapsulation and nasal delivery of lipophilic drugs, employing ionic gelation method. In the preparation of the lipid/alginate nanoparticles, apart from sodium alginate, lecithin S45 and cationic lipid dimethyldioctadecylammonium bromide (DDAB) were used. Properties of the developed nanoparticles depended on the cationic lipid-to-lecithin weight ratio. In the preparation of lipid nanoparticles, a cationic lipid-to-lecithin weight ratio higher than 3:50 resulted in positively charged nanoparticles. The polydispersity index was decreased by adding DDAB. The lipid/alginate nanoparticles were negatively charged, while nanoparticles prepared with cationic lipid-to-lecithin weight ratio higher than 3:50 were characterized by zeta-potential that ensures physical stability of nanoparticle suspensions (less than -30 mV). A significant enhancement in the size of lipid/alginate nanoparticles, in comparison with the lipid nanoparticles, was noticed at the same weight ratios. Increase in sodium alginate concentration above 200 μg/ml in aqueous solution used in the preparation of lipid/alginate nanoparticles did not influence properties of the prepared nanoparticles. Nanoparticles with the greatest potential for development of a drug delivery system for nasal application are nanoparticles with cationic lipid-to-lecithin weight ratio of 5:50, 7:50, 8:50 and 9:50; the weight ratio of lecithin and alginate was 10:1. Lipid/alginate nanoparticle suspensions in the tested concentrations (50-400 μg/ml) did not influence the viability of Caco-2 cells. Loratadine was successfully incorporated into the selected nanoparticles gaining the nanoparticle physiochemical properties as follows: mean diameter from 213.5 to 234.1 nm; polydispersity index from 0.21 to 0.29; zeta potential from -25.1 to -36.4 mV; entrapment efficacy of loratadine from 14.1 to 17.9%. The highest entrapment efficacy was achieved for nanoparticles with the lowest cationic lipid-to-lecithin weight ratio (5:50, w/w)