In vitro ocular safety assessment of melatonin-loaded lecithin/chitosan nanoparticles

Oftalmička primjena lijeka jedan je od najvećih farmaceutsko-tehnoloških izazova, s obzirom na specifičnu anatomiju i fiziologiju oka koje ograničavaju dostavu molekule lijeka na ciljno mjesto djelovanja u potrebnoj količini i trajanju. Danas se razvijaju inovativni terapijski nanosustavi koji mogu osigurati dulje vrijeme zadržavanja lijeka na mjestu primjene, te veću bioraspoloživost lijeka u oku, odnosno prevladati tkivne (biološke) i dinamičke barijere oka. Pri razvoju takvih terapijskih nanosustava vrlo je važno od samog početka razmatrati njihovu biokompatibilnost i toksičnost, s ciljem utvrđivanja sigurnosti njegove oftalmičke primjene. Cilj ovog rada bio je ispitati biokompatibilnost lecitinsko-kitozanskih nanočestica s melatoninom in vitro, koristeći imortalizirane stanice humanog epitela rožnice (HCE-T), kako bi se procijenila sigurnost njihove oftalmičke primjene u svrhu liječenja povišenog očnog tlaka. Lecitinsko-kitozanske nanočestice srednjeg promjera od 222,8 ± 1,0 nm, pozitivnog zeta-potencijala (21,4 ± 0,4 mV) te zadovoljavajućeg sadržaja melatonina (6,6 ± 1,0 %) uspješno su pripravljene ionskom interakcijom lecitina i kitozana. Uklapanje melatonina nije značajnije utjecalo na veličinu nanočestica niti na površinski naboj nanočestica, što pokazuje da je melatonin uspješno uklopljen unutar lipofilnih domena nanočestica. Oslobađanje melatonina iz lecitinsko-kitozanskih nanočestica bilo je sporije u odnosu na oslobađanje melatonina iz lecitinskih nanočestica. Biokompatibilnost nanočestica s melatoninom ispitana je praćenjem metaboličke aktivnosti stanica epitela rožnice (HCE-T) in vitro nakon izlaganja suspenzijama nanočestica. Izlaganje HCE-T stanica otopinama kitozana pri koncentraciji od 10 i 20 μg ml-1 rezultiralo je značajnim smanjenjem vijabilnosti stanica. Suprotno tome, vijabilnost HCE-T stanica nije se značajnije promijenila nakon izlaganja suspenzijama lecitinsko-kitozanskih nanočestica pri ispitivanim koncentracijama kitozana (2,5 – 20 μg ml-1). Time je pokazan potencijal razvijenih nanočestica s melatoninom za sigurnu oftalmičku primjenu.Ophthalmic drug delivery is one of the largest pharmaceutical and technological challenges, considering specific eye anatomy and physiology that limit efficient drug delivery to the target ocular tissue at sufficient extent and duration. Currently, innovative delivery nanosystems with the potential to ensure prolonged retention time at the administration site and improved eye-related drug bioavailability, overcoming biological and dynamic ocular barriers, are being developed. Concomitantly with the development of such nanosystems it is important to consider their biocompatibility and toxicity, with the aim to determine the safety of their ocular administration. The aim of this study was to determine the biocompatibility of melatonin-loaded lecithin/chitosan nanoparticles in vitro using immortalised cells of human corneal epithelia (HCE-T), with the aim to assess the safety of their ocular administration in the treatment of increased intraocular pressure. Lecithin/chitosan nanoparticles with mean diameter of 222.8 ± 1.0 nm, positive zeta potential (21.4 ± 0.4 mV) and appropriate melatonin content (6.6 ± 1.0 %) were successfully prepared by ionic interaction between lecithin and chitosan. Entrapment of melatonin did not influence the size or zeta-potential of nanoparticles, indicating that melatonin was successfully entrapped into lipophilic domains of nanoparticles. Melatonin release from lecithin/chitosan nanoparticles was slower than melatonin release from lecithin nanoparticles. Biocompatibility of nanoparticles was determined by monitoring of metabolic activity of HCE-T cells treated with the suspensions of nanoparticles. Treatment of HCE-T cells with chitosan solution at the concentrations of 10 and 20 μg ml-1 resulted in significant decrease of cell viability. On the contrary, there was no significant change in the viability of HCE-T cells treated with lecithin/chitosan nanoparticles at chitosan concentration ranging from 2.5 to 20 μg ml-1. Results obtained suggested that melatonin-loaded lecithin/chitosan nanoparticles could be safely applied to the ocular surface