Microemulsion systems: Characteristics and application in drug delivery

Abstract

During the last three decades there were intensive investigations on potential application of microemulsion colloidal vehicles in drug delivery. Researchers had put the greatest effort in investigation of oral, dermal/transdermal, ocular and parenteral delivery of drugs from microemulsions. Numerous applications of these systems lie in their unique properties: termodinamical stability, heterogenous microstructure with dynamic character, ultralow surface tension, large interface area and significant capacity for solubilisation of hydrophilic and lipophilic drugs. In general, the observations obtained within numerous studies, pointed out the efficacy of O/W, W/O and bicontinuous microemulsions, as well as Self-Microemulsifying Drug Delivery Systems (SMEDDS), to improve bioavailability of drugs with low solubility and/or low permeability. Therefore, microemulsions are current reaction media for synthesis of nanoparticulate carriers of drugs (Solid Lipid Nanoparticles (SLN), polymeric nanoparticles) as well as for nanoingenireeng of poorly soluble drugs.

Tokom poslednjih trideset godina intenzivno se istražuju mogućnosti za primenu koloidnih vehikuluma tipa mikroemulzija za isporuku lekovitih supstanci na odgovarajuće mesto u organizmu. Najveći napori uloženi su na polju istraživanja peroralne, dermalne/transdermalne, okularne i parenteralne isporuke lekova iz mikroemulzija. Raznovrsna primena ovih sistema zasniva se na njihovim jedinstvenim karakteristikama: termodinamička stabilnost, dinamički karakter i heterogenost mikrostrukture, izuzetno (ultra) nizak međupovršinski napon, velika međupovršina i značajan kapacitet za solubilizaciju/rastvaranje hidrosolubilnih i liposolubilnih lekovitih supstanci. Generalizovana zapažanja u sprovedenim istraživanjima ukazuju na efikasnost mikroemulzija tipa ulje u vodi (U/V), voda u ulju (V/U) i bikontinuiranih mikroemulzija, kao i samo-mikroemulgujućih sistema za isporuku lekova (eng. Self- Microemulsifying Drug Delivery Systems - SMEDDS), u smislu poboljšavanja biološke raspoloživosti slabo rastvorljivih i/ili slabo permeabilnih lekova. Osim toga, mikroemulzije se upotrebljavaju kao reakcioni medijumi za dobijanje nanočestičnih nosača za lekovite supstance tipa čvrstih lipidnih nanočestica (eng. Solid Lipid Nanoparticles - SLN) i polimernih nanočestica, kao i za nanoinžinjering slabo rastvorljivih lekovitih supstanci.