Uticaj holesterola na fluidnost membrane lipozoma, veličinu lipozomnih čestica i njihov zeta potencijal

Abstract

Cilj ove studije bilo je ispitivanje uticaja različitih sadržaja holesterola (0- 50 mol %) na fluidnost membrana, veličinu čestica, polidisperzni indeks (PDI) i zeta potencijal lipozoma, pripremljenih metodom tankog filma i upotrebom fosfatidilholina soje, Phospholipon 90 (Ph). Merenjem polarizacije (p) i anizotropije (r), u temperaturnom intervalu od 20 do 60˚C, upotrebom fluorofore 1,6-difenil-1,3,5-heksatrien (DPH), pokazano je da povećanjem koncentracije holesterola u lipozomima dolazi do smanjenja fluidnosti i povećanja rigidnosti membrane lipozoma. Foton korelaciona spektroskopija je kod malih unilamelarnih lipozoma (SUV) pokazala kontinuirano povećanje veličine čestica sa porastom koncentracije holesterola, dok kod multilamelarnih lipozoma (MLV) trend kontinuiranog rasta čestica nije primećen. U oba slučaja, statistički značajno veće čestice su dobijene sa najvišom koncentracijom holesterola (50 mol %). Prema dobijenim vrednostima PDI, samo SUV bez holesterola i sa 5, 30 i 40 mol % holesterola, poseduju usku raspodelu čestica po veličini (PDI manji od 0,2). Vrednosti zeta potencijala, kao važnog parametra stabilnosti sistema, bile su negativne u svim uzorcima, dok su najviše apsolutne vrednosti dostignute sa 50 mol % holesterola. Optimalna koncentracija holesterola za dobijanje lipozoma odgovarajuće stabilnosti i fluidnosti membrana jeste 50 mol %.

The aim of this study was examination of the influence of various cholesterol content (0-50 mol %) on membrane fluidity, vesicle size, polydispersity index (PDI) and zeta potential of liposomes prepared using the thin film method and phosphatidylcholine from soybean, Phospholipon 90 (Ph). Polarization (p) and anisotropy (r) measurements, within the temperature range of 20 to 60˚C, using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH), have shown that increasing the cholesterol content in the liposomes decreased the fluidity and enhanced the rigidity of liposomal membranes. The photon correlation spectroscopy data have shown that the size of small unilamellar vesicles (SUV) increased continuously with the increase in cholesterol concentration, while multilamellar vesicles (MLV) did not show similar trend. In both cases, significantly larger vesicles were obtained using the highest content of cholesterol (50 mol %). According to the PDI values, only SUV without cholesterol and with 5, 30 and 40 mol % of cholesterol exhibit narrow size distribution (PDI < 0,2). Furthermore, values of zeta potential, as an important parameter of system stability, were negative in all samples, while the highest absolute values were achieved with 50 mol % of cholesterol. The optimal concentration of cholesterol to obtain stabile liposomes and an appropriate fluidity of the membrane has been 50 mol %.