Charge reversal self-emulsifying drug delivery systems: A comparative study among various phosphorylated surfactants

Phosphorylated surfactants having ethoxylate spacer arms are promising excipients for charge reversal self-emulsifying drug delivery systems (SEDDS).

1,2-Dipalmitoyl-sn-glycero-3-phosphatidic acid disodium salt (PA), 2-((2,3-bis(oleoyloxy)propyl)dimethylammonio)ethyl hydrogen phosphate (DOCP), nonylphenol monophosphate ester (PNPP), C12-15 alcohol 3 ethoxylate phosphate ester (PME) and polyoxyethylene (9) dioctanoyl glycerol pyrophosphate (DGPP) loaded SEDDS were developed and characterized. Zeta potential of SEDDS was measured before and after incubation with intestinal alkaline phosphatase (IAP). Phosphate release was monitored by incubation of SEDDS with isolated as well as cell-associated IAP. Primary amine content on the surface of SEDDS was determined in parallel. Cytotoxicity was evaluated on Caco-2 cells and in vitro hemolysis test was performed. Cellular uptake studies were performed by confocal scanning microscopy.

SEDDS formulations exhibited a size in the range of 17 and 193 nm and a polydispersity index (PDI) ≤ 0.5. Charge reversal from negative to positive values could be achieved in case of PNPP and PME loaded SEDDS with a zeta potential changing from -13 mV to +9 mV and from -7 to +2 mV, respectively, within 6 h. Significant amounts of phosphate were released from PNPP and PME loaded SEDDS incubated with isolated IAP and from all formulations incubated with cell-associated IAP in accordance with an increase in primary amines on the surface of oily droplets. SEDDS exhibited a concentration and time-dependent cytotoxicity. PNPP and PME SEDDS displayed an increased cellular uptake.