Our previous study demonstrated that the retention of drug in the hydrophobic core of Soluplus micelle greatly impeded drug absorption from gastrointestinal tract. Using supersaturated polymeric micelles can improve drug release, however, insufficient maintaining of supersaturation of drug is still unfavorable for drug absorption. Here, we report adding small amount of small molecule, sodium dodecyl sulfate (SDS), to Soluplus solution can form a Soluplus-SDS complex. This complex not only showed a higher solubilization capability for the model drug cyclosporine A (CsA), but also maintained a longer period of and higher supersaturation than was achieved with Soluplus alone. The Soluplus-SDS interactions were characterized by analyzing surface tension, small-angle X-ray scattering (SAXS), fluorescence spectra, and nuclear magnetic resonance spectroscopy. The results demonstrated that the formation of Soluplus-SDS complex via SDS adsorption on hydrophobic segments of Soluplus, which have more hydrophobic domain than that of Soluplus micelle, contributed significantly to the solubilization and stabilization of supersaturated CsA. Using this amphiphilic copolymer-small molecule surfactant system, the cellular uptake and rat in vivo absorption of CsA were more effectively achieved than pure Soluplus. The area under the plasma concentration-time curve (AUC) and the maximal plasma concentration (Cmax) achieved by CsA-loaded Soluplus-SDS complex were 1.58- and 1.8-times higher than the corresponding values for CsA-loaded pure Soluplus, respectively. This study highlighted the benefits of Soluplus-SDS complex for optimizing the solubilization and oral absorption of a drug with low aqueous solubility.
Keywords: Amphiphilic polymer–ionic surfactant interaction; Sodium dodecyl sulfate; Solubilization; Soluplus; Supersaturation.
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