Anticancer therapeutic self-aggregates of sphingolipid metabolite-grafted poly(amino acid)-derivative and their enhanced intracellular delivery

Novel sphingolipid metabolite conjugated poly(amino acid)-derivative, poly-α,β-(2-hydroxylethyl l-aspartamide)-g-phytosphingosine copolymer, was designed as an anticancer prodrug-type carrier for enhanced intracellular uptake and physicochemical properties of polymeric micelle-like aggregates were evaluated. The resultant micelle-like aggregates showed a spherical shape and uniform size with a diameter less than 20 nm in an aqueous solution upon the increased number of phytosphingosine grafts. By the steady-state fluorescence of pyrene in aqueous polymer solutions, critical aggregation concentration (CAC) was obtained in the range of 0.166–0.0036 mg/ml and Kv, equilibrium partition constants of the pyrene in the self-aggregate solutions were estimated to be from 2.39 × 103 to 1.96 × 106. Phytosphingosine-grafted polymeric micelle-like aggregates as small as 20 nm were efficiently delivered into various cancer cell lines including oral, breast and colon carcinoma with the extent which is comparable to the level of targeting carrier system. The enhanced cellular uptake and anticancer therapeutic effect was evaluated by flow cytometry, confocal laser scanning microscopy (CLSM), and MTT assay.