Size effects of self-assembled block copolymer spherical micelles and vesicles on cellular uptake in human colon carcinoma cells

Block copolymers, poly(oligo ethylene glycol methyl ether methacrylate)-block-poly(styrene), POEGMEMA-b-PS, with various block lengths were prepared via RAFT polymerization and subsequently self-assembled into various aggregates to investigate their uptake ability into human colon carcinoma cell lines, WiDr. By varying the ratio of the hydrophobic to hydrophilic block lengths in the block copolymers various morphologies including spherical micelles, cylindrical micelles (rods), vesicles and large compound micelles could be generated. With increasing length of the hydrophobic block the micelles grew in size until chain stretching caused the transition to rods and then to other aggregates. Micelles of two sizes with a hydrodynamic diameter of 34 and 49 nm, respectively, and two different vesicles (hydrodynamic diameters 99 nm and 150 nm) were further studied towards their ability to be taken up by human colon carcinoma cells. Results indicated that the smaller sized micelles were taken up almost immediately while an increased sized micelle was taken up, however at a slower rate. Though larger vesicle aggregates were taken up at a slower rate, eventually all cells internalized aggregates to a similar amount after a few hours.