Intracellular uptake of Pluronic copolymer: effects of the aggregation state

The effect of the Pluronic P-105 aggregation state on its uptake by HL-60 cells was studied by flow cytometry, fluorescence spectroscopy, and confocal and fluorescence microscopy using a fluorescently labeled Pluronic P105. In the low concentration region below the critical micelle concentration (CMC), Pluronic uptake was proportional to the concentration in the incubation medium. The proportionality broke sharply above the CMC, revealing a less efficient intracellular uptake of Pluronic micelles than that of unimers. The data suggested that Pluronic micelles were internalized via fluid-phase endocytosis while unimers were internalized via diffusion through plasma membranes. Based on the above findings, the shielding effect of Pluronic micelles on drug intracellular uptake was explained.