The Effect of Polyoxyethylene-Polyoxypropylene Triblock Copolymers on the Loading Amount of Poly(Lactic-co-Glycolic Acid) Copolymer-based Microparticles Coupled with Chlorine <i>e</i><sub>6</sub> or Ethidium Bromide into Mesenchymal Stem Cells
In this study we investigated the effect of different polyoxyethylene-polyoxypropylene triblock copolymers, their concentrations and the way of influence on the loading of poly(lactic-co-glycolic acid) copolymer-based microparticles coupled with drugs, radachlorine (chlorine e <sub>6</sub>) or ethidium bromide, into mesenchymal stem cells. It is shown that drugs encapsulated in microparticles affect the loading of these particles into the cytoplasm of mesenchymal stem cells. The number of cells that have entrapped particles loaded with chlorine e<sub>6</sub> in the control is approximately twice as low as that in the experiments with ethidium bromide. Pretreatment of microparticles with triblock copolymers makes their loading into cells more efficient as compared to the situation when triblock copolymers and particles are simultaneously added into the growth medium. Treatment of ethidium bromide-coupled microparticles with triblock copolymers has no effect on their entrapment by mesenchymal stem cells as compared to the control. Pluronic 123 is an exception: treatment of particles with this compound at concentrations of 1 or 2%, the loading of particles into the cells increases by a factor of 11 and 5, respectively, as compared to the control. Pretreatment of particles coupled with chlorine e<sub>6</sub> with 4% of triblock copolymers is the most efficient procedure; the loading of the pretreated particles into cells increases by a factor of approximately 3 to 1.