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  • Pluronic  (2)
  • intestinal delivery  (2)
  • Springer  (4)
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  • Springer  (4)
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  • 1
    ISSN: 1573-904X
    Keywords: block copolymer ; cancer ; multidrug resistance ; Pluronic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Using monolayers of human pancreatic adenocarcinoma cells (Panc-1) that express multidrug resistance-associated protein (MRP), the present work investigates the effects of Pluronic block copolymers on the functional activity of MRP. Methods. The studies examined the accumulation and efflux of the MRP selective probe fluorescein (FLU) in Panc-1 cell monolayers with and without Pluronic P85 (P85), Pluronic L81 (L81) and Pluronic F108 (F108). Results. Treatment of Panc-1 cells with P85 resulted in concentration-dependent increases in FLU accumulation and elimination of FLU sequestration in vesicular compartments in these cells. The effects of P85 were selective for FLU in the Panc-1 cell monolayers. Inhibition of MRP-mediated transport was dependent on the composition of Pluronic block copolymer: the more hydrophobic copolymer had the greater effect on FLU uptake in Panc-1 monolayers (L81 〉 P85 〉 F108). Conclusions. This paper demonstrates for the first time that Pluronic block copolymers inhibit multidrug resistance-associated protein (MRP). The similarities in the effects of Pluronic block copolymers on MRP and P-glycoprotein drug efflux systems suggest that a single unifying mechanism may explain the inhibition observed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: doxorubicin ; rhodamine ; multidrug resistance ; Pluronic ; block copolymers ; hypersensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Previous studies have demonstrated that Pluronic block copolymers hypersensitize multiple drug resistant (MDR) cancer cells, drastically increasing the cytotoxic effects of anthracyclines and other anticancer cytotoxics in these cells. This work evaluates the dose dependent effects of these polymers on (i) doxorubicin (Dox) cytotoxicity and (ii) cellular accumulation of P-glycoprotein probe, rhodamine 123 (R123) in MDR cancer cells. Methods. Dox cytotoxicity and R123 accumulation studies are performed on monolayers of drug-sensitive (KB, MCF-7, Aux-Bl) and MDR (KBv, MCF-7/ADR, CHrC5) cells. Results. Both tests reveal strong effects of Pluronic copolymers observed at concentrations below the critical micelle concentration (CMC) and suggest that these effects are due to the copolymer single chains ('unimers'). Using block copolymers with various lengths of hydrophobic propylene oxide (PO) and hydrophilic ethylene oxide (EO) segments these studies suggest that the potency of Pluronic unimers in MDR cells increases with elevation of the hydrophobicity of their molecule. Optimization of Pluronic composition in R123 accumulation and Dox cytotoxicity studies reveals that Pluronic copolymers with intermediate lengths of PO chains and relatively short EO segments have the highest net efficacy in MDR cells. Conclusions. The relationship between the structure of Pluronic block copolymers and their biological response modifying effects in MDR cells is useful for determining formulations with maximal efficacy with respect to MDR tumors.
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  • 3
    ISSN: 1573-904X
    Keywords: block copolymer ; intestinal delivery ; drug ; micelles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The present work characterizes the effects of Pluronic copolymers on the transport of a P-gp-dependent probe, rhodamine 123 (R123) in Caco-2 cell monolayers. Methods. The accumulation and efflux studies were performed on the confluent Caco-2 monolayers using fluorescent probes with and without Pluronic copolymers. Results. At concentrations below the critical micelle concentration single chains ("unimers”) of Pluronic P85 enhanced the accumulation and inhibited the efflux of R123 in Caco-2 monolayers. The transport of the P-gp-independent probe, rhodamine 110 was not altered under these conditions. In contrast the micelles increased R123 accumulation to a much lower extent when compared to the unimers and enhanced R123 efflux in Caco-2 monolayers. Conclusions. Pluronic P85 unimers increase accumulation of a P-gp-dependent drug in Caco-2 monolayers through inhibition of the P-gp efflux system. The mechanism of the micelle effect is not known, however, it is very similar to the micelle effects in BBMEC. This has been previously shown to involve vesicular transport of the micelle-incorporated drug. The study suggests that Pluronic copolymers can be useful in increasing oral absorption of select drugs.
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  • 4
    ISSN: 1573-904X
    Keywords: pluronic block copolymer ; intestinal delivery ; drug ; micelles ; blood brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Using polarized bovine brain microvessel endothelial cells (BBMEC) monolayers as in vitro model of the blood brain barrier and Caco-2 monolayers as a model of the intestinal epithelium, the present work investigates the effects of Pluronic P85 block copolymer (P85) on the transport of the P-gycoprotein (P-gp)- dependent probe, rhodamine 123 (R123). Methods. The permeability and cell efflux studies are performed with the confluent cell monolayers using Side-Bi-Side diffusion cells. Results. At concentrations below the critical micelle concentration, P85 inhibits P-gp efflux systems of the BBMEC and Caco-2 cell monolayers resulting in an increase in the apical to basolateral permeability of R123. In contrast, at high concentrations of P85 the drug incorporates into the micelles, enters the cells and is then recycled back out to the apical side resulting in decrease in Rl 23 transport across the cell monolayers. Apical to basolateral permeability of micelle-incorporated R123 in BBMEC monolayers was increased by prior conjugation of P85 with insulin, suggesting that modified micelles undergo receptor-mediated transcytosis. Conclusions. Pluronic block copolymers can increase membrane transport and transcellular permeability in brain microvessel endothelial cells and intestinal epithelium cells. This suggests that these block copolymers may be useful in designing formulations to increase brain and oral absorption of select drugs.
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