Issue 4, 2013

Enhanced intracellular drug delivery of pH-sensitive doxorubicin/poly(ethylene glycol)-block-poly(4-vinylbenzylphosphonate) nanoparticles in multi-drug resistant human epidermoid KB carcinoma cells

Abstract

A pH-sensitive nanoparticle was prepared using our original amphiphilic block copolymer, poly(ethylene glycol)-b-poly(4-vinylbenzylphosphonate) (PEG-b-PVBP), which possesses phosphate groups as a side chain of its hydrophobic segment (termed here, phosphate nanoparticle (PNP)). The cationic anticancer drug, doxorubicin (DOX) was incorporated into a PNP (DOX@PNP), and its loading capacity was 320 mg g−1-PNP. Electrostatic and hydrophobic interactions in the core of the PNP might act synergistically to significantly improve its loading capacity. The cytotoxicity of the DOX@PNP was examined using the drug-sensitive human epidermoid KB carcinoma cell line (KB-3-1) and two different multi-drug resistance (MDR) KB cell lines (P-glycoprotein (P-gp) overexpressed (KB-C-2) and multidrug resistance protein 1 (MRP1) overexpressed (KB/MRP) cell lines). The DOX@PNP displayed a lower cytotoxic activity than free DOX against KB-3-1 cells. In contrast, the DOX@PNP showed a higher cytotoxic activity than free DOX against MDR cells. Of particular note, the cytotoxicity of the DOX@PNP against KB-C-2 cells was much higher than that against KB/MRP cells, suggesting that different mechanisms of drug reflux via the ATP binding cassette (ABC) transporting system play an important role in nanoparticle-assisted chemotherapy. Observation with confocal laser scanning microscopy (CLSM) indicated that the DOX@PNP was taken up by cells via the endocytosis pathway. The DOX@PNP was initially localized in the late endosome and lysosome, with the subsequent release of DOX from the DOX@PNP in response to the acidic pH of the late endosome and lysosome. Quantitative analysis using flow cytometry confirmed that the uptake of the DOX@PNP into KB-C-2 cells was much higher than that into KB/MRP cells, which was one of the reasons for the enhanced toxicity of the DOX@PNP against KB-C-2 cells compared to that against KB/MRP cells. Reflux of the liberated free DOX in the cytosol, via an endosomal membrane transporter, is considered one of the reasons for the low efficiency of DOX@PNP chemotherapy against KB/MRP cells. However, compared to the free DOX dose, a high dose of the DOX@PNP was effectively delivered to the nuclei of the KB/MRP cells. On the basis of these results, the pH-sensitive DOX@PNP is anticipated as one of the effective chemotherapeutic drugs with enhanced cytotoxicity for multiple types of MDR cancer cells.

Graphical abstract: Enhanced intracellular drug delivery of pH-sensitive doxorubicin/poly(ethylene glycol)-block-poly(4-vinylbenzylphosphonate) nanoparticles in multi-drug resistant human epidermoid KB carcinoma cells

Supplementary files

Article information

Article type
Paper
Submitted
23 Oct 2012
Accepted
18 Dec 2012
First published
30 Jan 2013

Biomater. Sci., 2013,1, 361-367

Enhanced intracellular drug delivery of pH-sensitive doxorubicin/poly(ethylene glycol)-block-poly(4-vinylbenzylphosphonate) nanoparticles in multi-drug resistant human epidermoid KB carcinoma cells

M. Kamimura, T. Furukawa, S. Akiyama and Y. Nagasaki, Biomater. Sci., 2013, 1, 361 DOI: 10.1039/C2BM00156J

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