Intracellular delivery of doxorubicin with RGD-modified sterically stabilized liposomes for an improved antitumor efficacy: In vitro and in vivo
Section snippets
Abbreviations:
- DOX
doxorubicin
- Chol
cholesterol
- SPC
soya phosphatidylcholine
- DSPE-PEG
methoxypolyetheleneglycol (Mw 2000)-distearylphosphatidylethanolamine
- DSPE-PEG-BTC
1,2-dioleyol-sn-glycero-3-phosphoethanolamine-n-[poly(ethyleneglycol)]-N-benzotriazole carbonate, PEG Mw 3400
- RGD
arginine–glycine–aspartic acid
- SSL
sterically stabilized liposomes
- SSL-DOX
DOX-loaded SSL
- RGD-SSL
RGD-modified SSL
- DOX-RGD-SSL
DOX-loaded RGD-SSL
- IC50
50% inhibitory concentration
- DMEM
Dulbecco's modification of Eagle's medium
- PBS
phosphate-buffered
INTRODUCTION
Liposomes have been extensively investigated as targeting carriers for a variety of anticancer agents. The drug-loaded liposomes are usually injected intravenously for systemic application. However, there is usually rapid clearance of them from the circulation by the reticuloendothelial system (RES). To avoid this disadvantage, “Stealth® technology” (or called sterically stabilized liposomes, SSL) has been developed.1 Growing solid tumors have capillaries with increased permeability and
Materials
Methoxypolyetheleneglycol (Mw 2000)-distearylphosphatidylethanolamine (DSPE-PEG) was purchased from NOF Co. (Tokyo, Japan). DSPE-PEG-BTC [1,2-dioleyol-sn-glycero-3-phosphoethanolamine-n-[poly(ethyleneglycol)]-N-benzotriazole carbonate, PEG Mw 3400] was purchased from Shearwater Polymers, Inc. (Huntsville, AL), and soya phosphatidylcholine (SPC) from Lucas Meyer (Hamburg, Germany). Cholesterol (Chol) and Sephadex G50 were obtained from Pharmacia Biotech (Piscataway, NJ).
Preparation of RGD-Modified SSL
An activated DSPE-PEG (DSPE-PEG-BTC) was used to conjugate RGD to DSPE-PEG. The reaction takes place between α-amines of the RGD and BTC group of the lipid, which acts as the linking agent. RGD was successfully covalently conjugated to the DSPE-PEG-BTC under the conditions of reaction (4 h at 4°C, pH 7.5, gentle stirring and 1:2 molar ratio). The disappearance of N-benzotriazole identified by NMR (data not shown) suggests that there was almost no existence of DSPE-PEG-BTC or uncoupled RGD in the
DISCUSSION
Drugs with intracellular targets or therapeutic genes are required to cross the cell membrane for pharmacological activity. Delivery of these agents into tumor tissue only represents part of the problems for tumor targeting, and other challenges for successful tumor targeting include drug release from the carrier and drug passage across the biomembranes. Rigid lipid was frequently used in the liposomes preparation to gain stability advantage. In this case the entrapped drugs were tightly
Acknowledgements
This work was supported in part by the Doctoral Foundation from Chinese Minister of Education (20040001141).
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