Peptide ligand and PEG-mediated long-circulating liposome targeted to FGFR overexpressing tumor in vivo

Abstract

Background and methods: Paclitaxel, a widely used antitumor agent, has limited clinical application due to its hydrophobicity and systemic toxicity. To achieve sustained and targeted delivery of paclitaxel to tumor sites, liposomes composed of egg phosphatidylcholine, cholesterol, and distearolyphosphatidyl ethanolamine-N-poly(ethylene glycol) (PEG(2000)) were prepared by a lipid film method. In addition, the liposomes also contained truncated fibroblast growth factor fragment-PEG-cholesterol as a ligand targeting the tumor marker fibroblast growth factor receptor. Physicochemical characteristics, such as particle size, zeta potential, entrapment efficiency, and release profiles were investigated. Pharmacokinetics and biodistribution were evaluated in C57BL/6 J mice bearing B16 melanoma after intravenous injection of paclitaxel formulated in Cremophor EL (free paclitaxel), conventional liposomes (CL-PTX), or in targeted PEGylated liposomes (TL-PTX).

Results: Compared with CL-PTX and free paclitaxel, TL-PTX prolonged the half-life of paclitaxel by 2.01-fold and 3.40-fold, respectively, in plasma and improved the AUC(0→t) values of paclitaxel by 1.56-fold and 2.31-fold, respectively, in blood. Biodistribution studies showed high accumulation of TL-PTX in tumor tissue and organs containing the mononuclear phagocyte system (liver and spleen), but a considerable decrease in other organs (heart, lung, and kidney) compared with CL-PTX and free paclitaxel.

Conclusion: The truncated fibroblast growth factor fragment-conjugated PEGylated liposome has promising potential as a long-circulating and tumor-targeting carrier system.

Keywords: liposomes; paclitaxel; poly(ethylene glycol); targeted drug delivery; truncated fibroblast growth factor fragment.

Figure 1

Synthetic scheme for preparation of targeted PEGylated liposomes. Abbreviations: PEG, poly(ethylene glycol); EPC, egg phosphatidylcholine; Chol, cholesterol; DSPE, distearolyphosphatidyl ethanolamine; EDC, 1-ethyl-3-(3- dimethylaminopropyl)-carbodiimide hydrochloride; NHS, N-hydroxysuccinimide; tbFGF, truncated basic fibroblast growth factor.

Figure 2

Particle size distribution of paclitaxel-loaded conventional liposomes (A) and paclitaxel-loaded targeted PEGylated liposomes (B), and typical atomic force microscopy image of paclitaxel-loaded targeted PEGylated liposomes (C).

Figure 3

Time course of paclitaxel release from TL-PTX (▲), CL-PTX (■), and free PTX(◆) at 37°C and pH 7.0. The paclitaxel Released was separated by dialysis and quantified using high-performance liquid chromatography. Notes: There were five mice per group per time point. Bars represent the mean ± standard deviation. Error bars correspond to 95% confidence intervals. Abbreviations: CL-PTX, paclitaxel-loaded conventional liposomes; TL-PTX, paclitaxel-loaded targeted PEGylated liposomes; Free PTX, paclitaxel dissolved in Cremophor EL.

Figure 4

Areas under the curve over 24 hours for paclitaxel in serum after treatment with free PTX (◆), CL-PTX (■), or TL-PTX (▲). Notes: There were five mice per group per time point. Bars represent the mean ± standard deviation. Abbreviations: CL-PTX, paclitaxel-loaded conventional liposomes; TL-PTX, paclitaxel-loaded targeted PEGylated liposomes; Free PTX, paclitaxel dissolved in Cremophor EL.

Figure 5

Mean paclitaxel concentration in tumor tissue at each time point after treatment with free PTX, CL-PTX, and TL-PTX. Paclitaxel was extracted from the tumors and measured by ultraperformance liquid chromatography. Notes: There were five mice per group per time point. Bars represent the mean ± standard deviation. Abbreviations: CL-PTX, paclitaxel-loaded conventional liposomes; TL-PTX, paclitaxel-loaded targeted PEGylated liposomes; Free PTX, paclitaxel dissolved in Cremophor EL.

Figure 6

Mean paclitaxel concentration in tumor, lungs, heart, spleen, liver, and kidneys of mice treated with free PTX, CL-PTX, and TL-PTX. Mice were sacrificed at the indicated time points of (A) 0.5, (B) 1, (C) 3, (D) 5, (E) 12, and (F) 24 hours after administration, and paclitaxel was extracted from the tissues and measured by ultraperformance liquid chromatography. Notes: There were five mice per group per time point. Bars represent the mean ± standard deviation. Abbreviations: CL-PTX, paclitaxel-loaded conventional liposomes; TL-PTX, paclitaxel-loaded targeted PEGylated liposomes; Free PTX, paclitaxel dissolved in Cremophor EL.