Paclitaxel-loaded star-shaped copolymer nanoparticles for enhanced malignant melanoma chemotherapy against multidrug resistance

Abstract

Malignant melanoma (MM) is the most dangerous type of skin cancer with annually increasing incidence and death rates. However, chemotherapy for MM is restricted by low topical drug concentration and multidrug resistance. In order to surmount the limitation and to enhance the therapeutic effect on MM, a new nanoformulation of paclitaxel (PTX)-loaded cholic acid (CA)-functionalized star-shaped poly(lactide-co-glycolide) (PLGA)-D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) nanoparticles (NPs) (shortly PTX-loaded CA-PLGA-TPGS NPs) was fabricated by a modified method of nanoprecipitation. The particle size, zeta potential, morphology, drug release profile, drug encapsulation efficiency, and loading content of PTX-loaded NPs were detected. As shown by confocal laser scanning, NPs loaded with coumarin-6 were internalized by human melanoma cell line A875. The cellular uptake efficiency of CA-PLGA-TPGS NPs was higher than those of PLGA NPs and PLGA-TPGS NPs. The antitumor effects of PTX-loaded NPs were evaluated by the MTT assay in vitro and by a xenograft tumor model in vivo, demonstrating that star-shaped PTX-loaded CA-PLGA-TPGS NPs were significantly superior to commercial PTX formulation Taxol^®. Such drug delivery nanocarriers are potentially applicable to the improvement of clinical MM therapy.

Keywords: drug delivery; enhanced therapeutic effects; malignant melanoma; nanoparticles; paclitaxel.

Figure 1

Characterization of copolymer CA-PLGA-TPGS: (A) typical ¹H NMR spectra and (B) gel permeation chromatographic analysis. Abbreviations: CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate; ¹H NMR, ¹H nuclear magnetic resonance.

Figure 2

Characterizations of PTX-loaded CA-PLGA-TPGS NPs: (A) DLS size distribution of NPs and (B) FESEM image of NPs. Magnification ×50.0 k. Abbreviations: PTX, paclitaxel; CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate; NPs, nanoparticles; DLS, dynamic light scattering; FESEM, field emission scanning electron microscopy.

Figure 3

In vitro stability of PTX-loaded NPs: (A) size distributions of PTX-loaded CA-PLGA-TPGS, PLGA-TPGS, and PLGA NPs during 90 days of storage; and (B) zeta potentials of PTX-loaded CA-PLGA-TPGS, PLGA-TPGS, and PLGA NPs during 90 days of storage. Error bars denote standard deviation. Abbreviations: PTX, paclitaxel; NPs, nanoparticles; CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate.

Figure 4

In vitro drug release profiles of PTX-loaded CA-PLGA-TPGS, PLGA-TPGS, and PLGA NPs. Error bars denote standard deviation. *P<0.05; **P<0.01. Abbreviations: PTX, paclitaxel; CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate; NPs, nanoparticles.

Figure 5

Confocal laser scanning microscopy images of A875 cells after 2 h of incubation with C6-loaded CA-PLGA-TPGS NPs. C6-loaded NPs were green, and the cells were stained by PI (red). The cellular uptake was observed by overlaying images obtained by FITC channel (green) and PI channel (red). Magnification ×0.5 k. Abbreviations: C6, coumarin-6; CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate; NPs, nanoparticles; PI, propidium iodide; FITC, fluorescein isothiocyanate.

Figure 6

Cellular uptake efficiencies of C6-loaded NPs at different NPs concentrations. Error bars denote standard deviation. *P<0.05; **P<0.01. Abbreviations: C6, coumarin-6; NPs, nanoparticles; CA, cholic acid; PLGA, poly-(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate.

Figure 7

Viability of A875 cells incubated with PTX-loaded NPs in comparison with that of Taxol at the same drug dose and drug-free CA-PLGA-TPGS NPs with the same amount of NPs: (A) 24 h and (B) 48 h. Error bars denote standard deviation. *P<0.05; **P<0.01. Abbreviations: PTX, paclitaxel; NPs, nanoparticles; CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate.

Figure 8

(A) Tumor growth curves of nude mice bearing A875 cells xenograft after intravenous injection of PTX-loaded CA-PLGA-TPGS NPs, Taxol, and saline. (B) Variations in body weights of nude mice bearing A875 cells xenograft treated with PTX-loaded CA-PLGA-TPGS NPs, Taxol, and saline. Error bars denote standard deviation. *P<0.05; **P<0.01 (n=6). Abbreviations: PTX, paclitaxel; CA, cholic acid; PLGA, poly(lactide-co-glycolide); TPGS, D-α-tocopheryl polyethylene glycol 1000 succinate; NPs, nanoparticles.