Codelivery of doxorubicin and triptolide with reduction-sensitive lipid-polymer hybrid nanoparticles for in vitro and in vivo synergistic cancer treatment

Abstract

Codelivery is a promising strategy to overcome the limitations of single chemotherapeutic agents in cancer treatment. Despite progress, codelivery of two or more different functional drugs to increase anticancer efficiency still remains a challenge. Here, reduction-sensitive lipid-polymer hybrid nanoparticles (LPNPs) drug delivery system composed of monomethoxy-poly(ethylene glycol)-S-S-hexadecyl (mPEG-S-S-C₁₆), soybean lecithin, and poly(D,L-lactide-co-glycolide) (PLGA) was used for codelivery of doxorubicin (DOX) and a Chinese herb extract triptolide (TPL). Hydrophobic DOX and TPL could be successfully loaded in LPNPs by self-assembly. More importantly, drug release and cellular uptake experiments demonstrated that the two drugs were reduction sensitive, released simultaneously from LPNPs, and taken up effectively by the tumor cells. DOX/TPL-coloaded LPNPs (DOX/TPL-LPNPs) exhibited a high level of synergistic activation with low combination index (CI) in vitro and in vivo. Moreover, the highest synergistic therapeutic effect was achieved at the ratio of 1:0.2 DOX/TPL. Further experiments showed that TPL enhanced the uptake of DOX by human oral cavity squamous cell carcinoma cells (KB cells). Overall, DOX/TPL-coencapsulated reduction-sensitive nanoparticles will be a promising strategy for cancer treatment.

Keywords: codelivery; reduction sensitive; synergistic effect; triptolide.

Figure 1

The schematic drawing of dual drug-loaded LPNPs. Abbreviations: DOX, doxorubicin; LPNPs, lipid–polymer hybrid nanoparticles; mPEG-S-S-C₁₆, monomethoxy-poly(ethylene glycol)-S-S-hexadecyl; PLGA, poly(d,l-lactide-co-glycolide); TPL, triptolide.

Figure 2

(A) Cytotoxicity of DOX-based combinations (DOX/TPL-1/0.05, 1/0.1, 1/0.2, 1/0.5, and 1/1) against KB cells after incubation for 48 h (n=4). (B) Plot of the combination index as the function of cell viability for KB cells treated with free DOX and free TPL combinations. Abbreviations: DOX, doxorubicin; TPL, triptolide.

Figure 3

CI values at ED₅₀ of DOX-based combinations (DOX dosage was 200 ng/mL). Abbreviations: CI, combination index; ED₅₀, 50% effective dose; DOX, doxorubicin; TPL, triptolide.

Figure 4

TEM image of DOX/TPL-loaded LPNPs. Abbreviations: DOX, doxorubicin; LPNPs, lipid–polymer hybrid nanoparticles; TEM, transmission electron microscopy; TPL, triptolide.

Figure 5

Redox-triggered release of (A) DOX and (B) TPL from DOX/TPL-1/0.2-loaded LPNPs in PBS (0.01 M, pH 7.4) with or without 10 mM DTT. Note: P-values were calculated by the Student’s t-test: **P<0.005. Abbreviations: DOX, doxorubicin; DTT, dithiothreitol; LPNPs, lipid–polymer hybrid nanoparticles; PBS, phosphate-buffered saline; TPL, triptolide.

Figure 6

(A) Cytotoxicity of drug-loaded LPNPs against KB cells after incubation for 48 h (n=4). (B) Plot of the CI as the function of cell viability for KB cells treated with drug-loaded LPNPs. P-values were calculated by the Student’s t-test: *P<0.05. Abbreviations: CI, combination index; DOX, doxorubicin; LPNPs, lipid–polymer hybrid nanoparticles; TPL, triptolide.

Figure 7

Antitumor effect of free drugs and drug-loaded LPNPs on H22 cell xenografts tumor. Note: P-values were calculated by the Student’s t-test: *P<0.05 and **P<0.005. Abbreviations: DOX, doxorubicin; LPNPs, lipid–polymer hybrid nanoparticles; PBS, phosphate-buffered saline; TPL, triptolide.

Figure 8

Flow cytometry analyses of KB cells incubated with (A) free drugs and (B) drug-loaded LPNPs for 6 h. Note: DOX dosage was 200 ng/mL, and TPL dosage was 40 ng/mL. Abbreviations: DOX, doxorubicin; LPNPs, lipid–polymer hybrid nanoparticles; TPL, triptolide.

Figure 9

Confocal laser scanning microscopy images of KB cells after treatment with (A) TPL-loaded LPNPs, (B) DOX-loaded LPNPs, and (C) DOX/TPL-1/0.2-loaded LPNPs for 6 h. Notes: DOX dosage was 200 ng/mL, and TPL dosage was 40 ng/mL. Magnification 60×. Abbreviations: DOX, doxorubicin; LPNPs, lipid–polymer hybrid nanoparticles; TPL, triptolide.