Redox potential ultrasensitive nanoparticle for the targeted delivery of camptothecin to HER2-positive cancer cells

Abstract

Ideal "smart" nanoparticles for drug delivery should enhance therapeutic efficacy without introducing side effects. To achieve that, we developed a drug delivery system (HCN) based on a polymer-drug conjugate of poly[2-(pyridin-2-yldisulfanyl)]-graft-poly(ethylene glycol) and camptothecin with an intracellularly cleavable linker and human epidermal growth factor receptor 2 (HER2) targeting ligands. An in vitro drug release study found that HCN was stable in the physiological environment and supersensitive to the stimulus of elevated intracellular redox potential, releasing all payloads in less than 30 min. Furthermore, confocal microscopy revealed that HCN could specifically enter HER2-positive cancer cells. As a consequence, HCN could effectively kill HER2-positive cancer cells while not affecting HER2-negative cells.

Figure 1

Syntheses of thiolated camptothecin (CPT-SH) (A) and the polymer–drug conjugate (CPDSG-NH₂) (B) and fabrication of a camptothecin nanoparticle (CN) and a Herceptin-functionalized camptothecin nanoparticle (HCN) (C).

Figure 2

Reaction kinetics of CPT-SH conjugation (A) and HPLC spectra of CPT, CPT-SH, and CPT-conjugated polymer (CPDSG) and the release of CPT-SH from CPDSG in an environment containing 10 mM DTT (B).

Figure 3

Hydrodynamic size (A), ξ potential (B), and TEM images (C) of nanoparticles and the kinetics of release of CPT-SH from CN in different environments (D). Data represent means ± the standard deviation (n = 3). Scale bars are 500 nm in panel C.

Figure 4

Cytotoxicity of CN and HCN for HER2-positive HCT-116 cells (A) and HER2-negative KB cells (C) after treatment for 48 h and Western blotting of HER2 expression in HCT-116 and KB cells (B). Data represent means ± the standard deviation (n = 3) (Student’s t test; *P < 0.05; ^#P < 0.01).

Figure 5

Cytotoxicity of Herceptin (A) and PDSG (B) for HER2-positive HCT-116 cells after treatment for 48 h. Data represent means ± the standard deviation (n = 3).

Figure 6

Confocal images and flow cytometry spectra of HCT-116 cells (A and C) and KB cells (B and D) treated with CN and HCN nanoparticles. Doxorubicin was encapsulated into CN and HCN nanoparticles as a fluorescence reporter (red, DOX); nuclei of the cells were stained with Hoechst 33342 (blue, DAPI) (A and B). Cells were cocultured with Cy3-labeled CN and HCN (C and D) for 4 h.