Dual-responsive dithio-polydopamine coated porous CeO2 nanorods for targeted and synergistic drug delivery

Abstract

Objective: The aim was to produce the first report of assembling degradable stimuli-responsive dithio-polydopamine coating with a cancer target unit for synergistic and targeted drug delivery.

Methods: A multifunctional drug delivery system was constructed by coating a dual-responsive dithio-polydopamine (PDS) on porous CeO₂ nanorods and subsequent conjugation of lactose derivative, where the PDS was formed by self-polymerization of dithio-dopamine (DOPASS).

Results: The multifunctional drug delivery system displayed excellent cancer targeted ability resulting from the conjugation of lactose derivative, which could specifically recognize the overexpressed asialoglycoprotein receptors on the surface of HepG2 cells. It also showed a dual-responsive property of glutathione and pH, achieving controllable drug release from the cleavage of disulfide bond and subsequent degradation of PDS in cancer cells. Moreover, the degradation of PDS led to the exposure of CeO₂ nanorods, which has a synergistic anticancer effect due to its cytotoxicity to cancer cells.

Conclusion: This work presents a good example of a rational design towards synergistic and targeted DDS for cancer chemotherapies.

Keywords: cerium oxide nanoparticles; degradable polydopamine; dual-responsiveness; synergistic anticancer; targeted drug delivery.

Figure 1

TEM images of (A) CeONRs; (B) PDS@CeONRs; (C) Lac-PDS@CeONRs; and (D) Lac-PDS@CeONRs after being treated with 10 mM GSH for 6 h. Note: The thickness of the PDS layer coated on the CeONRs were indicated by red arrows. Abbreviations: TEM, transmission electron microscope; CeONR, CeO₂ nanorod; PDS, dithio-polydopamine; GSH, glutathione.

Figure 2

DOX release profiles from Lac-PDS/DOX@CeONRs in PBS at different GSH concentrations and different pH values. Note: ^***P<0.001. Abbreviations: DOX, doxorubicin hydrochloride; PDS, dithio-polydopamine; CeONR, CeO₂ nanorod; PBS, phosphate-buffered saline; GSH, glutathione.

Figure 3

CLSM images of HepG2 cultured with Lac-PDS/DOX@CeONRs in the presence of 10 mM GSH for 4 h (A–D); HepG2 cultured with Lac-PDS/DOX@CeONRs for 4 h preincubated with LA for 4 h (E–H); HepG2 cultured with Lac-PDS/DOX@CeONRs as control (I–L) for 4 h; HepG2 cultured with free DOX (M–P). The DOX concentration is 5.0 μM. The nuclei were stained with DAPI; images were taken from DAPI channel (A, E, I, M), DOX channel (B, F, J, N), and the overlapped images (C, G, K, O). Scale bar: 50 μm (A–C, E–G, I–K, and M–O); the enlarged view of the marked area (D, H, L, P). Scale bar: 20 μm (D, H, L, and P). Abbreviations: CLSM, confocal laser scanning microscopy; PDS, dithio-polydopamine; DOX, doxorubicin hydrochloride; CeONR, CeO₂ nanorod; GSH, glutathione; LA, lactobionic acid; DAPI, 4′,6-diamidino-2-phenylindole.

Figure 4

Flow cytometry analysis of HepG2 cells after incubation for 4 h with Lac-PDS/DOX@CeONRs (B: orange line in F); PDS/DOX@CeONRs (C: green line in F); 5 μM DOX (D: blue line in F); Lac-PDS/DOX@CeONRs after pre-incubation with LA for 4 h (E: dark green line in F) and control (A: red line in F). Abbreviations: PDS, dithio-polydopamine; DOX, doxorubicin hydrochloride; CeONR, CeO₂ nanorod; LA, lactobionic acid.

Figure 5

(A) Cell viability of HepG2 cells and 293T cells incubated with CeONRs for 24 h; (B) Cell viability of HepG2 cells and 293T cells incubated with Lac-PDS/CeONRs for 24 h; (C) Cell viability of 293T cells incubated with Free DOX and Lac-PDS/DOX@CeONRs for 24 h, 48 h, and 72 h; (D) Cell viability of HepG2 cells incubated with Free DOX and Lac-PDS/DOX@CeONRs for 24 h, 48 h, 72 h. The DOX concentration is 1 μg/mL (^*P<0.5; ^**P<0.01). Abbreviations: CeONR, CeO₂ nanorod; PDS, dithio-polydopamine; DOX, doxorubicin hydrochloride.

Figure 6

(A) TEM image of HepG2 in blank control. (B) Enlarged view of the marked area of panel A. (C) TEM image of HepG2 incubated with Lac-PDS/DOX@CeONR at 5 μM for 24 h. (D) Enlarged view of the marked area of panel C. Abbreviations: TEM, transmission electron microscope; PDS, dithio-polydopamine; DOX, doxorubicin hydrochloride; CeONR, CeO₂ nanorod.

Figure 7

CLSM images of HepG2 cultured with 40 μg/mL CeONRs, and the control group cultured with the same amount of PBS. Scale bar: 5 μm. Abbreviations: CLSM, confocal laser scanning microscopy; CeONR, CeO₂ nanorod; PBS, phosphate-buffered saline.

Figure 8

Western blot analysis for Casp9, HepG2 cells cultured with 40 μg/mL CeONRs and Lac-PDS/CeONRs, and the control group treated with the same amount of PBS. Abbreviations: CeONR, CeO₂ nanorod; PDS, dithio-polydopamine; PBS, phosphate- buffered saline.

Scheme 1

Cartoon representation of (A) the construction process of the Lac-PDS/DOX@CeONRs and drug release upon the degradation of PDS under GSH and low pH; (B) its possible cellular pathway. Abbreviations: PDS, dithio-polydopamine; DOX, doxorubicin hydrochloride; CeONR, CeO₂ nanorod; GSH, glutathione.