K. ZHENG ET AL.Gold-nanoparticle-based multistage drug delivery system for antitumor therapy

Abstract

Nanoparticles can promote the accumulation of drugs in tumors. However, they find limited clinical applications because they cannot easily penetrate the stroma of cancer tissues, and it is difficult to control drug release. We developed a multiresponse multistage drug-delivery nanogel with improved tumor permeability and responsiveness to the tumor microenvironment for the controlled delivery of anticancer agents. For this purpose, ∼100 nm multistage drug delivery nanogels with pH, redox, near-infrared stimulation, and enzyme responsiveness were grown in situ using 20 nm gold nanoparticles (AuNPs) via an emulsion-aiding crosslinking technique with cysteine crosslinker. An alginate cysteine AuNP (ACA) nanocarrier can efficiently load the cationic drug doxorubicin (DOX) to produce a multistage drug delivery nanocarrier (DOX@ACA). DOX@ACA can maintain the slow release of DOX and reduce its toxicity. In cancer tissues, the high pH and reductase microenvironment combined with the in vitro delivery of alginate and near-infrared light drove drug release. The developed nanoparticles effectively inhibited cancer cells, and in vivo evaluations showed that they effectively enhanced antitumor activity while having negligible in vivo toxicity to major organs.

Keywords: Alginate; antitumor therapy; gold nanoparticle; multistage drug delivery; nanogel; pH/redox/enzyme responsiveness.

Scheme 1.

Schematic diagram of the development of nanogels as a novel selective drug delivery method for antitumor therapy.

Figure 1.

Structural characterization of ACA nanogels. (A) FTIR of ACA, AG, and AG-Cys; (B) Raman spectra of ACA, AG-Cys, and Cys; (C) size change of nanogels after loading AuNPs; and (D) zeta potential change of nanogels after loading AuNPs. Particle size distribution of ACA (E) and DOX@ACA (F).

Figure 2.

Microstructural characterization of ACA nanogels. TEM images of (A) pure AG nanogels, (B) AuNPs, (C) ACA nanogels, and (D) ACA nanogels degraded by alginate lyase.

Figure 3.

Drug loading and release properties of ACA nanogels: (A) entrapment efficiency of ACA nanogels; (B) particle size of ACA nanogels after DOX loading; (C) release behavior of DOX simulated in vitro at different pH values (5.0, 6.5, and 7.4); (D) DOX release at different DTT concentrations (0, 5, and 10 mM); (E) DOX release at different alginate lyase concentrations (0, 0.5, and 1 mg/mL); and (F) drug release ability of nanogels under laser irradiation (±standard deviation, n = 3, *p < .05, **p < .01, ***p < .001).

Figure 4.

In vitro cytocompatibility and cytotoxicity: (A) ACA-treated A549 cell activity and (B) cell viability of A549 cells treated with free DOX and DOX@ACA (same DOX concentration) for 48 h. (C) IC50 values for ACA and DOX@ACA. (± standard deviation, n = 3, *p < .05, **p < .01, ***p < .001).

Figure 5.

Inhibitory effect of DOX@ACA on tumors in mice: (A) weight changes in mice after treatment; (B) changes in tumor volume in mice after treatment; (C) representative images of tumor resection 15 days after PBS, DOX@ACA, and free DOX treatments; and (D) TUNEL staining of tumor sections: PBS, free DOX, and DOX@ACA treatments (scale: 200 μm).

Figure 6.

H&E-stained sections of vital organs (heart, liver, spleen, and kidney) (scale bar: 200 μm).