The synergistic radiosensitizing effect of tirapazamine-conjugated gold nanoparticles on human hepatoma HepG2 cells under X-ray irradiation

Abstract

Reductive drug-functionalized gold nanoparticles (AuNPs) have been proposed to enhance the damage of X-rays to cells through improving hydroxyl radical production by secondary electrons. In this work, polyethylene glycol-capped AuNPs were conjugated with tirapazamine (TPZ) moiety, and then thioctyl TPZ (TPZs)-modified AuNPs (TPZs-AuNPs) were synthesized. The TPZs-AuNPs were characterized by transmission electron microscopy, ultraviolet-visible spectra, dynamic light scattering, and inductively coupled plasma mass spectrometry to have a size of 16.6±2.1 nm in diameter and a TPZs/AuNPs ratio of ~700:1. In contrast with PEGylated AuNPs, the as-synthesized TPZs-AuNPs exhibited 20% increment in hydroxyl radical production in water at 2.0 Gy, and 19% increase in sensitizer enhancement ratio at 10% survival fraction for human hepatoma HepG2 cells under X-ray irradiation. The production of reactive oxygen species in HepG2 cells exposed to X-rays in vitro demonstrated a synergistic radiosensitizing effect of AuNPs and TPZ moiety. Thus, the reductive drug-conjugated TPZs-AuNPs as a kind of AuNP radiosensitizer with low gold loading provide a new strategy for enhancing the efficacy of radiation therapy.

Keywords:

• AuNPs
• radiation enhancement
• synergistic effect
• human hepatoma cells
• hydroxyl radical production

Supplementary materials

Figure S1 The absorbance at 460 nm of TPZs methanol aqueous solution at various concentrations.

Abbreviation: TPZs, thioctyl tirapazamine.

Figure S2 The dependence of fluorescence intensity change on the dose of X-rays (50 kVp).

Figure S3 The enhancement ratio of hydroxyl radical production induced by tirapazamine under X-ray irradiation.

Abbreviation: TPZ, tirapazamine.

Figure S4 The Cytotoxicity of TPZ, TPZs and PEG-AuNPs.

Notes: The normalized cell viability of HepG2 cells cocultured with (A) TPZ, (B) TPZs, and (C) PEG-AuNPs at various concentrations relative to that of untreated HepG2 cells at 24, 48, and 72 hours. *P<0.05 and **P<0.01, determined by the two-tailed Student’s t-test.

Abbreviations: TPZ, tirapazamine; TPZs, thioctyl tirapazamine; PEG-AuNPs, polyethylene glycol-capped gold nanoparticles.

Figure S5 The enhancement ratio of ROS in HepG2 cells after X-ray irradiation in the presence of PEG-AuNPs (20.0 µg/mL) and TPZs-AuNPs (5.0 µg/mL).

Note: **P<0.01 versus control group, determined by the two-tailed Student’s t-test.

Abbreviations: ROS, reactive oxygen species; PEG-AuNPs, polyethylene glycol-capped gold nanoparticles; TPZs-AuNPs, thioctyl tirapazamine-modified gold nanoparticles; AuNPs, gold nanoparticles.

Acknowledgments

This work was jointly supported by the Key Project of National Natural Science Foundation of China (Grant No U1232207), the National Key Technology Support Program (Grant No 2015BA101B11), National key Research and Development Program (Grant No 2016YFC0904602) of the Ministry of Science and Technology of China, and the National Natural Science Foundation of China (Grant No 11075191, 11205217, and 11475231).

Disclosure

The authors report no conflicts of interest in this work.