Nitroreductase-Induced Aggregation of Gold Nanoparticles for "Off-On" Photoacoustic Imaging of Tumor Hypoxia

Xin Li, Xueyang Fang, Shiying Li, Kwok Ho Lui, Wai Sum Lo, Yanjuan Gu, Wing Tak Wong

Research output: Journal article publicationJournal articleAcademic researchpeer-review

2 Citations (Scopus)


Hypoxia is an important phenomenon due to insufficient oxygen supply in tumor tissue, and nitroreductase (NTR) is a characteristic enzyme used for evaluating hypoxia level in tumors. In this work, we designed a smart gold nanoparticle (AuNPs), modified by 16-mercaptoundecanoic acid (MHDA) and hypoxia-responsive 11-(2-nitro-1H-imidazol-1-yl)undecane-1-thiol (NI) ligand, that responds to the hypoxic environment in tumor sites. With proper surface ligand composition, the responsive nanoprobe exhibited aggregation through the bioreduction of the nitro group on NI ligands under hypoxic conditions and the UV-vis absorption peak maximum would shift to 630 nm from 530 nm, which acts as an "off-on" contrast agent for tumor hypoxic photoacoustic (PA) imaging. In vitro and in vivo experiments revealed that AuNPs@MHDA/NO₂ exhibited an enhanced PA signal in hypoxic conditions. This study demonstrates the potential of hypoxia-responsive AuNPs as novel and sensitive diagnostic agents, which lays a firm foundation for precise cancer treatment in the future.

Original languageEnglish
Pages (from-to)2186-2197
Number of pages12
JournalJournal of Biomedical Nanotechnology
Issue number11
Publication statusPublished - 1 Nov 2021

ASJC Scopus subject areas

  • General Medicine


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