Quantitative monitoring of hypoxia-induced intracellular acidification in lung tumor cells and tissues using activatable surface-enhanced raman scattering nanoprobes

Article abstract of DOI:10.1021/acs.analchem.6b03590

Hypoxia is considered to contribute to pathophysiology in various cells and tissues, and a clear understanding about the relationship between hypoxia and intracellular acidification will help to elucidate the complex mechanism of glycolysis under hypoxia. However, current studies are mainly focused on overexpression of intracellular reductases accelerated by hypoxia, and the investigations focusing on the relationship between hypoxic degree and intracellular acidification remain to be explored. For this vacuity, we report herein a new activatable nanoprobe for sensing pH change under different degrees of hypoxia by surface-enhanced Raman spectroscopy (SERS). The monitoring was based on the SERS spectra changes of 4- nitrothiophenol (4-NTP)-functionalized gold nanorods (AuNR@4- NTP) resulting from the nitroreductase (NTR)-triggered reduction under hypoxic conditions while the as-generated 4-aminothiophenol (4-ATP) is a pH-sensitive molecule. This unique property can ensure the SERS monitoring of intracellular acidification in living cells and tissues under hypoxic conditions. Dynamic pH analysis indicated that the pH decreased from 7.1 to 6.5 as a function of different degrees of hypoxia (from 15 to 1%) due to excessive glycolytic activity triggered by hypoxia. Given the known advantages of SERS sensing, these findings hold promise in studies of pathophysiological pathways involving hypoxia.

Full text of DOI:10.1021/acs.analchem.6b03590

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Article
Quantitative Monitoring of Hypoxia-Induced Intracellular
Acidi#cation in Lung Tumor Cells and Tissues Using
Activatable Surface-Enhanced Raman Scattering Nanoprobes
Dandan Ma, Jing Zheng, Pinting Tang, Weijian Xu, Zhihe Qing, Sheng Yang, Jishan Li, and Ronghua Yang
Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.6b03590 • Publication Date (Web): 01 Nov 2016
Downloaded from http://pubs.acs.org on November 3, 2016
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Analytical Chemistry
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Quantitative Monitoring of Hypoxia-Induced Intracellular
Acidification in Lung Tumor Cells and Tissues Using
Activatable Surface-Enhanced Raman Scattering
Nanoprobes
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Dandan Ma,a Jing Zheng,a,* Pinting Tang,a Weijian Xu,a Zhihe Qing,b Sheng Yang,b Jishan
Li,a Ronghua Yang,a,b,*
aState Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical
Engineering, Hunan University, Changsha, 410082, China; bSchool of Chemistry and Biological
Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410004 China.
*To whom correspondence should be addressed:
Eꢀmail: zhengjing2013@hnu.edu.cn, Yangrh@pku.edu.cn.
Fax: +86ꢀ731ꢀ8882 2523
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Analytical Chemistry
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ABSTRACT: Hypoxia is considered to contribute to pathophysiology in various cells and
tissues, a clear understanding about the relationship between hypoxia and intracellular
acidification will help to elucidate the complex mechanism of glycolysis under hypoxia.
However, current researches are mainly focused on overexpressing of intracellular reductases
accelerated by hypoxia, and the investigations focusing on the relationship between hypoxic
degree and intracellular acidification remained to be explored. For this vacuity, we report
herein a new activatable nanoprobe for sensing pH change under different degrees of hypoxia
by surface enhanced Raman spectroscopy (SERS). The monitoring was based on the SERS
spectra changes of 4ꢀnitrothiophenol (4ꢀNTP)ꢀfunctionalized gold nanorods (AuNR@4ꢀNTP)
resulting from the nitroreductase (NTR)ꢀtriggered reduction under hypoxic conditions while
the asꢀgenerated 4ꢀaminothiophenol (4ꢀATP) is a pHꢀsensitive molecule. This unique property
can ensure the SERS monitoring of intracellular acidification in living cells and tissues under
hypoxic conditions. Dynamic pH analysis indicated the pH decreased from 7.1 to 6.5 as
functions of different degree of hypoxia (from 15% to 1%) due to the excessive glycolytic
activity triggered by hypoxia. Given the known advantages of SERS sensing, these findings
hold promise in studies of pathophysiological pathways involving hypoxia.
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Analytical Chemistry
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INTRODUCTION
Hypoxia, a condition of decreased oxygen availability, is considered to contribute
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to pathophysiology in various cells and tissues.1 Specifically, hypoxia can cause
pulmonary oxidative damage and imbalance of redox state in lung whose important
function is to maintain an adequate oxygenation in the oragnism.2 Most importantly, the
excessive glycolytic activity in lung triggered by hypoxia can result in vast production of
lactate and thus accompany by the intracellular acidification, which would in turn result
in inhibition of glycolysis.3 Therefore, demonstrating the hypoxiaꢀinduced intracellular
acidification in living systems is of great biomedical importance. However, current
researches have been mainly focused on overexpressing of intracellular reductases such
as DTꢀdiaphorase, azoreductase, and nitroreductase (NTR) accelerated by hypoxia,4ꢀ9
few effort has been explored for quantitative intracellular acidification monitoring in
living cells under the different hypoxic degree. Since a clear understanding about the
relationship between the hypoxia and intracellular acidification will contribute to
elucidate the complex mechanism of glycolysis under hypoxic conditions, efficient pH
indicators which can function well in living cells and tissues under hypoxia is thus a
challenging task.
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To date, several excellent techniques including fluorescence and nuclear magnetic
resonance (NMR), have been developed for the detection of pH under hypoxia.10ꢀ13 For
instance, Jongsma et al. proposed the 31P magnetic resonance spectroscopy to monitor
cerebral energy metabolism and acidꢀbase homeostasis during impaired oxygen supply in fetal
sheep while Hori et al. prepared a fluorescent probe by linking pꢀnitro benzyl moiety to
SNARF for monitoring intracellular pH of tumor cells under hypoxia.14,15 In spite of the
promising application capability, insufficient water solubility make these organic small
moleculesꢀbased strategies still difficult to implement for the intracellular sensing of pH in a
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