Abstract
Introduction
Extensive research over the past half a century indicates that reactive oxygen species (ROS) play an important role in cancer. ROS are small molecules from the partial reduction of molecular oxygen during oxygen consumption and cellular metabolism. Increased ROS levels have been observed in various cancers. The abnormal concentration of ROS can activate signaling pathways about cancer cell survival, tumor progression, drug resistance, and driven DNA damage and genetic instability [1]. Precisely regulated antioxidant defense system in cancer cells can detoxify elevated ROS levels while maintaining pro-tumorigenic signaling and resistance to apoptosis. However, if the balance of redox status was disturbed, ROS may exert a cytotoxic effect which induces malignant cell death. It has been explored to selectively kill cancer cells without damage normal cells by manipulating ROS levels and antioxidant systems [2]. ROS-generating and elimination agents have been applied and found effective in many cases. Arsenic trioxide can impair the respiratory chain and increase superoxide production while doxorubicin can induce ROS production by intracellular chelation of iron and trigger a Fenton-type reaction leading to the generation of the highly reactive hydroxyl radical. Depletion of the GSH pool, which is the major ROS-scavenging system in cells, can increase oxidative stress and cell death. To maximize the therapeutic effect, a combination of arsenic trioxide and ascorbic acid-mediated GSH depletion has been exploited and showed clinically effective in the treatment of myeloma. Thus the quantitative determination of ROS in cells is in great demand in clinical cancer treatment and basic research. The non-enzymatic electrochemical sensor is excellent stable, reproducible, and cost-effective with no need to immobilize enzymes on the electrode surface [4]. To increase the activity and selectivity, Au-based nanoparticles are of particular interest for their great conductivity and superior electrochemical properties. By introducing the MWCNTs as supporting material due to their excellent electrical conductivity and large surface area, the electrocatalytic activity can be further improved.
Method
An electrochemical biosensor consists of gold nanoparticles/multi-walled carbon nanotubes (AuNP/MWCNTs) decorated screen printing electrodes and lung cancer cells were developed to determine the change of ROS levels induced by chemical drugs. The nanocomposite of AuNPs/MWCNTs was prepared following the previous method with a slight modification [5]. 20 μL of the well-dispersed suspension was dropped onto the working electrode of the screen printing electrode. The AuNPs or MWCNTs modified electrodes were prepared under the same conditions as a control. A CHI660E electrochemical workstation with a three-electrode system was purchased from Chenhua Technology Co. Ltd. A 3D cell culture of GelMA/graphene oxide (GelMA/GO) was used to encapsulate A549 lung cancer cells [6]. The H2O2 levels of cancer cells under different drug treatments were detected and calculated with peak current in DPV analysis as a representative for oxidant stress. Conventional biological assays, including fluorescence detection, and cell apoptosis assay were applied to detect the ROS levels as control.
Results and Conclusions
The biosensor demonstrates good sensitivity towards hydrogen peroxide at PH 7 solution at a working potential of -0.50 V with a linear response range from 2.0 μM to 53.8 μM. We found that combining applying arsenic trioxide and ascorbic acid can effectively elevate oxidative stress level in A549 cells and induce cell apoptosis. This system is sensitive and simple to operate with the advantage to evaluate the oxidative stress level of different drugs by the detection of H2O2 in the cell membrane. In summary, this work describes a novel method for assessing the effect of ROS-target drugs using cell-based electrochemical signaling with a rapid screening pattern.
References
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Figure 1