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Updated: Nov 1, 2025
Quantitative, Real-time Analysis of Base Excision Repair Activity in Cell Lysates Utilizing Lesion-specific Molecular Beacons
Published on: August 6, 2012
Detecting Attomolar DNA-Damaging Anticancer Drug Activity in Cell Lysates with Electrochemical DNA Devices
Ashan P Wettasinghe1, Naveen Singh2, Colton L Starcher2
1Department of Physics, The University of Texas at Dallas, 800 W. Campbell Road, SCI 10, Richardson, Texas 75080, United States.
Abstract:
Here, we utilize electrochemical DNA devices to quantify and understand the cancer-specific DNA-damaging activity of an emerging drug in cellular lysates at femtomolar and attomolar concentrations. Isobutyl-deoxynyboquinone (IB-DNQ), a potent and tumor-selective NAD(P)H quinone oxidoreductase 1 (NQO1) bioactivatable drug, was prepared and biochemically verified in cancer cells highly expressing NQO1 (NQO1+) and knockdowns with low NQO1 expression (NQO1-) by Western blot, NQO1 activity analysis, survival assays, oxygen consumption rate, extracellular acidification rate, and peroxide production. Lysates from these cells and the IB-DNQ drug were then introduced to a chip system bearing an array of DNA-modified electrodes, and their DNA-damaging activity was quantified by changes in DNA-mediated electrochemistry arising from base-excision repair. Device-level controls of NQO1 activity and kinetic analysis were used to verify and further understand the IB-DNQ activity. A 380 aM IB-DNQ limit of detection and a 1.3 fM midpoint of damage were observed in NQO1+ lysates, both metrics 2 orders of magnitude lower than NQO1- lysates, indicating the high IB-DNQ potency and selectivity for NQO1+ cancers. The device-level damage midpoint concentration in NQO1+ lysates was over 8 orders of magnitude lower than cell survival benchmarks, likely due to poor IB-DNQ cellular uptake, demonstrating that these devices can identify promising drugs requiring improved cell permeability. Ultimately, these results indicate the noteworthy potency and selectivity of IB-DNQ and the high sensitivity and precision of electrochemical DNA devices to analyze agents/drugs involved in DNA-damaging chemotherapies.
Insights
Electrochemical DNA devices precisely quantify the cancer drug Isobutyl-deoxynyboquinone (IB-DNQ), revealing its high potency and selectivity for tumors expressing NAD(P)H quinone oxidoreductase 1 (NQO1). This technology identifies promising cancer therapies by measuring DNA damage at attomolar levels.
Area of Science:
- Biochemistry
- Molecular Biology
- Electrochemistry
Background:
- Emerging cancer drugs require precise quantification of their DNA-damaging activity.
- NAD(P)H quinone oxidoreductase 1 (NQO1) is a key enzyme in cancer drug bioactivation.
- Existing methods for drug activity assessment have limitations in sensitivity and selectivity.
Purpose of the Study:
- To develop and validate electrochemical DNA devices for quantifying cancer-specific drug activity.
- To assess the DNA-damaging potency and selectivity of Isobutyl-deoxynyboquinone (IB-DNQ) in cancer cells.
- To compare drug activity in cancer cells with high versus low NQO1 expression.
Main Methods:
- Preparation and biochemical verification of IB-DNQ.
- Culturing cancer cells with varying NQO1 expression levels (NQO1+ and NQO1-).
- Utilizing electrochemical DNA devices with DNA-modified electrodes to measure DNA damage via electrochemistry.
- Analyzing changes in DNA-mediated electrochemistry resulting from base-excision repair.
Main Results:
- Achieved a 380 attomolar (aM) limit of detection for IB-DNQ in NQO1+ lysates.
- Observed a 1.3 femtomolar (fM) midpoint of damage in NQO1+ lysates, significantly lower than in NQO1- lysates.
- Demonstrated that electrochemical devices can detect drug activity at concentrations 2 orders of magnitude lower in NQO1+ compared to NQO1- cells.
- Identified a large discrepancy between device-measured drug activity and cell survival, suggesting poor cellular uptake.
Conclusions:
- Electrochemical DNA devices offer high sensitivity and precision for analyzing DNA-damaging chemotherapies.
- IB-DNQ exhibits significant potency and selectivity for NQO1-expressing cancers.
- The developed device platform can identify promising drug candidates and highlight challenges like cell permeability.
