Electrochemical investigation of the interaction of 2,4-D and double stranded DNA using pencil graphite electrodes.

2,4-dichlorophenoxyacetic acid (2,4-D) is an auxinic herbicide used to control broadleaf weeds. It is also a threatening factor for not only aquatic life but also human health due to its genotoxicity and endocrine disruptive property. Herein, the interaction between 2,4-D and double stranded DNA was investigated by using single-use pencil graphite electrodes (PGE) in combination with electrochemical techniques. The detection mechanism was based on the monitoring of the changes at the guanine oxidation signal obtained before/after surface-confined interaction of 2,4-D and DNA at the surface of PGE. The electrochemical characterization of the interaction was studied by using microscopic and electrochemical techniques. The response obtained by interaction in the presence of another herbicide, glyphosate, which is widely used with 2,4-D for weed control, was compared to the one occurred in the presence of 2,4-D. Electrochemical monitoring of the interaction between the herbicide whose active molecule was 2,4-D and DNA was also investigated. The detection (LOD) and quantification limits (LOQ) for 2,4-D and the herbicide could be obtained in the linear concentration ranges of 30-70 µg/mL and 10-30 µg/mL, respectively and LOD and LOQ values were found to be 2.85 and 9.50 µg/mL for both 2,4-D and the herbicide. The sensitivity of the biosensor was calculated as 0.087 µA.mL / µg.cm2 .This is the first study in literature by means of not only voltammetric detection of 2,4-D and DNA interaction but also the herbicide-DNA interaction at the surface of PGE based on the changes at the guanine signal.

Monitoring of glyphosate-DNA interaction and synergistic genotoxic effect of glyphosate and 2,4-dichlorophenoxyacetic acid using an electrochemical biosensor.

Glyphosate (GLY) is a broad-spectrum herbicide used worldwide to control broadleaf sedge, and grass weeds to control non-specific vegetation. Although it was evaluated as non-toxic agent in 20th century, its carcinogenic and genotoxic potential has being intensively investigated all over the world in the last decade. Moreover, the combination of GLY and 2,4-dichlorophenoxyacetic acid (2,4-D) has been widely applied. Although genotoxicity of GLY has been evaluated in vivo studies, there is no report in the literature for the monitoring of in vitro biointeraction of GLY and double stranded DNA, or how effect the combination of GLY and 2,4-D onto DNA. Herein, an electrochemical biosensor platform was developed for detection of the pesticide-DNA interaction by using disposable pencil graphite electrodes (PGEs). First, voltammetric detection of the interaction between GLY and DNA was investigated and the electrochemical characterization of the interaction was achieved. Taking a step further, the synergistic genotoxic effect of the mixture of GLY and 2,4-dichlorophenoxyacetic acid (2,4-D) or the mixture of their herbicide forms onto DNA could be monitored. This effect was concentration dependent, and the herbicide of GLY or the use of mixture of herbicides of GLY and 2,4-D had more genotoxic effect than analytical grade of the active molecules, GLY and 2,4-D. The single-use PGEs provided to fabricate robust, eco-friendly and time saver recognition platform for monitoring of herbicide-DNA interaction with the sensitive and reliable results. It is expected that this study will lead to be designed miniaturized lab-on-a chip platforms for on-line analysis of the pesticide-nucleic acid interactions.

Intracellular uptake study of radiolabeled anticancer drug and impedimetric detection of its interaction with DNA.

Topoisomerase I inhibitor topotecan (TPT) is the only single-agent therapy certified for the remedy of repetitive small cell lung cancer (SCLC). In this study, TPT was labeled with (131)I via iodogen method and its quality control was determined using thin layer radiochromatography and paper electrophoresis methods. Intracellular uptake study was carried out with human lung adenocarcinoma cell line (A-549) and human lung fibroblast cell line (WI-38). The interaction of (131)I-TPT with healthy DNA and cancer DNA was also investigated using single-use sensor technology combined with electrochemical impedance spectroscopy (EIS). The change at the charge transfer resistance (Rct) obtained before/after interaction was evaluated. Similar to the results of intracellular uptake study, it was found that (131)I-TPT could more interact with the cancer DNA than healthy DNA according to the impedimetric results. (131)I-TPT is promising in terms of a new nuclear imaging agent for lung cancer.

Electrochemical monitoring of the interaction between Temozolamide and nucleic acids by using disposable pencil graphite electrodes.

Temozolomide (TMZ) is an anticancer drug used for the treatment of adult brain tumour and skin cancer. The biomolecular interaction between TMZ and DNA was investigated for the first time in this study using disposable pencil graphite electrodes (PGEs) in combination with electrochemical techniques. The surface confined interactions between TMZ and different type of nucleic acids were performed. Before/after surface confined interaction process, the oxidation signals of TMZ, guanine and adenine were measured using differential pulse voltammetry (DPV) and PGE and accordingly, the changes at the oxidation signals were evaluated. The detection limit (DL) was also estimated based on the oxidation signal of TMZ. The interaction of TMZ with single stranded poly [A], poly [G], or double stranded poly [A]-poly[T] and poly [G]-poly[C] was also explored. Moreover, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were utilized for detection the interaction between TMZ and DNA. The features of this single-use electrochemical sensor was discussed in comparison to other reports that were developed for TMZ detection.

Electrochemical investigation of the interaction between topotecan and DNA at disposable graphite electrodes.

Topotecan (TPT) is a semisynthetic, water soluble analog of the plant alkaloid camptothecin which has been widely used for the treatment of ovarian and cervical cancers. To obtain better understanding on how it can affect DNA structure, electrochemical biosensor platforms for the investigation of TPT-double stranded DNA (dsDNA) interaction were developed for the first time in this study. The electrochemical detection of TPT, and TPT-dsDNA interaction were investigated at the surface of pencil graphite electrodes (PGEs) and single-walled carbon nanotube (SWCNT) modified PGEs by using differential pulse voltammetry (DPV). The changes at the oxidation signals of TPT and guanine were evaluated before/after each modification/immobilization step. An enhanced sensor response was obtained by using SWCNT-PGEs compared to unmodified PGEs with resulting limits of detection (LODs) for TPT as 0.51 µg/mL, 0.45 µg/mL, 0.37 µg/mL (130 pmol, 117 pmol, 96.5 pmol in a 110 µL sample, respectively) by using electrochemically pretreated PGE, unmodified PGE and SWCNT modified PGE. In addition, electrochemical impedance spectroscopy (EIS) measurements were performed for the purpose of modification of PGEs by using SWCNTs and the interaction process at the surface of SWCNT-PGEs by evaluating the changes at the charge transfer resistance (Rct).

Impedimetric detection of in situ interaction between anti-cancer drug bleomycin and DNA.

Surface confined interaction of anti-cancer drug bleomycin (BLM) with nucleic acids: single stranded and double stranded DNA was investigated herein by using electrochemical impedance spectroscopy (EIS) technique in combination with a graphite sensor technology. The experimental conditions were optimized: such as, dsDNA concentration, BLM concentration and interaction time. The main features of impedimetric DNA biosensor, such as its detection limit and the repeatability, were also discussed. The in situ interaction of BLM with dsDNA was also tested impedimetrically in the absence or presence of other chemotherapeutic agents, such as mitomycin C (MC) and cis-platin (cis-DDP) for testing the selectivity.

Genomagnetic assay for electrochemical detection of osteogenic differentiation in mesenchymal stem cells.

The osteogenic differentiation of mesenchymal stem cells (MSCs) was assessed by determining the gene expression levels of proteins; osteocalcin (OSC), osteonectin (OSN) and osteopontin (OSP) based on electrochemical detection protocol combined with genomagnetic assay in parallel to real-time PCR analysis. Genomagnetic assay was performed using streptavidin coated commercial magnetic particles (magnetic beads, MBs) in combination with single-use electrochemical sensor technology. A biotinylated DNA probe was immobilized onto streptavidin coated magnetic particles, and then the hybridization process of the probe with its complementary DNA was performed. The oxidation signals of DNA electroactive bases guanine and adenine were measured voltammetrically using a pencil graphite electrode (PGE) before and after the hybridization process of OSC/OSN/OSP probe sequences with their complementary target sequences. The selectivity of the genomagnetic assay was also tested using each DNA probe individually related to osteogenic differentiations. The voltammetric detection of osteogenic differentiations was confirmed selectively by real-time PCR analysis.

Sensitive sepiolite-carbon nanotubes based disposable electrodes for direct detection of DNA and anticancer drug-DNA interactions.

A new surface based on the natural clay mineral sepiolite and a single-walled carbon nanotubes-modified graphite electrode was developed for the electrochemical detection of DNA, and also for anticancer drug-DNA interactions.

Graphene oxide integrated sensor for electrochemical monitoring of mitomycin C-DNA interaction.

We present a graphene oxide (GO) integrated disposable electrochemical sensor for the enhanced detection of nucleic acids and the sensitive monitoring of the surface-confined interactions between the anticancer drug mitomycin C (MC) and DNA. Interfacial interactions between immobilized calf thymus double-stranded (dsDNA) and anticancer drug MC were investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. Based on three repetitive voltammetric measurements of 120 µg mL(-1) DNA immobilized on GO-modified electrodes, the RSD % (n = 3) was calculated as 10.47% and the detection limit (DL) for dsDNA was found to be 9.06 µg mL(-1). EIS studies revealed that the binding of the drug MC to dsDNA leads to a gradual decrease of its negative charge. As a consequence of this interaction, the negative redox species were allowed to approach the electrode, and thus increase the charge transfer kinetics. On the other hand, DPV studies exploited the decrease of the guanine signal due to drug binding as the basis for specifically probing the biointeraction process between MC and dsDNA.