A Suggestion of Electrochemical Biosensor for Study of Platinum(II)-DNA Interactions

Electrochemical DNA biosensors developed for the monitoring of biointeractions with drugs: a review

The interaction of drugs with DNA is important for the discovery of novel drug molecules and for understanding the therapeutic effects of drugs as well as the monitoring of side effects. For this reason, many studies have been carried out to investigate the interactions of drugs with nucleic acids. In recent years, a large number of studies have been performed to electrochemically detect drug-DNA interactions. The fast, sensitive, and accurate results of electrochemical techniques have resulted in a leading role for their implementation in this field. By means of electrochemical techniques, it is possible not only to demonstrate drug-DNA interactions but also to quantitatively analyze drugs. In this context, electrochemical biosensors for drug-DNA interactions have been examined under different headings including anticancer, antiviral, antibiotic, and central nervous system drugs as well as DNA-targeted drugs. An overview of the studies related to electrochemical DNA biosensors developed for the detection of drug-DNA interactions that were reported in the last two decades in the literature is presented herein along with their applications and they are discussed together with their future perspectives.

Real-time detection of carboplatin using a microfluidic system

A novel on-line microfluidic assay for the chemotherapy agent carboplatin will allow sensitive detection of the drug directly applied to the tumour as it emerges from the tumour into healthy tissue.

A microfluidic sensor system based on a carbon nanotube-epoxy composite electrode was fabricated to allow detection of the presence of the anti-cancer drug carboplatin in healthy tissue in real time during chemotherapy. Detection of carboplatin was carried out by observing the effects of the drug on the differential pulse voltammetry of free purine bases using a novel carbon nanotube-epoxy composite electrode. In free solution these electrodes performed better than glassy carbon electrodes for oxidation of the free purine bases AMP and GMP, and than DNA-modified carbon nanotube-epoxy composite sensors for detection of carboplatin. On-line carboplatin detection was performed using a computer-controlled microfluidic platform. The methodology for on-line carboplatin detection was optimised in terms of the analysis time and to allow repeated carboplatin measurement using the same electrode. Microdialysis sampling and our microfluidic platform were combined to give a proof-of-concept system for real-time carboplatin detection with a limit of detection of 0.014 μM carboplatin in the sampled media. This paper is dedicated to Craig Lunte's pioneering work in analysis and microdialysis.

VPA does not enhance platinum binding to DNA in cisplatin-resistant neuroblastoma cancer cells

Neuroblastoma represents a malignancy of the sympathetic nervous system characteristic by biological heterogeneity. Thus, chemotherapy exhibits only low effectivity in curing high-risk forms. Previous studies revealed the cytotoxic potential of valproate on neuroblastoma cells. Nevertheless, these studies omitted effects of hypoxia, despite its undeniable tumorigenic role. In this study, we addressed the question whether valproate promotes binding of platinum-based anti-cancer drugs (cisplatin, carboplatin and oxaliplatin) to DNA and role of hypoxia, cellular antioxidant capacity and cisplatin resistance in this process. Following parameters differed significantly when cells were exposed to treatment with platinum-based drugs: elevation of platinum content bound to DNA, elevation of total thiol content, GSH/GSSG ratio, glutathione reductase and peroxidase, superoxide dismutase and elevation of antioxidant capacity. Hypoxia caused a decrease in cytosine/adenine peak, and no changes in platinum-DNA binding properties were observed. After valproate co-treatment, oxidative stress-related parameters and cytosine/adenine peak were only elevated. The amount of platinum bound to DNA was not changed significantly. Valproate is not able to enhance platinum binding to DNA in neuroblastoma cells, neither in case of intrinsic resistance (UKF-NB-4) nor in case of acquired resistance (UKF-NB-4^CDDP). Therefore, another mechanism different from increase in platinum binding to DNA should be considered as a synergistic effect of valproate by cisplatin treatment.

The Application of Curve Fitting on the Voltammograms of Various Isoforms of Metallothioneins-Metal Complexes

The translation of metallothioneins (MTs) is one of the defense strategies by which organisms protect themselves from metal-induced toxicity. MTs belong to a family of proteins comprising MT-1, MT-2, MT-3, and MT-4 classes, with multiple isoforms within each class. The main aim of this study was to determine the behavior of MT in dependence on various externally modelled environments, using electrochemistry. In our study, the mass distribution of MTs was characterized using MALDI-TOF. After that, adsorptive transfer stripping technique with differential pulse voltammetry was selected for optimization of electrochemical detection of MTs with regard to accumulation time and pH effects. Our results show that utilization of 0.5 M NaCl, pH 6.4, as the supporting electrolyte provides a highly complicated fingerprint, showing a number of non-resolved voltammograms. Hence, we further resolved the voltammograms exhibiting the broad and overlapping signals using curve fitting. The separated signals were assigned to the electrochemical responses of several MT complexes with zinc(II), cadmium(II), and copper(II), respectively. Our results show that electrochemistry could serve as a great tool for metalloproteomic applications to determine the ratio of metal ion bonds within the target protein structure, however, it provides highly complicated signals, which require further resolution using a proper statistical method, such as curve fitting.

Interaction of Heavy Metal Ions with Carbon and Iron Based Particles

Due to the rapid development of industry and associated production of toxic waste, especially heavy metals, there is a great interest in creating and upgrading new sorption materials to remove these pollutants from the environment. This study aims to determine the effectiveness of different carbon forms (graphene, expanded carbon, multi-wall nanotubes) and paramagnetic particles (Fe₂O₃) for adsorption of cadmium(II), lead(II), and copper(II) on its surface, with different interaction time from 1 min to 24 h. The main attention is paid to the detection of these metals using differential pulse voltammetry. Based on the obtained results, graphene and Fe₂O₃ are found to be good candidates for removal of heavy metals from the environment.

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.

An adsorptive transfer technique coupled with brdicka reaction to reveal the importance of metallothionein in chemotherapy with platinum based cytostatics

The drugs based on platinum metals represent one of the oldest, but also one of the most effective groups of chemotherapeutic agents. Thanks to many clinical studies it is known that resistance of tumor cells to drugs is a frequent cause of chemotherapy failure. With regard to platinum based drugs, multidrug resistance can also be connected with increased expression of low-molecular weight protein metallothionein (MT). This study aimed at investigating the interactions of MT with cisplatin or carboplatin, using the adsorptive transfer technique coupled with differential pulse voltammetry Brdicka reaction (AdTS DPV Brdicka reaction), and a comparison of in vitro results with results obtained in vivo. The results obtained from the in vitro study show a strong affinity between platinum based drugs and MT. Further, we analyzed extracts of neuroblastoma cell lines treated with cisplatin or carboplatin. It is clear that neuroblastoma UKF-NB-4 cisplatin-resistant and cisplatin-sensitive cell lines unlikely respond to the presence of the platinum-based cytostatics cisplatin and carboplatin. Finally, we determined the level of MT in samples from rabbits treated with carboplatin and patients with retinoblastoma treated with the same drug.

Electrochemical microsensors for the detection of cadmium(II) and lead(II) ions in plants

Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for easy-to-use and sensitive determination of cadmium(II) and lead(II) ions. The lowest detection limits (hundreds of pM) for both metals was achieved by using of the standard potentiostat, followed by the miniaturized potentiostat (tens of nM) and the homemade instrument (hundreds of nM). Nevertheless, all potentiostats were sensitive enough to evaluate contamination of the environment, because the environmental limits for both metals are higher than detection limits of the instruments. Further, we tested all used potentiostats and working electrodes on analysis of environmental samples (rainwater, flour and plant extract) with artificially added cadmium(II) and lead(II). Based on the similar results obtained for all potentiostats we choose a homemade instrument with a carbon tip working electrode for our subsequent environmental experiments, in which we analyzed maize and sunflower seedlings and rainwater obtained from various sites in the Czech Republic.

Protein-based electrochemical biosensor for detection of silver(I) ions

Silver(I) ions are extremely toxic to aquatic animals. Hence, monitoring of these ions in the environment is needed. The aim of the present study was to suggest a simple biosensor for silver(I) ions detection. The suggested biosensor is based on the modification of a hanging mercury drop electrode (HMDE) by the heavy metal binding protein metallothionein (MT) for silver(I) ions detection. Metallothionein accumulated for 120 s onto the HMDE surface. After rinsing the electrode, the biosensor (MT modified HMDE) was prepared prior to detection of silver(I) ions. The biosensor was immersed in a solution containing silver(I) ions. These ions were bound to the MT structure. Furthermore, the electrode was rinsed and transferred to a pure supporting electrolyte solution, in which no interference was present. Under these experimental conditions, other signals relating to heavy metals naturally occurring in MT were not detected. This phenomenon confirms the strong affinity of silver(I) ions for MT. The suggested biosensor responded well to higher silver(I) ion concentrations. The relative standard deviation for measurements of concentrations higher than 50 microM was approximately 2% (n = 8). In the case of concentrations lower than 10 microM, the relative standard deviation increased to 10% (n = 8). The detection limit (3 signal/noise) for silver(I) ions was estimated as 500 nM.

Study of Interactions between Metallothionein and Cisplatin by using Differential Pulse Voltammetry Brdickás reaction and Quartz Crystal Microbalance

Treatment strategies for tumour diseases are progressively focusing on personalization of medicine. However, this focus requires methods revealing the early general biological mechanisms, including the formation anti-cancer drugs’ resistance. The low molecular mass protein metallothionein is thought to be the crucial for the formation of resistance in tumour treatment based on the platinum-cytostatics. The interactions between metallothionein (MT) and cisplatin were determined by the adsorptive transfer stripping technique coupled with the differential pulse votlammetry Brdickás reaction. The signals related to the MT-cisplatin complex appeared at −0.9 V. The formation of this complex depended on the time of interaction between cisplatin and MT. The complex formation was consequently confirmed by quartz crystal microbalance analyses. The formation of this complex was detectable even after a 20 s long interaction. Moreover, we detected presence of MT-cisplatin complex in the blood of male rats treated with this drug.

Amperometric Sensor for Detection of Chloride Ions

Chloride ion sensing is important in many fields such as clinical diagnosis, environmental monitoring and industrial applications. We have measured chloride ions at a carbon paste electrode (CPE) and at a CPE modified with solid AgNO₃, a solution of AgNO₃ and/or solid silver particles. Detection limits (3 S/N) for chloride ions were 100 μM, 100 μM and 10 μM for solid AgNO₃, solution of AgNO₃ and/or solid silver particles, respectively. The CPE modified with silver particles is the most sensitive to the presence chloride ions. After that we approached to the miniaturization of the whole electrochemical instrument. Measurements were carried out on miniaturized instrument consisting of a potentiostat with dimensions 35 × 166 × 125 mm, screen printed electrodes, a peristaltic pump and a PC with control software. Under the most suitable experimental conditions (Britton-Robinson buffer, pH 1.8 and working electrode potential 550 mV) we estimated the limit of detection (3 S/N) as 500 nM.

Thermoresponsive polymeric gel as a medium for examining interactions between dsDNA and an anticancer drug

A piece of dry N-isopropylacrylamide polymer was soaked in phosphate buffer to obtain a hydrogel which was then employed in the examination of interactions between an anticancer drug C-1311 (5-diethylaminoethyl-amino-8-hydroxyimidazoacridinone) and dsDNA. dsDNA was introduced into the polymer at the polymerization stage. The drug was added to the buffer. Using the volume phase transition of the gel at 40 degrees C, the unbound drug could be determined in the solution released during the transition, which made the calculations more reliable. The interaction parameters were calculated using the McGhee and von Hippel model. It appeared that in the gel medium, the interaction between the drug and dsDNA is spatially limited, since the number of binding units of the polymer chain occupied by one drug molecule was found to be one, while it was two in the regular buffer solution.

An Electrochemical Detection of Metallothioneins at the Zeptomole Level in Nanolitre Volumes

An Electrochemical Detection of Metallothioneins at the Zeptomole Level in Nanolitre VolumesWe report on improvement of the adsorptive transfer stripping technique (AdTS) coupled with the differential pulse voltammetry Brdicka reaction to determine a thiol-protein. The current technique has been unable to generate reproducible results when analyzing very low sample volumes (nanolitres). This obstacle can be overcome technically by modifying the current transfer technique including cooling step of the adsorbed analyte. We tested the technique on determination of a promising tumour disease marker protein called metallothionein (MT). The detection limit (3 S/N) of MT was evaluated as 500 zeptomoles per 500 nL (1 pM) and the quantification limit (10 S/N) as 1,500 zeptomoles per 500 nL (3 pM). Further, the improved AdTS technique was utilized to analyze blood serum samples from patients with breast cancer. Based on the results obtained it can be concluded that the improved technique can be used to detect a thiolprotein in very low sample volumes and can also prevent interferences during the washing and transferring step.

Shapes of Differential Pulse Voltammograms and Level of Metallothionein at Different Animal Species

Metallothioneins play a key role in maintaining homeostasis of essential metals and in protecting of cells against metal toxicity as well as oxidative damaging. Excepting humans, blood levels of metallothionein have not yet been reported from any animal species. Blood plasma samples of 9 animal species were analysed by the adsorptive transfer stripping technique to obtain species specific voltammograms. Quite distinct records were obtained from the Takin (Budorcas taxicolor), while other interesting records were observed in samples from the European Bison (Bison bonasus bonasus) and the Red-eared Slider (Trachemys scripta elegans). To quantify metallothionein the catalytic peak Cat2 was used, well developed in the Domestic Fowl (Gallus gallus f. domestica) and showing a very low signal in the Red Deer (Cervus elaphus). The highest levels of metallothionein reaching over 20 µM were found in the Domestic Fowl. High levels of MT were also found in the Bearded Dragon (Pogona vitticeps) and the Grey Wolf (Canis lupus lupus). The lowest values of about 1-3 µM were determined in the Red-eared Slider, Takin and Red Deer. Employing a simple electrochemical detection it was possible to examine variation in blood metallothionein in different species of vertebrates.