Martin Bartošík

Electrochemistry of Nucleic Acids

Publisher Summary The electroactivity of nucleic acids was discovered several years ago. It was shown that at mercury electrodes, adenine and cytosine were reduced in ssDNA while guanine produced an anodic signal due to the oxidation of guanine reduction product. The DNA signals at mercury electrodes are highly sensitive to changes in DNA structure due to DNA denaturation and renaturation, as well as to minor structural changes resulting from DNA premelting and DNA damage. The changes in DNA structure are reflected not only by the DNA faradaic responses but also by non-faradaic signals due to adsorption/desorption of DNA. Several interesting principles have been used in the development of the DNA sensors—such as amplified electrochemical analysis, investigation of charge transport, and tracing of changes in conformation of DNA. The s ensors for DNA hybridization and DNA damage lead the field of the electrochemistry of nucleic acids. The chapter briefly summarizes some properties of the elimination voltammetry with linear scan (EVLS) method. Oscillographic polarography, at controlled alternating current, was used in the electrochemical analysis of nucleic acids.

Electrochemistry of Nonconjugated Proteins and Glycoproteins. Toward Sensors for Biomedicine and Glycomics

In this review, we wish to show that in the recent years a significant progress was done in the EC analysis of practically all proteins, based on electroactivity of amino acid (aa) residues in proteins. Also electrochemistry of polysaccharides, oligosaccharides and glycoproteins greatly advanced in creating important steps for its larger application in the glycoprotein research. In recent decades, a great effort was devoted to the discovery and application of biomarkers for analysis of different diseases, including cancer. In the following paragraphs, special attention will be paid (i) to intrinsic electroactivity of peptides and proteins, including the sensitivity to changes in protein 3D structures, as well as to recent advances in EC investigations of DNA-protein interactions, (ii) to intrinsic electroactivity of glycans and polysaccharides, advances in EC detection of lectin-glycoprotein interactions and to introduction of electroactive labels to polysaccharides and glycans and finally (iii) to EC detection of protein biomarkers, based predominantly on application of antibodies in immunoassays, nucleic acid and peptide aptamers for construction of aptasensors, and lectin biosensors for detection of glycoprotein biomarkers.

Ternary monolayers as DNA recognition interfaces for direct and sensitive electrochemical detection in untreated clinical samples.

Detection of specific DNA sequences in clinical samples is a key goal of studies on DNA biosensors and gene chips. Herein we present a highly sensitive electrochemical genosensor for direct measurements of specific DNA sequences in undiluted and untreated human serum and urine samples. Such genosensing relies on a new ternary interface involving hexanedithiol (HDT) co-immobilized with the thiolated capture probe (SHCP) on gold surfaces, followed by the incorporation of 6-mercapto-1-hexanol (MCH) as diluent. The performance of ternary monolayers prepared with linear dithiols of different lengths was systematically examined, compared and characterized by cyclic voltammetry and electrochemical impedance spectroscopy, with HDT exhibiting the most favorable analytical performance. The new SHCP/HDT+MCH monolayer led to a 80-fold improvement in the signal-to-noise ratio (S/N) for 1 nM target DNA in undiluted human serum over the common SHCP+MCH binary alkanethiol interface, and allowed the direct quantification of the target DNA down to 7 pM (28 amol) and 17 pM (68 amol) in undiluted/untreated serum and urine, respectively. It also displayed attractive antifouling properties, as indicated from the favorable S/N obtained after a prolonged exposure (24h) to untreated biological matrices. These attractive features of the SHCP/HDT+MCH sensor interface indicate considerable promise for a wide range of clinical applications.

Electrochemistry of riboflavin-binding protein and its interaction with riboflavin ☆

Riboflavin-binding protein (RBP, a carrier of riboflavin) plays an essential role in embryo development. Electrochemical studies of the riboflavin-RBP interactions have been so far limited to changes in polarographic and voltammetric responses of riboflavin because of lack of methods capable to detect electrochemical changes in the RBP responses. Here we used constant current chronopotentiometric stripping analysis (CPSA) with the hanging mercury drop electrode (HMDE) and square wave voltammetry (SWV) with carbon paste electrode (CPE) to investigate RBP. We found that CPSA of RBP produces electrocatalytic peak H, capable to discriminate between apoprotein and holoprotein forms of RBP. This peak is suitable for studies of RBP-riboflavin interaction at nanomolar concentrations. We observed no sign of a release of riboflavin from holoprotein adsorbed at the HMDE surface. SWV at CPE required higher concentrations of RBP and displayed almost identical oxidation peaks of apoprotein and holoprotein.

Electrochemical chip-based genomagnetic assay for detection of high-risk human papillomavirus DNA.

Cervical cancer, being the fourth leading cause of cancer death in women worldwide, predominantly originates from a persistent infection with a high-risk human papillomavirus (HPV). Detection of DNA sequences from these high-risk strains, mostly HPV-16 and HPV-18, represents promising strategy for early screening, which would help to identify women with higher risk of cervical cancer. In developing countries, inadequate screening options lead to disproportionately high mortality rates, making a fast and inexpensive detection schemes highly important. Electrochemical sensors and assays offer an alternative to current methods of detection. We developed an electrochemical-chip based assay, in which target HPV DNA is captured via magnetic bead-modified DNA probes, followed by an antidigoxigenin-peroxidase detection system at screen-printed carbon electrode chips, enabling parallel measurements of eight samples simultaneously. We show sensitive detection in attomoles of HPV DNA, selective discrimination between HPV-16 and HPV-18 and good reproducibility. Most importantly, we show application of the assay into both cancer cell lines and cervical smears from patients. The electrochemical results correlated well with standard methods, making this assay potentially applicable in clinical practice.

Investigation of protein FTT1103 electroactivity using carbon and mercury electrodes. Surface-inhibition approach for disulfide oxidoreductases using silver amalgam powder

Recently, it was shown that electrochemical methods can be used for analysis of poorly water-soluble proteins and for study of their structural changes and intermolecular (protein-ligand) interactions. In this study, we focused on complex electrochemical investigation of recombinant protein FTT1103, a disulfide oxidoreductase with structural similarity to well described DsbA proteins. This thioredoxin-like periplasmic lipoprotein plays an important role in virulence of bacteria Francisella tularensis. For electrochemical analyses, adsorptive transfer (ex situ) square-wave voltammetry with pyrolytic graphite electrode, and alternating-current voltammetry and constant-current chronopotentiometric stripping analysis with mercury electrodes, including silver solid amalgam electrode (AgSAE) were used. AgSAE was used in poorly water-soluble protein analysis for the first time. In addition to basic redox, electrocatalytic and adsorption/desorption characterization of FTT1103, electrochemical methods were also used for sensitive determination of the protein at nanomolar level and study of its interaction with surface of AgSA microparticles. Proposed electrochemical protocol and AgSA surface-inhibition approach presented here could be used in future for biochemical studies focused on proteins associated with membranes as well as on those with disulfide oxidoreductase activity.

Electrochemistry and electron paramagnetic resonance spectroscopy of cytochrome c and its heme-disrupted analogs

Cytochrome c (cyt c) is one of the most studied conjugated proteins due to its electron-transfer properties and ability to regulate the processes involved in homeostasis or apoptosis. Here we report an electrochemical strategy for investigating the electroactivity of cyt c and its analogs with a disrupted heme moiety, i.e. apocytochrome c (acyt c) and porphyrin cytochrome c (pcyt c). The electrochemical data are supplemented with low-temperature and spin-probe electron paramagnetic resonance (EPR) spectroscopy. The main contribution of this report is a complex evaluation of cyt c reduction and oxidation at the level of surface-localized amino acid residues and the heme moiety in a single electrochemical scan. The electrochemical pattern of cyt c is substantially different to both analogs acyt c and pcyt c, which could be applicable in further studies on the redox properties and structural stability of cytochromes and other hemeproteins.

Bioelectrochemistry of nucleic acids for early cancer diagnostics – analysis of DNA methylation and detection of microRNAs

Abstract Dysregulation of gene expression mechanisms has been observed in many tumors, making their analysis of utmost importance. These mechanisms include DNA methylation, an epigenetic mechanism in which 5-carbon of cytosine becomes methylated, leading to gene silencing, and action of short RNA molecules called microRNAs, which regulate protein synthesis at post-transcriptional level by binding to mRNAs. In this review, we describe major roles of both mechanisms in carcinogenesis, offer an overview of currently used methods for their analysis, and summarize most recent advances in electrochemical-based assays and strategies. Advantages of electrochemistry, including favorable cost, time of experiment, or simple instrumentation, are highlighted, along with current challenges that need to be addressed prior to successful application into clinical routine.

Titanocenes as anticancer agents: recent insights.

BACKGROUND Enormous success of antitumor agent cisplatin initiated interest in other organometallic complexes. A subclass of organometallic compounds termed metallocenes, characterized by a transition metal central atom (M) bound to cyclopentadienide (Cp-/[C5H5]-) ligands with the basic formula Cp2M, has gained increasing interest as promising anticancer agents. OBJECTIVES This review is aimed at a progress in the development of organometallic titanium-based compounds focusing primarily on the evaluation of their cytotoxic activity and mechanism of action in relation to potential utilization as anticancer drugs. RESULTS Metallocenes bearing titanium as central atom were sorted according to their structure and modifications and their anticancer activity is further discussed. CONCLUSION Titanocenes represent family of promising compounds exerting cytostatic activity. We suggest that their application not only as separate agents, but also in combination with newly developed carriers, e.g. nanomaterials, may lead to improvement of their delivery into tumor cells and following utilization in cancer treatment.

Human Papillomavirus – Role in Cervical Carcinogenesis and Methods of Detection

BACKGROUND Persistent infection with high-risk human papillomavirus (HPV) strains, especially HPV 16 and HPV 18, is associated with the onset of various malignant diseases, including cervical carcinoma in women. HPV DNA testing is thus being implemented as a complementary method to standard cytological examination, mainly due to its increased sensitivity. AIM This review outlines the role of HPV in cervical carcinogenesis, with a focus on the formation of cervical intraepithelial neoplasias (CIN1-3) and the molecular mechanism underlying cellular transformation. Current biomarkers used to screen premalignant lesions are described, including mRNA transcripts of the E6 and E7 genes, protein p16 (a cyclin-dependent kinase inhibitor that regulates cell cycle progression from G1 to S phase), altered DNA methylation patterns, and actions of specific microRNAs (short (18-22 bp), non-coding, single-stranded RNA molecules that regulate gene expression at the post-transcriptional level). This review also describes the advantages and drawbacks of commercial HPV tests, and depicts novel methods for more cost-effective and faster HPV diagnostics based on optical or electrochemical detection. CONCLUSION Although great progress has been made, the incidence and mortality rates of cervical malignancies remain relatively high, especially in developing countries. Incorporation of HPV testing into routine screening programs could help to decrease mortality rates; however, the cost of such testing must be reduced if it is to compete with current cytology-based examinations.Key words: HPV - cervical carcinoma - HPV testing - nucleic acid hybridization - mRNA - DNA methylation - microRNA This work was supported by MEYS-NPS I-LO1413 and GAČR 17-08971S. The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 25. 9. 2017Accepted: 26. 1. 2018.