Electrochemical probe DNA design in PCR amplicon sequence for the optimum detection of microbiological diseases

Electrochemical DNA Sensor Designed Using the Pencil Graphite Electrode to Detect Listeria monocytogenes

In the present work, a novel electrochemical DNA sensor was designed to detect L. monocytogenes. Two different gene fragments were selected for the sensor design. One is a 702 bp long fragment of the hlyA gene, encoding the synthesis of listeriolysin O toxin, which is unique only to pathogenic strains of L. monocytogenes and is essential for pathogenicity. The other is a 209 bp long fragment of the 16 S RNA gene found in all species of the Listeria genus. As the working electrode, the pencil graphite electrode was modified in various ways (activated or covered with polypyrrole), and six different combinations were constituted using three types of the modified working electrode and two different gene fragments. The developed system is based on differential pulse voltammetric transduction of guanine oxidation after hybridization between the selected gene fragment (38 µg/mL) and the selected fragment-specific inosine-modified probe (1.8 µmol/L) immobilized on a pencil graphite electrode surface. The comparison of all combinations demonstrates that the best results are obtained with the combination formed from a polypyrrole-coated pencil graphite electrode (prepared at 2 scans) and 702 bp fragment of the hlyA gene. The analysis time is less than 1 hour, and the necessary DNA concentrations for the analysis have been determined as 8.2 × 10-11 M DNA and 2.7 × 10-10 M DNA respectively, for the hlyA gene and 16 S RNA gene.

Prevalence and evaluation strategies for viral contamination in food products: Risk to human health-a review

Nowadays, viruses of foodborne origin such as norovirus and hepatitis A are considered major causes of foodborne gastrointestinal illness with widespread distribution worldwide. A number of foodborne outbreaks associated with food products of animal and non-animal origins, which often involve multiple cases of variety of food streams, have been reported. Although several viruses, including rotavirus, adenovirus, astrovirus, parvovirus, and other enteroviruses, significantly contribute to incidence of gastrointestinal diseases, systematic information on the role of food in transmitting such viruses is limited. Most of the outbreak cases caused by infected food handlers were the source of 53% of total outbreaks. Therefore, prevention and hygiene measures to reduce the frequency of foodborne virus outbreaks should focus on food workers and production site of food products. Pivotal strategies, such as proper investigation, surveillance, and reports on foodborne viral illnesses, are needed in order to develop more accurate measures to detect the presence and pathogenesis of viral infection with detailed descriptions. Moreover, molecular epidemiology and surveillance of food samples may help analysis of public health hazards associated with exposure to foodborne viruses. In this present review, we discuss different aspects of foodborne viral contamination and its impact on human health. This review also aims to improve understanding of foodborne viral infections as major causes of human illness as well as provide descriptions of their control and prevention strategies and rapid detection by advanced molecular techniques. Further, a brief description of methods available for the detection of viruses in food and related matrices is provided.

Sequence-specific label-free nucleic acid biosensor for the detection of the hepatitis C virus genotype 1a using a disposable pencil graphite electrode

In this paper, we demonstrate a simple, sensitive, inexpensive, disposable and label-free electrochemical nucleic acid biosensor for the detection of the hepatitis C virus genotype 1a (HCV1a). The nucleic acid biosensor was designed with the amino-linked inosine-substituted 20-mer probes, which were immobilized onto a disposable pencil graphite electrode (PGE) by covalent linking. The proposed nucleic acid biosensor was linear in the range of 0.05 and 0.75 μM, exhibiting a limit of detection of 54.9 nM. The single-stranded synthetic PCR product analogs of HCV1a were also detected with satisfactory results under optimal conditions, showing the potential application of this biosensor.

Detection of short oligonucleotide sequences of hepatitis B virus using electrochemical DNA hybridisation biosensor

A novel, sensitive and selective electrochemical hybridisation biosensor was developed for the detection of the hepatitis B virus (HBV) using a manganese(II) complex as electrochemical indicator and a DNA probe-modified carbon paste electrode as the biosensor (DNA/CPE). The results showed that this complex could be accumulated electrochemically the immobilised dsDNA layer rather than in the single-stranded DNA (ssDNA) layer. On the basis of this, the manganese complex was used as an electrochemical hybridisation indicator for the detection of oligonucleotides related to HBV. The hybridisation event was evaluated on the basis of the difference between the reduction signals of the manganese(II) complex with the probe DNA prior to and post hybridisation with a target sequence using a differential pulse mode. Several factors affecting the immobilisation and hybridisation of oligonucleotides as well as the indicator’s accumulation were investigated. Experiments with a noncomplementary and mismatch sequences demonstrated the good selectivity of the biosensor. Using this approach, the HBV target oligonucleotide’s sequence could be quantified over arange from 0.22 ng L

An electrochemical impedance sensor based on a small molecule modified Au electrode for the recognition of a trinucleotide repeat

A small molecule modified sensor was developed for the detection of XGG trinucleotide repeats (X = C, T) by electrochemical impedance spectroscopy.

Quantum dots self assembly based interface for blood cancer detection

Results of the studies related to fabrication of sensitive electrochemical biosensor using an interface based on quantum dots (QDs) self-assembly is reported. The QDs assembly is sought to provide improved fundamental characteristics to the electrode interface in terms of electroactive surface area, diffusion coefficient, and electron transfer kinetics. This QDs modified electrode has been utilized to serve as a transducer surface for covalent immobilization of chronic myelogenous leukemia (CML) specific probe oligonucleotide, designed from the BCR-ABL fusion gene. The electrochemical characteristics of this biosensor toward various designed synthetic oligonucleotides reveal a significant enhancement in its mismatch discrimination capability compared to the biosensing assay without QDs under similar experimental conditions. The sensing characteristics of this biosensor offer a potential for detection of target oligonucleotide at a concentration as low as 1.0 pM. Furthermore, the PCR-amplified CML-positive patient samples with various BCR-ABL transcript ratios can be electrochemically distinguished from healthy samples, indicating promising application of the QDs based biosensor for clinical investigations.

Readily reusable electrochemical DNA hybridization biosensor based on the interaction of DNA with single-walled carbon nanotubes

Carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) were assembled vertically on the glassy carbon electrode using ethylenediamine as linking agent to fabricate an aligned electrode (SWNTE). Single-stranded DNA (ssDNA) wrapped around the SWNTs to form ssDNA-wrapped SWNTE structures based on the interaction between ssDNA and SWNT. A sensitive differential pulse voltammetric (DPV) response was obtained at the ssDNA-wrapped SWNTE owing to the electrooxidation of guanine bases. Double-stranded DNA (dsDNA) was formed when ssDNA on the ssDNA-wrapped SWNTE was hybridized with complementary ssDNA (cDNA). The dsDNA was removed from the SWNTs by undergoing a process of preconditioning at -0.6 V. Consequentially, the DPV response of guanine bases decreased. The used SWNTE could be renewed easily via ultrasonically rinsing. On the basis of this mechanism, a label-free and readily reusable electrochemical DNA hybridization biosensor was designed by directly monitoring the current change of guanine bases. Under optimum conditions, the plot of the measurement signal of guanine bases versus the cDNA concentrations was a good straight line in the range of 40-110 nM with a detection limit of 20 nM (3s). The biosensor can be switched to detect different target DNAs easily.

Electrochemical techniques on sequence-specific PCR amplicon detection for point-of-care applications

Nucleic acid based analysis provides accurate differentiation among closely affiliated species and this species- and sequence-specific detection technique would be particularly useful for point-of-care (POC) testing for prevention and early detection of highly infectious and damaging diseases. Electrochemical (EC) detection and polymerase chain reaction (PCR) are two indispensable steps, in our view, in a nucleic acid based point-of-care testing device as the former, in comparison with the fluorescence counterpart, provides inherent advantages of detection sensitivity, device miniaturization and operation simplicity, and the latter offers an effective way to boost the amount of targets to a detectable quantity. In this mini-review, we will highlight some of the interesting investigations using the combined EC detection and PCR amplification approaches for end-point detection and real-time monitoring. The promise of current approaches and the direction for future investigations will be discussed. It would be our view that the synergistic effect of the combined EC-PCR steps in a portable device provides a promising detection technology platform that will be ready for point-of-care applications in the near future.

Recent advances in DNA sensors

The concept of DNA biosensors is sustained by the need for rapid and highly sensitive analytical tools for genetic detection. Their implementation is based on three key steps: (i) immobilization of single-stranded oligonucleotide probes onto a substrate; (ii) hybridization and (iii) reading. These steps involve complementary knowledge in various disciplinary fields such as surface physics and chemistry, molecular electrochemistry, micro-technologies, optics, electronics and biochemistry. We present here, in a non-exhaustive way, the recent advances in the two steps of immobilization and detection that rely upon increasing integration of the number of reading points or/and of the reading strategy.