Electrochemical detection of hepatitis C virus with signal amplification using BamHI endonuclease and horseradish peroxidase-encapsulated nanogold hollow spheres

Artificial Heme Enzymes for the Construction of Gold-Based Biomaterials

Many efforts are continuously devoted to the construction of hybrid biomaterials for specific applications, by immobilizing enzymes on different types of surfaces and/or nanomaterials. In addition, advances in computational, molecular and structural biology have led to a variety of strategies for designing and engineering artificial enzymes with defined catalytic properties. Here, we report the conjugation of an artificial heme enzyme (MIMO) with lipoic acid (LA) as a building block for the development of gold-based biomaterials. We show that the artificial MIMO@LA can be successfully conjugated to gold nanoparticles or immobilized onto gold electrode surfaces, displaying quasi-reversible redox properties and peroxidase activity. The results of this work open interesting perspectives toward the development of new totally-synthetic catalytic biomaterials for application in biotechnology and biomedicine, expanding the range of the biomolecular component aside from traditional native enzymes.

Magnetic bead/capture DNA/glucose-loaded nanoliposomes for amplifying the glucometer signal in the rapid screening of hepatitis C virus RNA

A digital detection strategy based on a portable personal glucometer (PGM) was developed for the simple, rapid, and sensitive detection of hepatitis C virus (HCV) RNA, involving the release of glucose-loaded nanoliposomes due to coupling-site-specific cleavage by the endonuclease BamHI. The glucose-loaded nanoliposomes were synthesized using a reversed-phase evaporation method and provided an amplified signal at the PGM in the presence of HCV RNA. Initially, a 21-mer oligonucleotide complementary to HCV RNA was covalently conjugated to a magnetic bead through the amino group at the 5' end of the oligonucleotide, and then bound to a glucose-loaded liposome by typical carbodiimide coupling at its 3' end. In the presence of the target HCV RNA, the target hybridized with the oligonucleotide to form double-stranded DNA. The symmetrical duplex sequence 5'-GGATCC-3' between guanines was then catalytically cleaved by BamHI, which detached the glucose-loaded liposome from the magnetic bead. Following magnetic separation of the bead, the detached glucose-loaded liposome was lysed using Triton X-100 to release the glucose molecules within it, which were then detected as an amplified signal at the digital PGM. Under optimal conditions, the PGM signal increased with increasing HCV RNA, and displayed a strongly linear dependence on the level of HCV RNA for concentrations ranging from 10 pM to 1.0 μM. The detection limit (LOD) of the system was 1.9 pM. Good reproducibility and favorable specificity were achieved in the analysis of the target HCV RNA. Human serum samples containing HCV RNA were analyzed using this strategy, and the developed sensing platform was observed to yield satisfactory results based on a comparison with the corresponding results from a Cobas^® Amplicor HCV Test Analyzer. Graphical abstract A digital detection strategy utilizing a personal glucometer was developed for the detection of hepatitis C virus RNA. The strategy involved the use of the endonuclease BamHI along with a 21-mer oligonucleotide conjugated to both a magnetic bead and a glucose-loaded nanoliposome. Hybridization of the nucleotide with the target RNA triggered the coupling-site-specific cleavage of the duplex by BamHI, leading to the release of the glucose-loaded nanoliposome. Following separation of the magnetic bead, the free nanoliposome was dissolved, liberating the glucose molecules within it, which in turn were detected as an amplified signal by the glucometer.

Enzyme-assisted target recycling (EATR) for nucleic acid detection

Fast, reliable and sensitive methods for nucleic acid detection are of growing practical interest with respect to molecular diagnostics of cancer, infectious and genetic diseases. Currently, PCR-based and other target amplification strategies are most extensively used in practice. At the same time, such assays have limitations that can be overcome by alternative approaches. There is a recent explosion in the design of methods that amplify the signal produced by a nucleic acid target, without changing its copy number. This review aims at systematization and critical analysis of the enzyme-assisted target recycling (EATR) signal amplification technique. The approach uses nucleases to recognize and cleave the probe-target complex. Cleavage reactions produce a detectable signal. The advantages of such techniques are potentially low sensitivity to contamination and lack of the requirement of a thermal cycler. Nucleases used for EATR include sequence-dependent restriction or nicking endonucleases or sequence independent exonuclease III, lambda exonuclease, RNase H, RNase HII, AP endonuclease, duplex-specific nuclease, DNase I, or T7 exonuclease. EATR-based assays are potentially useful for point-of-care diagnostics, single nucleotide polymorphisms genotyping and microRNA analysis. Specificity, limit of detection and the potential impact of EATR strategies on molecular diagnostics are discussed.

Graphene quantums dots combined with endonuclease cleavage and bidentate chelation for highly sensitive electrochemiluminescent DNA biosensing

A novel strategy for highly sensitive electrochemiluminescence (ECL) detection of DNA was proposed based on site-specific cleavage of BamHI endonuclease combined with the excellent ECL activity of graphene quantum dots (GQDs) and bidentate chelation of the dithiocarbamate DNA (DTC-DNA) probe assembly. The difference between photoluminescence and ECL spectral peaks suggested that a negligible defect existed on the GQDs surface for generation of an ECL signal. The formed DTC-DNA was directly attached to the gold surface by bidentate anchoring (S-Au-S bonds), which conferred a strong affinity between the ligands and the gold surface, increasing the robustness of DNA immobilization on the gold surface. BamHI endonuclease site-specifically recognized and cleaved the duplex symmetrical sequence, which made the double-stranded DNA fragments and GQDs break off from the electrode surface, inducing a decrease of the ECL signal. Using hepatitis C virus-1b genotype complementary DNA (HCV-1b cDNA) as a model, a novel signal-off ECL DNA biosensor was developed based on variation of the ECL intensity before and after digestion of the DNA hybrid. Electrochemical impedance spectroscopy confirmed the successful fabrication of the ECL DNA biosensor. This ECL biosensor for HCV-1b cDNA determination exhibited a linear range from 5 fM to 100 pM with a detection limit of 0.45 fM at a signal-to-noise ratio of 3 and showed satisfactory selectivity and good stability, which validated the feasibility of the designed strategy. The proposed strategy may be conveniently combined with other specific biological recognition events for expansion of the biosensing application, especially in clinical diagnoses.

Ultrasensitive electrochemical biosensing for DNA using quantum dots combined with restriction endonuclease

A sensitive platform using endonuclease and AuNPs as well as environmental Bi film for the detection of DNA has been developed.

Diagnostic tests for hepatitis C: Recent trends in electrochemical immunosensor and genosensor analysis

Hepatitis C is a liver disease that is transmitted through contact with the blood of an infected person. An estimated 150 million individuals worldwide have been chronically infected with the hepatitis C virus (HCV). Hepatitis C shows significant genetic variation in the global population, due to the high rate of viral RNA mutation. There are six variants of the virus (HCV genotypes 1, 2, 3, 4, 5, and 6), with 15 recorded subtypes that vary in prevalence across different regions of the world. A variety of devices are used to diagnose hepatitis C, including HCV antibody test, HCV viral load test, HCV genotype test and liver biopsy. Rapid, inexpensive, sensitive, and robust analytical devices are therefore essential for effective diagnosis and monitoring of disease treatment. This review provides an overview of current electrochemical immunosensor and genosensor technologies employed in HCV detection. There are a limited number of publications showing electrochemical biosensors being used for the detection of HCV. Due to their simplicity, specificity, and reliability, electrochemical biosensor devices have potential clinical applications in several viral infections.

Bioresponsive controlled release from mesoporous silica nanocontainers with glucometer readout

A portable and quantitative biosensing platform for monitoring proteins and small molecules without the need for sample separation and washing is developed by using a commercialized personal glucose meter based on bioresponsive controlled release of glucose from aptamer-gated mesoporous silica nanocontainers.

A novel LTCC electrochemical cell construction and characterization: a detection compartment for portable devices

In this work we described for the first time the construction of a 25 μL electrochemical cell from low temperature co-fired ceramic (LTCC) material and carbon screen-printed electrode applicable in portable devices. Firstly, a carbon screen-printed electrode was prepared and characterized by cyclic voltammetry and scanning electron microscopy. Afterwards carbon polymeric film and metal pastes were dropped into the LTCC cell cavities in order to determine the device electrodes, and this arrangement was also electrochemically characterized. The great advantage of this promising device is the simple construction method and its widespread applicability in reusable portable devices.

Nanogold-based bio-bar codes for label-free immunosensing of proteins coupling with an in situ DNA-based hybridization chain reaction

A label-free, non-enzyme immunosensing strategy is designed for ultrasensitive electronic detection of disease-related proteins (carcinoembryonic antigen as a model) by using gold nanoparticle-based bio-bar codes and an in situ amplified DNA-based hybridization chain reaction.