In recent years new nucleic acid and protein‐based combinatorial molecules have attracted the attention of researchers working in various areas of science, ranging from medicine to analytical ...chemistry. These molecules, called aptamers, have been proposed as alternatives to antibodies in many different applications. The aim of this Review is to illustrate the peculiarities of these combinatorial molecules which have initially been explored for their importance in molecular medicine, but have enormous potential in other biotechnological fields historically dominated by antibodies, such as bioassays. A description of these molecules is given, and the methods for their selection and production are also summarized. Moreover, critical aspects related to these molecules are discussed.
Antibody alternatives: This Review covers the peculiarities of the two major classes of affinity molecules produced by evolutionary approaches: nucleic acid aptamers and combinatorial non‐immunoglobulin proteins (termed here, for convenience, simply peptide aptamers). The applications of these molecules in the bioanalytical field are discussed.
MicroRNAs (miRNAs) are a family of non-protein-coding, endogenous, small RNAs. They are a group of gene regulators that function mainly by binding the 3′ untranslated regions of specific target ...messenger RNA (mRNA) leading to gene inactivation by repression of mRNA transcription or induction of mRNA. Mature miRNAs are short molecules approximately 22 nucleotides in length. They regulate a wide range of biological functions from cell proliferation and death to cancer progression. Cellular miRNA expression levels can be used as biomarkers for the onset of disease states and in gene therapy for genetic disorders. Methods for detection of miRNA mainly include northern blotting, microarray, polymerase chain reaction (PCR). This review focuses on the use of electrochemical biosensors for the detection of microRNA.
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•Mature miRNAs are short molecules approximately 22 nucleotides in length.•Biosensor has an essential role in fundamental research and clinical practice.•This paper reviews biosensing of microRNAs by electrochemical devises.•There are several publishing reviews about microRNAs biosensors.•This study reviews the latest published paper in this area.
The DNA thrombin aptamer has been extensively investigated, and the coupling of this aptamer to different transduction principles has demonstrated the wide applicability of aptamers as bioreceptors ...in bioanalytical assays. The goal of this work was to design an aptamer-based sandwich assay with electrochemical detection for thrombin analysis in complex matrixes, using a simple target capturing step by aptamer-functionalized magnetic beads. The conditions for the aptamer immobilization and for the protein binding have been first optimized by surface plasmon resonance, and then transferred to the electrochemical-based assay performed onto screen-printed electrodes. The assay was then applied to the analysis of thrombin in buffer, spiked serum, and plasma and high sensitivity and specificity were found. Moreover, thrombin was generated in situ in plasma by the conversion of its precursor prothrombin, and the formation of thrombin was followed at different times. The concentrations detected by the electrochemical assay were in agreement with a simulation software that mimics the formation of thrombin over time (thrombogram). The proposed work demonstrates that the high specificity of aptamers together with the use of magnetic beads are the key features for aptamer-based analysis in complex matrixes, opening the possibility of a real application to diagnostics or medical investigation.
Nucleic acid-based biosensors are finding increasing use for the detection of environmental pollution and toxicity. A biosensor is defined as a compact analytical device incorporating a biological or ...biologically-derived sensing element either integrated within or intimately associated with a physicochemical transducer. A nucleic acid-based biosensor employs as the sensing element an oligonucleotide, with a known sequence of bases, or a complex structure of DNA or RNA. Nucleic acid biosensors can be used to detect DNA/RNA fragments or either biological or chemical species. In the first application, DNA/RNA is the analyte and it is detected through the hybridization reaction (this kind of biosensor is also called a genosensor). In the second application, DNA/RNA plays the role of the receptor of specific biological and/or chemical species, such as target proteins, pollutants or drugs. Recent advances in the development and applications of nucleic acid-based biosensors for environmental application are reviewed in this article with special emphasis on functional nucleic acid elements (aptamers, DNAzymes, aptazymes) and lab-on-a-chip technology.
In this paper, two simple and sensitive approaches for prostate specific antigen (PSA) detection are presented, by using antibody modified paramagnetic microparticles coupled to multiplexed ...electrochemical platforms. The first proposed approach is based on 8‐sensors screen‐printed arrays as candidate for electrochemical transducers and a simple target capturing step by means of antibody‐functionalised magnetic beads. In order to improve the performances of the immunosensing, a second approach is developed by using GRAVI‐Cell. This is microfluidic‐based affinity assay device for running bead‐protocols. This innovative system combines a special chip containing eight polymer microchannels, with a portable, computer‐controlled instrument. Both immunosensing strategies developed promise to be a sensitive, multiplexed tool for fast and easy PSA analysis.
The application of a novel gold-based screen-printed sensor to lead detection is described. The sensor consists of a screen-printed three electrode cell: a gold working electrode, a silver ...pseudo-reference electrode and a graphite counter electrode. It is used in combination with square wave anodic stripping voltammetry (SWASV). Sensor characterisation experiments as well as the optimisation of the analytical procedure are reported. The optimised parameters allow the detection of micrograms per litre of lead concentrations following short analysis time (detection limit 0.5
μg
l
−1 at 120
s deposition). Measurements of other metals such as copper, cadmium and mercury are reported.
The display of glucose oxidase (GOx) on yeast cell surface using a-agglutinin as an anchor motif was successfully developed. Both the immunochemical analysis and enzymatic assay showed that active ...GOx was efficiently expressed and translocated on the cell surface. Compared with conventional GOx, the yeast cell surface that displayed GOx (GOx-yeast) demonstrated excellent enzyme properties, such as good stability within a wide pH range (pH 3.5–11.5), good thermostability (retaining over 94.8% enzyme activity at 52 °C and 84.2% enzyme activity at 56 °C), and high d-glucose specificity. In addition, direct electrochemistry was achieved at a GOx-yeast/multiwalled-carbon-nanotube modified electrode, suggesting that the host cell of yeast did not have any adverse effect on the electrocatalytic property of the recombinant GOx. Thus, a novel electrochemical glucose biosensor based on this GOx-yeast was developed. The as-prepared biosensor was linear with the concentration of d-glucose within the range of 0.1–14 mM and a low detection limit of 0.05 mM (signal-to-noise ratio of S/N = 3). Moreover, the as-prepared biosensor is stable, specific, reproducible, simple, and cost-effective, which can be applicable for real sample detection. The proposed strategy to construct robust GOx-yeast may be applied to explore other oxidase-displaying-system-based whole-cell biocatalysts, which can find broad potential application in biosensors, bioenergy, and industrial catalysis.
An electrochemical nucleic acid (NA)-based biosensor is a biosensor that integrates a nucleic acid as the biological recognition element and an electrode as the electrochemical signal transducer. The ...present report provides concepts, terms, and methodology related to biorecognition elements, detection principles, type of interactions to be addressed, and construction and performance of electrochemical NA biosensors, including their critical evaluation, which should be valuable for a wide audience, from academic, biomedical, environmental, and food-testing, drug-developing, etc. laboratories to sensor producers.
Xylose is an important and major monosaccharide that extensively exists in the cellulose fermentation industry. Here we present the first report on the direct energy conversion from xylose achieved ...by using novel xylose dehydrogenase (XDH) surface displayed bacteria (XDH-bacteria) based enzymatic biofuel cell. The maximum power density and the open-circuit potential of the cell are 63μWcm−2 and 0.58V, respectively. The as-prepared BFC holds great potential to make use of biomass from lignocellulose degradation as source energy, which avoids the bottleneck in conversion of xylose to ethanol met by conventional fermentation method.
► First report on the direct energy conversion from xylose using xylose dehydrogenase displayed bacteria based biofuel cell. ► Maximum power density of the cell up to 63μWcm−2. ► The open-circuit potential of the cell up to 0.58V.
Surface plasmon resonance imaging (SPRi) is at the forefront of optical sensing, allowing real-time and label free simultaneous multi-analyte measurements. It represents an interesting technology for ...studying a broad variety of affinity interactions with impact in chemistry, both in fundamental and applied research. Signal sampling and management is a key step in SPRi measurements to achieve successful performances. This work aims to develop a strategy for selecting the sensing areas, called Regions of Interest (ROIs), to be sampled for recording SPRi signals that could results in improved sensor performances. The approach has been evaluated using antigen-antibody interaction: anti-human IgGs are immobilized on the chip surface in an array format, while the specific ligand (hIgG antigen) is in solution. This approach has general applicability and demonstrates that rational selection of sensitive areas and standard management of SPRi data has dramatic impact on sensor behaviour. The criteria of the method are: (a) creation of high density maps of ROIs, (b) evaluation of the SPRi binding signals on all the ROIs during a pre-analysis step, (c) 3D elaboration of the results, and (d) ranking of the ROIs for their final selection in further biosensor analysis. Using standard solution of antigen, three different ROIs selection approaches have been compared for their analytical performances. The proposed innovative method results to be the best one for SPRi-based sensing applications.
