Aptamers as a replacement for antibodies in enzyme-linked immunosorbent assay

The application of antibodies in enzyme-linked immunosorbent assay (ELISA) is the basis of this diagnostic technique which is designed to detect a potpourri of complex target molecules such as cell surface antigens, allergens, and food contaminants. However, development of the systematic evolution of Ligands by Exponential Enrichment (SELEX) method, which can generate a nucleic acid-based probe (aptamer) that possess numerous advantages compared to antibodies, offers the possibility of using aptamers as an alternative molecular recognition element in ELISA. Compared to antibodies, aptamers are smaller in size, can be easily modified, are cheaper to produce, and can be generated against a wide array of target molecules. The application of aptamers in ELISA gives rise to an ELISA-derived assay called enzyme-linked apta-sorbent assay (ELASA). As with the ELISA method, ELASA can be used in several different configurations, including direct, indirect, and sandwich assays. This review provides an overview of the strategies involved in aptamer-based ELASA. (C) 2014 Elsevier B.V. All rights reserved

Aptamers as a replacement for antibodies in enzyme-linked immunosorbent assay

The application of antibodies in enzyme-linked immunosorbent assay (ELISA) is the basis of this diagnostic technique which is designed to detect a potpourri of complex target molecules such as cell surface antigens, allergens, and food contaminants. However, development of the systematic evolution of Ligands by Exponential Enrichment (SELEX) method, which can generate a nucleic acid-based probe (aptamer) that possess numerous advantages compared to antibodies, offers the possibility of using aptamers as an alternative molecular recognition element in ELISA. Compared to antibodies, aptamers are smaller in size, can be easily modified, are cheaper to produce, and can be generated against a wide array of target molecules. The application of aptamers in ELISA gives rise to an ELISA-derived assay called enzyme-linked apta-sorbent assay (ELASA). As with the ELISA method, ELASA can be used in several different configurations, including direct, indirect, and sandwich assays. This review provides an overview of the strategies involved in aptamer-based ELASA. (C) 2014 Elsevier B.V. All rights reserved

Current aspects in immunosensors

Sensing applications can be used to report biomolecular interactions in order to elucidate the functions of molecules. The use of an analyte and a ligand is a common set-up in sensor development. For several decades, antibodies have been considered to be potential analytes or ligands for development of socalled "immunosensors." In an immunosensor, formation of the complex between antibody and antigen transduces the signal, which is measurable in various ways (e.g., both labeled and label-free based detection). Success of an immunosensor depends on various factors, including surface functionalization, antibody orientation, density of the antibody on the sensor platform, and configuration of the immunosensor. Careful optimization of these factors can generate clear-cut results for any immunosensor. Herein, current aspects, involved in the generated immunosensors, are discussed

Separation and identification of bioactive peptides from stem of Tinospora cordifolia (Willd.) Miers

Enzyme hydrolysates (trypsin, papain, pepsin, a-chymotrypsin, and pepsin-pancreatin) of Tinospora cordifolia stem proteins were analyzed for antioxidant efficacy by measuring (1) 1,1-diphenyl-2-picrylhydrazyl (DPPH center dot) radical scavenging activity, (2) 2,20-azinobis(3-ethyl-benzothiazoline- 6-sulfonic acid) (ABTS(+)) radical scavenging capacity, and (3) Fe2+ chelation. Trypsin hydrolysate showed the strongest DPPH center dot scavenging, while alpha-chymotrypsin hydrolysate exhibited the highest ABTS(+) scavenging and Fe2+ chelation. Undigested protein strongly inhibited the gastrointestinal enzymes, trypsin (50% inhibition at enzyme/substrate ratio = 1: 6.9) and a-chymotrypsin (50% inhibition at enzyme/substrate ratio = 1: 1.82), indicating the prolonged antioxidant effect after ingestion. Furthermore, gel filtration purified peptide fractions of papain hydrolysates exhibited a significantly higher ABTS(+) and superoxide radical scavenging as compared to non-purified digests. Active fraction 9 showing the highest radical scavenging ability was further purified and confirmed by MALDI-TOF MS followed by MS/MS with probable dominant peptide sequences identified are VLYSTPVKM-WEPGR, VITVVATAGSETMR, and HIGININSR. The obtained results revealed that free radical scavenging capacity of papain hydrolysates might be related to its consistently low molecular weight hydrophobic peptides

Synthesis of silicon carbide nanomaterials by microwave heating: Effect of types of carbon nanotubes

One-dimensional silicon carbide nanomaterial (SiCNM) is the leading potential material for high temperature, high power and harsh environment components and devices. This is due to the outstanding properties of the one-dimensional SiCNMs such as high mechanical properties, high hardness, good chemical inertness and excellent electronic properties. In this paper, we reported the successful synthesis of one-dimensional SiCNMs from blend of SiO2 particles with two types of CNTs, namely MWCNTs and SWCNTs by using microwave heating and the effect of types of CNTs on the synthesis of one-dimensional SiCNMs. The result of x-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and thermo-gravimetric analysis revealed that high purity of β-SiC nanotube was obtained from blend of SiO2 particles and MWCNTs while solid SiC nanowire was synthesized from blend of SiO2 particles and SWCNTs and associated with the presence of residual of unreacted SiO2 particles. This clearly shows that types of one dimensional SiCNMs (hollow or solid) can be controlled by using different types of CNTs and thus this study proposed a high efficiency microwave heating method for the synthesis of one-dimensional SiCNMs with controllable morphology. © 2019 Elsevier Masson SA

Aptamer-based impedimetric determination of the human blood clotting factor IX in serum using an interdigitated electrode modified with a ZnO nanolayer

This article describes a sensitive impedimetric method for the determination of human blood coagulation factor IX protein (FIX) which is present in extremely low concentration in serum. An interdigitated electrode (IDE) whose surface was layered with zinc oxide was modified with two kinds of probes. One is an antibody, the other an aptamer against FIX. A comparative study between anti-FIX aptamer and anti-FIX antibody showed the aptamer to possess higher affinity for FIX. A sandwich aptamer assay was worked out by using the FIX-binding aptamer on the surface of the IDE. It has a detection limit as low as 10 pM which makes it 4 to 30-fold more sensitive than any other method reported for FIX. Moreover, to practice detection in clinical samples, FIX was detected from the human blood serum by spiking. In our perception, the sensitivity of the ZnO-modified IDE presented here makes it a promising tool for sensing clinically relevant analytes that are present in very low (sub-pM) concentrations