Electrochemical determination of carbohydrate-binding proteins using carbohydrate-stabilized gold nanoparticles and silver enhancement

Highly Efficient Gold Nano-Flower Optical Biosensor Doped in a Sol-Gel/PEG Matrix for the Determination of a Calcitonin Biomarker in Different Serum Samples

We developed a novel, simple, sensitive, accurate, and precise method for the determination of calcitonin in different serum samples with medullar thyroid carcinoma. The designed flower-like thin film gold nanoparticles doped in a sol-gel/polyethylene glycol mold are used as an optical biosensor for the efficient determination of calcitonin. The sensor was characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray microanalysis, and Fourier-transform infrared spectroscopy. The efficiency of the considered bio-sensor is done using the quencher calcitonin of the emission band at 360 nm of biomarker obtained at λ_ex = 333 nm in acetonitrile solvent. The sensing mechanism was based on fluorescence resonance energy transfer. The remarkable quenching of the fluorescence intensity at 360 nm of optical sensor by various concentrations of calcitonin was successfully used as an optical biosensor for the assessment of calcitonin for different serum samples of patients with medullar thyroid carcinoma. The calibration plot was prepared for the concentration range 0.01-1000 pg/mL of calcitonin with a correlation coefficient of 0.99 and a detection limit of 0.707 pg/mL. The suggested method augments the sensitivity of calcitonin as a useful biomarker for the early diagnosis of medullar thyroid carcinoma. This method is considered as a gateway for the construction of a new prototype for the follow-up of thyroid cancer in the spinal cord during and after treatment.

A novel oriented antibody immobilization based voltammetric immunosensor for allergenic activity detection of lectin in kidney bean by using AuNPs-PEI-MWCNTs modified electrode

As a well-known allergenic indicator in kidney beans, lectins have always been the serious threats for human health. Herein, we introduced a new label-free voltammetric immunosensor for the direct determination of kidney bean lectin (KBL) with potential allergenic activity. Gold nanoparticles-polyethyleneimine-multiwalled carbon nanotubes nanocomposite was one-pot synthesized and modified onto the glass carbon electrode to enhance catalytic currents of oxygen reduction reaction. The KBL polyclonal antibody, acquired from rabbit immunization, was orientedly immobilized on the electrode modified with recombinant staphylococcal protein A via fragment crystallizable (Fc) region of antibody. Under the optimized condition, the immunosensor displayed a good linear response (R² = 0.978) to KBL with a range from 0.05 to 100 μg/mL and a detection limit of 0.023 μg/mL. Simultaneously, the immunosensor exhibited well selectivity, interference-resistant ability, stability (4 °C) and reproducibility. Compared with the conventional enzyme-linked immunosorbent assay (ELISA) method, the immunosensor was successfully applied to quantify allergenic activity of lectin in raw and cooked (boiled for 30 min) kidney bean milk samples. This new approach provides new perspectives both for rapid quantification of lectin in kidney beans-derived foodstuffs and as a real-time monitoring tool for the allergenic potential during the whole production and consumption process.

Applications of Gold Nanoparticles in Non-Optical Biosensors

Due to their unique properties, such as good biocompatibility, excellent conductivity, effective catalysis, high density, and high surface-to-volume ratio, gold nanoparticles (AuNPs) are widely used in the field of bioassay. Mainly, AuNPs used in optical biosensors have been described in some reviews. In this review, we highlight recent advances in AuNP-based non-optical bioassays, including piezoelectric biosensor, electrochemical biosensor, and inductively coupled plasma mass spectrometry (ICP-MS) bio-detection. Some representative examples are presented to illustrate the effect of AuNPs in non-optical bioassay and the mechanisms of AuNPs in improving detection performances are described. Finally, the review summarizes the future prospects of AuNPs in non-optical biosensors.

Glyconanomaterials for biosensing applications

Nanomaterials constitute a class of structures that have unique physiochemical properties and are excellent scaffolds for presenting carbohydrates, important biomolecules that mediate a wide variety of important biological events. The fabrication of carbohydrate-presenting nanomaterials, glyconanomaterials, is of high interest and utility, combining the features of nanoscale objects with biomolecular recognition. The structures can also produce strong multivalent effects, where the nanomaterial scaffold greatly enhances the relatively weak affinities of single carbohydrate ligands to the corresponding receptors, and effectively amplifies the carbohydrate-mediated interactions. Glyconanomaterials are thus an appealing platform for biosensing applications. In this review, we discuss the chemistry for conjugation of carbohydrates to nanomaterials, summarize strategies, and tabulate examples of applying glyconanomaterials in in vitro and in vivo sensing applications of proteins, microbes, and cells. The limitations and future perspectives of these emerging glyconanomaterials sensing systems are furthermore discussed.

Recent Progress in Lectin-Based Biosensors

This article reviews recent progress in the development of lectin-based biosensors used for the determination of glucose, pathogenic bacteria and toxins, cancer cells, and lectins. Lectin proteins have been widely used for the construction of optical and electrochemical biosensors by exploiting the specific binding affinity to carbohydrates. Among lectin proteins, concanavalin A (Con A) is most frequently used for this purpose as glucose- and mannose-selective lectin. Con A is useful for immobilizing enzymes including glucose oxidase (GOx) and horseradish peroxidase (HRP) on the surface of a solid support to construct glucose and hydrogen peroxide sensors, because these enzymes are covered with intrinsic hydrocarbon chains. Con A-modified electrodes can be used as biosensors sensitive to glucose, cancer cells, and pathogenic bacteria covered with hydrocarbon chains. The target substrates are selectively adsorbed to the surface of Con A-modified electrodes through strong affinity of Con A to hydrocarbon chains. A recent topic in the development of lectin-based biosensors is a successful use of nanomaterials, such as metal nanoparticles and carbon nanotubes, for amplifying output signals of the sensors. In addition, lectin-based biosensors are useful for studying glycan expression on living cells.

Ultrasensitive electrochemical immunoassay of proteins based on in situ duple amplification of gold nanoparticle biolabel signals

An electrochemical sandwich immunoassay method that can be sensitive to a few protein molecules (human immunoglobulin G or human prostate-specific antigen) is reported based on in situ duple amplification of gold nanoparticle biolabel signals.

Anthraquinonyl glycoside facilitates the standardization of graphene electrodes for the impedance detection of lectins

Background

Construction of electrochemical impedance sensors by the self-assembly technique has become a promising strategy for the ‘label-free’ detection of protein-ligand interactions. However, previous impedance sensors are devoid of an inherent electrochemical signal, which limits the standardization of the sensors for protein recognition in a reproducible manner.

Results

We designed and synthesized an anthraquinonyl glycoside (AG) where the anthraquinone (AQ) moiety can bind to the surface of a graphene-based working electrode while the glycoside serving as a ligand for lectin. By measuring the inherent voltammetric signal of AQ, the glycosides decorated on the working electrode could be simply quantified to obtain electrodes with a unified signal window. Subsequently, impedance analysis showed that the ‘standardized’ electrodes gave a reproducible electrochemical response to a selective lectin with no signal variation in the presence of unselective proteins.

Conclusion

Anthraquinone-modified ligands could be used to facilitate the standardization of electrochemical impedance sensors for the reproducible, selective analysis of ligand-protein interactions.

Electronic supplementary material

The online version of this article (doi:10.1186/s13065-014-0067-y) contains supplementary material, which is available to authorized users.

Complex thiolated mannose/quinone film modified on EQCM/Au electrode for recognizing specific carbohydrate-proteins

A complex thiolated mannose (TM)/quinone functionalised polythiophene (QFPT) thin film was modified on EQCM/Au electrode for recognition of specific carbohydrate-proteins. Different lectins such as those from Sambucus nigra (elder berry), Arachis hypogaea (peanut), Ulex europaeus (gorse, furze), Triticum vulgaris and Concanavalin A (ConA) was used for probes to evaluate bio-sensing performance of the TM/QFPT film. A specific response was observed for ConA from lectins when using the TM/QFPT film as sensing material and employing either elelctrochemical or the QCM method. No response was detected between thiolated mannose and other lectins. The linear relationship between current and ConA concentration is in the range of 0.5-17.5 nM by the elelctrochemical method and the linear relationship between frequency change and ConA concentration is in the range of 0.5-4.5 nM by the QCM method. This shows that the TM/QFPT-modified EQCM biosensor presents a paralleled determination by using electrochemical and the QCM method. The elelctrochemical method of the biosensor can be applicable in a large concentration range and its frequency change can be more precise.

Sensitive and visible detection of apoptotic cells on Annexin-V modified substrate using aminophenylboronic acid modified gold nanoparticles (APBA-GNPs) labeling

A new strategy for sensitive detection of early stage apoptosis was proposed based on silver-enhanced gold nanoparticle (GNP) label method. Annexin-V modified substrate was constructed via layer-by-layer (LBL) method for specific capture of early stage apoptotic Jurkat cells. A new kind of aminophenylboronic acid modified gold nanoparticle (APBA-GNP) was synthesized and utilized for labeling cells, followed by silver enhancement. Anodic stripping voltammetry (ASV) was applied to sensitive detection of Ag(+) dissolved from the deposited silver particles, which reflected the number of cells. A good linear range from 1 × 10(2) to 3.5 × 10(3) cells was achieved, with a detection limit of 38 apoptotic cells. Moreover, the gray color of silver enhancement could be observed by the naked eye, which could be used to tell apoptotic cells apart from normal cells. Therefore, using the silver-enhanced GNP label method, apoptotic cells could not only be sensitively detected via electrochemical technique, but also can be discriminated from normal cells by the naked eye.

GOLD NANOPARTICLES-BASED BIOSENSORS FOR BIOMEDICAL APPLICATION

Gold nanoparticles are the most extensively studied nanomaterials for biomedical application due to their unique properties, such as rapid and simple synthesis, large surface area, strong adsorption ability and facile conjugation to various biomolecules. The remarkable photophysical properties of gold nanoparticles have provided plenty of opportunities for the preparation of gold nanoparticles-based optical biosensors, while the excellent biocompatibility, conductivity, catalytic properties and large surface-to-volume ratio have facilitated the application of gold nanoparticles in the construction of electrochemical biosensors. In this review, we mainly detail the gold nanoparticles-based optical and electrochemical biosensors for biomedical application in the recent two years, which have exhibited greatly enhanced analytical performances in the detection of DNA, proteins and some important small molecules.

Fast protein detection using absorption properties of gold nanoparticles

In this study we describe the use of gold nanoparticles as a fast detection system for the sensitive analysis of proteins. The immunological method allows for protein analysis at the nanogram level, as required for clinical diagnosis. Initially a test protein is used for the development of the assay. The system is subsequently adopted for alpha-fetoprotein, which is a relevant tumor marker. This work demonstrates that antibody functionalized gold nanoparticles can be used for the detection of proteins by forming gold nanoparticle aggregates. The influence of the size of the gold nanoparticles on the sensitivity of the assay is investigated in the range from 20-60 nm particles; the larger particles show here the highest relative changes. The formation of antigen-gold nanoparticle aggregates is detected by an increase in hydrodynamic diameter by dynamic light scattering (DLS). UV/Vis spectroscopy also allows assay monitoring by quantifying the red shift of the plasmon resonance wavelength. Alpha-fetoprotein can be analysed in the concentration range of 0.1-0.4 μg ml(-1). The influence of pH, ionic strength and ratio of sample to Au-NP solution is studied. With this method, the protein AFP can be rapidly detected as demanded for clinical diagnosis.

Comparative Study of the Binding of Concanavalin A to Self-Assembled Monolayers Containing a Thiolated α-Mannoside on Flat Gold and on Nanoporous Gold

We have prepared SAMs containing 8-mercaptooctyl α-D-mannopyranoside, either as a single component or in mixed SAMs with n-octanethiol on flat gold surfaces and on nanoporous gold. Electrochemical impedance spectroscopy showed that the mixed SAMs on flat gold surfaces showed the highest Con A binding near 1:9 solution molar ratio of thiolatedα-mannoside to n-octanethiol whereas those on NPG showed the highest response at 1:19 solution molar ratio of thiolated α-mannoside to n-octanethiol. Atomic force microscopy was employed to image the monolayers, and also to image the bound Con A protein.