Development of an electrochemical biosensor utilizing a combined aptamer and MIP strategy for the detection of the food allergen lysozyme.

This study aims to develop a MIP-Apt-based electrochemical biosensor for the sensitive and selective determination of Lysozyme (Lyz), a food allergen. For the development of the sensor, in the first stage, modifications were made to the screen-printed electrode (SPE) surface with graphene oxide (GO) and gold nanoparticles (AuNPs) to increase conductivity and surface area. The advantages of using aptamer (Apt) and molecularly imprinted polymer (MIP) technology were combined in a single biointerface in the prepared sensing tool. Surface characterization of the biosensor was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), contact angle measurements, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). A wide linear range from 0.001 to 100 pM was obtained under optimized conditions for the determination of Lyz detection using the proposed MIP-Apt sensing strategy. The limit of detection (LOD) and limit of quantification (LOQ) for Lyz were 3.67 fM and 12 fM, respectively. This biosensor displays high selectivity, repeatability, reproducibility, and long storage stability towards Lyz detection. The results show that a sensitive and selective sensor fabrication is achieved compared with existing methods.

Selective determination of non-organophosphorus insecticide using DNA aptamer-based single-use biosensors.

In the present study, we developed a disposable aptamer-based biosensor for rapid, sensitive, and reliable detection of acetamiprid (ACE). To improve the sensitivity of the aptasensor, poly-5-amino-2-mercapto-1,3,4-thiadiazole [P(AMT)] and gold nanoparticles (AuNPs) were progressively electrodeposited on the screen-printed electrode (SPE) surface by using cyclic voltammetry (CV) technique. For the determination of ACE, thiol-modified primary aptamer (Apt1) was selected by using the SELEX method and immobilized on the surface of the P(AMT) and AuNPs-modified SPE (SPE/P(AMT)/AuNPs) via AuS bonding. Then, the surface-bound aptamer was incubated with ACE for 45 Min. After that, the biotin-labeled aptamer 2 (Apt2) was interacted with the ACE, then the enzyme-labeled step was performed. In this step, alkaline phosphatase (ALP) was bound to the surface through the interaction between Apt2 labeled with biotin and streptavidin (strep)-ALP conjugate. The determination of ACE was achieved by measuring the oxidation signal of α-naphthol, which is formed on the electrode surface through the interaction of ALP with α-naphthyl phosphate. The working range of the developed aptasensor was determined as 5 × 10-12 -5 × 10-10  mol L-1 with a low limit of detection (1.5 pmol L-1 ). It was also found that the proposed aptasensor possessed great advantages such as low cost, good selectivity, and good reproducibility.

Development of a facile electrochemical sensor based on GCE modified with one-step prepared PNMA-CeO2-fMWCNTs composite for simultaneous detection of UA and 5-FU.

In this study, a poly(N-methyl aniline)-cerium oxide-functionalized MWCNTs (PNMA-CeO2-fMWCNTs) composite was synthesized in a one-step preparation technique. As a highly efficient modifier, the composite was used to modify the glassy carbon electrode surface for simultaneous detection of uric acid (UA) and 5-fluorouracil (5-FU). Morphological characterization of the GCE/PNMA-CeO2-fMWCNTs was studied using scanning electron microscopy. Structural characterization of the composite was performed using X-ray diffraction and Fourier-transformed infrared spectroscopy. Electron transfer properties of the prepared electrodes were carried out with electrochemical impedance spectroscopy and cyclic voltammetry. The linear working range for UA and 5-FU was found to be 0.25-50 µM and 0.5-750 µM, respectively. The limit of detection values for UA and 5-FU were 0.04 µM and 0.19 µM, respectively. The effects of various interfering substances on the electrochemical response of UA and 5-FU were investigated. The GCE/PNMA-CeO2-fMWCNTs sensor has excellent stability, reproducibility, anti-interference ability, and reproducibility. To demonstrate the practical application of the sensing platform, fetal bovine serum was selected and tested in the spiked samples, and satisfactory results were obtained. The prepared composite proved to be a promising platform for simple, rapid, and simultaneous analysis of UA and 5-FU.

Evaluation of aptamer and molecularly imprinted polymers as a first hybrid sensor for leptin detection at femtogram levels.

Selective and sensitive determination of macromolecules maintains its importance in diagnosing and determining diseases to protect human health. In this study, a hybrid sensor designed with dual recognition elements consisting of both aptamers (Apt) and molecularly imprinted polymers (MIPs) was carried out for the ultra-sensitive determination of Leptin. Firstly, the screen-printed electrode (SPE) surface was coated with platinum nanospheres (Pt NSs) and gold nanoparticles (Au NPs) to provide immobilization of the Apt[Leptin] complex on the surface. In the next step, the formed polymer layer around the complex using the electropolymerization of orthophenilendiamine (oPD) kept the Apt molecules on the surface more effectively. As expected, a synergistic effect occurred between the formed MIP cavities by removing Leptin from the surface and the embedded Apt molecules to fabricate a hybrid sensor. Under optimal conditions, responses in differential pulse voltammetry (DPV) currents showed a linear response over a wide concentration range from 1.0 fg/mL to 10.0 pg/mL with a limit of detection (LOD) of 0.31 fg/mL for Leptin detection. Moreover, the effectiveness of the hybrid sensor was assessed using real samples, such as human serum and plasma samples, and satisfactory recovery findings (106.2-109.0%) were found.

A novel tool for the adsorption of dsDNA: Electrochemical reduction of Pd nanoparticles onto reduced-keratin particles extracted from wool wastes.

This work outlines the fabrication of a novel electrochemical platform for the dsDNA adsorption, using one of the most sustainable materials, wool fabric waste, and Pd2+ ions. To develop a functional material with a significant adsorption capability, the waste wool was subjected to the chemical reduction process, and the keratin-SH (KerSH) particles were extracted in powder form. These particles were used in the adsorption of Pd2+ ions by monitoring with the UV-vis spectra. The dispersion of the KerSH-Pd2+ particles was subsequently drop-casted onto a glassy carbon electrode (GCE) and electrochemically reduced to the GCE/KerSH-PdNPs composite by chronoamperometry at -0.4 V for 500 s. It was found that the KerSH particles were self-assembled by revealing chemically attractive NH2 groups after the electrochemical PdNPs deposition. A GCE/KerSH-PdNPs composite was then employed in the electrochemical dsDNA detection by Differential Pulse Voltammetry (DPV), using the oxidation signals of guanine and adenine bases at 0.8 V and 1.2 V, respectively. Accordingly, relatively stable, repeatable, and reproducible dsDNA adsorption was ensured through the positively charged-NH2 groups of KerSH-PdNPs. This finding reveals the potential of textile waste for various electrochemical applications, such as DNA biosensors for environmental, pharmaceutical, and medicinal fields.

An electrochemical sandwich-type aptasensor for determination of lipocalin-2 based on graphene oxide/polymer composite and gold nanoparticles.

In this work, we reported an electrochemical aptasensor based on the poly-3-amino-1,2,4-triazole-5-thiol/graphene oxide composite (P(ATT)-GO) and gold nanoparticles (AuNPs) modified graphite screen-printed electrode (GSPE) (GSPE/P(ATT)-GO/AuNPs) for determination of lipocalin-2 (LCN2) (neutrophil gelatinase-associated lipocalin). A sandwich based strategy was utilized to enhance the electrochemical signal. First, a thiol tethered DNA aptamer was immobilized onto the composite electrode. Then, the LCN2 solution was incubated with the aptamer modified GSPE/P(ATT)-GO/AuNPs. Secondary aptamer (Apt2) peculiar to the LCN2 and labeled with biotin was interacted with the LCN2. A streptavidin-alkaline phosphatase conjugate was then applied to the surface. The determination of LCN2 was performed by using the electroactive property of α-naphthol which is acquired the product from the interaction between alkaline phosphatase and α-naphthyl phosphate. The constructed electrode was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The aptamer modified GSPE/P(ATT)-GO/AuNPs showed the superior electrocatalytic performance towards the voltammetric determination of LCN2 with a wide linear range (1.0-1000.0 ng/mL) and a low limit of detection (LOD) (0.3 ng/mL). The proposed aptasensor revealed the excellent sensitivity, anti-interference ability and reproducibility which approved that the GSPE/P (ATT)-GO/AuNPs is a promising composite for the sensitive detection of LCN2. The fabricated aptasensor was applied for the determination of LCN2 in fetal bovine serum samples using the standard addition method and the recovery values were in the range of 99.2% and 103.22%.

Interaction of prednisone with dsDNA at silver nanoparticles/poly(glyoxal-bis(2-hydroxyanil))/dsDNA modified electrode and its analytical application.

This paper reports the fabrication of an electrochemical DNA biosensor for the electrochemical determination of prednisone (PRD), which is a synthetic corticosteroid. For this purpose, silver nanoparticles (AgNPs) and a new polymer film poly(glyoxal-bis(2-hydroxyanil)) (P(GBHA)) were electrochemically deposited on a glassy carbon electrode (GCE), respectively. Then, an electrochemical DNA biosensor was prepared onto this electrode surface (GCE/AgNPs/P(GBHA)) by the immobilization of dsDNA using a chronoamperometry method. The proposed electrode was characterized by FESEM, XPS, and cyclic voltammetry (CV). The interaction between the PRD and dsDNA immobilized on the GCE/AgNPs/P(GBHA) electrode was investigated via a differential pulse voltammetry (DPV) method and UV-Vis spectrophotometry. The experimental factors affecting the interaction between the PRD concentration and dsDNA were optimized. The fabricated biosensor showed a wide linear response in a PRD concentration range of 1.0-50.0 µg mL-1 depending on both the adenine and guanine base signals. The detection limit based on the guanine and adenine signals was 0.3 µg mL-1 and 0.25 µg mL-1, respectively. The sensor exhibited excellent anti-interferential ability, good stability and reproducibility and was satisfactorily employed for the electrochemical assay of PRD in serum samples. The new DNA biosensor can be utilized for the sensitive, accurate and rapid analysis of PRD.

Highly sensitive amperometric biosensor for determination of NADH and ethanol based on Au-Ag nanoparticles/poly(L-Cysteine)/reduced graphene oxide nanocomposite.

This work presents the fabrication of a novel nicotinamide adenine dinucleotide (NADH) sensor using gold-silver bimetallic nanoparticles (Au-AgNPs), poly(L-Cysteine) (P(L-Cys)) and electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE/Au-AgNPs/P(L-Cys)-ERGO). The composite electrode exhibited an excellent electrocatalytic response towards NADH at a low oxidation potential (+ 0.35V) and minimization of surface contamination due to the synergistic effects of the Au-AgNPs, polymer and ERGO. Under optimum conditions, modified sensors allowed the detection of NADH with a wide linear range from 0.083µM to 1.05mM with a low detection limit of 9.0nM (S/N = 3). Moreover, this modified electrode was also used as a sensitive ethanol biosensor, which was prepared with alcohol dehydrogenase (ADH) via glutaraldehyde, bovin serum albumin and nafion (Naf). There was a linear response for ethanol in the concentration range from 0.017 to 1.845mM with a low detection limit of 5.0µM (S/N = 3). The GCE/Au-AgNPs/P(L-Cys)-ERGO/ADH/Naf electrode can be successfully used for the determination of ethanol in different commercial beverages.