Ultrasensitive electrochemiluminescent salbutamol immunoassay with dual-signal amplification using CdSe@SiO2 as label and gold nanoparticles as substrate

Recent progress in assembly strategies of nanomaterials-based ultrasensitive electrochemiluminescence biosensors for food safety and disease diagnosis

The Electrochemiluminescence (ECL)-based biosensors have received considerable attention in food contaminants and disease diagnosis, due to their fascinating advantages such as low cost, fast analysis speed, wide linear range, high sensitivity, and excellent anti-interference ability. Meanwhile, with the vigorous development and improvement of nanotechnology, biosensor assembly strategies tend to diversify and be multifunctional. This review focuses on the representative ECL biosensors in food safety and disease diagnosis reported by our research group and other research groups based on nanomaterials assembly strategies in recent years. According to the different roles of nanomaterials played in the constitution of ECL biosensors, nanomaterials would be divided into the following two categories to be summarized: (1) Nanomaterials for signal amplification. (2) Nanomaterials as ECL emitters. Finally, this review prospects the perspectives on the future development direction of ECL biosensor in food safety and disease diagnosis.

Current Advances in Immunoassays for the Detection of β2-Agonists

β2-agonists are a group of synthetic phenylethanolamine compounds which are traditionally used for treating bronchospasm. These compounds can also increase skeletal muscle mass and decrease body fat. The illegal use of β2-agonists in food-producing animals results in residue of β2-agonists in edible tissues and causes adverse health effects in humans. Thus, the detection of β2-agonists at trace level in complex sample matrices is of great importance for monitoring the abuse of β2-agonists. Many methods have been developed to detect β2-agonists. Among them, a variety of antigen–antibody interaction-based techniques have been established to detect β2-agonists in various samples, including animal feed, urine, serum, milk, tissues and hair. In this review, we summarized current achievement in the extraction of β2-agonists from testing samples and detection of β2-agonists using immunological techniques. Future perspectives were briefly discussed.

Electrochemical Discrimination of Salbutamol from Its Excipients in VentolinTM at Nanoporous Gold Microdisc Arrays

The emergence of specific drug–device combination products in the inhalable pharmaceutical industry demands more sophistication of device functionality in the form of an embedded sensing platform to increase patient safety and extend patent coverage. Controlling the nebuliser function at a miniaturised, integrated electrochemical sensing platform with rapid response time and supporting novel algorithms could deliver such a technology offering. Development of a nanoporous gold (NPG) electrochemical sensor capable of creating a unique fingerprint signal generated by inhalable pharmaceuticals provided the impetus for our study of the electrooxidation of salbutamol, which is the active bronchodilatory ingredient in Ventolin^TM formulations. It was demonstrated that, at NPG-modified microdisc electrode arrays, salbutamol is distinguishable from the chloride excipient present at 0.0154 M using linear sweep voltammetry and can be detected amperometrically. In contrast, bare gold microdisc electrode arrays cannot afford such discrimination, as the potential for salbutamol oxidation and chloride adsorption reactions overlap. The discriminative power of NPG originates from the nanoconfinement effect for chloride in the internal pores of NPG, which selectively enhances the electron transfer kinetics of this more sluggish reaction relative to that of the faster, diffusion-controlled salbutamol oxidation. Sensing was performed at a fully integrated three-electrode cell-on-chip using Pt as a quasi-reference electrode.

A highly selective and simple fluorescent probe for salbutamol detection based on thioglycolic acid-capped CdTe quantum dots

In this paper, a highly fluorescent water-soluble CdTe quantum dots (CdTe QDs) stabilized with thioglycolic acid (TGA) were synthesized for the quantitative and selective determination of salbutamol (SAL). When ten different of 2.09 × 10^-6 mol L^-1 alpha-2 adrenoceptor agonist were added to 4.38 × 10^-4 mol L^-1CdTe QDs solution, the fluorescence signal of the CdTe QDs quenched obviously by SAL with 57.32% and 0.815% - 7.00% for other nine kinds of veterinary medicine, such as tulobuterol, fenoterol, phenylethanamine A, simatero, penbutolol, clenbuterol, ractopamine, terbutaline and clorprenaline. The result shows that the CdTe QDs is highly sensitive sensor for SAL. The quenching mechanism has been investigated by absorption spectroscopy and K_SV at different temperatures, and shew a static quenching process than dynamic quenching. Under the optimal conditions, respectively the straight line equation (F₀/F = 0.1491 × 10⁶ C + 1.3078) was found between the relative fluorescence intensity and the concentration of SAL was in the range of 6.27 × 10^-8 to 2.09 × 10^-7 mol L^-1, and the limit of detection was 4.2 × 10^-8 mol L^-1. The proposed method has been applied to the determination of SAL in pig urine samples.

Enhanced biosensing strategies using electrogenerated chemiluminescence: recent progress and future prospects

An overview of enhancement strategies for highly sensitive ECL-based sensing of bioanalytes enabling early detection of cancer.

Electrochemiluminescent immunoassay for neuron specific enolase by using amino-modified reduced graphene oxide loaded with N-doped carbon quantum dots

An ultrasensitive electrochemiluminescence based sandwich immunoassay is presented for determination of neuron specific enolase. The method uses silver-cysteine nanowires as the capture probe and a composite made of amino-modified reduced graphene oxide and nitrogen-doped carbon quantum dots as the signal probe. It was synthesized by covalent coupling of amino-modified reduced graphene oxide to the carboxy groups of nitrogen-doped carbon quantum dots. The nanowires possess a large specific surface and abundant functional groups which facilitate immobilizing the primary antibody (Ab₁). The amino-modified reduced graphene oxide is employed as a carrier for loading a large number of the quantum dots and secondary antibody (Ab₂). This increases the electrochemiluminescence intensity of quantum dots. Response to neuron specific enolase is linear in the 0.55 fg·mL^-1 to 5.5 ng·mL^-1 concentration range. It has a detection limit of 0.18 fg·mL^-1 (at S/N = 3). The relative standard deviation (for n = 6) is less than 2.9%. The assay is highly sensitive, reproducible, selective and stable. Graphical abstractA novel electrochemiluminescence immunosensor is described that uses amino-modified reduced graphene oxide (amino-rGO), nitrogen-doped carbon quantum dots (N-CQDs) and silver-cysteine nanowires (SCNWs). It was applied to the determination of neuron specific enolase (NSE). Bovine serum albumin: BSA;1-ethyl-3-(3-dimethylaminopropyl)carbodiimide: (EDC;, N-hydroxysuccinimide: NHS.

Development of a highly sensitive time-resolved fluoroimmunoassay for the determination of trace salbutamol in environmental samples

Veterinary drug residues have become a major source of environmental pollutants. To monitor trace salbutamol (SAL) in the environment, a highly sensitive and reliable time-resolved fluoroimmunoassay (TRFIA) was developed. Under the optimum parameters, the half-maximal inhibition concentration (IC₅₀) and the limit of detection (LOD, IC₁₀) were determined to be 0.08 μg/L and 0.66 ng/L with a linear range (IC₂₀ - IC₈₀) of 0.0028-2.25 μg/L for SAL. The IC₅₀ and LOD of the TRFIA improved approximately 5-fold and 31-fold, respectively, when compared with our previously reported ELISA data. When compared to most other conventional methods, the TRFIA also showed an excellent sensitivity and accuracy for the detection of SAL. Recoveries from 83.4 to 111.3% and standard deviations (RSDs) from 3.9 to 14.0% were observed in various environmental SAL-spiked samples, including river water, paddy water, livestock wastewater, vegetable field soil and rice paddy soil. In addition, the developed TRFIA showed largely consistent with analytic results from UPLC-MS/MS (R² = 0.9825, n = 15). These results suggest that the proposed TRFIA can be applied as a sensitive and reliable monitoring method to detect trace SAL in environmental samples.

Antibody conjugation to carboxyl-modified microspheres through N-hydroxysuccinimide chemistry for automated immunoassay applications: A general procedure

Immunochemical techniques are the workhorse for sample enrichment and detection of a large variety of analytes. In contrast to classical microtiter plate-based assays, microparticles are a next generation solid support, as they promote automation of immunoassays using flow-based techniques. Antibody immobilization is a crucial step, as these reagents are expensive, and inefficient coupling can result in low sensitivities. This paper proposes a general procedure for efficient immobilization of antibodies onto TentaGel particles, via N-hydroxysuccinimide chemistry. The goal was the preparation of solid supports with optimum immunorecognition, while increasing the sustainability of the process. The influence of buffer composition, activation and coupling time, as well as the amount of antibody on the immobilization efficiency was investigated, resorting to fluorophore-labeled proteins and fluorescence imaging. Buffer pH and activation time are the most important parameters for efficient coupling. It is demonstrated, that the hydrolysis of N-hydroxysuccinimide esters occurs at similar rates as in solution, limiting the utilizable time for coupling. Finally, applicability of the generated material for automated affinity extraction is demonstrated on the mesofluidic platform lab-on-valve.

Peroxydisulfate/oxygen system-based electrochemiluminescent immunosensing of Hg2+ using Pt/Pd nanodendrites-thiosemicarbazide/norfloxacin as a signal enhancer

Herein, we described a competitive-type ECL strategy for Hg²⁺ detection based on S₂O₈²⁻/O₂ system by using Pt/Pd nanodendrites-thiosemicarbazide/norfloxacin covered gold nanoparticles (Pt/Pd-TNG₅₀) as signal enhancer.

Sensitive detection of enrofloxacin using an electrochemiluminescence immunosensor based on gold-functionalized C60 and Au@BSA nanoflowers

A novel competitive electrochemiluminescence (ECL) immunosensor based on CdSe quantum dots was developed for the detection of enrofloxacin (Enro).