Development of analytical method for ultrasensitive detection of salbutamol utilizing DNA labeled-immunoprobe

Docking guided phase display to develop fusion protein with novel scFv and alkaline phosphatase for one-step ELISA salbutamol detection

Introduction

Salbutamol (SAL) is a β2 adrenergic receptor agonist which has potential hazardous effects for human health. It is very important to establish a sensitive and convenient method to monitor SAL.

Methods

Here we introduce a method to combine the information from docking and site specific phage display, with the aim to obtain scFv with high affinity to SAL. First, single chain variable fragment (scFv) antibodies against SAL were generated through phage display. By using molecular docking approach, the complex structure of SAL with antibody was predicted and indicated that H3 and L3 contribute to the binding. Then new libraries were created by randomization specific residues located on H3 and L3 according to the docking results.

Results and discussion

Anti-SAL scFv antibodies with high efficiency were finally identified. In addition, the selected scFv was fused with alkaline phosphatase and expressed in E coli to develop a rapid and low-cost one step ELISA to detect SAL.

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.

Complete antigen-bridged DNA strand displacement amplification immuno-PCR assay for ultrasensitive detection of salbutamol

Monitoring of low-level analytes are typical examples for analytical challenges. Salbutamol (SAL), a phenol-β2-agonist, has a very low residual content in the environment. Here, we present an ultrasensitive complete antigen-bridged PCR assay for detecting salbutamol (SAL). These DNA probes modified SAL complete antigens target recognition SAL antibodies and agglutinate synthetic DNA conjugates, thus enabling ligation of DNA probes to form a full-length DNA amplicon that contained a recognition site for cleavage endonuclease and subsequent quantification by qPCR. Moreover, SAL antibodies were modified with magnetic beads which were used to reduce the background noise and sample matrix effect, and the DNA signals were isothermally amplified by strand displacement amplification technology. Some key parameters which influence assay performance were optimized: the length of the bridge oligonucleotide, the concentration of immunomagnetic beads, SAL probes, and initiation chain, etc. Under the optimum conditions, the signal amplification of proposed Immuno-PCR assay for the detection of SAL was exponential, resulting in high potential sensitivity(~1 fg/mL) and a broad detection dynamic range (> 10⁵ fold). Using this proposed method, we detected SAL in spiked tap water and urine samples with acceptable recoveries ranging from 88.1 to 103.3%. Theoretically, the method developed here has broad applicability and practical utility in immunoassays of a wide variety of analytes.

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.

Highly efficient detection of salbutamol in environmental water samples by an enzyme immunoassay

Salbutamol (SAL) has potential hazardous effects on health, and has been found in natural water globally. To protect consumers from risks related to SAL residues, a fast and highly sensitive enzyme-linked immunosorbent assay (ELISA) was developed for the detection of SAL in environmental water samples. SAL hapten was synthesized and conjugated to proteins to be used as the immunogen for producing polyclonal antibodies. Under optimized conditions, the ELISA showed a 50% inhibitory concentration (IC₅₀ value) of 0.466μg/L, with a limit of detection (LOD, IC₁₀ value) of 0.021μg/L. The LOD of the ELISA was 5-fold lower than the maximum residue limits. The average recoveries of SAL from environmental samples, including tap water, river water and wastewater, ranged from 80.1 to 115.6%, which is well within the requirements of residue detection. Moreover, the results of the ELISA correlated well with high-performance liquid chromatography results, with a correlation coefficient of 0.988. These results suggest that the proposed ELISA method has potential application for the monitoring of SAL residues in environmental water samples.