Highly specific nanobody against herbicide 2,4-dichlorophenoxyacetic acid for monitoring of its contamination in environmental water
SCIENCE OF THE TOTAL ENVIRONMENT
Authors: Li, Zhen-Feng; Dong, Jie-Xian; Vasylieva, Natalia; Cui, Yong-Liang; Wan, De-Bin; Hua, Xiu-De; Huo, Jing-Qian; Yang, Dong-Chen; Gee, Shirley J.; Hammock, Bruce D.
2,4-dichlorophenoxyacetic acid (2,4-D), a widely used herbicide, is a small organic chemical pollutant in the environment. To develop a nanobody-based immunoassay for monitoring trace levels of 2,4-D, a step-wise strategy for the generation of nanobodies highly specific against this small chemical was employed. Firstly, we synthesized three novel haptens mimicking 2,4-D and assessed their influence on the sensitivity and specificity of the existing antibody-based assay. Polyclonal antibodies (pAb) from rabbits showed good sensitivity and moderate specificity for 2,4-D, pAb from llama based on selected haptens showed similar performance when compared to those from rabbits. Secondly, nanobodies derived from llama were generated for 2,4-D by an effective procedure, including serum monitoring and one-step library construction. One nanobody, NB3-9, exhibited good sensitivity against 2,4-D (IC50 = 29.2 ng/mL) had better specificity than the rabbit pAb#1518, with no cross-reactivities against the 2,4-D analogs tested. Thirdly, one-step fluorescent enzyme immunoassay (FLEIA) for 2,4-D based on a nanobody-alkaline phosphatase (AP) fusion was developed with IC50 of 1.9 ng/mL and a linear range of 0.4-8.6 ng/mL. Environmental water samples were analyzed by FLEIA and LC-MS/MS for comparison, and the results were consistent between both methods. Therefore, the proposed step-wise strategy from hapten design to nanobody-AP fusion production was successfully conducted, and the resulting nanobody based FLEIA was demonstrated as a convenient tool to monitor 2,4-D residuals in the environment. (C) 2020 Elsevier B.V. All rights reserved.
Fluorescent and electrochemical bimodal bioplatform for femtomolar detection of microRNAs in blood sera
SENSORS AND ACTUATORS B-CHEMICAL
Authors: Zayani, Riham; Rabti, Amal; Ben Aoun, Sami; Raouafi, Noureddine
Noncoding RNAs such as miRNAs (miRs) are extensively researched as a novel class of cancer biomarkers. Herein, we describe a new method to sensitively determine the levels miRNAs via dual signal readout involving competitive hybridization between the miR-21 target and its biotinylated analog towards the same thiolated DNA probe attached onto the surface of gold nanoparticles. Hybridization of the DNA probes by the biotinylated miRs followed by conjugation with streptavidin-horseradish peroxidase, which catalyzes the oxidation of o-phenylenediamine into 2,3-diaminophenazine, allows detecting the target using fluorescence and electrochemistry. The two signals varied in a miRNA concentration-dependent manner. The bioplatform has limits of detection of 15 fmol/L and 19 fmol/L (0.15 and 0.19 attomol in 20 mu L, respectively). Furthermore, it displays a wide linear calibration range varying from 19 fmol/L to 100 pmol/L and 15 fmol/L to 100 pmol/L using voltamperometry and fluorescence, respectively. The bioplatform is able to provide very low detection limits without any DNA/RNA amplification step, an excellent selectivity toward non-complementary miRs along with an acceptable distinction with a single nucleotide mismatched sequence. Finally, the method was used to determine miR-21 expression levels in blood sera from patients diagnosed with breast cancer.