Lateral flow immunoassay for small-molecules detection in phytoproducts: a review

Phytoproducts are involved in various fields of industry. Small-molecule (Mw < 900 Da) organic compounds can be used to indicate the quality of plant samples in the perspective of efficacy by measuring the necessary secondary metabolites and in the perspective of safety by measuring the adulterant level of toxic compounds. The development of reliable detection methods for these compounds in such a complicated matrix is challenging. The lateral flow immunoassay (LFA) is one of the immunoassays well-known for its simplicity, portability, and rapidity. In this review, the general principle, components, format, and application of the LFA for phytoproducts are discussed.

Sodium periodate-mediated conjugation of harringtonine enabling the production of a highly specific monoclonal antibody, and the development of a sensitive quantitative analysis method

Harringtonine (HT) is a promising natural product that is mainly isolated from plants of the genus Cephalotaxus. Due to its remarkable antileukemic activities, HT has been utilized clinically in China for the treatment of acute promyelocytic leukemia (APL). No antibody that recognizes free HT has been reported to date due to the difficulty of preparing antigen conjugates in which haptens bind to a carrier protein. To overcome this difficulty, we focused on sodium periodate (NaIO₄), which catalyzes unique oxidative reactions; the resulting conjugates enabled the production of a highly specific monoclonal antibody (MAb) against HT (MAb 1D2) and the establishment of an indirect competitive enzyme-linked immunosorbent assay (icELISA) for the determination of HT. Further analysis revealed that MAb 1D2 was produced by the HT3 (8-carbonyl HT)-based conjugate antigen; HT3 was synthesized by a NaIO₄-mediated oxidative reaction. The minimum detectable concentration for HT in the icELISA system was found to be 0.76 ng mL^-1, which is approximately 13 to 160 times more sensitive than a conventional HPLC system. Several validation analyses revealed that the icELISA using MAb 1D2 is sufficiently accurate, reliable, and sensitive to assess small amounts of HT in plant samples.

An immunochromatographic assay for rapid etection of salvinorin A

We developed an immunochromatographic assay (ICA) that enables rapid analysis of salvinorin A (Sal A) in Salvia divinorum within 10 min. The result shows that no Sal A in other samples of Lamiaceae plants was detected, but it could recognize Sal A among other substances in complex samples. The main advantage of the ICA is its high performance in combination with low cost, simplicity, and speed. Our newly developed combined ICA/indirect competitive ELISA(icELISA) system enables analysis of large numbers of samples over short periods of time without cumbersome pretreatments in complex mixtures. This method can complement other instrumental analyses for salvinorins, and could be used to deter S. divinorum abuse.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Development of an immunoassay using an anti-wogonin glucuronide monoclonal antibody

Wogonin 7-O-β-D-glucuronide (Wgn) is a bioactive flavone present in the dried root of Scutellaria baicalensis Georgi. To generate a monoclonal antibody (MAb) against Wgn, BALB/c mice injected with Wgn-bovine serum albumin yielded splenocytes that we fused with SP2/0 myeloma cells using the polyethylene glycol method. We obtained a hybridoma designated 315A that produced a MAb reactive to Wgn. The anti-Wgn MAb 315A was applied to an indirect competitive enzyme-linked immunosorbent assay (icELISA) to quantify Wgn. Subsequent validation revealed that icELISA using the 315A anti-Wgn MAb is an accurate and reliable method for the quantification of Wgn in S. baicalensis.

Development of an enzyme immunoassay using a monoclonal antibody against the psychoactive diterpenoid salvinorin A

Salvinorin A (1), the main active constituent in Salvia divinorum, is a highly selective kappa-opioid receptor agonist with hallucinogenic effects, which is regulated in several countries. In the present study, a monoclonal antibody (mAb) against 1 was prepared, and an indirect competitive enzyme-linked immunosorbent assay (icELISA) system was developed for the detection of salvinorins. To raise mAbs against 1, salvinorin B (2) hemisuccinate was synthesized and used to prepare the immunogen 2-bovine serum albumin conjugate. This technique was used to prepare a hybridoma cell line, 3D5, which secreted a mAb that recognized 1. The mAb was shown to have specificity for 1 and other salvinorins in cross-reactivity tests. The intra-assay calibration range by icELISA using the mAb against 1 was 0.0195-0.625 μg/mL. After validating the icELISA using intra- and interassays, a recovery experiment and analysis of several plants in the family Lamiaceae, including S. divinorum, confirmed that the analytical method based on ELISA is not only simple but also precise, accurate, sensitive, and sufficiently reliable. The results indicate that icELISA is a useful tool in the identification of S. divinorum.

Production of polyclonal antibody against madecassoside and development of immunoassay methods for analysis of triterpene glycosides in Centella asiatica

INTRODUCTION

Centella asiatica (L.) Urban consists of two major triterpene glycosides, asiaticoside (AS) and madecassoside (MA), as active components used for wound healing and enhancing memory.

OBJECTIVE

To produce a polyclonal antibody against madecassoside (MA-PAb) and develop enzyme-linked immunosorbent assay (ELISA) and Eastern blotting methods for quantitative analysis of triterpene glycosides in Centella asiatica.

METHODS

An ELISA method was developed using polyclonal antibody against MA. An Eastern blotting method on the PES membrane was established for determination of MA and AS. The immunoassays were validated for sensitivity, precision, specificity and accuracy.

RESULTS

The prepared MA-PAb shows specificity to MA and AS. The measuring range of triterpene glycosides was 0.39-50 µg/mL using the ELISA method. An Eastern blotting method was developed for determining individual MA and AS, which could be detected in the range of 62.5-500 ng. The limit of detection for MA and AS was 31.25 ng. The two methods developed showed good specificity, precision, and accuracy, and also correlated with high-performance liquid chromatography.

CONCLUSION

These immunoassays have several advantages that include high sensitivity as well as being rapid and facile for determination of the triterpene glycosides in C. asiatica.

Preparation of a single-chain variable fragment and a recombinant antigen-binding fragment against the anti-malarial drugs, artemisinin and artesunate, and their application in an ELISA

Two different recombinant antibodies, a single-chain variable fragment (scFv) and an antigen-binding fragment (Fab), were prepared against artemisinin (AM) and artesunate (AS) and were developed for use in an enzyme-linked immunosorbent assay (ELISA). The recombinant antibodies, which were derived from a single monoclonal antibody against AM and AS (mAb 1C1) prepared by us, were expressed by Escherichia coli cells and their reactivity and specificity were characterized. As a result, to obtain sufficient signal in indirect ELISA, a much greater amount of a first antibody was needed in the use of scFv due to the differences of the secondary antibody and conformational stability. Therefore, we focused on the development of the recombinant Fab antibodies and applied it to indirect competitive ELISA. The specificity of the Fab was similar to that of mAb 1C1 in that it showed specific reactivity toward AM and AS only. The sensitivity of the icELISA (0.16 μg/mL to 40 μg/mL for AM and 8.0 ng/mL to 60 ng/mL for AS) was sufficient for analysis of antimalarial drugs, and its utility for quality control of analysis of Artemisia spp. was validated. The Fab expression and refolding systems provided a good yield of high-quality antibodies. The recombinant antibody against AM and AS provides an essential component of an economically attractive immunoassay and will be useful in other immunochemical applications for the analysis and purification of antimalarial drugs.