Development of a monoclonal antibody-based enzyme-linked immunosorbent assay for the analysis of glycyrrhizic acid

Novel hapten design, highly sensitive monoclonal antibody production, and immunoassay development for rapid screening of illegally added chloramphenicol in cosmetics

Hapten design and synthesis have been regarded as the key factor to generate high-quality antibodies. In the present study, a novel hapten of chloramphenicol was synthesized, characterized and compared with two conventional haptens. The new hapten generated mAb 4B5 showed higher sensitivity and titer than the other two haptens-based mAbs. The haptens synthesized with the structure of chloramphenicol base generated more sensitive antibodies than the hapten with chloramphenicol succinate, and the spacer arm linked to the phenyl group hapten elicited the strongest antibody response. After optimization, a direct competitive enzyme-linked immunosorbent assay (dcELISA) and a lateral flow immunoassay (LFIA), both based on the mAb 4B5, were developed. The dcELISA had a half maximum inhibition concentration of 0.23 ng/mL and the LFIA showed a cutoff value of 5-10 ng/mL. The LFIA was applied to detect illegally-added chloramphenicol samples in anti-acne cosmetics, five out of 19 samples were tested chloramphenicol containing within 10 min, which result was confirmed with the dcELISA and HPLC. The LFIA has an adequate sensitivity and can be used as a point of care diagnostic device for rapidly screening chloramphenicol in cosmetics.

Development of Magnetic Lateral Flow and Direct Competitive Immunoassays for Sensitive and Specific Detection of Halosulfuron-Methyl Using a Novel Hapten and Monoclonal Antibody

Halosulfuron-methyl (HM) is widely used for the removal of noxious weeds in corn, sugarcane, wheat, rice, and tomato fields. Despite its high efficiency and low toxicity, drift to nontarget crops and leaching of its metabolites to groundwater pose potential risks. Considering the instability of HM, the pyrazole sulfonamide of HM was used to generate a hapten and antigen to raise a high-quality monoclonal antibody (Mab, designated 1A91H11) against HM. A direct competitive immunoassay (dcELISA) using Mab 1A91H11 achieved a half-maximal inhibitory concentration (IC50) of 1.5 × 10^-3 mg/kg and a linear range of 0.7 × 10^-3 mg/kg-10.7 × 10^-3 mg/kg, which was 10 times more sensitive than a comparable indirect competitive ELISA (icELISA) and more simple to operate. A spiking recovery experiment performed in tomato and maize matrices with 0.01, 0.05, and 0.1 mg/kg HM had average recoveries within 78.9-87.9% and 103.0-107.4% and coefficients of variation from 1.1-6.8% and 2.7-6.4% in tomato and maize, respectively. In addition, a magnetic lateral flow immunoassay (MLFIA) was developed for quantitative detection of low concentrations of HM in paddy water. Compared with dcELISA, the MLFIA exhibited 3.3- to 50-fold higher sensitivity (IC50 0.21 × 10^-3 mg/kg). The average recovery and RSD of the developed MLFIA ranged from 81.5 to 92.5% and 5.4 to 9.7%. The results of this study demonstrated that the developed dcELISA and MLFIA are suitable for rapid detection of HM residues in tomato and maize matrices and paddy water, respectively, with acceptable accuracy and precision.

Uncovering a Phenomenon of Active Hormone Transcriptional Regulation during Early Somatic Embryogenesis in Medicago sativa

Somatic embryogenesis (SE) is a developmental process in which somatic cells undergo dedifferentiation to become plant stem cells, and redifferentiation to become a whole embryo. SE is a prerequisite for molecular breeding and is an excellent platform to study cell development in the majority of plant species. However, the molecular mechanism involved in M. sativa somatic embryonic induction, embryonic and maturation is unclear. This study was designed to examine the differentially expressed genes (DEGs) and miRNA roles during somatic embryonic induction, embryonic and maturation. The cut cotyledon (ICE), non-embryogenic callus (NEC), embryogenic callus (EC) and cotyledon embryo (CE) were selected for transcriptome and small RNA sequencing. The results showed that 17,251 DEGs, and 177 known and 110 novel miRNAs families were involved in embryonic induction (ICE to NEC), embryonic (NEC to EC), and maturation (EC to CE). Expression patterns and functional classification analysis showed several novel genes and miRNAs involved in SE. Moreover, embryonic induction is an active process of molecular regulation, and hormonal signal transduction related to pathways involved in the whole SE. Finally, a miRNA–target interaction network was proposed during M. sativa SE. This study provides novel perspectives to comprehend the molecular mechanisms in M. sativa SE.

Design and Characterization of a Novel Hapten and Preparation of Monoclonal Antibody for Detecting Atrazine

This study provides the first design and synthetic protocol for preparing highly sensitive and specific atrazine (ATR) monoclonal antibodies (mAbs). In this work, a previously unreported hapten, 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine, was designed and synthesized, which maximally exposed the characteristic amino group ATR to an animal immune system to induce the expected antibody. The molecular weight of the ATR hapten was 259.69 Da, and its purity was 97.8%. The properties of the anti-ATR mAb were systematically characterized. One 9F5 mAb, which can detect ATR, was obtained with an IC₅₀ value (the concentration of analyte that produced 50% inhibition of ATR) of 1.678 µg/L for ATR. The molecular weight for the purified 9F5 mAb was approximately 52 kDa for the heavy chain and 15 kDa for the light chain. The anti-ATR mAb prepared in this study was the IgG₁ type. The working range of the standard curve (IC₂₀ (the concentration of analyte that produced 20% inhibition of ATR)_-IC₈₀ (the concentration of analyte that produced 80% inhibition of ATR)) was 0.384 to 11.565 µg/L. The prepared anti-ATR mAb had high specificity, sensitivity, and affinity with low cross-reactivity. The prepared anti-ATR mAb could provide the core raw material for establishing an ATR immunoassay.

Green synthesis and characterization of gold nanoparticles and their application for the rapid detection of glycyrrhizin with immunochromatographic strips

Glycyrrhizin-reduced and stabilized gold nanoparticles were used for a rapid method of detecting glycyrrhizin content.

Development of an Enzyme-Linked Immunosorbent Assay Method for the Detection of Rhein in Rheum officinale

Rhein is an important quality-control marker of Rheum officinale. The aim of this study was to develop an indirect competitive enzyme-linked immunosorbent assay (icELISA) for rhein detection, which acts as a powerful tool for quality control and proper usage of Rheum officinale. First, a specific and sensitive monoclonal antibody (mAb) against rhein was produced from a stable hybridoma cell line, 1F8, generated by the fusion of mouse myeloma sp2/0 with spleen cells obtained from a Bal b/c mouse immunized with rhein-BSA. Then, an icELISA method was developed with an IC₅₀ value and working range of 0.05 μg L⁻¹ and 0.02–0.11 μg L⁻¹, respectively. The icELISA revealed high assay specificity, since it only had a relatively high cross reactivity with aloe-emodin (27%) and almost no cross reactivity with any other anthraquinones (<1%). When spiked with 0.2–2 mg kg⁻¹ of rhein, the recoveries ranged from 84.19% to 102.90%. Finally, icELISA was used to detect rhein contents of Rheum officinale collected from different regions, and the results corresponded well with those of HPLC. Overall, the developed icELISA with high specificity and sensitivity provided a rapid and simple method for rhein detection, and it may be a powerful tool for quality control and proper usage of Rheum officinale.

Biosynthesis and Signal Transduction of ABA, JA, and BRs in Response to Drought Stress of Kentucky Bluegrass

Kentucky bluegrass (KB, Poa pratensis) is one of the most widely used cool-season turfgrass species, but it is sensitive to drought stress. Molecular studies in KB are hindered by its large and complex genome structure. In this study, a comparative transcriptomic study was conducted between a short and long period of water deficiency. Three transcriptome libraries were constructed and then sequenced by using leaf RNA samples of plants at 0, 2, and 16 h after PEG6000 treatment. A total of 199,083 differentially expressed genes (DEGs) were found. The Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation revealed that DEGs were enriched in "Plant hormone signal transduction" and "MAPK signaling pathway-Plant". Some key up-regulated genes, including PYL, JAZ, and BSK, were involved in hormone signaling transduction of abscisic acid, jasmonic acid, and brassinosteroid and possibly these genes play important roles in coping with drought stress in KB. Furthermore, our results showed that the concentrations of ABA, JA and BR increased significantly with the extension of the drought period. The specific DEGs encoding functional proteins, kinase and transcription factors, could be valuable information for genetic manipulation to promote drought tolerance of KB in the future.

Biosynthesis and Signal Transduction of ABA, JA, and BRs in Response to Drought Stress of Kentucky Bluegrass

Kentucky bluegrass (KB, Poa pratensis) is one of the most widely used cool-season turfgrass species, but it is sensitive to drought stress. Molecular studies in KB are hindered by its large and complex genome structure. In this study, a comparative transcriptomic study was conducted between a short and long period of water deficiency. Three transcriptome libraries were constructed and then sequenced by using leaf RNA samples of plants at 0, 2, and 16 h after PEG6000 treatment. A total of 199,083 differentially expressed genes (DEGs) were found. The Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation revealed that DEGs were enriched in "Plant hormone signal transduction" and "MAPK signaling pathway-Plant". Some key up-regulated genes, including PYL, JAZ, and BSK, were involved in hormone signaling transduction of abscisic acid, jasmonic acid, and brassinosteroid and possibly these genes play important roles in coping with drought stress in KB. Furthermore, our results showed that the concentrations of ABA, JA and BR increased significantly with the extension of the drought period. The specific DEGs encoding functional proteins, kinase and transcription factors, could be valuable information for genetic manipulation to promote drought tolerance of KB in the future.

Development of Monoclonal Antibodies Recognizing Linear Epitope: Illustration by Three Bacillus thuringiensis Crystal Proteins of Genetically Modified Cotton, Maize, and Tobacco

Bacillus thuringiensis Cry1Ac, Cry1Ia1, and Cry1Ie are δ-endotoxin insecticidal proteins widely implemented in genetically modified organisms (GMO), such as cotton, maize, and potato. Western blot assay integrates electrophoresis separation power and antibody high specificity for monitoring specific exogenous proteins expressed in GMO. Procedures for evoking monoclonal antibody (mAb) for Western blot were poorly documented. In the present study, Cry1Ac partially denatured at 100 °C for 5 min was used as an immunogen to develop mAbs selectively recognizing a linear epitope of Cry1Ac for Western blot. mAb 5E9C6 and 3E6E2 selected with sandwich ELISA strongly recognized the heat semidenatured Cry1Ac. Particularly, 3E6E2 recognized both E. coli and cotton seed expressed Cry1Ac in Western blot. Such strategy of using partially denatured proteins as immunogens and using sandwich ELISA for mAb screening was also successfully demonstrated with production of mAbs against Cry1Ie for Western blot assay in maize.

Development of a Specific Monoclonal Antibody for the Quantification of Artemisinin in Artemisia annua and Rat Serum

Artemisinin, extracted from Artemisia annua, and its derivatives are important frontline antimalarials. To produce specific antibodies for the detection and quantification of artemisinin, artemisinin was transformed to 9-hydroxyartemisinin by microbial fermentation, which was used to prepare a 9-succinate artemisinin hapten for conjugation with ovalbumin. A monoclonal antibody (mAb), designated as 3H7A10, was selected from hybridoma cell lines which showed high specificity to artemisinin. No competitive inhibition was observed with artesunate, dihydroartemisinin, and artemether for up to 20,000 ng mL(-1). An indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed, which showed a concentration causing 50% of inhibition (IC50) for artemisinin as 2.6 ng mL(-1) and a working range of 0.6-11.5 ng mL(-1). The icELISA was applied for the quantification of artemisinin in crude extracts of wild A. annua and the study of pharmacokinetics of artemisinin in rat serum after intraperitoneal injection. The results were highly correlated with those determined by HPLC-UV analysis (R(2) = 0.9919). In comparison with reported antiartemisinin mAbs which have broad cross-reactivity with other artemisinin derivatives, the high specificity of 3H7A10 for artemisinin will enable development of methods for quantification of artemisinin in Artemisia plants and antimalarial drugs such as Arco and for pharmacokinetic studies.

Rapid evaluation of artesunate quality with a specific monoclonal antibody-based lateral flow dipstick

Artesunate is a frontline antimalarial drug for treating Plasmodium falciparum malaria. To produce specific antibodies to artesunate, the carboxyl group of artesunate was directly conjugated to carrier protein as the immunogen. A specific monoclonal antibody (mAb) 3D82G6 against artesunate was obtained by high-throughput screening of positive hybridoma clones. This monoclonal antibody had 4.0, 0.5, and 0.9 % cross reactivities with artemisinin, dihydroartemisinin, and artemether, respectively. A dipstick immunoassay was developed, and the indicator range for artesunate was 1000-2000 ng mL(-1). No interference was observed with artemisinin, dihydroartemisinin, artemether, and other commonly used antimalarial drugs for up to 20,000 ng mL(-1). The dipsticks were used for determination of artesunate contents in commercial drugs, and the results were agreeable with those determined by high-performance liquid chromatography. This dipstick, with its specificity and sensitivity for artesunate and simplicity to use, makes it a potential point-of-care device for rapid quality evaluation of artesunate-containing antimalarial drugs. Graphical Abstract Specific monoclonal antibody-based lateral flow dipstick for artesunate.

Development of a Monoclonal Antibody-Based icELISA for the Detection of Ustiloxin B in Rice False Smut Balls and Rice Grains

Rice false smut is an emerging and economically-important rice disease caused by infection by the fungal pathogen Villosiclava virens. Ustiloxin B is an antimitotic cyclopeptide mycotoxin isolated from the rice false smut balls that formed in the pathogen-infected rice spikelets. A monoclonal antibody (mAb) designated as mAb 1B5A10 was generated with ustiloxin B—ovalbumin conjugate. A highly-sensitive and specific indirect competitive enzyme-linked immunosorbent assay (icELISA) was then developed. The median inhibitory concentration (IC₅₀) of the icELISA was 18.0 ng/mL for the detection of ustiloxin B; the limit of detection was 0.6 ng/mL, and the calibration range was from 2.5 to 107.4 ng/mL. The LOD/LOQ values of the developed ELISA used for the determination of ustiloxin B in rice false smut balls and rice grains were 12/50 μg/g and 30/125 ng/g, respectively. The mAb 1B5A10 cross-reacted with ustiloxin A at 13.9% relative to ustiloxin B. Average recoveries of ustiloxin B ranged from 91.3% to 105.1% for rice false smut balls at spiking levels of 0.2 to 3.2 mg/g and from 92.6% to 103.5% for rice grains at spiking levels of 100 to 5000 ng/g. Comparison of ustiloxin B content in rice false smut balls and rice grains detected by both icELISA and high performance liquid chromatography (HPLC) demonstrated that the developed icELISA can be employed as an effective and accurate method for the detection of ustiloxin B in rice false smut balls, as well as rice food and feed samples.

Monoclonal antibody-based immunoassay for analysis of octopamine in housefly

Octopamine (OA) is one of the biogenic monoamines in the housefly, which acts as an important neurohormone in the physiological process of this pest. In this study, a new hapten of OA was synthesized via aldol condensation. With the hapten, monoclonal antibodies (MAb) were generated and their characterizations were investigated. An indirect competitive enzyme-linked immunosorbent assay (icELISA) based on MAb 3C11-E3 was established, which required simple sample pre-treatments and had low cross-reactivity with OA structural analogise. The half maximal inhibition concentration (IC50) and the detected range (IC20-IC80) of the icELISA were 128 ng/mL and 12-1438 ng/mL, respectively. Average recoveries of OA ranged from 73 to 129% in the housefly.

Development of a specific monoclonal antibody-based ELISA to measure the artemether content of antimalarial drugs

Artemether is one of the artemisinin derivatives that are active ingredients in antimalarial drugs. Counterfeit and substandard antimalarial drugs have become a serious problem, which demands reliable analytical tools and implementation of strict regulation of drug quality. Structural similarity among artemisinin analogs is a challenge to develop immunoassays that are specific to artemisinin derivatives. To produce specific antibodies to artemether, we used microbial fermentation of artemether to obtain 9-hydroxyartemether, which was subsequently used to prepare a 9-O-succinylartemether hapten for conjugation with ovalbumin as the immunogen. A monoclonal antibody (mAb), designated as 2G12E1, was produced with high specificity to artemether. 2G12E1 showed low cross reactivities to dihydroartemisinin, artemisinin, artesunate and other major antimalarial drugs. An indirect competitive enzyme linked immunosorbent assay (icELISA) developed showed a concentration causing 50% of inhibition for artemether as 3.7 ng mL⁻¹ and a working range of 0.7-19 ng mL⁻¹. The icELISA was applied for determination of artemether content in different commercial drugs and the results were comparable to those determined by high-performance liquid chromatography analysis. In comparison with reported broad cross activity of anti-artemisinin mAbs, the most notable advantage of the 2G12E1-based ELISA is its high specificity to artemether only.

Highly sensitive nanomechanical assay for the stress transmission of carbon chain

Here, we report the first quantitative experimental study into the molecular basis of the transmission of mechanical signal that originates from biochemical reaction focusing on the length of carbon chain. We designed an experiment by using n-alkanethiols with a same carboxyl group and different chain lengths (n = 1, 5, 10 and 15) to immobilize a same receptor molecule on the gold surface of a microcantilever, and detected the nanomechanical response of biochemical reaction. The sensitivity of the microcantilever was found to be greatly influenced by the chain length of linker that is between the receptor molecule and the microcantilever surface. The efficiency of stress transmission increases significantly with decreasing length of carbon chain. At the same time, we develop a label-free microcantilever sensor for highly sensitive detection of Glycyrrhizic acid (GL). The detection limit of the microcantilever sensor for GL is found to be as low as 20 pg/mL for the shortest linker (n = 1), which is 500 times lower than the longest linker (n = 15) and 50 times lower than that of the corresponding icELISA. These findings will provide new insights into the fundamental mechanisms of stress transmission, which may be exploited for biochemical sensor and nanoactuation applications.

Effect of water deficit on biomass production and accumulation of secondary metabolites in roots of Glycyrrhiza uralensis

Two-year-old seedlings of licorice plant (Glycyrrhiza uralensis Fisch) were exposed to three degrees of water deficit, namely weak (60-70%), moderate (40-50%), and strong (20-30%) relative water content in soil, whereas control plants were grown in soil with 80-90% water content. Moderate and strong water deficit decreased the net photosynthetic rate, stomatal conductance, and biomass production. Water use efficiency and the root-to-shoot ratio increased significantly in response to water deficit, indicating a high tolerance to drought. Weak water deficit did not decrease root biomass production, but significantly increased the production of glycyrrhizic acid (by 89%) and liquiritin (by 125%) in the roots. Therefore, a weak water deficit can increase the yield of root medical compounds without negative effect on root growth.

Development of a sensitive monoclonal antibody-based enzyme-linked immunosorbent assay for the antimalaria active ingredient artemisinin in the Chinese herb Artemisia annua L

Artemisinin is an endoperoxide sesquiterpene lactone isolated from the Chinese medicinal plant Artemisia annua L. It has been widely used in South-East Asia and Africa as an effective drug against sensitive and multidrug-resistant Plasmodium falciparum malaria. A monoclonal antibody (mAb), designated as 3H2, was generated with artesunate-bovine serum albumin conjugate as the immunogen. mAb 3H2 was used to develop a highly sensitive and specific indirect competitive enzyme-linked immunosorbent assay (icELISA) for artemisinin. The concentration of analyte producing 50% of inhibition (IC(50)) and the working range of the icELISA were 1.3 and 0.2-5.8 ng/mL, respectively. The mAb 3H2 recognized the artemisinin analogs artesunate, dihydroartemisinin, and artemether with cross-reactivity of 650%, 57%, and 3%, respectively, but negligibly recognized deoxyartemisinin and the artemisinin precursors arteannuin B and artemisinic acid. The average recoveries of artemisinin fortified in A. annua samples at concentrations from 156 to 5,000 microg/g determined by icELISA ranged from 91% to 98%. The icELISA was applied for the determination of artemisinin in different wild A. annua samples and the results were confirmed by high-performance liquid chromatography (HPLC) analysis. The correlation coefficient (R(2)) between the two assays was larger than 0.99, demonstrating a good agreement between the icELISA and HPLC results. This ELISA is suitable for quality assurance of A. annua L. materials.

Monoclonal antibody-based enzyme linked immunosorbent assay for the analysis of jasmonates in plants

Methyl jasmonate (MeJA) and its free-acid form, jasmonic acid (JA) are naturally occurring plant growth regulators widely distributed in higher plants. In order to improve the sensitivity for the analysis of MeJA at low levels in small amounts of plant samples, a monoclonal antibody (MAb) (designated as MAb 3E(5)D(7)C(4)B(6)) against MeJA was derived from a JA-bovine serum albumin (BSA) conjugate as an immunogen. The antibody belongs to the IgG(1) subclass with a kappa type light chain and has a dissociation constant of approximately 6.07 x 10(-9) M. MAb3E(5)D(7)C(4)B(6) is very specific to MeJA. It was used to develop a direct competitive enzyme-linked immunosorbent assay (dcELISA), conventional and simplified indirect competitive ELISAs (icELISA). JA was derivatized into MeJA for the ELISA analysis. The IC(50) value and detection range for MeJA were, respectively, 34 and 4-257 ng/mL by the conventional icELISA, 21 and 3-226 ng/mL by the simplified icELISA and 5.0 and 0.7-97.0 ng/mL by the dcELISA. The dcELISA was more sensitive than either the conventional or simplified icELISA. The assays were used to measure the content of jasmonates as MeJA in tobacco leaves under drought stress or inoculated with tobacco mosaic virus and tomato leaves inoculated with tomato mosaic virus or Lirioinyza sativae Blanchard as compared with the corresponding healthy leaves. The increased jasmonates content indicated its role in response to the drought stress and pathogens.