Preparation and characterization of an immunoaffinity column for the selective extraction of azaspiracids

Preparation and utilization of an immunoadsorption column for aflatoxin B1 composed of nanobodies and pre-crosslinked agarose microspheres

Recent studies on immunoaffinity chromatography (IAC) columns for aflatoxin B1 (AFB1) have not provided a comprehensive preparation procedure or explored their capacity, reusability, and stability. In this study, we outline a preparation process for an AFB1 immune affinity column filler (AFB1-IAC) for extracting AFB1 from food sources like rice, peanuts, and soybeans. Using commercially available IAC is often limited due to high costs, low capacity, slow flow rates, and poor reusability. To overcome these issues, we developed succinic anhydride (SA)-modified agarose pre-crosslinked microspheres (SA-A) activated with 1,1'‑carbonyldiimidazole (CDI). The activated microspheres were coupled with the anti-AFB1 nanobody Nb02, creating an immunoaffinity packing called CDI-SA-A-Nb02 (D1-IAC). After verification, the results indicated that the column capacity of D1-IAC was about 4.67 times that of several commercial IAC brands. Additionally, the maximum flow rate at a pressure of 0.04 MPa was 25 % greater than specific commercial IAC, and the recovery rate remained above 80 % after being reused five times. This method is considered effective for extracting and detecting AFB1 in food products. The preparation process for D1-IAC shows great consistency, and the column's performance is better than that of available immunoaffinity columns. This study explores using an IAC to extract and purify AFB1, which is then quantified using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

Current Research Status of Azaspiracids

The presence and impact of toxins have been detected in various regions worldwide ever since the discovery of azaspiracids (AZAs) in 1995. These toxins have had detrimental effects on marine resource utilization, marine environmental protection, and fishery production. Over the course of more than two decades of research and development, scientists from all over the world have conducted comprehensive studies on the in vivo metabolism, in vitro synthesis methods, pathogenic mechanisms, and toxicology of these toxins. This paper aims to provide a systematic introduction to the discovery, distribution, pathogenic mechanism, in vivo biosynthesis, and in vitro artificial synthesis of AZA toxins. Additionally, it will summarize various detection methods employed over the past 20 years, along with their advantages and disadvantages. This effort will contribute to the future development of rapid detection technologies and the invention of detection devices for AZAs in marine environmental samples.

Preparation of 18O-labelled azaspiracids for accurate quantitation using liquid chromatography-mass spectrometry

Azaspiracids (AZAs) are a group of polyether marine algal toxins known to accumulate in shellfish, posing a risk to human health and the seafood industry. Analysis of AZAs is typically performed using LC-MS, which can suffer from matrix effects that significantly impact the accuracy of measurement results. While the use of isotopic internal standards is an effective approach to correct for these effects, isotopically labelled standards for AZAs are not currently available. In this study, 18O-labelled AZA1, AZA2, and AZA3 were prepared by reaction with H218O under acidic conditions, and the reaction kinetics and sites of incorporation were studied using LC-HRMS/MS aided by mathematical analysis of their isotope patterns. Analysis of the isotopic incorporation in AZA1 and AZA3 indicated the presence of four exchangeable oxygen atoms. Excessive isomerization occurred during preparation of 18O-labelled AZA2, suggesting a role for the 8-methyl group in the thermodynamic stability of AZAs. Neutralized mixtures of 18O-labelled AZA1 and AZA3 were found to maintain their isotopic and isomeric integrities when stored at -20 °C and were used to develop an isotope-dilution LC-MS method which was applied to reference materials of shellfish matrices containing AZAs, demonstrating high accuracy and excellent reproducibility. Preparation of isotopically labelled compounds using the isotopic exchange method, combined with the kinetic analysis, offers a feasible way to obtain isotopically labelled internal standards for a wide variety of biomolecules to support reliable quantitation.

Immunoaffinity separation of miroestrol and deoxymiroestrol from Pueraria candollei var. mirifica (Airy Shaw & Suvat.) Niyomdham using fragment antigen-binding antibody produced via Escherichia coli

INTRODUCTION

Miroestrol and deoxymiroestrol are potent phytoestrogens and are oestrogen markers of Pueraria candollei var. mirifica. However, purifying these compounds is difficult because they only exist in trace amounts.

OBJECTIVES

Active fragment antigen-binding (Fab) antibodies were produced via Escherichia coli SHuffle® T7 and used to selectively separate these compounds.

MATERIALS AND METHODS

Two immunoaffinity separation approaches were developed, namely the immunoaffinity column (IAC) and a cell-based method. Group-specific Fab antibodies against miroestrol and deoxymiroestrol (anti-MD Fab) were used as biological binding reagents for selective separation.

RESULTS

The Fab-based IAC effectively separated miroestrol and deoxymiroestrol (0.65 and 2.24 μg per 2 mL of resin, respectively) from P. mirifica root extract. When P. mirifica extract was added to E. coli cultures during Fab expression via a cell-based method, the target compound accumulated in intracellular compartments and, thus, were separated from E. coli cells after the removal of other compounds. A yield of 1.07 μg of miroestrol per gram of cell pellet weight was obtained. Miroestrol and deoxymiroestrol were successfully purified from P. mirifica extract using anti-MD Fab via the IAC and an intracellular cell-based method.

CONCLUSION

The proposed methods can simplify the miroestrol and deoxymiroestrol extraction process and provide a basis for applications utilising recombinant antibodies to separate target compounds.

Solid-phase immunoextraction followed by liquid chromatography-tandem mass spectrometry for the selective determination of thyroxine in human serum

In this work, an analytical method based on solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry analysis (LC-MS/MS) has been developed for the selective determination of thyroxine (T4) in human serum. For this purpose, two immunosorbents (ISs) specific to T4 were synthesized by grafting two different T4-specific monoclonal antibodies on a cyanogen bromide (CNBr)-activated-Sepharose® 4B solid support. The grafting yields obtained from the immobilization of each antibody on the CNBr-activated-Sepharose® 4B were over 90%, demonstrating that most of the antibodies were covalently bound to the solid support. The SPE procedure was optimized by studying the retention capability and selectivity of the two ISs in pure media fortified with T4. Under the optimized conditions, high elution efficiencies were achieved in the elution fraction for both specific ISs (i.e., 85%), whereas low ones were obtained in the control ISs (ca. 2%), showing the selectivity of the specific ISs. The ISs were also characterized by studying extraction and synthesis repeatability (RSD <8%), and capacity (104 ng of T4 per 35 mg of ISs, i.e., 3 μg g^-1). Finally, the methodology was applied to a pooled human serum sample in order to study its analytical utility and accuracy. Relative recovery (RR) values between 81 and 107% were obtained, showing no matrix effects during the global methodology. Furthermore, the need to perform the immunoextraction was evidenced by comparing the LC-MS scan chromatograms and RR values with and without applying the immunoextraction procedure on a serum sample submitted to protein precipitation. This works exploits, for the first time, the use of an IS on the selective determination of T4 in human serum samples.