Easypure 2

Anti-17-estradiol antibody and 17β-estradiol were purchased from Abcam (Cambridge, UK). The Alexa fluor 488-conjugated goat anti-rabbit IgG (H + L) cross-adsorbed secondary antibody was purchased from Thermo Fisher Scientific (Massachusetts, USA). Cysteamine hydrochloride (≥99%), bovine serum albumin (BSA, ≥99%), phosphate-buffered saline (PBS, 1X), (3-aminopropyl)triethoxysilane (APTES, 99%), ethanol (EtOH, 99.8%), polytetrafluoroethylene (PTFE, 99%), perfluoro(n-butyltetrahydrofuran) (FC-40, 99%), and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (97%) were purchased from Sigma Aldrich. A soda-lime glass substrate was bought from ISOLAB Laborgeräte GmbH. Ag and Au pellets (99.99%) were bought from iTASCO (Taewon Scientific Co., Ltd, Korea). Aqueous solutions were prepared using ultrapure water (Thermo Scientific Easypure II, Göteborg, Sweden) with a resistivity of 18.2 MΩ cm.

Xylene (isomer mixture, histological grade), aqueous formaldehyde solution (≥36.0%, for molecular histology), and paraffin wax (for histology) were all purchased from Sigma Aldrich, Buchs, Switzerland. Ultra-pure water (resistivity 18.2 MΩ cm) was dispensed from a Barnstead EASYPURE II water system (ThermoFisher Scientific, Marietta, OH). Ethanol, toluene, (3-aminopropyl)-triethoxysilane (APES), acetone, and nitrate salts of Na, K, Mg, Mn, Fe, Cu, and Zn were all of p.a. quality and purchased from Sigma Aldrich, Buchs, Switzerland. Conc. HNO₃ was of p.a. quality and obtained from Merck, Darmstadt, Germany.

Aflatoxin B1 (AFB1) and Zearalenone (ZEA), both of analytical grade, were obtained from Fermentek Ltd., Jerusalem, Israel. Phosphate buffered saline (PBS) was obtained from Sigma-Aldrich, Darmstadt, Germany. All solvents used for chromatography were of HPLC analysis grade. All other reagents were of analytical purity or chromatographic grade. The ultra-pure water was obtained using a water purification system (Barnstead, EASYPURE II, ThermoScientific, Waltham, MA, USA). All solutions were stored at 4 °C and protected from light, and were filtered before analysis using nonsterile micro-centrifugal filters 0.2 μm (regenerated cellulose, Thermo Fisher Scientific, Waltham, MA, USA).
The solid toxins (AFB1 and ZEA) were dissolved in acetonitrile (HPLC grade) to obtain stock solutions of AFB1 and ZEA (1 mg/mL), which were stored in the dark at 4 °C. A binary-mycotoxin standard solution containing 100 μg/mL of each toxin (AFB1 and ZEA) was prepared by mixing equal volumes of mycotoxin stock solutions. Subsequently, this solution was appropriately diluted with PBS buffer at different pH values to prepare the mycotoxin working solutions for binding experiments. The mycotoxin stock solution was separately appropriately diluted with acetonitrile in order to prepare the standard samples for UHPLC calibration curves in the range of 0.05–6.25 μg/mL.

All the chemicals used in this article were of analytical grade. Gold(iii) chloride trihydrate (HAuCl₄·3H₂O, 99.9%), sodium citrate tribasic dihydrate (HOC(COONa)(CH₂COONa)₂·2H₂O, 99.0%), and (3-aminopropyl)trimethoxysilane (H₂N(CH₂)₃Si(OCH₃)₃, APTMS, 97%) were provided by Sigma-Aldrich Co., Ltd (USA). Sodium hydroxide (NaOH, 96%) was provided by Guangdong Guanghua Sci-Tech Co., Ltd (China). Deionized water (DI, resistivity: 18 MΩ cm, Thermo Scientific Easypure II, Göteborg, Sweden) was synthesized in the Center for Innovative Materials and Architectures (INOMAR), Vietnam National University, Ho Chi Minh City (VNUHCM). Hydrogen peroxide (H₂O₂, 30%) was obtained from Merck KGaA (Germany). Sulfuric acid (H₂SO₄, 96%) was acquired from Acros Organics (USA). Ethanol (C₂H₅OH, EtOH, 99.8%) and methanol (CH₃OH, 99.8%) were procured from Fisher Ltd (UK). Microscope glass slides (soda-lime glass, chemical composition: SiO₂ = 75 ± 5 wt%; Na₂O = 15 ± 2 wt%; CaO + MgO = 10 ± 2 wt%) were purchased from ISOLAB Laborgeräte GmbH, Eschau, Germany.

The certified standard solutions of Cd, Cr, Pb, As, and Hg (1 mg/mL) were purchased from the National Institute of Metrology, China. The working standard solutions were prepared from the standard solutions with Milli-Q water (18.2 MΩ cm resistivity) from a Millipore Milli-Q system (Thermo Scientific EASYpure II, Waltham, MA, USA). Calibration was performed by analyzing the prepared working standard solutions and two agent blank samples. Concentrations of Cd, Cr, and Pb were determined using an Inductively Coupled Plasma-Atomic Emission Spectrometry instrument (SPECTRO Analytical Instruments GmbH, Kleve, Germany) with axial viewing configuration. Total concentrations of As and Hg were determined using Atomic Fluorescence Spectrometry (AFS-930) (Beijing Jitian instrument Ltd., Beijing, China).

Alanine anhydride (AA, 3,6-dimethyl-2,5-piperazinedione) and sarcosine anhydride (SA, 1,4-dimethyl-2,5-piperazinedione) are commercial products with at least 99% purity, and they were dried before the experiments. The organic compounds were purchased from Aldrich (purity >98%). The compounds studied as solvents were dried and purified according to the method in [30 ]. The water content was estimated by Karl Fischer’s titration method; the content did not exceed 0.05%. Water was prepared by double distillation followed by purification with the system Thermo Scientific Easy Pure II (USA); the electrical resistivity of water was at least Ω = 18.2 ΩΩm.