Penicillin binding proteins-based immunoassay for the selective and quantitative determination of beta-lactam antibiotics

An immunoassay method based on penicillin-binding protein (PBP) was developed for the quantitative determination of 10 kinds of beta-lactam antibiotics (BLAs). First, two kinds of PBPs, which are named PBP1a and PBP2x, were expressed and purified, and they were characterized by SDS-PAGE and western blotting analysis. Then, the binding activity of PBP1a and PBP2x to template BLAs, cefquinome (CEFQ) and ampicillin (AMP), was determined. The effect of the buffer solution system, e.g., pH, ion concentration, and organic solvent, on the immune interaction efficiency between PBPs and BLAs was also evaluated. In the end, the PBP-based immunoassay method was developed and validated for the detection of 10 kinds of BLAs. Under optimal conditions, PBPs exhibited high binding affinity to BLAs. In addition, this method showed a high sensitivity for the detection of 10 kinds of BLAs with the limits of detection from 0.21 to 9.12 ng/mL, which are much lower than their corresponding maximum residual limit of European Union (4-100 ng/mL). Moreover, the developed PBP-immunoassay was employed for BLA detection from milk samples, and satisfactory recoveries (68.9-101.3 %) were obtained.

Selective adsorption and identification of penicillin G sodium in milk by molecularly imprinted polymer doped carbon dot

A carbon dot (CD) was prepared by o-phenylenediamine and water, which showed bright yellow fluorescence under ultraviolet light irradiation (λ = 580 nm), and verified good fluorescence quenching effect on penicillin G sodium (Png-Na). Using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, and Png-Na as a template, a kind of composite microsphere combining CD and molecularly imprinted polymer (MIP) was synthesized by surface-initiated atomic transfer radical polymerization (SI-ATRP). For reasons of comparison, we also prepared MIP without CD and non-imprinted polymers (NIPs). Through static and dynamic adsorption experiments, the maximum adsorption capacity was 47.05 mg g-1 and the equilibrium time was 30 min. High-performance liquid chromatography (HPLC) was utilized to determine the content of Png-Na in the spiked milk samples. A sensitive, rapid, and simple method for determination of Png-Na in food samples was developed. The utilized approach enabled the quantification of Png-Na within the concentration range 20-1000 μg L-1 (with a limit of detection of 5 μg L-1). The recoveries achieved were in the range 93.3-98.2%, with a relative standard deviation of 1.2-4.2%. The results demonstrated that CD@MIP possessed the capability of specific adsorption and fluorescence detection of Png-Na, enabling simultaneous detection and enrichment of Png-Na in real samples.

Metal chelate-epoxy bifunctional membranes for selective adsorption and covalent immobilization of a His-tagged protein

The preparation and application of metal chelate-epoxy bifunctional membranes for the selective adsorption and covalent immobilization of His-tagged protein switch RG13 were shown in this study. By controlling the concentration of iminodiacetic acid (IDA) and reaction time during the conjugation of IDA on to the epichlorohydrin-activated regenerated cellulose membrane, 5 metal chelate-epoxy bifunctional membranes, with degrees of IDA conjugation in the range of 20%-81%, were prepared. The bifunctional membrane with an IDA conjugation degree of 30%, designated as BFM₃₀, exhibited a sound adsorption capacity of 0.203 mg/cm² with a relatively high content of epoxy groups for covalent immobilization, were selected. The concomitant selective adsorption and covalent immobilization of the His-tagged RG13 with BFM₃₀ were carried out by 2-h incubation for protein adsorption and subsequent 16-h incubation for covalent immobilization after the removal of undesired proteins with wash buffer, giving an immobilization yield of 63% and a global activity yield 40%. The RG13 immobilized on the metal chelate-epoxy bifunctional membrane exhibited superior operational stability in a repeated batch process, retaining 94% of its initial activity after 20 cycles. The employment of the bifunctional membranes could significant facilitate enzyme immobilization processes by eliminating the need for prior protein purification.

Silver nanoparticle-decorated TiO2 nanotube array for solid-phase microextraction and SERS detection of antibiotic residue in milk

The excessive use or abuse of antibiotics on dairy cows leads to residues in milk, which can represent a public health risk. However, in recent years the β-Lactamase was illegally used to degrade residual antibiotics in milk, which makes the traditional antibiotic detection methods ineffective. Therefore, there is an extremely urgent need for multi-analyte analysis techniques for the detection of antibiotic residues. Herein, we reported an ultra-fast, facile, and sensitive solid-phase microextraction (SPME)-surface enhanced Raman scattering (SERS) platform for the detection of degraded antibiotics-2-mercapto-5-methyl-1,3,4-thiadiazole (MMT). The results showed that the log-log plot of SERS intensity to MMT concentration exhibits a superior linear relationship (R² = 0.992) in the concentration range of 0.5-1000 μM, with a detection limit of 0.11 μM. The silver nanoparticle-decorated TiO₂ nanotube array was successfully used as an all-in-one SPME-SERS substrate in the extraction and identification of the antibiotic degradation products in real milk. Due to the rapid pre-treatment, good reproducibility, and self-cleaning, the proposed SPME-SERS method has a great promise to be applied as a powerful tool for on-site detection in the field of food safety.

A highly selective and light-up red emissive fluorescent probe for imaging of penicillin G amidase inBacillus cereus

A highly selective and red-emissive fluorescent probe (HCyNB) for penicillin G amidase (PGA) has been prepared and used for imaging of endogenousPGAin penicillinase-producingBacillus subtilis.

Preparation of Ampicillin Surface Molecularly Imprinted Polymers for Its Selective Recognition of Ampicillin in Eggs Samples

Surface-imprinted polymers (MIPs) microspheres with the ability to specifically recognize water-soluble molecules were prepared using self-made monodisperse porous poly(chloromethylstyrene-co-divinylbenzene) beads as the solid-phase matrix and ampicillin (AMP) as the template molecule. MIPs were synthesized using different template molecule: monomer: crosslinker ratios and the optimum preparation ratio were obtained by measuring adsorption. The maximum equilibrium amount of adsorption by the MIPs reached 115.62 mg/g. Scatchard analysis indicated that the MIPs contained two types of recognition sites: specific and nonspecific. Based on the adsorption kinetics, adsorption equilibrium was reached after 30 minutes. Penicillin G, amoxicillin, and sulbactam acid were used as competitive molecules to research the selective adsorption capacity of the MIPs. The imprinted material was found to have good selectivity with selectivity coefficients for penicillin G, amoxicillin, and sulbactam acid of 5.74, 6.83, and 7.25, respectively. The MIPs were used as solid-phase extraction filler, resulting in successful enrichment and separation of ampicillin residue from egg samples. Standard addition recovery experiments revealed that recovery was good with recoveries from the spiked samples ranging from 91.5 to 94.9% and relative standard deviations from 3.6 to 4.2%. The solid-phase extraction MIPs microcolumn was reused 10 times, where it maintained a recovery rate of over 80%. This work presents a sensitive, fast, and convenient method for the determination of trace ampicillin in food samples.