Bacteria-based electro-optical platform for ampicillin detection in aquatic solutions

We have shown for the first time that it is possible to use a bacteria-based sensory system consisting of the bacterium Pseudomonas putida TSh-18 and an electro-optical sensor to detect ampicillin in the concentration range 0.5-600 μg/mL. Changes in the anisotropy of cell polarizability were detected at 900 and 2100 kHz; these represented the state of the cytoplasm and of the cell membrane, respectively. The changes indicate the quickest cell response to changes in the characteristics of the bacterial culture exposed to ampicillin. We have also shown that it is possible to monitor the ampicillin in the presence of kanamycin. In control experiments, we examined the effects of ampicillin and kanamycin on bacterial cells by phase-contrast microscopy and by standard microbiological tests on solid media. P. putida TSh-18 is recommended as a sensor system for ampicillin detection. Electro-optical analysis ensures detection of ampicillin in aquatic solutions in real-time, takes 10 min, and offers a lower limit of ampicillin detection of 0.5 μg/mL, which is lower than the European Community's maximum residue limit standards for penicillin antibiotics.

Electrochemical assay of ampicillin using Fe3N-Co2N nanoarray coated with molecularly imprinted polymer

Self-supported Fe₃N-Co₂N nanoarray with high electric conductivity and large surface area was prepared for growth of MIPs and further constructing a sensitive and stable electrochemical sensor. For the evaluation of its performance, Fe₃N-Co₂N is used as sensing electrode material, and AMP is used as template molecule to construct the MIP electrochemical sensor. Under the optimized conditions, the developed MIPs electrochemical sensor detects AMP with a low detection limit of 3.65 × 10^-10 mol L^-1 and shows outstanding reproducibility and stability. When the MIPs electrochemical sensor was applied to detect AMP in milk samples via standard addition method, the recovery within 97.06-102.43% with RSD of 1.05-2.11% was obtained. The fabrication of MIPs electrochemical sensor is highly promising for sensitive and selective electrochemical measurement and food safety testing. This work can provide theoretical guidance for truly challenging problems. Graphical abstract Principle diagram of MIP-EC sensor for detecting AMP Molecular imprinted polymers (MIPs) are widely performed for construction of electrochemical (EC) sensors especially for detecting small molecules in complex environment. However, the large-scale and robust preparation of MIPs in situ on sensor platform limits their practical applications. We fabricated a MIPs EC sensor based on Fe₃N-Co₂N in situ grown on carbon cloth (CC) as the substrate platform (Fe₃N-Co₂N/CC) combining with MIPs as the target recognition element for the label-free detection of AMP. Under the optimal conditions, the developed MIPs EC sensor can detect AMP with a low detection limit of 3.65 × 10^-10 mol L^-1. When the AMP in milk is detected by the proposed EC sensor, it shows ideal results. Therefore, the use of self-supported Fe₃N-Co₂N nanoarray as the platform for the fabrication of MIPs EC sensors is highly promising for sensitive and selective EC measurement and point-of-care testing.

A reagentless and reusable electrochemical aptamer-based sensor for rapid detection of ampicillin in complex samples

We report the design and fabrication of a "signal-on" electrochemical aptamer-based (E-AB) sensor for detection of ampicillin. The signaling of the sensor is based on target binding-induced changes in the conformation and flexibility of the methylene blue-modified aptamer probe. The sensor's response is fast; signal saturation can be reached in ~ 200s. Since all the sensor components are surface-immobilized, it is regenerable and can be reused for at least three times. It has demonstrated good specificity and is capable of differentiating between ampicillin and structurally similar antibiotics such as amoxicillin. More importantly, it is selective enough to be employed directly in complex samples, including serum, saliva, and milk. Although both alternating current voltammetry (ACV) and square wave voltammetry (SWV) are suitable sensor characterization techniques, our results show that ACV is better suited for target analysis. Even under the optimal experimental conditions, the limit of detection of the sensor obtained in ACV (1µM) is significantly lower than that obtained in SWV (30µM).

Analysis of cephalosporin antibiotics

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.