Fabrication of an ultrasensitive aptasensor for precise electrochemical detection of the trace amounts of streptomycin in milk

A highly sensitive luminescent aptasensor utilizing MOF-74-co encapsulation of luminol in a 'turn-on' mode for streptomycin detection

This study focused on detecting streptomycin (STR) residues using a luminescent aptasensor encapsulated with aptamer. Utilizing MOF-74-Co with peroxidase-like activity, luminol was enclosed in its pores. The specific STR aptamer acted as a gatekeeper, ensuring excellent performance. Upon exposure to STR, the aptamers detached, releasing luminol and amplifying the luminescent signal through MOF-74-Co catalytic activity. A linear relationship between fluorescence intensity and STR concentration (50 nM ∼ 5 × 106 nM) was established, with a limit of detection of 0.065 nM. The sensor exhibited high selectivity for STR even in the presence of other aminoglycoside antibiotics. Applied to tea, egg, and honey samples, the sensor showed recovery rates of 91.38-100.2%, meeting safety standards. This MOF-based aptasensor shows promise for detecting harmful residues.

Graphene-based biosensors in milk analysis: A review of recent developments

Cow's milk, an excellent source of fat, protein, amino acids, vitamins and minerals, is currently one of the most consumed products worldwide. Contaminations originating from diverse sources, such as biological, chemical, and physical, cause dairy product quality problems and thus dairy-related disorders, raising public health issues. For this reason, legal authorities have deemed it necessary to classify certain contaminations in commercial milk and keep them within particular limitations; therefore, it is urgent to develop next-generation detection systems that can accurately identify just the contaminants of concern to human health. This review presents a detailed investigation of biosensors based on graphene and its derivatives, which offer superior sensitivity and selectivity, by classifying the contaminants under the headings biological, chemical, and physical, in cow's milk according to their sources. We reviewed the current status of graphene-based biosensor (GBs) technology for milk or dairy analysis, highlighting its strengths and weaknesses with the help of comparative studies, tables, and charts, and we put forward a novel perspective to handle future challenges.

Development of aptasensor for chlorpyrifos detection using paper-based screen-printed electrode

Novel Carbon quantum dots-graphite composite ink-based Screen-printed electrodes (CQDs/SPEs) were used to assemble a highly sensitive electrochemical aptasensor against chlorpyrifos (CPF). The aptasensor showed a broad linear range from 1 pM (0.445 ng/ml) to 500 nM (0.22 mg/ml) with a detection limit (LOD) 0.834 pM (0.37 ng/ml); sensitivity 21.39 μA pM-1 cm- 2 and with good linearity of R2 = 0.973. Moreover, the aptasensor's showed better selectivity among few other pesticides. Further, the aptasensor electrode showed high stability for five months when stored at 4 °C. In the final step, the aptasensor's ability to identify CPF in real samples was evaluated on spiked potato (Solanum tuberosum) extract samples. Potato extract spiked with CPF in the electrochemical aptasensing platform showed excellent linearity of R2 = 0.981. The developed aptasensor showed good response to without spiked potato extract with increasing volumes. Hence, the developed aptasensor demonstrated reasonable applicability in real food and agriculture samples.

Smartphone-based pH responsive 3-channel colorimetric biosensor for non-enzymatic multi-antibiotic residues

Antibiotic residues in animal-derived food pose a risk to food safety and human health. Here, a smartphone-based pH-responsive 3-channel colorimetric biosensor is constructed for rapid detection of non-enzymatic multi-antibiotic residues in milk. In this system, a magnetic separation and enrichment approach is designed to specifically capture different antibiotic residues in complex environment. Indicators loaded on polydopamine-silver nanoparticles with excellently pH responsive visualization properties are utilized to ensure the high sensitivity of detection system. Moreover, smartphones are introduced to fulfill the demand for portable and on-site inspection of practical applications. It achieves simultaneous detection of oxytetracycline, kanamycin and streptomycin in the linear range of 1-105 pg/mL with detection limits of 0.085, 0.168, and 0.307 pg/mL, respectively. The practicality of the reported multi-antibiotic residues detection system is successfully demonstrated and evaluated challenging milk samples. Therefore, this system demonstrates the wide applications in multi-antibiotic residue analysis and food safety guarantee.

A novel electrochemical aptasensor based on eco-friendly synthesized titanium dioxide nanosheets and polyethyleneimine grafted reduced graphene oxide for ultrasensitive and selective detection of ciprofloxacin

Developing a rapid, sensitive, and efficient analytical method for the trace-level determination of highly concerning antibiotic ciprofloxacin (CIP) is desirable to guarantee the safety of human health and ecosystems. In this work, a novel electrochemical aptasensor based on polyethyleneimine grafted reduced graphene oxide and titanium dioxide (rGO/PEI/TiO2) nanocomposite was constructed for ultrasensitive and selective detection of CIP. Through the in-situ electrochemical oxidation of Ti3C2Tx nanosheets, TiO2 nanosheets with good electrochemical response were prepared in a more convenient and eco-friendly method. The prepared TiO2 nanosheets promote charge transferring on electrode interface, and [Fe(CN)6]3-/4- as electrochemical active substance can be electrostatically attracted by rGO/PEI. Thus, electrochemical detection signal of the aptasensor variates a lot after specific binding with CIP, achieving working dynamic range of 0.003-10.0 μmol L-1, low detection limit down to 0.7 nmol L-1 (S/N = 3) and selectivity towards other antibiotics. Additionally, the aptasensor exhibited good agreement with HPLC method at 95% confidence level, and achieved good recoveries (96.8-106.3%) in real water samples, demonstrating its suitable applicability of trace detection of CIP in aquatic environment.

An Aptasensor Based on a Flexible Screen-Printed Silver Electrode for the Rapid Detection of Chlorpyrifos

In this work, we propose a novel disposable flexible and screen-printed electrochemical aptamer-based sensor (aptasensor) for the rapid detection of chlorpyrifos (CPF). To optimize the process, various characterization procedures were employed, including Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Initially, the aptasensor was optimized in terms of electrolyte pH, aptamer concentration, and incubation time for chlorpyrifos. Under optimal conditions, the aptasensor showed a wide linear range from 1 to 105 ng/mL with a calculated limit of detection as low as 0.097 ng/mL and sensitivity of 600.9 µA/ng. Additionally, the selectivity of the aptasensor was assessed by identifying any interference from other pesticides, which were found to be negligible (with a maximum standard deviation of 0.31 mA). Further, the stability of the sample was assessed over time, where the reported device showed high stability over a period of two weeks at 4 °C. As the last step, the ability of the aptasensor to detect chlorpyrifos in actual samples was evaluated by testing it on banana and grape extracts. As a result, the device demonstrated sufficient recovery rates, which indicate that it can find application in the food industry.