Electrochemical Aptasensors for Antibiotics Detection: Recent Achievements and Applications for Monitoring Food Safety

Adjustable crystallinity of covalent organic frameworks for electrochemical aptasensing of penicillin

Covalent organic frameworks (COFs) show a great potential application in the field of constructing electrochemical aptasensors due to their high specific surface area, abundant pores, and good stability. Crystallinity (i.e., orderliness) is directly related to the structural characteristics of porous frameworks and affects their sensing performance. However, few reports focus on the influence of crystallinity on electrocatalytic aptasensing performance. This work develops copper porphyrin-based COFs with different crystallinity to fabricate electrochemical aptasensors for detecting penicillin. The research results indicate that highly ordered COF has higher specific surface area and ordered pores, which can significantly improve sensing performance.

Multiplex electrochemical aptasensor for the simultaneous detection of linomycin and neomycin antibiotics

The escalating use of antibiotics across diverse sectors, including human healthcare, agriculture, and livestock, has led to their pervasive presence in the environment, raising concerns about their impact on ecosystems and human health. Traditional detection methods, reliant on high-performance liquid chromatography and immuno-assays, face challenges of complexity, cross-reactivity, and limited specificity. Aptamer-based biosensors offer a promising alternative, leveraging the specificity, stability, and cost-effectiveness of aptamers. Herein, we present a novel dual-screen-printed carbon electrode (SPCE) biosensor, modified with a nanocomposite of gold nanoparticles (AuNPs) and carbon nanofibers (CNFs), for the label-free electrochemical detection of lincomycin and neomycin antibiotics. Lincomycin and neomycin, two antibiotics of environmental concern due to their widespread usage and potential ecological impact, were simultaneously detected using square wave voltammetry. The aptasensors showed high sensitivity with detection limits of 0.02 pg/mL and 0.035 pg/mL for lincomycin and neomycin, respectively. The developed biosensor exhibited high selectivity and reproducibility in detecting both antibiotics. This multiplex biosensing platform offers a promising strategy for efficient and cost-effective monitoring of antibiotic residues in environmental samples, addressing the critical need for robust detection methods in environmental monitoring and public health surveillance.

Electrochemical Aptasensor with Antifouling Properties for Label-Free Detection of Oxytetracycline

Oxytetracycline (OTC) is a widely employed antibiotic in veterinary treatment and in the prevention of infections, potentially leaving residues in animal-derived food products, such as milk, that are consumed by humans. Given the detrimental effects of prolonged human exposure to antibiotics, it has become imperative to develop precise and sensitive methods for monitoring the presence of OTC in food. Herein, we describe the development and results of a preliminary label-free electrochemical aptasensor with antifouling properties designed to detect OTC in milk samples. The sensor was realized by modifying a gold screen-printed electrode with α-lipoic acid-NHS and an amine-terminated aptamer. Different electrochemical techniques were used to study the steps of the fabrication process and to quantify OTC in the presence of the Fe(CN)64-/Fe(CN)63- redox couple The detectable range of concentrations satisfy the maximum residue limits set by the European Union, with an limit of detection (LOD) of 14 ng/mL in phosphate buffer (BP) and 10 ng/mL in the milk matrix, and a dynamic range of up to 500 ng/mL This study is a steppingstone towards the implementation of a sensitive monitoring method for OTC in dairy products.

Green synthesis of silver nanoparticles from Manilkara zapota leaf extract for the detection of aminoglycoside antibiotics and other applications

Antibiotics of aminoglycoside (AMG) class, such as streptomycin (STR), have been widely used to treat infectious diseases caused by Gram-negative bacteria in livestock and humans. In this study, a selective and sensitive colorimetric probe for the determination of STR was proposed based on eco-friendly green synthesized AgNPs from the leaf extract of Manilkara zapota. The mechanism for the detection of STR is based on the electrostatic interaction of opposite charges between negatively charged silver nanoparticle-Manilkara zapota leaf (AgNP-MZL) and STR, causing an aggregation-induced characteristic shift of the SPR band (from 390 nm to 570 nm wavelength) of AgNP-MZL. The morphology, size distribution and optical properties of AgNP-MZL were characterized using UV/visible absorption spectroscopy, FTIR spectroscopy, XRD, DLS, zeta-potential measurements and TEM. The selective determination of STR was experimentally confirmed by performing controlled testing with other classes of antibiotics. To test the sensitivity level of this method, the ratio of these two A 390/A 570 absorbance wavelengths was selected to provide a linear concentration plot between 5 and 100 ng mL-1 STR. The LOD and LOQ were calculated to be 3.5 ng mL-1 and 26.8 ng mL-1, respectively. Good precision was evaluated with a standard deviation of 0.45 ng mL-1 and a relative standard deviation of 2.0% (intraday) and 2.42% (interday) at 10 ng mL-1 for 3 replicate measurements. Advantages of the green synthesis of AgNP-MZL include its eco-friendly nature and it is easy, efficient, cost effective and selective for the detection of the AMG class of antibiotics, i.e. STR, in agricultural and environmental samples.

Isothermal Reciprocal Catalytic DNA Circuit for Sensitive Analysis of Kanamycin

Inappropriate use of veterinary drugs can result in the presence of antibiotic residues in animal-derived foods, which is a threat to human health. A simple yet efficient antibiotic-sensing method is highly desirable. Programmable DNA amplification circuits have supplemented robust toolkits for food contaminants monitoring. However, they currently face limitations in terms of their intricate design and low signal gain. Herein, we have engineered a robust reciprocal catalytic DNA (RCD) circuit for highly efficient bioanalysis. The trigger initiates the cascade hybridization reaction (CHR) to yield plenty of repeated initiators for activating the rolling circle amplification (RCA) circuit. Then the RCA-generated numerous reconstituted triggers can reversely stimulate the CHR circuit. This results in a self-sufficient supply of numerous initiators and triggers for the successive cross-invasion of CHR and RCA amplifiers, thus leading to exponential signal amplification for the highly efficient detection of analytes. With its flexible programmability and modular features, the RCD amplifier can serve as a universal toolbox for the high-performance and accurate sensing of kanamycin in buffer and food samples including milk, honey, and fish, highlighting its enormous promise for low-abundance contaminant analysis in foodstuffs.

Comparative Analysis of pH and Target-Induced Conformational Changes of an Oxytetracycline Aptamer in Solution Phase and Surface-Immobilized Form

To date, numerous aptamer-based biosensing platforms have been developed for sensitive and selective monitoring of target analytes, relying on analyte-induced conformational changes in the aptamer for the quantification of the analyte and the conversion of the binding event into a measurable signal. Despite the impact of these conformational rearrangements on sensor performance, the influence of the environment on the structural conformations of aptamers has rarely been investigated, so the link between parameters directly influencing aptamer folding and the ability of the aptamer to bind to the target analyte remains elusive. Herein, the effect a number of variables have on an aptamer's 3D structure was examined, including the pH of the buffering medium, as well as the anchoring of the aptamer on a solid support, with the use of two label-free techniques. Circular dichroism spectroscopy was utilized to study the conformation of an aptamer in solution along with any changes induced to it by the environment (analyte binding, pH, composition and ionic strength of the buffer solution), while quartz crystal microbalance with dissipation monitoring was employed to investigate the surface-bound aptamer's behavior and performance. Analysis was performed on an aptamer against oxytetracycline, serving as a model system, representative of aptamers selected against small molecule analytes. The obtained results highlight the influence of the environment on the folding and thus analyte-binding capacity of an aptamer and emphasize the need to deploy appropriate surface functionalization protocols in sensor development as a means to minimize the steric obstructions and undesirable interactions of an aptamer with a surface onto which it is tethered.

Electrochemical Biosensors for the Detection of Antibiotics in Milk: Recent Trends and Future Perspectives

Antibiotics have emerged as ground-breaking medications for the treatment of infectious diseases, but due to the excessive use of antibiotics, some drugs have developed resistance to microorganisms. Because of their structural complexity, most antibiotics are excreted unchanged, polluting the water, soil, and natural resources. Additionally, food items are being polluted through the widespread use of antibiotics in animal feed. The normal concentrations of antibiotics in environmental samples typically vary from ng to g/L. Antibiotic residues in excess of these values can pose major risks the development of illnesses and infections/diseases. According to estimates, 300 million people will die prematurely in the next three decades (by 2050), and the WHO has proclaimed "antibiotic resistance" to be a severe economic and sociological hazard to public health. Several antibiotics have been recognised as possible environmental pollutants (EMA) and their detection in various matrices such as food, milk, and environmental samples is being investigated. Currently, chromatographic techniques coupled with different detectors (e.g., HPLC, LC-MS) are typically used for antibiotic analysis. Other screening methods include optical methods, ELISA, electrophoresis, biosensors, etc. To minimise the problems associated with antibiotics (i.e., the development of AMR) and the currently available analytical methods, electrochemical platforms have been investigated, and can provide a cost-effective, rapid and portable alternative. Despite the significant progress in this field, further developments are necessary to advance electrochemical sensors, e.g., through the use of multi-functional nanomaterials and advanced (bio)materials to ensure efficient detection, sensitivity, portability, and reliability. This review summarises the use of electrochemical biosensors for the detection of antibiotics in milk/milk products and presents a brief introduction to antibiotics and AMR followed by developments in the field of electrochemical biosensors based on (i) immunosensor, (ii) aptamer (iii) MIP, (iv) enzyme, (v) whole-cell and (vi) direct electrochemical approaches. The role of nanomaterials and sensor fabrication is discussed wherever necessary. Finally, the review discusses the challenges encountered and future perspectives. This review can serve as an insightful source of information, enhancing the awareness of the role of electrochemical biosensors in providing information for the preservation of the health of the public, of animals, and of our environment, globally.

Recent Advances in Polymer-Based Biosensors for Food Safety Detection

The excessive use of pesticides and drugs, coupled with environmental pollution, has resulted in the persistence of contaminants on food. These pollutants tend to accumulate in humans through the food chain, posing a significant threat to human health. Therefore, it is crucial to develop rapid, low-cost, portable, and on-site biosensors for detecting food contaminants. Among various biosensors, polymer-based biosensors have emerged as promising probes for detection of food contaminants in recent years, due to their various functions such as target binding, enrichment, and simple signal reading. This paper aims to discuss the characteristics of five types of food pollutants-heavy metals, pesticide residues, pathogenic bacteria, allergens, and antibiotics-and their adverse effects on human health. Additionally, this paper focuses on the principle of polymer-based biosensors and their latest applications in detecting these five types of food contaminants in actual food samples. Furthermore, this review briefly examines the future prospects and challenges of biosensors for food safety detection. The insights provided in this review will facilitate the development of biosensors for food safety detection.

Size-controlling preparation of covalent organic framework nanospheres for electrochemical impedimetric aptasensing of oxytetracycline

Covalent organic framework (COF) nanospheres with controlled size of ∼500 and ∼1100 nm were successfully prepared by adjusting the HOAc amount in the synthetic system. The as-synthesized COFs have large conjugate aromatic skeleton, excellent stability, abundant pore, and uniform morphology. These advantages of COFs are benefit for immobilizing aptamers to fabricate the targeted electrochemical aptasensor. The commonly used oxytetracycline (OTC) is an analytic model to explore the sensing performance of the COF-based aptasensor, indicating that the smaller COF (∼500 nm) is more conducive to acquiring the sensitive sensor than that of the larger COF (∼1100 nm). Moreover, the limitation of detection of the COF (∼500 nm)-based aptasensor is calculated to be 7.4 fg mL^-1 using the response impedance signal. Additionally, the aptamer-based biosensor has fine reproducibility, good stability, excellent specificity, and available usability even in real samples.

Aptamer Sensors for the Detection of Antibiotic Residues- A Mini-Review

Food security is a global issue, since it is closely related to human health. Antibiotics play a significant role in animal husbandry owing to their desirable broad-spectrum antibacterial activity. However, irrational use of antibiotics has caused serious environmental pollution and food safety problems; thus, the on-site detection of antibiotics is in high demand in environmental analysis and food safety assessment. Aptamer-based sensors are simple to use, accurate, inexpensive, selective, and are suitable for detecting antibiotics for environmental and food safety analysis. This review summarizes the recent advances in aptamer-based electrochemical, fluorescent, and colorimetric sensors for antibiotics detection. The review focuses on the detection principles of different aptamer sensors and recent achievements in developing electrochemical, fluorescent, and colorimetric aptamer sensors. The advantages and disadvantages of different sensors, current challenges, and future trends of aptamer-based sensors are also discussed.

Different Strategies for the Microfluidic Purification of Antibiotics from Food: A Comparative Study

The presence of residual antibiotics in food is increasingly emerging as a worrying risk for human health both for the possible direct toxicity and for the development of antibiotic-resistant bacteria. In the context of food safety, new methods based on microfluidics could offer better performance, providing improved rapidity, portability and sustainability, being more cost effective and easy to use. Here, a microfluidic method based on the use of magnetic microbeads specifically functionalized and inserted in polymeric microchambers is proposed. The microbeads are functionalized either with aptamers, antibodies or small functional groups able to interact with specific antibiotics. The setup of these different strategies as well as the performance of the different functionalizations are carefully evaluated and compared. The most promising results are obtained employing the functionalization with aptamers, which are able not only to capture and release almost all tetracycline present in the initial sample but also to deliver an enriched and simplified solution of antibiotic. These solutions of purified antibiotics are particularly suitable for further analyses, for example, with innovative methods, such as label-free detection. On the contrary, the on-chip process based on antibodies could capture only partially the antibiotics, as well as the protocol based on beads functionalized with small groups specific for sulfonamides. Therefore, the on-chip purification with aptamers combined with new portable detection systems opens new possibilities for the development of sensors in the field of food safety.