Introduction: In addition to treating infectious diseases, antibiotics made many modern medical procedures possible, including cancer treatment, organ transplants, and open-heart surgery. However, the misuse of these valuable compounds has led to a rapid increase in antimicrobial resistance, and some infections are currently not effectively treatable [1]. According to the WHO, antimicrobial resistance is considered one of the most serious global threats, increasing many drug-resistant diseases and infections in the near future. Antibiotics are mutant and resistant bacteria. They do not kill the drug and only kill the infected bacteria. These drugs are not completely metabolized in the human or animal body, so they are excreted into the environment and enter the food cycle through animals and the environment. Besides, antibiotics can indirectly reach humans through meat and dairy products, as they are widely used in veterinary medicine [2]. Therefore, developing more accurate, faster, and cheaper methods for detecting antibiotic residues in the environment and food is of great importance [3]. In recent years, rapid tests for detections have got a special place in the world. For example, nowadays, paper-based pregnancy tests are very popular and valuable. Paper-based biosensors have made it possible to create flexible, simple, and portable diagnostic devices at low cost [4]. The main advantages of paper are absorption properties, Capillary action, large surface-to-volume ratio, and functionalization with various functional groups [5]. Other advantages of paper-based biosensors include simple and fast production, easy disposal, biodegradability, portability, user-friendliness, low cost, and low waste in the environment [6,7].
Methods: In recent years, the overuse of antibiotics has caused more and more serious environmental pollution. The uncontrolled abuse of antibiotics makes bacteria produce resistance to antibiotics faster than the replacement rate of antibiotics themselves, leading to the emergence of super drug-resistant bacteria. Therefore, it is of great practical significance to establish a simple, rapid and sensitive method for the detection of antibiotics. By integrating natural nano-clay (Atta) and carbon dots (CDs), the real-time and rapid visual detection of tetracycline (TC) in the sample can be realized by chromaticity pick-up APP on smartphones. The nano-sensor can detect tetracycline in the concentration between 25 nM and 20 μM with the detection limit of 8.7 nM. The low detection limit coupled with good accuracy, sensitivity and specificity meets the requirements for the detection of tetracycline in food. More importantly, the test paper and fluorescent stick-like nano-sensor are designed to detect tetracycline by polychromatic fluorescence changes [8]. A novel “turn-on” fluorescent sensor based on R-CDs was developed for the selective detection of Tetracyclines (TCs) and pH. The R-CDs with red emission were prepared via hydrothermal treatment using neutral red and thiourea as carbon source. Besides, the R-CDs showed a distinct pH-sensitive luminescence emission feature in the pH range of 6.0–8.0 with a pKa of 7.08 [9].
Results: When the TCs were directly mixed with CDs, the fluorescence quenching phenomenon appeared. Since different TCs exhibited different affinities for sensing elements, the sensor array displays a distinct fluorescence pattern of the fluorescence intensity variation (F0 − F)/F0 for each of these TCs, which is further analyzed by principal component analysis (PCA). The present fluorescent sensor array has the capacity to differentiate TCs at a low concentration of 1 μM. Meanwhile, quantitative detection with a lower limit (0.30 μM) for TCs could be achieved by applying a single element. Moreover, a high accuracy (100%) examination of unknown samples is acquired. Finally, the fluorescent sensor array performs well in distinguishing binary mixtures and could also recognize TCs in milk [10].
Conclusion: An important challenge in nanomaterial-based antibiotic biosensors is the practical application, such as on-site analysis of analytes for the real samples and complex environments. For this reason, all biosensing devices should eventually be suitable for the end-user. Unfortunately, so far, biosensor-related innovations are limited to the laboratory scale, and less attention has been paid to the end-users' needs. Therefore, effective technology is still highly desired, enabling the rapid production of large amounts of nanomaterial-based biosensors with high-quality specifications and relatively low cost. Such a technique is the prerequisite for the successful commercial application of any biosensing device. Future efforts should focus on developing multifunctional nanomaterials and making the antibiotic biosensors more robust [11].