Review on sensing detection progress of "lean meat agent" based on functional nanomaterials

The "lean meat agents" is a class of β-agonists with a similar structure, which had been abused as an animal growth promoter to improve carcass lean meat rate. However, the drug residue accumulation in meat and body tissues would cause acute poisoning after eating, which gave rise to muscular pain, dizziness, cardiacpalpitation and vomiting, so China has banned its application for growth promotion in animal breeding processes since 2010. But the illegal abuse of "lean meat agents" still frequently occurs in some animal farms. Besides, the plenty of substitutes and increasingly concealing performance still pose a great threat to the safety of animal products and human health. The frequently abused ''lean meat agents'' include clenbuterol (CLE), ractopamine (RAC), salbutamol (SAL), terbutaline, cimaterol, phenylethanolamine A, etc. At present, various analytical methods have been developed to detect the drug residue, including high performance liquid chromatography (HPLC), gas chromatography mass spectrometry (GC-MS), liquid chromatography mass spectrometry (LC-MS), capillary electrophoresis (CE) and enzyme-linked immunoassay (ELISA), lateral flow chromatography, surface-enhanced Raman immunity, and molecular imprinting polymers, and so on. While these chromatographic methods all require complicated sample pre-treatments, which is not only laborious and time consuming but also sophisticated and large apparatus. Thus, they are most often used as precise quantitative and confirmatory methods, and not fit to the rapid screening. The ELISA and lateral flow chromatography are suitable for field analysis and extensive screening, but the sensitivity is not unsatisfactory in most time. So the routine methods have been unable to meet the requirements of multiple application scenarios and the complex sample substrates. In the past decades, the nanotechnology has made great progress. The functional nanomaterials possess a lot of extraordinary property, such as large surface-to-volume ratio, excellent electrical conductivity, high chemical stability, good biological compatibility, etc. At the time, sensors have interdisciplinary applications in many fields, including chemistry, biology and electronics, industry, agriculture, clinical medicine, environmental protection, food safety jaince and the other fields. The special structure and properties of functional nanomaterials have greatly improved the performance of the existing sensing technologies, making the sensing technologies develop towards the direction of sensitivity, efficiency, simplicity, low cost and increasing anti-interference ability. In addition, the sensing instrument is easier to be miniaturized, portable and automatic, combining with the functional nanomaterials, which is expected to achieve real-time, online, simple, sensitive, high-flux and portable drug residue detection, having a promising application prospects. So far, the wide and common use functional nanomaterials in sensing detection include gold nanomaterials, carbon nanomaterials, quantum dots and other new nanomaterials (such as Phosphorene, Janus nanoparticles, CeO2 nanoparticles), so the above-mentioned functional nanomaterials were summarized with the various detection principle of sensing test, such as colorimetric methods, surface enhanced Raman scattering, immunoassay, electrochemical and electrochemiluminescence methods in this review. In generally, functional nanomaterials and composite nanomaterials usually improve sensor performance from the following aspects, as a reaction substrate, load the specific molecular recognition, improve electrical conductivity, surface enhancement effect, signal conduction properties, catalytic properties and good biocompatibility, and so on. In the future, in order to improve the performance of sensor, the functional nanomaterials can be improved in the following aspects. Firstly, the specificity of the nanomaterials in free-label sensor should be enhanced to ensure the detection methods suitable to the needs of actual detection. Secondly, development and screening of new kind of functional nanomaterial, or synthesis the nanomaterial contains two or more elements or has special structure, to obtain the superior performance. Thirdly, make further study of the strengthening mechanism of nanomaterial, and innovate the modification methods for identifying molecules. With the rapid development in nanotechnology, the functional nanomaterials in sensing technology will make greater function to develop more sensitive, accurate, simple, high throughput and low-cost detection methods for drug residue detection.