# Electrochemical Detection of Penicillin G Using Molecularly Imprinted Conductive Co-Polymer Sensor
## 1 Introduction  
A significant increase has been observed in the use of antibiotics, which is generally due to their specific activity against bacteria or fungi in human and animal organisms and, in addition, to their ability to increase growth rates and improve feed efficiency [1] in the field of animal husbandry. The presence of antibiotics in the environment leads to an increase in the number of multi-resistant bacteria, with serious consequences for human and animal health [2; 3; 4]. In Europe, in order to protect consumers from excessive consumption of these products, strict legislation has been imposed on the treatment of farm animals with antibiotics. Following this idea, food products of animal origin are subject to maximum residue limits (MRL). These limits differ for each of the antibiotics used in this field [5]. Their detection has become a major issue in many fields such as water analysis, food control, health, etc. An interesting example concerns the wide variety of antibiotics that might be found in milk, the milk matrix being one of the most complex ones. The case of penicillin G (hereafter called PenG) is no exception to this rule. European Commission established a maximum residue limit (MRL) in milk of 4 \(\mu\)g/L (which is equivalent to 4 ppb or to 12 nmol/L) mentioned in its council regulation 2377/90/EC [2; 5]. The choice of PenG lies essentially in the fact that this MRL imposed by the European Union is the lowest among the various potentially undesirable compounds in milk. If we manage to achieve this detection, we can assume that it will be possible to detect other compounds in higher concentration ranges. Nowadays, the methods used for antibiotic detection in milk are mainly based on chromatographic, immunological, and microbiological test approaches [6; 7; 8; 9; 10]. The use ofchromatographic methods, even if they are very sensitive, are not adapted for simple, cheap, and fast measurements, which would be the most suitable method to perform antibiotic detection in the agri-food industry. The most appropriate detection method for this type of measurement would therefore be the use of sensors. There are a wide variety of sensors aiming to detect antibiotics, many of them are biosensors. The first specific kind of antibiotic sensors is the enzyme-based biosensors. These biosensors use enzymes to generate a specific bio-recognition reaction. This usually generates electrochemical or optical response that is often measured by surface plasmon resonance (SPR). However, these sensors are often more expensive, and the assay time is often a bit long [11; 12; 13]. Besides that, there are a few biosensors based on the enzymatic activity of microorganisms. In general, those kinds of biosensors are based on the measurement of the inhibition of bacterial growth due to the presence of antibiotics [6; 7; 8; 9]. The main drawbacks of these sensors are their response time and their implementation. The largest group of antibiotic biosensors for detection in milk is the immunosensors. They are based on the exploitation of immunochemical biorecognition reactions. Even if this kind of sensors is very selective, they suffer from long response and regeneration time [12]. Another kind of sensor used to detect antibiotics is the aptasensors. These sensors use aptamers which can be considered chemical or synthetic antibodies. They are indeed produced in vitro based on the systematic evolution of ligands by exponential enrichment. However, this kind of sensor presents a major problem in milk analyses due to the presence of proteins and fat. Moreover, the non-transparency of the samples prevents the use of optical methods. The only way to solve the problem is to perform pretreatment on milk samples [14]. A rapid, easy, and sensitive immunodromagnatographic test strip has been developed for the detection of Ciprofloxacin in milk [15]. This method is based on antibody-antigen affinity.