Electrochemical Aptasensors as an Ultra-Sensitive Tool for the Detection of Antibiotics after Cattle Antibiotic Therapy ^†

Currently, mastitis has become a multifactorial disease of the bovine mammary gland characterized by high clinical and economic significance. Studies show that excessive antibiotic treatment results in the greater resistance of mastitis pathogens. Therefore, the development of technologies for the detection of antibiotics able to be used on-site in the field diagnostics of bovine mastitis are very desirable and would permit for rapid intervention to stop and prevent mastitis. Therefore, it is very important to develop a very sensitive, simple, cheap, and selective antibiotic detection tool applicable for therapy effects in order to perform a considerable amount of analyses in a short time. Electrochemical biosensors meet such requirements.

To date, several systems have been developed for the electrochemical detection of antibiotics. However, the simultaneous detection of many antibiotics during one measurement cycle on a single working electrode using redox markers is a considerable challenge and has not been presented to date. In this paper, we report on the development electrochemical systems allowing the detection of at least two antibiotics on a single measurement electrode. For the construction of these systems, we used aptamers as the receptor elements. Aptamers are single-stranded DNA or RNA oligonucleotides, which can specifically bind to target molecule, such as nucleic acids, proteins, metal ions, and other small molecules with high affinity, selectivity, and sensitivity, and are of particular interest. The idea of aptasensors evolved from the applications of oligonucleotide probes modified with redox active markers (such as ferrocene, anthraquinone, thionine, and methylene blue) for covalent attachment to the gold electrode surface. The changes in the efficiency of electron transfer between the electrode and redox label underlie the principles of the mechanism of analytical signal generation. The electrochemical aptasensors were successfully applied in milk samples.