NEW IMMUNOSENSOR METHOD FOR β-LACTAM ANTIBIOTICS DETERMINATION IN BOVINE MILK

β-lactam antibiotics are frequently used to prevent bacterial infections in humans and cattle. But improper use of β-lactam antibiotics can leave residues in cow milk and cause serious problems to human health. The intake of β-lactam antibiotics, which may be partly involuntary, since the food chain itself leads to its ingestion, or voluntary, in order to combat bacterial infections, more and more often causes bacterial resistance toward β-lactam antibiotics. It is also well known that the intake of β-lactam antibiotics can cause allergic potential in presensitized people. This is causing growing alarm among healthcare specialists as it can offset or prevent the use of one of the most important drugs ever discovered and produced by pharmaceutical chemistry. This explains the need felt for frequent, fast, simple and cheap tests that can be applied not only to human biological fluids but also performed directly in the cow’s milk and dairies produced and used directly in human food. Of course there is no lack of analytical methods to test for β-lactam antibiotics, such as penicillins and cephalosporins. Nevertheless the need for rapid tests with low LOD values has also encouraged the use of sensor, biosensor and immunosensor methods. In this context relatively sophisticated sensors have been developed [1-5]. The present article reports the our last research in this field, consisting in both the development of a competitive format ( see Figure 1) based on the BSA-Penicillin G conjugated immobilized on a polymeric active membrane, and the application of a new immunodevice to the analysis of real samples, such as of cow milk and urine. The new device uses an amperometric electrode for hydrogen peroxide as transducer, the BSA-Penicillin G immobilized on polymeric membrane overlapping the amperometric transducer and the peroxidase enzyme as marker. It proved to be highly sensitive, inexpensive and easily reproducible; LOD was of the order of 10-11 M. Lastly, the new immunosensor displayed low selectivity versus the entire class of β-lactam antibiotics and higher selectivity toward other classes of non β-lactam antibiotics. Good results were obtained by analysing samples of cow milk from healthy or sick animals, and satisfactory results were obtained in the recovery tests. The developed immunosensor method appears to afford a number of advantages in terms of simplicity, sensitivity, the possibility of “in situ” analysis and especially lower costs, compared with other existing more sophisticated devices or different chemical instrumental methods, owing to the fact that the immunosensor proposed by the authors is inexpensive; this is true even in the light of the fact that, to construct the present immunosensor, completely commercial components were used.