Avaliação da influência de diferentes tióis no desempenho de biossensores magnetielásticos para detecção de escherichia coli

Abstract

The magneto-elastic sensors are detection devices that can be remotely accessed and applied as biosensors having a mass sensitivity for detection of biological specimens, offering reliability in the detection of pathogens such as Escherichia coli. The pathogen detection methods generally require days to identify the pathogenic micro-organism, so there is interest in a rapid and accurate detection in real time. The magneto elastic biosensors are a promising alternative for this task. In this work, amorphous ribbons of Metglas 2826MB3 were coated with Au by the processes of sputtering and electrodeposition and segmented into 5 x 1 mm strips. We evaluated the roughness parameters arithmetic average height (Ra), root mean square roughness (Rq) and skewness (Rsk) using atomic force microscopy applied on three different surfaces (smooth, rough and polished). Seeking to improve the detection sensitivity of the device, the performance of the biosensors was evaluated in terms of the effects of different thiols on their performance. The compounds used differ in the size of the carbon chain and the terminal grouping which binds to the antibody. On the polished surface coated with Cr/Au by sputtering, we deposited the compounds cystamine (CYS), mercaptopropionic acid (MPA) and cysteamine (CYSTE), followed by antibodies. The biosensors were exposed to the bacteria E. coli in solution and the variation of the resonance frequency was measured with a network analyzer. It was found that the polished surface coated with Cr/Au by sputtering process showed lower values of Ra and Rq and a better distribution profile (Rsk) in relation to other surface studied. Biosensors employing the compound MPA showed an increase in attracting bacteria in relation to biosensors with CYS and CYSTE, but high standard deviations were observed, thus hampering the reproducibility and reliability of the biosensor. Biosensors tested with CYSTE showed higher efficiency and lower detection limit with respect to biosensors tested with CYS, indicating an improvement in the use of this compound. The results were favorable for the detection of E. coli, indicating that the size of carbon chain and the terminal grouping influence the effectiveness of immobilization of the magneto elastic biosensors.