Surface plasmon resonance-based sensor for Escherichia coli monitoring with novel green-synthesized silver/rGO/L-Histidine as an interface layer

초록

Surface plasmon resonance (SPR)-based sensors are being developed to detect pathogenic bacteria such as Escherichia coli (E. coli). Fast, accurate, and sensitive detection of foodborne pathogens is very important in early disease detection. This study reports using Ag/rGO/L-His as an interface layer in SPR-based sensors to detect E. coli bacteria. Ag/rGO/L-His with various rGO concentrations were green-synthesized utilizing spinach (Amaranthus viridis) extract. Localized surface plasmon resonance (LSPR) behaviour of Ag/rGO/L-His (AGL) was investigated utilizing the Kretschmann configuration with pris/Au/AGL/E. coli/air array. The concentration of E. coli was varied, and the sensor performance was analysed to evaluate the effect of varying bacterial concentration on the LSPR curve parameters. The analysis results show that there is an LSPR angle shift between pris/Au /air and pris/Au/AGL/air of 0.21 degrees for Ag/rGO1 and 0.34 degrees for Ag/rGO5. The angle shift value increases as the concentration of rGO added increases. The angle of Ag/rGO1/L-His shifted by 0.32, 0.46, and 0.58 after detecting E. coli at concentrations of 6 x 106 CFU/mL, 6 x 107CFU/mL, and 6 x 108 CFU/mL, respectively. The same results also occur in Ag/rGO5/L-His, where resulted an increase in the LSPR angle shift values of 0.51, 0.65, and 0.74. In addition, the minimum reflectance value increased in both samples along with the increase in E. coli concentration. Furthermore, the effectiveness of the SPR sensor was calculated by the low detection limit (LOD). The results showed that the application of Ag/rGO/L-His nanocomposite resulted in a lower LOD ranging from 0.22-0.27 CFU/mL. The low LOD value indicates that the incorporation of rGO into Ag/rGO/L-His plays an important role in enhancing the signal of the SPR-based sensor to detect E. coli bacteria. In addition, the sensor showed good repeatability. Therefore, the use of green-synthesized Ag/rGO/L-His nanocomposite as an interface layer can be a promising alternative to improve the performance of SPR biosensors in detecting various biomolecules such as viruses, bacteria, and other microorganisms.

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