Silicon nitride sugar chips for detection of Ricinus communis proteins and Escherichia coli O157 Shiga toxins.

Lactosides having either an amino-triethylene glycol or an azido-triethylene glycol were designed and synthesized, and the two derivatives were immobilized onto silicon nitride (SiN) surfaces. When a click reaction was applied for the immobilization of the azido-sugar, a Ricinus communis lectin (RCA 120) was detected with a higher response by reflectometric interference spectroscopy (RIfS). When an N -hydroxysuccinimide (NHS) method was applied for the sugar immobilization, the response was less than that of the click one. The response of bovine serum albumin (BSA) as the negative control was negligible, but the lactose-SiN chip prepared by the click method suppressed nonspecific binding more effectively than did the chip from the NHS method. Next, we examined an antibody-immobilized SiN chip prepared by the click reaction. The detection response was, however, lower than that of the lactose-SiN chip, meaning that the sugar-chip by the click reaction was superior to the antibody-chip. Finally, to detect Shiga toxins from Escherichia coli O157:H7, globotrisaccharide (Gb 3) with an azido-triethylene glycol was synthesized and immobilized onto the SiN chip by the click reaction. The Gb 3 -SiN chips enabled us to detect the toxins at concentrations less than 100 ng/mL. RCA 120 , horse gram, gorse lectins and BSA showed no response to the Gb 3 -SiN chip, showing a high specificity for the toxin. Image 1 • Silicon nitride chips were modified with lactose by a click reaction or N -hydroxysuccinimide (NHS) method. • Lactose chips by the click chemistry showed a better sensitivity than those by the NHS method. • Detection response of the antibody-SiN chip was lower than that of the Lac SiN chip. • Shiga toxins were detected at 100 ng/mL with globotrisaccharide chips made by the click reaction. [ABSTRACT FROM AUTHOR]