Label-free detection of carbohydrate-protein interactions using nanoscale field-effect transistor biosensors.

Carbohydrate-protein interactions play a significant role in cell communication, cell adhesion, cell trafficking, and immune responses. Many efforts have been made to demonstrate detection of carbohydrate-protein interactions. However, the existing methods are still tedious and expensive. Therefore, the detection of carbohydrate-protein interactions is of great significance, and new, efficient methods are required for fast and sensitive recognition testing. In this report, we, for the first time, developed the silicon nanowire (SiNW)-based biosensor capable of label-free electrical detection of carbohydrate-protein interactions with high selectivity and sensitivity by covalently immobilizing unmodified carbohydrates on the sensor surface. We fabricated new SiNW sensor chips with more SiNW arrays for potential detection of multiple analytes. In order to realize the immobilization of the unmodified carbohydrates on the SiNW surface, we used X-ray photoelectron spectra and fluorescence microscopy to verify the successful surface functionalization on the silicon surface. Furthermore, we demonstrated real-time detection of carbohydrate-protein interactions using the carbohydrate-modified SiNW sensor chips. The results show good specificity between galactose-lectin EC and mannose-Con A, which is in good agreement with that reported previously. Finally, the results also show that we are able to use the galactose-modified SiNW biosensor to detect lectin EC as low as 100 fg/mL, which is 4 orders of magnitude lower than that reported by other technologies. We believe that the developed SiNW biosensor paves a novel way for studying carbohydrate-protein interactions.