Facile fabrication of branched-chain carbohydrate chips for studying carbohydrate-protein interactions by QCM biosensor

A novel approach for fabricating branched-chain (BC) carbohydrate chips to study carbohydrate-protein interactions using Quartz Crystal Microbalance (QCM) biosensor was developed. This approach utilizes functional alkynyl-branch molecule modified chip surfaces, which through the terminal alkynyl group for covalent linking of unprotected azide-carbohydrates. The unprotected azide-carbohydrates were syhthesized in one-step using 2-azido-1,3-dimethyl-imidazolinium as catalyst, avoiding complex chemical modifications. Additionally, the branch surface modified with the carbohydrates not only supplies more specific binding site but also reveals significant cluster effect. To exemplify the sugar cluster effect on BC carbohydrate chips, BC Galactose and Mannose chips prepared in this work were used to determine carbohydrate-lectin interactions using QCM biosensor. The results clearly showed that BC chip significantly improves the detection sensitivity compared with the straight-chain (SC) chip. More importantly, the BC galactose chip sensitivity was enhanced 40% compared with the SC galactose chip.