In this study, a surface biosensing platform was developed for detecting protein binding events based on surface plasmon resonance (SPR) sensing techniques. A dextran layer was engineered to enhance the density of carboxyl groups on the detection surface, enabling strong covalent attachment of small molecules. This dextran layer was anchored to a gold substrate via thiol-based linkage. Subsequent epoxidation transformed the hydroxyl groups on the dextran into carboxyl groups, facilitating the immobilization of target molecules. The resulting carboxymethylated (CM) dextran was utilized to detect protein binding through SPR, demonstrating a binding efficiency comparable to that of the commercial CM5 sensor.