Nitrogen-Doped Carbon Hollow Spheres for Immobilization, Direct Electrochemistry, and Biosensing of Protein

Nitrogen-doped carbon hollow spheres (NCHS) were designed for the immobilization and biosensing of proteins. Chitosan was first functionalized with glutaraldehyde to form cross-linked chitosan with free ?CHO groups (GCS). The as-prepared GCS was used for dispersion of nitrogen-doped carbon hollow spheres. Using glucose oxidase (GOD) as a model, the NCHS was tested for immobilization of redox proteins and the design of electrochemical biosensors. GOD molecules immobilized in the nanocomposites showed direct electrochemistry with a formal potential of -0.448 V and well electrochemical performance. The proposed biosensor exhibited a linear response to glucose concentrations ranging from 3.7 mu M to 18.0 mM with a detection limit of 1.2 mu M and a sensitivity of 11.85 mu A?mM-1. This biosensor was also applied to detect glucose in human serum samples, accomplishing good recovery in the range of 92105?%. The nanocomposites provided a good matrix for protein immobilization and biosensor fabrication.