(54d) Immobilization of Antibodies on Cellulose Nanocrystals for the Detection of Cancer Biomarkers

Cellulose nanocrystals (CNC) are an intriguing, sustainable material for biosensors due to their exceptional mechanical properties and nanoscale structure. However, relatively little is known about antibody immobilization on CNC; this is particularly true for the commonly available CNC that are produced by sulfuric acid extraction from woody biomass. This research used APTES-GA chemistry for immobilization of model antibodies on sulfonated CNC from the US Forest Products Lab. The following monoclonal antibodies were chosen for their use in cancer biomarker detection: alpha-fetoprotein (AFP) used in liver cancer detection, prostate-specific antigen (PSA) used in prostate cancer detection, and carcinoembryonic antigen (CEA) used in ovarian cancer detection. The results of immobilization of each of these biomarkers on solid CNC films and dispersed CNC were compared using thermogravimetric analysis (TGA), attenuated total reflection infrared spectroscopy (ATR-IR), and atomic force microscopy (AFM). Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to follow each step of the immobilization in real time as well as to detect the antigen binding. In addition, QCM-D was used to quantify the amount of antibody immobilized as well as binding of the corresponding antigen. Both schemes resulted in antibody immobilization. Immobilization on the films was the simplest method, but greater immobilization and antigen binding were achieved on dispersed CNC. This is attributed to accessibility of the entire CNC’s surface area in the dispersions. However, functionalization of dispersed CNC tended to result in CNC cross-linking and aggregation unless the reaction was performed at relatively dilute conditions. Furthermore, the presence of the APTES on the CNC surface inhibited the formation of highly aligned films. These results highlight that sulfonated CNC can be used for antibody immobilization and are an interesting green material for biosensors.