Investigation Of Immune Molecules With Atomic Force Microscopy And Exploration Of Potentiometric Immunosensor

Preparation methods for biological sample imaged with atomic force microscope (AFM) are reviewed and explored. Results show that mica especially activated mica is most fit for biomolecules.High resolution images of IgG and Anti-IgG are obtained with AFM. IgG and Anti-IgG are diluted to 1.6 X 10 -4mg/mL and 1.45 X 10-4mg/mL respectively, molecules disperse well for getting clear single molecule image. For protein with molecule weight above 30000D, clear images of single molecule can be obtained.Observing IgG in air with AFM continually, we found that IgG aggregated into different ring-like structures gradually, and subunits of the structure are productions of self-assembly with different shapes.Direct measurement of single immunocomplex formation by AFM as ultra-sensitive immunoassay is developed and applied to IgG/Anti-IgG system.Through vertically scanning Anti-IgG molecules with IgG modified tip, we got force vs. distance curve, and measured the unbinding force between IgG and Anti-IgG 1.6~4.1nN approximately.A potentiometric immunosensor is composed of Ag electrode with immobilized Anti-IgG, a reference electrode and a solution of given concentration IgG. Results show that the IgG concentration is correlated with the potential of the Ag electrode, and correlation coefficient is 0.9644. The linear response range was 0.2-6.4ng/mL for IgG solution.