Study of Recognition between Bacteria and Antibody Molecules on Peg Tethered Silicon-Based Biosensors by Atomic Force Microscopy

Ting Cao1, Anfeng Wang1, Xuemei Liang1, Haiying Tang1, Gregory W. Auner2, Steven O. Salley1, and K. Y. Simon Ng1. (1) Department of Chemical Engineering and Materials Science, Wayne State University, 5050 Anthony Wayne Dr., Detroit, MI 48202, (2) Department of Electrical and Computer Engineering, Wayne State University, 5050 Anthony Wayne Dr., Detroit, MI 48202

To overcome the problem of losing bioactivity in covalent coupling in chemical sensor, a potential approach is to employ a long chain spacer to immobilize the antibody indirectly while maintaining separation of the biomolecule from the substrate.

In this study, Poly (ethylene glycol) (PEG) spacers were employed for tethering E.Coli K99 pilus antibody to silicon wafer surfaces for the purpose of increasing the flexibility of antibody as well as reducing the steric hindrance. To illustrate the effect of spacer length, a series of spacer lengths were used to covalently attach the antibodies to silicon surfaces. XPS and AFM were used to characterize the surface morphology and chemical composition at each reaction step. The effect of spacer length in improving the specificity of immobilized antibody and the recognition process for bacteria-antibody was investigated by attaching E.Coli on the end of an AFM tip. Distribution of unbinding force and rupture distance from the force-distance curved obtained by AFM showed that the introduction of PEG spacer facilitates bacterial recognition which can improve the detected specific interaction up to 90%. J600 exhibited better flexibility in overcoming the steric hindrance experienced with direct immobilization than other spacer lengths. Moreover, binding efficiency, rupture distance and force distribution of bacteria-antibody pairs can be elucidated with AFM for measurement