Measurement of adhesive forces between S. epidermidis and fibronectin-coated surfaces using optical tweezers.

BACKGROUND AND OBJECTIVES

Biomaterial-mediated infection, a common cause of medical device failure, is initiated by bacterial adhesion to an adsorbed protein layer on the implant surface. This adhesion is thought to be mediated by specific molecules present on the bacterial cell surface. Optical tweezers can be used to measure the adhesive force between a single bacterium and a protein-coated surface.

STUDY DESIGN/MATERIALS AND METHODS: Using optical tweezers, a bacterium was trapped and brought in contact with a 10-microm diameter polystyrene microsphere coated with fibronectin. The minimum force required to detach the cell from the bead was determined over a range of fibronectin concentrations and contact times.

RESULTS

The detachment forces were integer multiples of an 18-pN base value that was independent of contact time and coating concentration; we propose that the variation in force is related to the number of bonds formed.

CONCLUSIONS

These experiments demonstrate that optical tweezers can be used to investigate the adhesion of individual bacteria to surfaces. The results suggest that S. epidermidis has surface proteins capable of binding fibronectin.