Manipulation of bacterial adhesion and proliferation by surface charges of electrically polarized hydroxyapatite

The manipulation of bacterial adhesion and proliferation by surface charges built onto the surfaces of electrically polarized bioceramic hydroxyapatite (HAp) was investigated. The gram-positive bacteria Staphylococcus aureus (S. aureus) and the gram-negative bacteria Escherichia coli (E. coli) were cultivated on negatively charged, positively charged, and non-charged HAp surfaces (denoted as N-, P-, and 0-surface, respectively). The electrostatic force caused by the surface charges experimentally was proven to affect both adhesion and proliferation. Compared with the 0-surface of HAp ceramics over a 3-h cultivation, the population of adhered bacteria rapidly multiplied on the N-surface whereas it multiplied quite slowly on the P-surface. Compared with the 0-surface over a cultivation period of 12 to 72 h, the proliferation rate of the bacterial cell density per colony was accelerated on the N-surface and decelerated on the P-surface. The above results are attributed (1) to the electrostatic interaction between the cell surfaces and the charged surfaces of the polarized HAp, (2) to the stimulus of the electrostatic force for bacterial cells, and (3) to the concentration of the nutrient for the bacteria.