Investigation on the Antibacterial Activity and Mechanism of C12A7-O- Particles

The [Ca24Al28O64](4+)center dot 4O(-)(C12A7-O-) particle was firstly investigated its antibacterial activity against bacteria E. Coli in aqueous solution and phosphate buffered saline (PBS). The C12A7-O- particles were synthesized by gas-solid reaction method with CaCO3 and gamma-Al2O3 in a molar ratio of 12:7. The structure change of the C12A7-O- particles was measured by X-ray diffraction (XRD) and electron spin resonance (ESR) after antibacterial test. The results show that the structure of the C12A7-O- particles is completely changed into the structure of (CaO)(3)Al2O3 center dot 6H(2)O and Al(OH)(3). In the C12A7-O- solution (1 mg/mL), the concentration of atomic oxygen anion (O-) in the solution is 4 X 10(16) cm(-3). In the antibacterial test with the particle concentration of 3 mg/mL in aqueous solution, the bacteria concentration in decreased by 99.98% in 1 h from the original concentration of 10(5) cfu/mL. When the particle concentration is 1 mg/mL m PBS, the pH is 7.4 and the pH effect of the solution could be neglected, but the bacteria concentration still deduces to 3.7 x 10(3) cfu/mL from the original concentration in 24 h. In briefly, O- is the main factor in the antibacterial test in the C12A7-O- PBS solution with the neutral pH environment.