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

The [Ca24Al28O64]4+.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 γ-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)3Al2O3.6H2O and Al(OH)3.In the C12A7-O-solution(1 mg/mL),the concentration of atomic oxygen anion(O-)in the solution is 4×1016 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 105 cfu/mL.When the particle concentration is 1 mg/mL in PBS,the pH is 7.4 and the pH effect of the solution could be neglected,but the bacteria concentration still deduces to 3.7×103 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.