Antibacterial activity of poloxamer-modified montmorillonite clay against E. coli

The aim of this study was to understand the antibacterial activity of poloxamer-modified montmorillonite (MMT) clay and to elucidate its possible mechanism. Modified MMT clay was first examined for characterizations of morphology, composition, crystal structure, thermal behavior, and Fourier transform infrared (FTIR) and X-ray photoelectron spectrometry (XPS), exhibiting a weight fraction of approximately 24% of poloxamer, and mainly consisting of Ca, Mg, Al, Si, and O elements in the clay. Pathogenic Gram-negative bacteria, Escherichia coli (E. coli), were chosen as the antibacterial evaluation indicator of this clay by determining the minimum inhibitory concentration (MIC) in nutrient broth (NB). The amount of cations releasing into NB was also analyzed via inductively coupled plasma mass spectrometry (ICP-MS). Poloxamer-modified MMT clay with a concentration of 2310 ppm was found to depress the growth of E. coli and exhibited a high calcium concentration of approximately 101 ppm releasing into NB. However, it was found that after being used once in the antibacterial test, the modified MMT clay did not retain any antibacterial activity in fresh NB; this is believed to be a result of the loss of poloxamer and decreased numbers of calcium ions incorporated into the used MMT clay, thus lowering bactericide induction, as indicated by the FTIR, XPS and ICP results. (C) 2011 Elsevier B.V. All rights reserved.