CIGMAT Report 2013

By C. Vipulanadan, PhD, P.E., professor and director of Center for Innovative Grouting Materials and Technology (CIGMAT) and Texas Hurricane Center for Innovative Technology (THC-IT), Department of Civil and Environmental Engineering, University of Houston | October 2013, Vol. 68 No. 10
Figure 1. Piezo-resistive behavior of modified oil well cement

Nanoparticles: bacteria interaction
Nanoparticles are being used in number of applications and new generation materials. Hence the effect of different metallic nanoparticles including iron (Fe), silver (Ag), gold (Au) and titanium (Ti) on the bacterial growth are being studied, related to biomedical field, textile field and as antimicrobial agents. Nanoparticles have anti-bacterial properties by either leading to cell wall breakage or by causing oxidative stresses. Several studies also have shown that nanoparticles can promote the growth of bacteria or have no clear toxicity to bacteria. The overall objective of CIGMAT study was to compare and quantify the effects of Au/Fe and Fe nanoparticles not only on the bacterial growth (Serratia sp.) but also on the production of a biosurfactant. The nanoparticles were prepared using the foam method. The concentrations of the nanoparticles used for the bacterial interaction study were varied from 1 mg/L to 10 g/L. The study included the growth of bacteria and production of a biosurfactant when exposed to the nanoparticles up to eight days. In Fig. 5, interactions of nanoparticles with bacterial (Serratia sp.) are shown. The test results showed that the effect of nanoparticles on the bacterial growth and biosurfactant production varied with nanoparticle type, shape and concentrations. Different exposure times of the bacteria to the nanoparticles had varying effects on the bacterial growth. Biosurfactant production was affected by the type and concentrations of nanoparticles. Based on the trends observed in the tests, analytical models have been developed to predict the bacterial growth and biosurfactant production with varying amount of nanoparticle concentrations.

Figure 5. Micrograph of nanoparticle-bacteria interaction of (a) bacteria only; (b) bacteria- Au/Fe nanoparticles; and (c) bacteria-Fe nanoparticles