Page 442 - Polymer-based Nanocomposites for Energy and Environmental Applications

Development of polymer nanocomposites 399

14.2.3 Preparation of silver nanoparticle-coated cellulose
composite films
A simple casting method was used to prepare silver nanocomposite films using dif-
ferent concentrations of cellulose (1, 2, 3, 4, and 5 mM). The microbial derived
bioflocculant-containing compounds were used as a reducing agent for preparing
the silver nanocomposites [15]. The silver nanoparticle-coated composite films pre-
pared were cut into circles of diameter 5 cm for further antifouling studies, with the
pure cellulose film as a control. The Ag nanocomposite films were further used for
antifouling studies [16].

14.2.4 Quantitative crystal violet-binding assay for biofilm
detection by the TCP method
Antifouling activity of Ag nanocomposites was determined by the tissue-culture plate
method, with some modifications [13]. To the 24 wells of a microplate, 2 mL of TSB
broth containing 1% glucose were added, with each well further inoculated with
0.1 mL of a log-phase culture of E. coli. The silver-nanocoated films prepared were
incubated undisturbed inside the wells for 48 h, after which the culture was drained out
and the films washed with 2 mL of PBS to remove planktonic cells. The plate was
further stained with 200 μL of 0.1% crystal violet solution and the absorbance of
the solution read in a spectrophotometer at 600 nm. Biofilm inhibition percentage
was calculated as follows:

CV OD 600 CompositeÞ=Average CV OD 600 ControlÞ 100 (14.1)
ð
ð
The result was verified with multiple triplicates. The biofilm reduction was further
confirmed in terms of colony forming units/mL (CFU) [5].
14.2.5 Microscopic examination of nanocoated polymers

The AgNPs formed inside the film were observed using a Zeiss O18 scanning electron
microscope operated at an accelerating voltage of 20 kV and a Hitachi electron micro-
scope (model H-800) at an accelerating voltage of 300 kV. The antifouling effect of
AgNP-coated thin cellulose films was analyzed by scanning electron microscopy. The
inhibition of bacterial colonies in relation to morphological changes in the polymer
nanocomposites was also analyzed.

14.3 Results and discussion

14.3.1 Qualitative conformation of biofilm formation

Early-stage biofilm was detected by the test tube method. The E. coli culture selected
formed a moderate biofilm on the inner surface of the test tubes upon incubation.
Appearance of a dark-blue-stained material was observed on the inner surface of
the stained test tube [17] (Fig. 14.1).