Purple nanocomposites

Bromley, KM., Patil, A.J., Seddon, A. M., Booth, P. and Mann, S. (2007) Bio-functional mesolamellar nanocomposite based on inorganic/ polymer intercalation in purple membrane (Bacteriorhodopsin) films. Advanced Materials, 19, 2433—2438. 

In order to produce nanocomposite films, thiol-derivatized gold nanoparticles were dispersed in a chloroform solution of polystyrene (PS, Aldrich, = 230,000 amu). High-transparent purple-colored nanocomposite films resulted by solution casting process (see Figure 5.2). 

The fundamental knowledge on the preparation and nature of metal-polymer nanocomposites has a long history that is connected to the names of many famous scientists. The oldest technique for the preparation of metal-polymer nanocomposites that can be found in the literature was described in an abstract that appeared in 1835. In an aqueous solution, a gold salt was reduced in the presence of gum arabic, and subsequently a nanocomposite material was obtained in the form of a purple solid simply by coprecipitation with ethanol. Around 1900, widely forgotten reports describe the... 

FIGURE 12.5 Polyamide-6 nanocomposite after 1 min of processing (purple, intercalated) and 7 min of processing (red, exfoliated). (From Ref. [98].) See insert for color represent of figure.)... 

The MIC value which is defined as the minimum concentration of an antimicrobial that is able to restrict the growth of microbial after whole night incubation have been determined by broth dilution method. Initial concentration of the nanocomposites for the test is taken as 10 mg/ml and diluted twice in each time up to a concentration of 0.0195 mg/ml. Nanocomposites with different concentrations have been subjected to E. coli and S. aureus to investigate the value of MIC. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoIiiun bromide) is added to the solution after 16 h incubation in Luria Berteni media in 96 well microtiter plate and incubated for 45 min in dark. Live bacterial cells which are capable to produce succinate dehydrogenase (enzyme) which reacts with MTT and forms formazan complexes with purple appearance. So the well having minimum concentration of sample where the complex does not form i.e. which does not appear purple is considered as the MIC value of the compound and is presented in the Table 7. It is observed that the MIC value of the nanocomposites decreases with the increase in Ag-NPs concentration in the nanocomposites and is minimum in the case of nanocomposites with 15 wt% of Ag-NPs. 

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