N-Dimethyl Formamide

2.1 Material

N,N-Dimethyl formamide (DMF), 2,2-Azobisisobutyronitrile (AIBN), Silver nitrate (AgNO3) and Methanol were purchased from the lobachemie Pvt. Ltd. (India). Styrene monomer was procured from the sigma-Aldrich. Co. The solvents DMF and methanol were distilled for purification. Other chemicals were used as obtained.

2.2 Preparation of polystyrene (PS)

Polystyrene prepared by free radical polymerization of styrene monomer. Styrene (1 mole) was taken in a round bottom flask (RBF) fitted with a reflux condenser. DMF was used as a solvent and AIBN (0.5% w/w of total monomer) as free radical initiator .The reaction was carried out at 70±2° C for 6 hour with constant stirring. After completion of the process it was cooled to room temperature and resultant polymer solution was poured in the large amount of methanol with stirring when polymer precipitated out. It was filtered and washed with methanol. The polymer was purified by repeated precipitation using methanol from solution in DMF and then it dried.

2.3 Preparation of PS

All microorganism cultures were prepared from their respective slants. Cultures were grown over 24 hour at 37 °C and optical density was adjusted to 0.1, which corresponds to 108 CFU (colony forming unit)/ ml at 600 nm. About 100 µL bacteria were added to 100 ml of a nutrient broth solution to give bacteria concentration about 108 CFU/ ml. 4.2 Well diffusion method

This method was employed to essay antimicrobial activity of pure PS nanofiber and Ag nano particle doped PS composite nanofibers. The bacterial suspension (100 µL 108 CFU) was spread uniformly on the nutrient agar plate and 50 µL solution of each of PS and Ag/ PS prepared in DMSO was loaded in each well on nutrient agar plate The plate was then put in incubator for 24 hour at 37 °C to record inhibition zone [38]. 4.3 Viable cell counting