Antibacterial Efficacy of AgNPs and AgNPs-PVP
Two gram-positive bacteria, Streptococcus pneumoniae (S.
pneumoniae ) and Streptococcus mutans (S. mutans ), and one
gram-negative bacteria, non-typeable Haemophilus influenzae(NTHi), were chosen to test antibacterial effects of AgNPs-PVP. In
short, S. mutans was cultured in Brian Heart Infusion (BHI) broth
(BD Bioscience, USA), and both S. pneumoniae and NTHi were
cultured in BHI medium with defibrinated horse blood and nicotinamide
adenine dinucleotide (NADH) in a humidified 5%
CO2-conatining balanced-air incubator at 37°C according
to established protocols48–50.
The suspension assay for estimation of the minimum inhibitory
concentration (MIC) values was carries out to evaluate the antibacterial
activity. The MIC values were determined on 96-well plates. Bacteria
were cultured to serial dilutions of the AgNPs-PVP or AgNPs (3.125 µM,
6.25 µM, 12.5 µM, 25 µM, 50 µM, and 100 µM), and the end time points
were determined when control group (bacteria only) grew to the
stationary phase. Background from the nanoparticles alone was subtracted
from the final reading. All assays were carried out in triplicates. All
bacterial growth status were monitored by optical density at a
wavelength of 600 nm (OD600) using a UV–Vis Spectrophotometer
(Infinite® M1000 PRO).