Direct evaluation of microbial growth dynamics and colloidal stability of silver nanoparticles stabilized by poly(vinyl pyrrolidone) and poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) are examples of non-ionic polymers commonly used to stabilize silver nanoparticle (AgNP) aqueous dispersions. However, the role of these polymers in time-resolved growth analysis of microorganisms in culture media, including the influence on microbicidal activity, has not yet been described. To elucidate those aspects, in this study, zeta potential measurements combined with dynamic light scattering, electronic absorption spectroscopy, and transmission electron microscopy were used to assess the stabilization effects of PVA and PVP. The zeta potential of the dispersion of AgNP shifted from - 25 mV to near zero with the addition of the polymers. Large aggregates were detected when more than 10 wt% of the polymer was added, diminishing the colloidal stability. The amount of silver ions released from the nanoparticles stabilized with PVA or PVP was lower than for neat AgNP. Time-resolved growth analysis against the pathogens C. albicans, E. coli, and S. aureus were performed. AgNP dispersions without stabilizers or containing up to 5 wt% of PVA or PVP showed good colloidal stability and consequently microbicidal activity against E. coli and S. aureus. However, those containing more than 5 wt% of those polymers had their effect diminished. C. albicans was the most sensitive microorganism to the type and amount of stabilizer in the AgNP dispersions.