Cytotoxicity Induced by Engineered Silver Nanocrystallites is Dependent on Surface Coatings and Cell Types...

Due to their unique antimicrobial properties silver nanocrystallites have garnered substantial recognition and are used extensively in biomedical applications such as wound dressing, surgical instruments and as bone substitute material. They are also released into unintended locations such as the environment or biosphere. Therefore it is imperative to understand the potential interactions, fate and transport of nanoparticles with environmental biotic systems. Although numerous factors including the composition, size, shape, surface charge and capping molecule of nanoparticles are known to influence the cell cytotoxicity, our results demonstrate for the first time that surface coatings are a major determinant in eliciting the potential cytotoxicity and cell interactions of silver nanoparticles. In the present investigation, silver nanocrystallites with nearly uniform size and shape distribution but with different surface coatings, imparting overall high negativity to high positivity, were synthesized. These nanoparticles were poly (diallyldimethylammonium) chloride-Ag, biogenic-Ag, colloidal-Ag (uncoated) and oleate-Ag with zeta potentials +455 mV, -122 mV, -425 mV and -455 mV respectively; the particles were thoroughly purified so as to avoid false cytotoxicity interpretations. A systematic investigation on the cytotoxic effects, cellular response and membrane damage caused by these four different silver nanoparticles were evaluated using multiple toxicity measurements on mouse macrophage (RAW-264.7) and lung epithelial (C-10) cell lines. From a toxicity perspective, our results clearly indicated that the cytotoxicity was depend on various factors such as synthesis procedure, surface coat or surface charge and the cell-type for the different silver nanoparticles that were investigated. Poly (diallyldimethylammonium) chloride -Ag was found to be the most toxic, followed by biogenic-Ag and oleate-Ag, whereas uncoated-Ag was found to be least toxic to both macrophage and epithelial cells. Also, based on our cytotoxicity interpretations, epithelial cells were found to be more resistant to the silver nanoparticles than the macrophage cells, regardless of the surface coating.