Transport of Industrial PVP-Stabilized Silver Nanoparticles in Saturated Quartz Sand Coated with Pseudomonas aeruginosa PAO1 Biofilm of Variable Age

Abstract

Understanding the environmental fate and transport of engineered nanoparticles (ENPs) is of paramount importance for the formation and validation of regulatory guidelines regarding these new and increasingly prevalent materials. The present study assessed the transport of an industrial formulation of poly(vinylpyrrolidone)-stabilized silver nanoparticle (PVP-nAg) in columns packed with water-saturated quartz sand and the same sand coated with Pseudomonas aeruginosa PAO1 biofilm of variable age (i.e., growth period). Physicochemical characterization studies indicate that the PVP-nAg is stable in suspension and exhibits little change in size or electrophoretic mobility with changing ionic strength (IS) in either NaNO3 or Ca(NO3)2. The collector surface had a relatively homogeneous biofilm coating, as determined by CLSM, and a near uniform distribution of biomass and biofilm thickness following column equilibration. Transport experiments in clean sand revealed changes in the particle deposition behavior only at and above 10 mM IS Ca(NO3)2 and showed no discernible change in PVP-nAg transport behavior in the presence of 1 to 100 mM NaNO3. Transport experiments in P. aeruginosa-coated sand indicated significantly reduced retention of PVP-nAg at low IS compared to clean sand, irrespective of biofilm age. Nanoparticle retention was also generally reduced in the biofilm-coated sand at the higher IS, but to a lesser extent. The decreased retention of PVP-nAg in biofilm-coated sand compared to clean sand is likely due to repulsive electrosteric forces between the PVP coatings and extracellular polymeric substances (EPS) of the biofilm. Additionally, the slope of the rising portion of the PVP-nAg breakthrough curve was noticeably steeper in biofilm conditions than in clean sand. More mature biofilm coating also resulted in earlier breakthrough of PVP-nAg compared to younger biofilm coatings, or to the clean sand, which may be an indication of the effect of repulsive surface forces combined with selective pore size exclusion from the pores of denser, more developed biofilm. These results, when considered with other literature, indicate the importance in considering the flow dynamics, pore network and structure, the effective particle size, and particle permeability with regard to the biofilm matrix when considering the possible influence of biofilms on ENP transport.

Biofilms and extracellular polymeric substances mediate the transport of graphene oxide nanoparticles in saturated porous media

“…Obviously, this research is aimed at clarifying the fundamental mechanism among complex interactions of ENPs transport and deposition in biofilm-laden granular media. However, heterogeneous biofilm, multilayer coating formed from different bacterial species [22], various growth phase [24] or environmental conditions [14,19,25], complicates the interpretation of ENPs transport behavior. Further studies are needed to accurately distinguish the contributions of biofilm on the transport of GONPs and other ENPs in more complex granular media such as natural soils and aquifer sediments.…”

“…Jiang et al [15] concluded that the greater deposition of ZnO nanoparticles may also contribute to the rougher sand surface with biofilm when comparing SEM images to the bare one. Recently, Mitzel and Tufenkji [24] illustrated biofilm grown on collector surface may be more accurately consisting of patchy or inhomogeneous biofilm coatings. Likewise, Fig.…”

“…EPS are a major component of biofilm that are highly likely to affect colloids (e.g., bacteria and virus) and nanoparticles (e.g., ZnO, C 60 , and Ag) transport in porous media [15,[19][20][21][22]. Thus far, very limited investigations [14,15,18,[22][23][24][25] have been focused on the influence of biofilm on the fate and transport of engineered nanoparticles (ENPs) in porous media. For example, Xiao and Wiesner [22] examined the transport of aqueous C 60 , fullerol, and (polyvinylpyrrolidone (PVP) and citrate coated) silver nanoparticles (AgNPs) in Pseudomonas aeruginosa and Bacillus cereus biofilm-laden glass beads.…”

“…Interestingly, these observations cannot be quantitatively explained by classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [27,28]. By contrast, Mitzel and Tufenkji [24] assessed the transport of PVP-AgNPs in quartz sand with and without P. aeruginosa PAO1 biofilm of variable bacterial growth period. Reduced retention of PVP-AgNPs was observed in P. aeruginosacoated sand column, regardless of biofilm age, which was likely due to electrosteric repulsions between PVP coatings and biofilm.…”

Influence of natural organic matter on fate and transport of silver nanoparticles in saturated porous media: laboratory experiments and modeling

“…A number of recent studies have examined the transport of unmodified and surface-modified AgNPs in saturated porous media (e.g., unmodified AgNPs (Lin et al 2011), citrate-stabilized AgNPs (El Badawy 2011Sagee et al 2012;Taghavy et al 2013), polyvinylpyrrolidone (PVP)-AgNPs Flory et al 2013;Lin et al 2012b;Mitzel and Tufenkji 2014;Sagee et al 2012;Song et al 2011), Gum Arabic-AgNPs (Lin et al 2012a;Song et al 2011), branched polyethyleneimine-coated AgNPs (El Badawy 2011), and proteinate-AgNPs (Ren and Smith 2013). These studies have reported the effect of flow velocity, pH, and ionic strength on AgNP transport.…”