EPA Science Inventory

General linear model-predicted and observed toxicity of three organo-coated silver nanoparticles: Impacts of particle size, surface charge and dose

Citation:

Pokhrel, L. AND B. Dubey. General linear model-predicted and observed toxicity of three organo-coated silver nanoparticles: Impacts of particle size, surface charge and dose. Presented at World Environmental & Water Resources Congress, Portland, OR, June 01 - 05, 2014.

Description:

Intrinsic to the myriad of nano-enabled products are atomic-size multifunctional engineered nanomaterials, which upon release contaminate the environments, raising considerable health and safety concerns. Despite global research efforts, mechanism underlying nanotoxicity has remained elusive. Here we consider three types of organo-coated silver nanoparticles (AgNPs): citrate–coated AgNP (Citrate–AgNP), polyvinylpyrrolidone-coated AgNP (PVP–AgNP), and branched polyethyleneimine-coated AgNP (BPEI–AgNP), with different surface charge scenarios and core particle sizes, and systematically evaluate the potential role of particle size, surface charge, and concentration on the toxicity of the three types of AgNPs against two model organisms, Escherichia coli and Daphnia magna. We found particle size, surface charge, and concentration dependent toxicity of all the three types of AgNPs against both the test organisms. Notably, Ag+ (as added AgNO3) toxicity was greater than each type of AgNPs tested and the toxicity followed the trend: AgNO3 > BPEI–AgNP > Citrate–AgNP > PVP–AgNP. Modeling AgNP physicochemical properties using the General linear model (GLM), a significant interaction effect of primary particle size and surface charge emerged that explained empirically-derived acute toxicity with great precision. The model explained 99.9 % variation of toxicity in E. coli and 99.8% variation of toxicity in D. magna, revealing satisfactory predictability of the models to predict nanotoxicity of the three organo-coated AgNPs. We anticipate that the use of GLM to satisfactorily predict nanotoxicity based on NP physicochemical characteristics could contribute to our understanding of nanotoxicology, and suggest considering interaction effects among nanoparticle properties when explaining nanotoxicity.

Purpose/Objective:

Many consumer products that use engineered nanomaterials to improve their performance can release nanoparticles into the environments, raising considerable health and safety concerns. Unlike other chemicals, nanoparticles behave as colloids in suspension and therefore toxicity may be related to factors such as surface charge, particle size, or other factors in addition to concentration. A better understanding of the relationship between particle characteristics and their inherent toxicity may enable the Agency to predict the toxicity of new nanoparticles as they are developed. In order to provide information on how physicochemical properties of particles influence toxicity, we considered three types of organo-coated silver nanoparticles (AgNPs): citrate–coated AgNP (Citrate–AgNP), polyvinylpyrrolidone-coated AgNP (PVP–AgNP), and branched polyethyleneimine-coated AgNP (BPEI–AgNP), each with unique characteristics in suspension. Since silver is soluble, we also examined the toxicity of ionic silver. Toxicity was examined in Escherichia coli, a bacterium, and Daphnia magna, a type of water flea. We found that particle size, surface charge, and concentration all influenced toxicity of all the three types of AgNPs in both the test organisms, but all were less toxic than ionic silver. Using a linear model, we showed that toxicity was most closely related to particle size and surface charge of the AgNPs. This information will be useful for predicting the toxicity of new particles, and will contribute to the larger database being developed to classify nanoparticles into toxicity classes based on specific particle characteristics. In addition, the information may be useful for ‘green chemistry’ efforts that are underway to design new nanomaterials without the characteristics that make them toxic.

URLs/Downloads:

ABSTRACT - POKHREL.PDF   (PDF,NA pp, 61.068 KB,  about PDF)

Record Details:

Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Completion Date: 06/09/2014
Record Last Revised: 06/09/2014
Record Created: 06/09/2014
Record Released: 06/09/2014
OMB Category: Other
Record ID: 277995

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB

WESTERN ECOLOGY DIVISION

ECOLOGICAL EFFECTS BRANCH