Citation:

Ubah, B.Sc., C., L. Pokhrel, Ph.D., AND Christian P Andersen, Ph.D. Differential Effects of Monovalent Cations and Anions on Key Nanoparticle Attributes. 2018 Philadelphia ACS Younger Chemists Committee Poster Session, Philadelphia, PA, April 10, 2018.

Impact/Purpose:

Engineered nanoparticles (ENPs) have been recognized as valuable components of novel technologies and are currrently being used in a variety of consumer products and medical applications including drug delivery systems. The properties that make these particles functionally unique also influence their interactions with other biological and environmental constituents, and these interactions need to be understood in order to predict and model potential target effects. EPA scientists, along with colleagues at Temple University, are examining how background electrolytes alter the measurement and characterization of important particle attributes of nano-formulations using dynamic light scattering (DLS). They examined citrate-functionalized silver nanoparticles in the presence of physiologically and ecologically relevant background electrolytes to determine how the electrolytes affected the measurement of particle size, size distribution, and surface charge of the nanoparticles. The results showed that the presence of various electrolytes significantly altered the measurement of particle attributes and need to be considered when characterizing nanomaterial suspensions. In addition to providing better understanding of the underlying chemistry of ENPs, the results may provide insight into how to engineer or alter NP’s to minimize variability in endpoint assessments due to electrolyte interactions. .

Description:

Understanding the key particle attributes such as particle size, size distribution and surface charge of both the nano- and micron-sized particles is the first step in drug formulation as such attributes are known to directly influence several characteristics of drugs including drug dosage, release, dissolution, absorption, and (re)action at the target site, and, therefore, the efficacy of any given drug. Dynamic light scattering (DLS) is a widely used tool to measure such important attributes of any formulation containing nano- and micron-sized particles. This poster investigates how background electrolytes can alter DLS measurements of particle size, size distribution and surface charge of Citrate-functionalized silver nanoparticles (Citrate–AgNPs) under different physiologically and ecologically relevant background electrolytes such as potassium (K+), sodium (Na+), chloride (Cl-), and nitrite (NO2-). DLS estimates size and size distribution of the particles in suspension utilizing the concept of random Brownian motion and the Stokes-Einstein equation. Surface charge of the formulation is determined using the Doppler effect. Results are compared with water-only controls. Our results show that particle size, size distribution and surface charge of the model Citrate–AgNPs formulation could be significantly modified by the common background electrolytes tested. The results also demonstrate that DLS can serve as a useful tool to elucidate the dynamics of critical attributes of nanoformulations in both biological and ecological media, and thus allows us to better understand potential human health and ecological implications.

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