Nanoparticles tend to clump together, or “agglomerate,” in a solution. How clusters are formed and what shape they assume can influence a number of factors including their toxicity, how they interact with their environment, and their suitability for use in biosensors. To better understand nanoparticle agglomeration, researchers at the National Institute of Standards and Technology (NIST) have developed a method of precisely measuring cluster-size distribution and the resulting characteristic light absorption.
The research could assist with the development of ultra-sensitive pregnancy tests, according to NIST biomedical engineer Justin Zook. Such tests could be created by coating gold nanoparticles with antibodies to a human chorionic gonadotropin (hCG), a hormone produced by an embryo following conception.
As the press release explains:
Multiple gold nanoparticles can bind to each hormone, forming clusters that have a different color from unclustered gold nanoparticles. But only certain size clusters are optimal for this measurement, so knowing how light absorbance changes with cluster size makes it easier to design the biosensors to result in just the right sized clusters.
The scientists used analytical ultracentrifugation in the research to both determine the clusters’ size distribution and measure their light absorption.
Image credit: Keene, FDA
Abstract from ACS Nano: Measuring Agglomerate Size Distribution and Dependence of Localized Surface Plasmon Resonance Absorbance on Gold Nanoparticle Agglomerate Size Using Analytical Ultracentrifugation