Instrument Characterizes Colloids

Steve Miller

Researchers at Los Alamos National Laboratory have developed a system that characterizes the properties and behavior of colloids. Originally developed to analyze particulate pollution in the environment, especially radioactive elements such as plutonium, the system has potential for applications in environmental, medical and pharmaceutical research.

Colloids, particles that range from 1 nm to 1 µm in diameter and that are evenly dispersed in a carrier, include such materials as gels and emulsions. Colloidal systems play a crucial role in paints and coatings, mineral and environmental pro-cesses and biological applications ranging from studies of protein suspensions to the distribution of viruses and bacteria, to the delivery of pharmaceuticals.

The Automated Video Microscopic Imaging and Data Acquisition System combines video imaging techniques with a modified version of dark-field microscopy.

A 300-W halogen bulb illuminates a colloid suspension, and a dark-field condenser and iris diaphragm regulate the illumination so that the colloid particles are visualized against a dark background. A CCD camera records the movement of the particles at 30 fps. The researchers wrote software to perform image processing and data extraction functions.

"The characterization of colloids is important because their interactions with other substances have unique characteristics," said Amr Abdel-Fattah, the lead researcher on the project. "For example, the behavior of proteins in different environments, how they attach and detach from surfaces, and how they interact with other substances are important parameters for understanding biological systems."

Besides characterizing particle sizes and concentrations, the system offers information about their surface interactions and the electrical charges on the particles' surfaces, known as zeta potential. "There is no other instrument available that can perform this range of analyses, and certainly not for the same cost," said Abdel-Fattah. "Instruments that just characterize the particle size and concentration cost about $50,000; the apparatus for surface-charge analysis is about $70,000." He said that the Automated Video Microscopic Imaging and Data Acquisition System, however, could be marketed for as little as $16,000.

The laboratory has applied for a patent for the system and is discussing its commercialization with industrial partners.