470342 Determining the Size of Protein Conjugated Nanoparticles By Quantifying Brownian Motion
Determining the Size of Protein Conjugated Nanoparticles by Quantifying Brownian Motion
Katherine N. Clayton1, Janelle W. Salameh2, Julia G. Fraseur2*, Nelda Portalatin-Vasquez2*, Alyssa Panitch2, Steven T. Wereley1, Tamara L. Kinzer-Ursem2
1School of Mechanical Engineering, Purdue University
2Weldon School of Biomedical Engineering, Purdue University
As the field of colloidal science continues to expand, tools for rapid and accurate physiochemical characterization of colloidal particles will become increasingly important. Here, we present Particle Scattering Diffusometry (PSD), a nanoparticle measurement technique that uses low sample volumes that can be integrated into micro- or nanofluidic systems. Based on the fundamental principles of diffusion, gold nanoparticles (100 nm) in a 4 mL sample volume (or less) undergoing Brownian motion are imaged under dark field microscopy and recorded with a CCD camera for ~8 seconds then processed using a MATLAB algorithm. The diffusion coefficient of the particles is calculated by correlating successive particle images (at time Dt) to one another (cross-correlation, sc) and the particle image with itself (autocorrelation, sa) at a magnification (M).
The size of the gold nanoparticles is then calculated from the Stokes-Einstein equation.
We initially characterized the size of gold nanoparticles with calmodulin (CaM), bovine serum albumin (BSA), and lysozyme (Lyso) conjugated to the particle surface. PSD was used to calculate the diffusion coefficient, polydispersity, and biomolecule layer thickness on the gold nanoparticles. Post-characterization, the presence of protein monolayers on gold nanoparticle surfaces was measured in order to investigate the sensitivity in diffusion coefficient measurements of PSD. Differentiating the change in the gold nanoparticle diffusion coefficient down to protein enables PSD to be used in lieu of common laboratory workflows. Therefore, we are currently applying PSD for the detection of inflammatory cytokines and characterization of proteins involved in learning and memory.
In summary, we have established a rapid (seconds) and sensitive (protein monolayer) technology for characterizing biomolecular surface modifications in very low sample volumes (microliters) using instrumentation and tools that are common to most laboratory settings. In this presentation we will to discuss the development of the PSD technique, our current results and challenges associated with PSD measurements, as well as future work to size particle samples and as a tool for molecular diagnostics and characterizing protein dynamics.