Quantifying the Surface Coverage of Conjugate Molecules on Functionalized Nanoparticles

High Resolution Image Download MS PowerPoint Slide Here we present a method to determine the surface coverage or surface density of biological molecules conjugated to nanoparticle surfaces. Electrospray-differential mobility analysis (ES-DMA) is used to determine a coating thickness by measuring the change in the size of gold nanoparticles before and after modification with thiol-derivatized single-stranded DNA. The DNA surface coverage is then obtained from the coating thickness through the use of a simple random coil model. The method requires neither fluorescent tagging nor calibration curves. We believe ES-DMA to be a broadly applicable nanometrology tool for the characterization of biologically conjugated nanoparticles.