Tips & Tricks for Nanoparticle Characterization

Q: If I have a mixture of micelles and liposomes, with DLS, which measurement method will give a true reflection of size distribution? Intensity, volume or number? What’s the advantage and drawback of each? A: If you have small micelles and bigger liposomes, then the intensity distribution will show a larger contribution from the liposomes (by scattering intensity) whereas the number distribution will show a larger contribution from the micelles (by number). These results are both correct. Number distributions emphasize the species with the highest number of particles (which often tend to be the smaller ones). Intensity distributions emphasize the species with the largest scattering intensity contributing to the overall result (which often tend to be the larger particles). If you are trying to make very clean samples without any large aggregates, use the intensity distribution, which by the way is the preferred method for DLS in any case. If you are trying to see mostly the smallest nanoparticles in your preparation, try the number distribution (provided the DLS results are of good data quality).