The second protocol, that utilizes PVA, will generate silk spheres with a size range between 300 nm to 20 μm. The size of the spheres can be controlled by changing the concentration of the silk or PVA solutions or by sonicating to the solution prior to casting the film. In order to characterize these spheres a few techniques of been employed including dynamic light scattering to determine the size of the nanometer spheres, laser light diffraction to determine the size of the microspheres, and SEM to image the morphology. Confocal microscopy was also used to determine model drug loading. Drugs may be encapsulated in these spheres by adding the drug to the silk solution prior to mixing with the PVA. In general we start with loading a mass ratio of 100:1 silk to drug. Drug loading efficiency is specific to each case due to molecular weight, charge, and hydrophobicity and therefore must be determined for each drug.