This document provides an extraction method using the proteinase K (PK) for nanomaterials deposited in the lung. This document specifies the advantages of the PK digestion method and examples of nanomaterials to which it can be applied. This document focuses on extracting nanomaterials from lung tissue and separating nanoparticles from their ionic counterparts. This method is potentially (or theoretically) applicable to any particles that are insoluble during the PK digestion process.