Nanomaterials promise to improve disease diagnosis and treatment by enhancing the delivery of
drugs, genes, biomolecules and imaging agents to specific subcellular targets. In order to optimize nanomaterial
design for this purpose, a comprehensive understanding of how these materials are taken up and transported
within the cell is required. In this review, we discuss the endocytic pathways employed by different
types of nanoparticles with emphasis on the influence of nanoparticle surface modification. The use of pharmacological
inhibition to probe internalization and intracellular trafficking pathways of nanoparticles is critically evaluated.
Finally, approaches to target-specific delivery of therapeutics via nanoparticles into the cytoplasm and nucleus are addressed.