Nanoparticles such as quantum dot nanocrystals are the size of a protein molecule or short stretch of DNA. Quantum dots can be engineered to absorb and emit many wavelengths of light with very sharp precision.
This makes them ideal for protein-protein interaction studies as they can be linked to molecules to form long-lived probes. They can track biological events by tagging specific proteins or DNA in order to follow their progress through biological pathways. In medicine, quantum dots could be used for diagnostic purposes.
Dendrimers are another interesting and powerful use of nanotechnology in medicine. Dendrimers are nanostructured synthetic molecules with a regular branching structure projecting from a central core. Dendrimers form one layer at a time so the size of the dendrimer is determined by the number of synthetic steps.
Each dendrimer is usually only a few nanometers wide. The outside layer can be engineered to be composed of specific functional groups that can act as hooks to specifically bind other molecules such as DNA. Dendrimers may act as effective agents for delivering DNA into cells during gene therapy. While viral vectors typically trigger an immune response, in principle, dendrimers should not.