Abstract: Metal and semiconductor nanoparticles provide unique scaffolds for covalent and non-covalent attachment of biomolecular systems. In our research, we combine synthesis, materials science, and biology to create nanoparticles that bind to specific biomacromolecular targets, including proteins, nucleic acids, and polysaccharides. The use of nanoparticles to create new systems for chemotherapeutics and diagnostics, including gene and drug delivery will be discussed. These studies use two unique attributes of nanoparticles: 1) Nanoparticles can be imprinted with target molecules, providing a means for enhancing specificity 2) They have surface areas well-suited to binding of protein and DNA surfaces. The use of nanoparticle-based receptors for recognition and sensing of proteins and DNA will be discussed.