Nanotechnology in Drug Delivery: Past, Present, and Future

Abstract

The word ‘‘nanotechnology’’ began as a technical term, but recently it became a popular term representing the current state-of-the-art technology. On the website of USNational Science Foundation (NSF), nanotechnology is defined as research and technology development at the atomic, molecular, or macromolecular level, in the length scale of approximately 1–100 nm range, to provide a fundamental understanding of phenomena and materials at the nanoscale and to create and use structures, devices, and systems that have novel properties and functions because of their small and/or intermediate size (N.S.F., February 2000). The earliest definition concerned only the size of materials (1–100 nm) (Franks, 1987). The current term nanotechnology, however, covers almost all fields of science and engineering (Salamanca-Buentello, Persad, Court, Martin, Daar, & Singer, 2005), and the size of materials of interest can be much larger than 100 nm. The biomedical and pharmaceutical fields have been utilizing nanomaterials for various applications, such as tissue engineering, gene therapy, chemotherapy, peptide/protein delivery, molecular imaging, and high-throughput screening/assay, so the exact definition of nanotechnology is difficult to make solely based on size. As the concept and applications of nanotechnology are evolving, we are left with a question: ‘‘What does nanotechnology really mean and what can it do for the drug delivery area? ’’ Finding answers to this question will be benefited from a brief review of the past and current drug delivery technologies. The two fabrication methods in nanotechnology are ‘‘bottom-up’’ and ‘‘top-down.’’ The former builds nanomaterials from the atomic and molecular levels, whereas the latter generates nanostructures out of macro-sized materials. Fabricated nano-sized devices or drug carriers, often called nanocarriers or nanovehicles, provide various advantages for effective drug delivery. Nanocarriers can carry poorly soluble, unstable, or systemically toxic drugs with extended blood half-lives and reduced side effects.