[Kamat2010]

Nanotechnology has become a vastly explored area of research in the present times mainly in the biomedical research. Nanoparticles have found importance in the drug delivery, disease diagnosis, as well as therapeutic applications. Nanotechnology deals with the particles having length in the nanometer scales i.e one billionth of a meter. At such small sizes, the particles have high ratio of size to volume, which influences their reactivity and their properties as a whole changes from that of their native element.

In the biological system, drug delivery to the target system or organ has become a major issue. For instance, drug delivery through the BBB is a tough challenge. Though many drugs have proved effective potent drugs for the CNS, but due to improper drug delivery system through the BBB to the brain, successful treatment of brain-related diseases has not made much progress. It is here that nanotechnology has made a mark because of its size, surface functionalization, and other factors.

Many varieties of nanoparticles are available which have created impact in different ways such as nanotubes, liposomes, polymer of nanoparticles, dendrimer, quantum dots, micelles, etc. Nanotubes are carbon rods with diameter half as that of a DNA molecule. They are studied extensively for successful gene delivery, as well as delivering plasmid DNA, proteins, synthetic enzymes, etc. into the living system. A number of vectors like fungi, bacteria are available for gene delivery into the cells but many factors like toxicity, biodegradability, evoking immune response, etc while using those vectors have opened research in this field. Hence, nanotubes have gained much importance in this area. The nanotubes are hollow tubes with either both sides open or one side closed with a cap made of nanoparticles known as nanocap. The bioactive agent is attached to the nanotubes and then it is delivered to the target cell in the animal body or the target site in the plant by different routes such as intra-dermal, intravenous, trans-mucosal sites, etc., within the body (human or animal) or by application on the plants mechanically. The nanotubes are made with biodegradable material, which degrades after reaching the target site with time thereby releasing the bioactive agent within the body. The biodegradable material with which the nanotubes are made, are carefully selected such that it helps in the proper delivery of the bioactive agent to the target site and the nanotubes are degraded only after reaching the site of action thus releasing the bioactive agent. The nanotubes have also found application in the detection of mutations within the DNA whereby the mutated regions of the DNA are tagged using bulky molecule with tags specific for the mutated sequence. The needle-like tip of the nanotubes is then used to trace the mutated DNA, which has been tagged, and to identify alteration in the shape of the specific DNA. Thus, nanotubes play a very important part in detecting different diseases like cancer and this uniqueness of the nanotubes have made them have different applications in various fields of research like biomedicine, agriculture, industry, environmental science, etc.

Gold nanoparticles (GNPs) or Colloidal Gold has been widely used as drug delivery agents and in targeting of cancer cells due to their minimal reactivity within the biological system. Colloidal gold refers to the suspension of the nanoparticles in fluid, mainly water. Colloidal gold has been proved effective in the treatment of Rheumatoid arthritis and in the destruction of the beta amyloid plaques in the Alzheimer’s disease. Detection of the tumors in-vivo has been possible due to the GNPs with the help of SERS, Surface Enhanced Raman Spectroscopy. Other radiative applications of the colloidal gold are yet to be explored. The GNPs have also been used in many sensitive assays for diagnosis, radiotherapy, etc.

Two other nanotechnological products: Quantum dots and Nanoshells are used in diagnosis and therapy of cancer respectively. The quantum dots glow under UV light stimulation. Hence, specifically designed quantum dots can be used that bind to mutated DNA and the site of this mutated DNA can be identified in-vivo when the bound quantum dots glow under the stimulation of UV light, thus exposing the regions of localisation of mutated DNA specific for causing cancer. The nanoshells have the property of absorbing near-infrared light resulting in heat resulting in cell death. The nanoshells can be made to reach the tumor region by linking them with antibodies specific to the tumor cells and destroy the cancer cells, without affecting the neighbouring cells. Thus, nanotechnology has made great advancement in medical science.