LITMIR.BIZ

Figure 1.16 Silver nanoparticles attacking bacteria. Electron microscope image of P. aeruginosa⁵ bacteria after exposure to silver nanoparticles. The particles with size ranges 1–10 nm are active in disrupting the cell function. The inset shows a high‐resolution image of some particles attached to the cell's outer membrane.

      Source: Reproduced with the permission of the Institute of Physics from J. R. Morones et al. [19].

      Since the original work, silver nanoparticles have demonstrated strong antiviral potential against several other viruses, including herpes simplex, hepatitis A virus, hepatitis B virus, huma papillomavirus, and respiratory syncytial virus [21, 22]. All of these viruses have a similar general morphology to that shown Figure 1.17a with a roughly spherical shape and a diameter in the range 40–200 nm, that is straddling the boundary of the nanoworld. They all have an array of glycoproteins on the surface and it is thought that the silver nanoparticles act against them in the same way as in the case of HIV, that is, binding to the glycoproteins and locking the virus out of the host cells. As in the case of bacteria, it is harder for viruses to become resistant to silver nanoparticles as compared to conventional antiviral agents

      Here, we have only encountered very brief sketches of a couple of examples of applications of nanoparticles in healthcare. This is a huge and burgeoning field and a more comprehensive discussion is postponed until Chapter 8. As a final example in this chapter, it is worth noting that there is increasing use of nanoparticles in cosmetics such as face creams. In order to replenish certain compounds in the skin, whose reduced concentration is partly responsible for the effects of aging, it is necessary to enable these compounds to penetrate the outermost layers. This can either mean producing the compounds themselves as nanoparticles or binding them onto “carrier” particles that transport them to the deeper layers. Some sunscreen manufacturers now use titanium dioxide nanoparticles in new products as the carriers.

The key aims of this chapter have been to give an impression of the nanometer size scale and to introduce the idea that sufficiently small pieces of matter behave differently from the bulk material. In addition, the novel behavior of nanoparticles depends on their size and several examples have been introduced where the unusual behavior can be put to good use in technology. All the topics discussed fall into the category of Incremental Nanotechnology, and it is evident that this category is already being used or will shortly be used in industrial sectors as diverse as magnetic recording to medicine. All the types of nanoparticles presented here are artificially produced but in the following chapter, naturally occurring nanoparticles and their effect on the environment and our health will be discussed.