Sample Solution

selectively damaged by controlling the temperature range, it is difficult to have this level of control with traditional heat sources, and this can lead to healthy cells being damaged alongside the tumour.6 This is where laser light is especially suited, due to the light being in a small, in-phase beam – although even laser light presents difficulties, as it will destroy anything in its path.6

A potential application to solve the issues of non-selectivity is to couple the laser light with gold nanostructures which are near-IR absorbing: that is, they absorb in the near-infrared region of the electromagnetic spectrum, 700-2500nm.7 Examples of the gold nanostructures with near-IR absorption include gold-gold sulfide nanoparticles8, gold-chitosan nanocomposites9, and Fe3O4 polymer nanoparticles with a gold shell10, to name a few, and these will be discussed in further detail later in this review. When nanostructures which absorb in the NIR region are treated with such light, they convert the energy of the light into heat – enough to destroy a tumour, and thus can be used to selectively destroy tumours by being injected into them and irradiated with NIR laser light.11 NIR light is attractive due to the fact that it does not harm the tissue itself; it is only when coupled with the gold nanostructures that any damage is caused.12

An alternate method to photothermal therapy but still utilising the NIR absorption of gold nanostructures is to use NIR light to initiate the release of an anti-cancer drug, and use the gold nanostructures as a carrier for such drugs. An example of this is gold/gold-sulfide nanoparticles, and their synthesis and detailed application will be discussed further.8

This literature review will discuss the history and basic chemistry of gold nanoparticles, various methods of synthesising gold nanostructures with NIR absorption, and the ways in which they have been applied (or have the potential to be applied) in studies in order to detect and treat cancer and tumours, as well as exploring the ethical considerations of this branch of science and suggesting areas in which further research should be undertaken.
The earliest known use of gold nanoparticles (and perhaps the most famous) is the Lycurgus cup, a Roman cup from roughly the 4th Century which appears green when ill