discussed in previous methods, due to the magnetic nanoparticles at the core. The resulting magnetism introduces a level of controllability that is not present in, for example, the gold-chitosan nanocomposites or the multi-layered gold nanoshells, both discussed above.
The nanostructures discussed so far have mainly been spherical in geometry – Huang et al (2005) proposed a method of preparing gold nanorods with near-infrared absorption which could be applied in both the detection and treatment of malignant cells.

The first stage in synthesising the gold nanorods was the preparation of a “seed solution”, from the reduction of 0.0005M chloroauric acid in 0.2M cetyltrimethylammonium bromide (CTAB), by 0.01M sodium borohydride. Next, a “growth solution” was prepared. Chloroauric acid (0.001M) was reduced by 0.2M cetyltrimethylammonium bromide, 0.15M benzyldimethylhexadecylammonium chloride, 0.004M silver salt, and 0.0788M ascorbic acid. Gold nanorods were then achieved by adding 8L of the seed solution into the prepared growth solution and storing until nanorods had formed.

Following the formation of gold nanorods, they were conjugated to anti-epidermal growth factor receptor. First, any excess cetyltrimethylammonium bromide was removed by centrifugation, and then the precipitate suspended in HEPES (N-(2-hydroxyethyl) piperazine-N’-2-ethanesulfonic acid) solution of pH 7.4, then added to an antibody solution and allowed to mix for 20 minutes. This solution was then centrifuged, and the precipitate suspended in phosphate buffered saline of pH 7.4.27
Chloroauric acid, CTAB, sodium borohydride and ascorbic acid are all extremely costly, and although BAC, HEPES and phosphate buffered saline solution are relatively inexpensive, they are outweighed by these four expensive materials (however, these costs were based on the assumption that the highest purity was required). As the method did not specify which silver salt was used, no price could accurately be given for this material. This makes it difficult to comment on the total cost incurred in synthesising these nanorods and conjugating them to anti-EGFR. Compared to other methods discussed, this is simple with few steps, and no time is consumed in leaving the reaction mixture for hours at a time.
Silica nanoparticles were first prepared using the Stober process, where tetraethyl orthosilicate (TEOS) was reduced by ethanol, with ammonia being used as a catalyst.28 (3-aminopropryl) triethoxysilane (APTES) was added to the silica nanoparticles to allow the gold colloid to adsorb to the nanoparticle surface in the next step.29

Gold colloid was synthesised according to a method detailed by Duff et al, 1993. In this