These facts—strong absorption, deep penetration, and easy modular functionality—show gold nanorods to be an attractive NIR light-mediated multifunctional platform for cancer theranostics [ 26 , 27 , 28 ]. Received Oct 20; Accepted Nov
Introduction In recent years, near-infrared light-mediated multifunctional platforms based on inorganic nanomaterials for cancer diagnosis and treatment have been explored widely [ 1 , 2 , 3 ], including carbon [ 4 , 5 , 6 ], semiconductors [ 7 , 8 , 9 ], and noble metals [ 10 , 11 , 12 , 13 ]. This is consistent with the results of previous studies of Au NR growth kinetics Seo et al. The solutions were mixed a few times by inversion. Suslick, Catherine J. Synthesis of Small Gold Nanorods The synthesis of monodispersed small gold nanorods has attracted much attention for their optical properties and biomedical applications. The synthesis of the NRs can be scaled up by using higher concentrations of reagents and adding an optimum concentration of HCl in the growth solution.
In comparison, it takes a growth time of 4. For the higher HAuCl4 concentrations, the added seed solution was increased in proportion to the HAuCl4 concentrations. Generally, two steps are included for the seed-mediated method: the first step is to prepare a small-sized gold seed; the second step is the growth of gold nanorods, which is initiated by the gold seed in the growth solution. The maximum is followed by a sharp decrease in the plasmon peak position in both cases, with the resonance levelling off at a longer wavelength for the smaller concentration of HAuCl4. We show that the increase in growth rate of NRs by increasing the reagent concentration in solution can be neutralised by decreasing the pH of the growth solution. However, the yield in this case was lower as well.
Murphy, Pinshane Y. Secondly, the SPR absorption of the gold nanorods can be easily tuned to the near-infrared NIR window — nm [ 20 , 21 ] where light can penetrate more deeply because of scarce absorption by tissues and blood [ 22 ]. As is evident from the SEM images Fig. Then, the growth of the gold nanorods was started by adding the freshly-prepared ascorbic acid to the mixture of gold seed and growth solution in the presence of AgNO3. The solution was mixed by inversion a few times.
Lastly, the gold nanorods can be more easily modified by the thiol compounds via strong Au-S bonds, formed by the thiol group and the surface of gold nanorods [ 23 ]. McClure, Kyle N.
Consequently, much higher growth rates are expected which will ultimately lead to the formation of more isotropic NRs, i. However, there is still a noticeable concentration of spherical nanoparticles in the final yield, as seen from the transverse plasmon peak. Great efforts have been made by the researchers to synthesize the high quality and yield gold nanorods with tunable SPR absorption to investigate the great potential for cancer theranostics [ 15 , 29 ]. Journal of the American Chemical Society , 27 ,
However, there is still a noticeable concentration of spherical nanoparticles in the final yield, as seen from the transverse plasmon peak. It has been suggested that ascorbate is a stronger reducing agent compared to AA, and it accelerates the reduction of Au ions Busbee et al. Hofmann, Khoi Nguyen L. This solution was cooled down to room temperature before further processing. Mbalaha, Paul R.
However, in most of the reported protocols, dilute concentrations 0. In this review, we summarize the recent advances of synthesis of the small gold nanorods and their application for near-infrared light-mediated bio-imaging and cancer therapy. This procedure ensures the same Au concentration per seed for all samples.
Multiple batches of NRs, prepared even under identical conditions, do not necessarily provide NRs of the same dimensions and dispersion, which is often a drawback if large concentrations of identical NRs are needed e. ACS Nano , 12 6 ,