Desorption of gold ions from liver tissue sections, in which intravenously injected gold nanorods were accumulated, were studied to evaluate properties of gold nanorods as a "mass-tag". Gold ions were sensitively detected by using a conventional MALDI-MS machine. When 50-µm-thick blank sections without gold nanorods were placed on or beneath a sample section, desorption of gold ions was almost suppressed. It was found that the escape depth of gold ions from liver tissue sections was less than 50 µm. It was found that we do not have to take account of the escape depth of gold ions if a section were sliced into 10-20 µm thickness.

Gold nanorods (NRs) were fixed on an ITO plate and used for the Surface-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (SALDI-MS) of oligopeptides (angiotensin I). The SALDI-MS measurements had a high sensitivity to the angiotensin on the ITO plate on which isolated NRs were deposited. Angiotensin molecules in a very diluted solution (1 × 10-11 M) could be detected at m/z = 1297 with a good signal/noise ratio (S/N = 18). In contrast, alternatively deposited NR an ITO plate, which present broad surface plasmon bands, was found to be inactive for SALDI measurements.

Exchange of solubilizers adsorbed on single-walled carbon nanotubes (CNTs) is probed by analysis of the peak shifts of the absorption bands of CNTs in the near-infrared region. Equilibrium constants and thermodynamic parameters of the exchange of sodium cholate for DNA (15-mers of oligo-DNAs, cytosine) on CNTs of different chirality are determined.