Scaling down the bioimaging of metals by laser microdissection inductively coupled plasma mass spectrometry (LMD-ICP-MS)

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a powerful quantitative elemental imaging technique in routine mode for biological tissue with a spatial resolution of 12-160 mu m. Several applications necessitate an improved spatial resolution of LA-ICP-MS at the low micrometre scale and below. To achieve the improvement of spatial resolution of LA-ICP-MS we created a new experimental arrangement by coupling a laser microdissection system (LMD) used for laser ablation of tissue with a sensitive quadrupole-based inductively coupled plasma mass spectrometer for the subsequent analysis of ablated material. A flat laser ablation chamber made of glass was inserted into the LMD, fitted to the microscope slide with the specimen. The biological tissue fixed on the glass slide was ablated using the focused solid-state Nd:YAG laser of the LMD. The laser ablated material was transported by argon as carrier gas into the inductively coupled plasma of the mass spectrometer and analysed according to the mass-to-charge ratio. Using this novel LMD-ICP-MS arrangement, in initial experiments ion signals of 63Cu* and 65Cte were measured from a 30-p.m-thick cryosection impregnated with a droplet of a Cu solution. A spatial resolution of about 3 pm was obtained using the modified LMD system coupled to the ICP-MS. Laser-induced mass spectrometric measurements of metal distributions can be performed together with simultaneous inspection of the tissue section via the microscope of the LMD and be combined with other modalities of the LMD system. In future, a more powerful laser in the LMD apparatus will allow ablation down to the sub-micrometre scale to study the elemental distribution in small tissue sections. (C) 2010 Elsevier By. All rights reserved