Diode lasers and Small Nanoparticulate Matrices Combine to Elevate Sensitivity of MILDI-MSI

Imaging of molecular components of plant tissue (roots, leaves, seeds etc.) by microfocused laser desorption is maturing into a useful tool for describing plant molecular biology. Due to pioneering work in DOE laboratories and elsewhere the detection sensitivity of laser desorbed molecules is increased by the addition microscale sized colloidal metals (e.g. Sliver) or graphite to aid as a “matrix” in the laser desorption/ionization process. (The colloidal microparticle “matrix” evaporates after preferentially absorbing the laser energy. The vapor from the microparticle gently lifts and ionizes the neighboring plant molecules from the tissue and into a mass spectrometer where their mass can be uniquely identified). Numerous libraries of mass spectrometric determined exact masses of plant molecules have been recorded by this technique and, now, published libraries are available to international workers of the world due to this technique. Ionwerks and collaborators have introduced an alternative to the colloidal micromaterial matrix through a new technique involving silver nanoparticulate ion implantation into the near surface (50 millionths of a mm) of animal tissues. Extremely good reproducibility of images has been achieved (<10% variation from successive tissue slices from the same tissue type) in animal models of disease and injury. We propose in phases I to apply these new AgNP implantation techniques to the interrogation of plant biology (Arabidopsis thaliana) to provide a solution to the problem of uniform incorporation of silver nanoparticulate matrices below the surface of any plant tissue. We will determine efficiencies of this process by simultaneously lipid and fatty acid standards applied to the surfaces of both animal (known performance) and plant tissue (unknown performance) by comparing image quality of both. We anticipate good sensitivity and minimal fragmentation of plant lipids to be demonstrated in phase I. Phase I and continuation into Phase II will more extensively determine the applicability of this technique to biomolecules which are present in plant biology only. Ionwerks now offers the implantation technology for sale, so proof of its viability for plant tissue imaging would afford new domestic and international markets. The DOE mission priority of tuning plant biology to practical usage will also benefit.