Positron Annihilation Spectroscopy as a Tool to Determine Nanosized Voids in Tumours

CECILIA Y. CHAIN; MARIANELA GALLE; MARGARITA M. GARCíA DE BRAVO; LAURA C. DAMONTE; ALBERTO F. PASQUEVICH

Gijón

Simposio; 18th International Symposium on Metastable, Amorphous and Nanostructured Materials; 2011

Universidad de Oviedo

Positron Annihilation Lifetime Spectroscopy (PALS) is a branch of gama- ray spectroscopy that gives account of the characteristics positron lifetimes in a material, fact that is associated with the size and relative fraction of the nano- free volumes or nanopores present in the sample. The physical basis of positron annihilation resides in its capability to sense electron density in the bulk of a material. Although this spectroscopy is a powerful technique in the determination of vacancies and defects in solid state materials, it has been scarcely applied in the field of life science research. Meanwhile, in the last two decades, PALS has been used to study free volume properties and free radical status in a variety of chemical and biological systems including polymers, contact lenses and biomembranes. Concerning PALS studies in tumoral tissues, significant discrepancies in positron lifetimes can be found among the reports. In this sense, the obtained results strongly depend on the way in which the samples were treated prior to the measurements. The goal of this communication is to determine the optimal tumour preparation that is necessary to obtain results that well correlate with the characteristic voids of the tumour (but not with artefacts of the tumour preparation). With this aim, we report here a study of nanovoids in samples that were preserved in different manners, namely formaldehyde-fixed paraffin and (wet and dried) formol-fixed tumour tissues. A brief discussion of the advantages and disadvantages of each procedure and the optimal way to measure the relevant voids of these biological samples is presented.