Analysis of aluminosilicate particles in biological matrices using histochemistry and X-ray microanalysis

Aluminosilicates are a group of ubiquitous environmental particles that, in some cases, have been implicated in human disease. Characterisation of aluminosilicates in tissue samples requires, first, their in situ identification and, secondly, analysis of their aluminium and silicon content or, at least, aluminium:silicon ratio. Here, histochemical staining, microscopy and X-ray microanalysis were investigated as potential methods for the detection of aluminosilicates in biological samples. In contrast to aluminium phosphate or hydroxide, aluminosilicates were refractory to histochemical staining for aluminium. However, using electron microscopy, back scattered electrons allowed identification of aluminosilicates in tissue-like (gelatine) sections. X-ray microanalysis, using conventional peak:background ratios, did not provide a sufficiently accurate assessment of the aluminium content of various standard aluminosilicates to allow their identification. However, the similar spectral energies of aluminium and silicon allowed spectral peak heights to be directly compared and, using simple standards, aluminium:silicon ratios were found for a range of reference particles. Application of this technique should allow the localisation and identification of aluminosilicates in biological samples.