In this work, silicon micromachined structures (SMS), consisting of arrays of 3-µm-thick silicon walls separated by 50-µm-deep, 5-µm-wide gaps, were applied to investigate the behaviour of eight tumour cell lines, with different origins and biological aggressiveness, in a three-dimensional (3D) microenvironment. Several culture experiments were performed on 3D-SMS and cells grown on silicon were stained for fluorescence microscopy analyses. Most of the tumour cells belonging to lines recognized in the literature as highly aggressive (OVCAR-5, A375, MDA-MB-231, and RPMI-7951) exhibited a great ability to enter and colonize the narrow deep gaps of the SMS whereas less aggressive cell lines (OVCAR-3, Capan-1, MCF7 and NCI-H2126) demonstrated less penetration capability and tended to remain on top of the SMS. Quantitative image analyses of several fluorescence microscopy fields of silicon samples were performed for automatic cell recognition and count, in order to quantify the fraction of cells inside the gaps, with respect to the total number of cells in the examined field. Our results show that higher fractions of cells in the gaps are obtained with more aggressive cell lines, thus supporting in a quantitative way the observation that the behaviour of tumour cells on the 3D-SMS depends on their aggressiveness level.
