Three-dimensional (3D) microfluidic biosystems that mimic in vivo environment and allow live observation of cells with a high microscopic resolution over long time periods are of great interest for cancer research. Specifically, transparent glass biochips that can be optically interrogated by imaging techniques for sub-cellular characteristics are essential for understanding mechanism of cancer cell migration, in particular in submicrometric, constrictive environments. Femtosecond laser assisted chemical etching (FLAE) is a subtractive processing technology of glass that can be employed to develop 3D microfluidics embedded in a microchip. We report herein on the fabrication of ultrathin glass microfluidic biochips with nanoscale characteristics by using FLAE followed by an controlled subsequent annealing treatment near glass transition temperature. This allows downsizing architectural dimensions to nanofluidics inside microchannels.

Relevant glass model platforms that mimic metastatic intravasation-extravasation processes are further designed and fabricated. They proved capable to offer both observation of collective cancer cells migration over long periods and individual visualization at unicellular and subcellular levels on the target cell. The fabricated 3D glass nanofluidics is then applied to observe behavior of cancer cell in narrow spaces and provides new findings. Specifically, it could be demonstrated that prostate cancer cells were capable of breaking narrow submicrometric space barriers while keeping 100% viability with no obvious damages. In addition, the cells were able to divide after migration or even in such narrow environments while probability of division was retained after the migration, which confirmed the dynamic adaptability of cancer cells even when they were passing through the confining spaces much smaller than their nucleus volume.