Metastatic potential and drug resistance screening of cancer cells based on micro-fabricated devices

Abstract

It has been increasingly realized that the mechanical response of living cells plays critical roles in biological processes such as cell adhesion, migration and endocytosis. Furthermore, accumulating evidence has also indicated that the physical properties of cells are intimately related to their pathological state. Clinically, the altered mechano-phenotype of cells during disease development may provide a new way to detect such disorder in a label-free manner. For this reason, intense efforts have been made in the past few decades to use techniques like atomic force microscopy (AFM), magnetic tweezer, optical tweezer and micropipette aspiration in measuring the physical characteristics of cells. Limited by their complex and tedious testing procedures and lower measurement efficiency, however, it is hard to apply these techniques to clinical practice for disease assessment. Fortunately, with the rapid development of micro-fabrication technology, patterns and structures with length scale similar to that of cells can be fabricated easily nowadays, making it possible to probe the response of cells via different self-designed chips. In this thesis, several micro-fabricated devices to achieve drug resistance and metastatic potential screening of cancer cells from their mechanical properties will be introduced in detail. First of all, based on previous findings that the resistance to Erlotinib, a widely used drug in treating non-small cell lung cancer (NSCLC), of NSCLC cells is correlated to their membrane resealing response, we developed an AFM-based system capable of introducing multiple membrane pores on a cell monolayer and hence allowing us to evaluate the drug resistance of cells from their resealing behavior more efficiently. In addition, an electroporation-based device was also developed where micro-sized electrodes were used to apply an electric pulse to cells and induce transit pores on their membrane in a controllable manner. Interestingly, we found an inverse relationship between the drug resistance of cancer cells and their electroporation efficiency. It was also observed that the electroporation efficiency was regulated by the membrane tension, which was consistent with our previous findings. In total, six NSCLC cell lines have been tested on our platform that all supported the aforementioned conclusion, highlighting the potential of such an approach in real clinical applications. Besides poration devices, we have also developed a microfluidic system capable of imposing cyclic deformation, with precisely controlled duration and amplitude, on individual cells and then quantitatively monitoring their shape recovery upon unloading from which the viscoelastic and plastic characteristics of the cell can be extracted. Interestingly, it was found that plastic deformation can accumulate in highly invasive breast cancer MDA-MB-231 cells with a characteristic time of ~5s while the timescale associated with the recovery of viscoelastic strain is the order of magnitude larger (i.e. ~ 80s). Furthermore, after several cycles of loading, the plastic strain level in MDA-MB-231 cells reached over 20% whereas no apparent irreversible deformation was observed in the less invasive MCF7 cell line. Interestingly, a similar trend was also observed in cancerous and normal nasopharyngeal cell line pairs, indicating the direct correlation between the metastatic potential of cells and their plastic response.