Microfluidic Modules for Enabling Point-of-Care Biopsy-based Cancer Diagnostics
The analyses of patient tumor biopsy samples and biopsy-based diagnostics have emerged as important tools for cancer diagnostics. However, the techniques employed currently are restricted to centralized laboratories as they are time-consuming, manual labor intensive and vary considerably in their effectiveness amongst institutions and countries. Point of Care testing (POCT) for cancer with the capacity for multiplexed detection of numerous biomarkers in biopsy samples in a rapid, precise and portable manner is emerging as an area with enormous potential to disseminate universal diagnostics to cancer patients. Additionally, POCT can be used as a screening tool, to discern malignant from benign tumors at the physician's office, and lead to reduction in the need for expensive and time-consuming laboratory tests, hence minimizing the cost and anxiety, for patients with benign tumors. A POCT platform for multiple biomarker analysis can not only improve the operational characteristics of assays but can also help ascertain drug efficacy, ushering in personalized medicine for the patients. The reduced volumes and diffusion distances, which enable multiplexed, portable and quick assays, in microfluidic devices makes such devices a promising platform to realize POCT systems. But current microfluidic devices for cancer diagnostics suffer from the lack of a generalized on-chip sample preparation module and a simplified fluid actuation technique.
The overall goal of the reported dissertation research is to develop microfluidic modules that will enable the development of integrated microfluidic diagnostic platforms for the multiplexed detection of cancer biomarkers in tumor biopsy samples. The main focus of the thesis is on the development of novel microfluidic sample preparation modules. The purpose of the sample preparation component is to pre-concentrate cancerous cells, remove background proteins in the sample and to subsequently lyse the cells to release the proteins of interest. The pre-concentration of the adherent cells, including the cancerous cells, in the sample is reported by trapping them using a novel hydrodynamic cell trap. The sample washing methods, to remove extracellular proteins that could interfere with downstream assays, is also optimized. An electrochemical lysis technique is then integrated to the cell pre-concentration module, to effectively lyse the cells without having to add external reagents. Microfluidic modules for the separation of bacterial and mammalian cells from mixed samples are also reported. The immortalized cancer cell lines used in this research include the human breast cancer cell lines BT-474, known to over express the Her-2 protein, and T47D along with cervical cancer cell line HeLa.
The development of a novel fluid actuation technique, termed Proximal Degas-driven Flow (PDF), is also reported in this thesis. PDF takes advantage of the high porosity and air solubility of PDMS to reduce the pressure inside the fluidic channels leading to fluid flow in the channel. This actuation technique enables bubble-free fluid flow, can be used to fill up dead-end chambers in contrast to traditional pressure (positive or negative) driven flows and does not require the priming of the channels. Unlike degas-driven flow, PDF alleviates the need for pre-degassed and sealed devices, enabling consistent and longer-lasting fluid flow. This portable technique also requires very simple and cheap hardware like a vacuum bulb or membrane pump (thumb pump).
In conclusion, several microfluidic modules to enable Point of Care biopsy-based cancer diagnostics are introduced. The research presented in this dissertation is an effort to transform point-of-care cancer testing and provide universal diagnostics and personalized medicine to cancer patients.