(395e) Shear-Enhanced Microfluidic Platform for Antibody Purification, in-Situ Efficacy Testing, and Bio-Diagnostics

Selectivity is often the dominant term that is the cause of worry for diagnostic devices for either point-of-screening or point-of-care devices. It is worthwhile to note that similar worries are manifested for the purification of antibodies from cell culture fluid. To separate, filter and purify antibodies the selectivity of Protein A is altered by using pH gradients or different ionic solutions. However, this often leads to post modifications in the purified antibodies leading to reduced efficiency. This becomes paramount for monoclonal antibodies (mAbs) whose extraordinary binding affinity and specificity are used to treat multiple diseases from cancer to cardiovascular diseases. Hence, there is an urgent need to develop processed that allow for antibody purification without using a harsh purification protocol. Here, we show an affinity based lab-on-a-chip microfluidic platform to purify mAbs without post-modification damages, unlike current processes. Further, the inbuilt Electrical Impedance Spectroscopy on this chip, allows for a scrutinization of the binding efficiency of the mAbs antigen pair, replacing diffusion-limited, operator dependent and costly antigen microarray assay or enzyme-linked immunosorbent assay (ELISA). The lab-on-a-chip device has interdigitated electrodes with a channel packed with nanotubes and nanofibers that form a dense matrix. The high packing density allows for modulation of the shear stress in the device. At low flow rates, the mAbs are captured from the cell culture by the matrix post cell lysis, while at high velocities the attached antibody is stripped away by the shear force. Finite elements simulations of the fluid characteristics in the packed device show shear forces in the microchannel of the order of the hydrogen bond strength. Multiple materials are being considered for this shear enhanced platform from Carbon Nanotubes, Carbon Nanofibers to Graphene Oxide. We believe that the control over the shear force will strengthen if a 2D material is taken. This binding and stripping event of the mAbs to the CNT-antigen complex triggers changes in electrochemical impedance spectroscopy (EIS) signal observed from the interdigitated electrodes. The EIS signal is interpreted to obtain a measure of the binding strength and structural changes of the mAbs. Further, the aliquot of purified antibodies is tested using Western Blot and ELISA to show that they are as and often more viable than those collected using other techniques. The tuning of the shear force by the flow allows us to also use this platform as a diagnostic device. Further, the dominant convective transport in the pores, the high sensitivity from the packed matrix, and interdigitated micro electrodes ensures a high signal to noise ratio. This allows for sensitive detection of different biologicals from target DNA to a sandwitched ELISA. As a diagnostic device, we are developing a point-of-screening device that makes it possible to test for cancer panels like Ovarian Cancer. This platform also detects pharmaceutical molecules, like Ibuprofen, Methotrexates, and other NSAIDs in water. Different nanomaterials will be chosen so that the users can use spectroscopy techniques like Infrared and Raman to detect any structural changes of the monoclonal antibodies. The modified platform will allow us to observe the effect of force on the mAbs-antigen binding and resultant physio-chemical structural changes.