A New Way of Fabricating High-Porosity Parylene Membranes for High-Throughput Capturing of Viable Circulating and Exfoliated Tumor Cells from Large-Volume Bodily Fluids

Abstract

We report a simple method using just photolithography and reactive ion etching to fabricate high porosity Parylene-C porous membranes to process large volume of samples for liquid biopsy. A range of membranes have been fabricated with porosity ranging from 39 to 76 %. In comparison, track-etched polycarbonate membrane has a 5% porosity, and previously reported Parylene membrane had a ~ 45% porosity. A surprising vertical sidewall was observed in etched Parylene pores, which was contributed to the photoresist melting during high DC bias (420V) plasma etching. A circulating tumor cell (CTC) capture device was developed, and buffer sample processing rate up to 200 ml/min (limited by the device’s geometry) was obtained for membranes with porosity of > 47%. A low cell count method with ±1 cell accuracy was developed to characterize the spiked cell capture. The device showed high capture efficiency of 87 to 92% for low spiked cell numbers (< 50 cells). Preliminary results also showed over 90% viability for the captured cells. The simple Parylene etching process is promising for low cost fabrication of high porosity Parylene membranes for liquid biopsy applications.