One-step glass-like coating of polycarbonate for seamless DNA purification and amplification on an integrated monolithic microdevice

Abstract

We present a new method for realizing a glass-like, sol-gel coating on a polycarbonate (PC) surface by simply applying bis[3-(trimethoxysilyl)propyl]aminosilane (ABPTMS) at room temperature. ABPTMS, an amine-terminated silane coupling reagent bearing secondary amine groups, can form strong urethane bonds by reacting with the carbonate groups of PC, requiring neither heat nor surface oxidation of PC. In this study, a thin glass-like sol-gel layer was formed on PC via self-aggregation of the silanol groups of ABPTMS as the sole component for sol-gel formation on the PC surface. The resulting sol-gel coating also facilitated one-step bonding of two PC substrates by forming siloxane bonds (SiOSi) at a relatively mild temperature and under atmospheric pressure within 30min. Bond strength was measured through shear strength tests, high-throughput leak tests, and delamination tests, and the highest measured bond strength was approximately 950kPa. The bond was sufficiently robust to endure intense introduction of liquid with a per-minute injection volume that was nearly 2000 times the total internal volume of the microchannel tested. As a practical application, the sol-gel-coated PC microdevice was adopted for DNA purification, and was integrated with a flow-through polymerase chain reaction (PCR) unit to realize seamless DNA purification and amplification simultaneously on a monolithic PC device. 230bp Escherichia coli DNA was successfully purified and amplified using the microdevice in 70min, facilitating the otherwise most cumbersome and time-consuming operations of DNA analysis.