Biosensor-compatible encapsulation for pre-functionalized nanofluidic channels using asymmetric plasma treatment

Using asymmetric oxygen plasma treatment, we demonstrate the compatibility of a room-temperature sealing process with the use of functional biosensors embedded in nanofluidic channels. This method relies on the permanent bond between a plasma-treated polysilsesquioxane (PSQ) layer and a glass chip bearing nanochannels pre-biofunctionalized in an open-top fashion. The key feature of our method is to achieve selective surface modification of the fluidic chip right after a cleaning step in order to preserve the functionality of the silanol groups at the chip surface. For subsequent bonding, the oxygen plasma applies only to the PSQ gasket layer but not the pre-functionalized substrate to preserve its biosensing capability. We have used this technique to seal nanoslits previously grafted with oligonucleotides and biotins and demonstrated sensing of breast cancer BRCA1 genes and proteins, respectively, using fluorescence imaging. This encapsulation technique, along with our selective surface modification strategy, provides a viable solution for the fabrication of nanofluidic devices integrating biofunctional parts for miniaturized biosensing platforms where most conventional bonding processes are often incompatible with pre-biofunctionalized nanofluidic sensors.