Parylene-C coated micro-apertures with painted synthetic lipid bilayer membranes for the investigation of outer-membrane-vesicle fusion

We present a Parylene-C coated aperture realized in a silicon/silicon-nitride substrate to investigate the fusion of outer-membrane-vesicles (OMV) in synthetic lipid bilayers (LBL). The finalized chip was realized by employing standard silicon nitride membrane fabrication methods and the aperture was coated with 10 μm Parylene-C. It makes the chip surface hydrophobic and lipophilic, preventing time consuming pretreatments (e.g. with organic solvents) before the formation of the LBL. Within a few seconds the LBL is formed. Our experiments show that the Parylene-C insulation is highly sufficient to achieve a low noise performance (1 pA RMS noise or ca. 2 to 4 pA peak-to-peak) at a 10 kHz sampling frequency and low-pass filtering at 1 kHz. Due to the quick LBL construction, the fusion of OMVs, extracted from the outer cellular wall of gram-negative bacteria took place within a few minutes. In addition, the proposed microfluidic system effectively detects the fast (1 ms) monomeric gating of outer membrane protein F (OmpF) pore proteins.