Microfluidic devices for investigation of biomimetic membranes for sensor and separation applications

The term biomimetic membrane denotes membrane that mimics biological cell membrane. Artificially made membranes are powerful tools for the fundamental biophysical studies of membrane proteins. Moreover, they may be used in biomedicine, serving as biosensors in high-throughput screening of potential drug candidates and in separation technologies, where an exciting example is water purification device based on biomimetic membranes containing aquaporins (highly water selective proteins). However, there are many challenges that must be overcome in order to build biomimetic membrane-based devices for industrial applications. Among them are the inherent fragility of lipid membranes, the challenge of up-scaling the effective membrane area and the quantification of the protein delivery to the lipid membrane which may determined the biomimetic membrane application. This PhD thesis addresses the above mentioned difficulties. First, a device that facilitates atomic force microscopy (AFM) measurements of biomimetic membranes is presented. The microfluidic device was specifically designed and fabricated to accommodate the AFM probes that were used to study micrometer-sized fluid polymeric membranes. Second, membrane arrays stability was increased by two ways; surface modification of support partitions and by involving fully closed and automated microfluidic device. The surface was covalently modified by plasma resulting in a hydrophobic coating and thus greatly improved the average membrane array lifetimes (up to 6 days) with a bilayer membrane area ~50% of the available aperture area. Highly stable membranes (up to 2 days) with a bilayer membrane area ~24% of the available aperture area were created in the developed microfluidic device. Further, reconstitution of α-hemolysin (α-HL) membrane proteins in the biomimetic membranes was performed. Third, an outer membrane porin (OMP) fusion efficacy assay was established and used to quantify protein delivery to an array of planar membranes. Incorporation was established as a process with either first order or exponential kinetics. This may be of interest to microfluidic designs involving protein delivery to biomimetic membranes developed for sensor and separation applications. Finally, an OMP functionality modulation with β-cyclodextrin (β-CD) was shown and revealed the protein potential application as a sensor. Moreover, the β-CD blocker may be used to prevent human dental plaque formation and the development of periodontitis.