Earth’s crust and primordial ocean formed more than 4 billion years ago and life is believed to have originated on earth at least 3.6 billion years ago. This suggests that primitive cellular life must have evolved from non-living matter during that period of several hundred million years. To study the transition from chemistry to biology, a simple vesicular system called a protocell is an ideal model that is self-organized and contains informational or metabolic materials. This thesis starts by exploring the replication of a model genetic material under plausible prebiotic conditions. The non-enzymatic copying of RNA was found to be catalyzed by Fe2+, which used to be abundant in aqueous environments on the early anoxic earth. Fe2+ was found to be a better catalyst of non-enzymatic RNA copying and ligation in slightly acidic to neutral pH conditions than Mg2+, the divalent cation used to catalyze these reactions in previous studies. This finding suggests that ferrous iron could have facilitated the replication and evolution of RNA on the prebiotic earth. To gain a better understanding of the properties of protocell membranes, the impact of membrane composition and multi-bilayer structure on non-enzymatic and enzymatic biochemical reactions was studied. A fatty acid/phospholipid hybrid membrane system was proposed as a potential intermediate state in protocellular evolution. This membrane composition was investigated for its stability and permeability, two fundamental features of functional protocells. The system proved stable in the presence of divalent cations and retained permeability to small building block molecule. Vesicles with this composition were shown to host faster non-enzymatic RNA copying, and to enable enzymatic protein synthesis. To study the effects of multi-lamellarity, giant multilamellar vesicles (GMVs) were prepared by an extrusion-dialysis method. Compared with small unilamellar vesicles (SUVs), GMVs show slightly better ability to retain encapsulated RNA, while maintaining good permeability for small charged molecules. The multilamellar structure also promotes non-enzymatic RNA copying, providing preliminary evidence that membranes could also mediate catalytic functions as well as acting as a compartment. / 2020-07-02T00:00:00Z

Inspired by the roles of hair cells in nature, this study aims to develop and characterize two new sets of novel flow sensors. One set of sensors developed and studied in this work are flow sensors fabricated using carbon nanomaterials. These sensors are made by embedding carbon nanotubes (CNT) and carbon nanohorns (CNH) into a polymeric substrate and then tested by flowing a conductive aqueous solution over the surface of the exposed CNT and CNH. In response, a flow-dependent voltage is generated. The surface coverage and the electrical relationship between the sensor and water is investigated and the voltage measurements of sensors with different levels of resistance were tested in varying fluid velocities. In response to these fluid velocities, the least resistive sensor showed small, but detectable changes in voltages, while higher resistance sensors showed less response. In addition, plasma treatment of the carbon nanomaterial/PDMS films were conducted in order to render the PDMS on the surface hydrophilic and in turn to pull more fluid towards the carbon material. This showed to improve the sensitivity of the flow sensors. This work also builds on previous research by investigating the flow dependent electrical response of a "skin"-encapsulated artificial hair cell in an aqueous flow. An artificial cell membrane is housed in a flexible polyurethane substrate and serves as the transduction element for the artificial hair cell. Flow experiments are conducted by placing the bio-inspired sensor in a flow chamber and subjecting it to pulse-like flows. This study demonstrates that the encapsulated artificial hair cell flow sensor is capable of sensing changes in flow through a mechanoelectrical response and that its sensing capabilities may be altered by varying its surface morphology. Furthermore, the sensor's response and dynamics as a function of its surface morphology and structural properties are investigated through synchronized motion tracking of the hair with a laser vibrometer and current measurements across the artificial cell membrane. / Master of Science