Micro- and Nanostructures for Studies of Model Biological Systems

Abstract: Sub-cellular biological components are complex systems that work together to control and maintain cellular activity and health. It is useful to study the basic elements that constitute the sub-cellular components using model systems, which mimic certain parts of the overall system, in order to better understand the system as a whole. Here we present a number of tools, which enable the study of a few model systems that mimic specific components of molecular motors and cellular membranes. The tools we use are nano- and microstructures that allow for the control and monitoring of two model biological systems: synthetic molecular motors and supported lipid bilayers, in order to probe their basic functions and interactions with the artificial environment. The two synthetic motors of interest, that mimic cellular bipedal molecular motors, utilize either rectified diffusive motion or changes in motor conformation to take steps. The synthetic motors have been designed to isolate these aspects previously observed in natural bipedal motor stepping. We have fabricated and tested microand nanofluidic devices which make it possible to control the motors’ stepping with simultaneous observation using optical microcopy. Additionally, these devices are designed to enable testing of the motors’ performance against a load force. We have also used a microfluidics device with a natural helicase motor that moves along DNA, in much the same way as one of the synthetic motors is designed to do. In this study we have successfully controlled the motor motion with addition and withdrawal of the motor’s fuel supply, ATP, in the surrounding solution, and we have monitored single protein motors as they move and stop along the DNA track. These devices and techniques set the stage for future measurements of the synthetic molecular motors. Additionally, these fluidic devices have a number of other potential applications in single-molecule studies, as they allow for the changing of the chemical environment surrounding single-molecules whilst causing little disturbance to these. Supported lipid bilayers are a simplified model version of the complex cell membrane, which contains not only lipids, but also a number of other intra-membrane components needed for cellular function. We have used a substrate with a large number of vertical nanowires standing parallel to one another to study the bilayer interaction on a highly curved support. This type of support has interesting applications in the field of localized injection into cells. In this application it is still unclear how the cellular membrane responds to the nanowire supports, and how injection can occur. Using the nanowire devices, we have formed a supported lipid bilayer that follows the nanowires, which could allow for future studies focusing on the interaction between lipid membranes and the nanowires. Additionally, because the membrane follows the nanowires, this device could be used as a platform to study lipids at high curvature, for example membrane components, such as proteins, that favor high curvature. Each of the devices we have developed will hopefully bring insight into the working of these model biological systems, which in turn could reveal information about how components of the natural sub-cellular system are functioning.