By copying the physical features of a biological cell, including size, organized structure and nanoscale detail, a universal platform capable of multiple functions is possible. These functions include multiple sensing capabilities, signal amplification, logic processing, chemical release, mechanical actuation, and energy transformation.
UT-Battelle LLC’s (Oak Ridge, TN) scientists have created devices that use nanofibers as membranes for controlling molecular transport, according to U.S. Patent 7,641,863 These devices provide nanoscale control of molecular transport by mimicking biological cellular membranes. Semi-permeable membranes can be created from the directed self-assembly of nanofibers, allowing for the passage of molecules smaller than the wall-to-wall spacing of the nanofibers. The diffusion limits can be controlled by the separation of the fibers, both laterally and along the direction of transport. Chemical potential gradients can be engineered and used to direct transport.
The membranes were developed by Oak Ridge National Laboratory scientists Mitchel J. Doktycz (Biological and Nanoscale Systems), Michael L. Simpson (Principal Investigator of the Molecular-Scale Engineering and Nanoscale Technologies Research Group), Timothy E. McKnight, Anatoli V. Melechko, Douglas H. Lowndes, Michael A. Guillorn, and Vladimir I. Merkulov.
These membranes can involve chemical derivatization of the fibers to further affect the diffusion limits or affect selective permeability or facilitated transport. Additionally, individually addressable nanofiber electrodes can be integrated with the membrane to provide an electrical driving force for transport and an electronic interface to the fluid for control and detection.
Mimicking the function of natural cellular membranes presents both a significant challenge and a significant opportunity to modern analytical technology. Synthetic microcells with dimensions similar to common biological cells would offer many benefits. Similar to biological cells, these structures could allow for chemical reactions to be localized allowing detailed organization.
Microscale chemical "factories" could be constructed enabling sample-to-answer biological fluid assays, allowing real-time, unobtrusive monitoring and control of a person's health parameters. These biomimetic systems could combine features such as chemical sensing, chemical logic and chemical signaling, again analogous to biological systems.
Compartmentalized structures, segregated by semi-permeable membranes constructed as would allow for localization and communication between reaction centers. Discrete compartmentalized structures with defined connectivity would permit specialized "cells" to reside in close proximity, consequently allowing for multifunctional activity to occur in a mesoscale object.
Some of the prime limitations to building cellular mimics are the construction and filling of cells separated by semi-permeable membranes. Cell sizes of a few microns correlate to fluid volumes on the order of femtoliters.
Advances in micromachining technology are allowing for the routine construction of micron scale devices. Similarly, advances in fluid handling are beginning to enable the manipulation of small volumes of fluid. For example, ink jet technology allows for the deposition of chemical reagents with footprints of a few microns, while chemical stamping, or writing technology, is able to print on even smaller scales.
Though challenging, the construction of arrayed fluid filled cells, with dimensions similar to natural cells, is technically achievable. However, for these cells to function analogously to biological cells, the incorporation of semi-permeable barriers, or membranes, is a necessity. These membranes must be able to control selectively the transport of molecular species, requiring engineering on the nanometer scale. This capability is becoming possible through advances in nanoscale science, engineering, and technology.
The inventors directly addressed these limitations to constructing cellular mimics. The nanoengineered membranes will enable the engineered construction of joined cellular structures capable of chemical communication. Further, the incorporation of artificial, electronic-based control mechanisms is readily incorporated. A hybrid electronic/chemical system may allow for a unique control of chemical reactions.
Potentially, complex chemical reaction systems could be used to power electronic circuits or electronic logic system could control and power chemical systems. By "complex chemical reaction system", they mean a reaction that involves feedback control. The nanoscale features of the artificial membranes may enable devices with a direct interface to biological systems. Such a device could allow for an unprecedented view of biological systems, perhaps leading to metabolic control.
The membrane includes a substrate and a cover. The substrate and the cover at least partially define a channel between the substrate and the cover. The membrane also includes a plurality of fibers connected to and extending away from a surface of the substrate. The fibers are positioned in the channel and are aligned within 45 degrees of perpendicular to the surface of the substrate. The fibers have a width of 100 nanometers or less, and at least a portion of the fibers have a coating. In one example form, the fibers are carbon fibers. However, the fibers may be formed from silicon, metal, or plastic.
The diffusion limits for material transport are controlled by the separation of the fibers, both laterally and along the direction of material transport in the channel of the membrane. To achieve this, recent advances in nanofabrication can allow for synthesis of physical features on length scales ranging from nanometers to centimeters.
These fabrication techniques allow for the construction of cellular mimetics that incorporate features of semi-permeable membranes, chemical sensing and actuation in a footprint of less than 100 .mu.m. The nanostructured features are derived from the synthesis of carbon nanofibers and allow for control on the molecular scale.
FIG. 1 shows an outline for the synthesis of vertically aligned carbon nanofibers.
FIG. 2 shows electron micrographs of vertically aligned carbon nanofibers. Images (a), (b), and (c) display fibers grown randomly from a stripe of catalyst. Images (c) and (d) display fibers grown from individual catalyst particles positionally defined by lithography techniques.
FIG. 1 shows an outline for the synthesis of vertically aligned carbon nanofibers.
FIG. 2 shows electron micrographs of vertically aligned carbon nanofibers. Images (a), (b), and (c) display fibers grown randomly from a stripe of catalyst. Images (c) and (d) display fibers grown from individual catalyst particles positionally defined by lithography techniques.
