‘Bionanoelectronic’ technology may help prosthetic devices talk to the body on a molecular level.
Neuroprosthetic devices of all kinds, from myoelectric prostheses to cochlear implants, depend on biological interfaces to function. Unfortunately, the juncture between human and machine has always been imperfect, with less than clear communication between nerves and componentry, and, in implanted devices, high risks of device corrosion and other problems.
While modern communication devices rely on electric fields and currents to carry the flow of information, biological systems are much more complex. They use an array of membrane receptors, ion channels, and molecular pumps to control signal transduction in a way that is unmatched by even the most powerful computers. For example, conversion of sound waves into nerve impulses is a very complicated process, yet the human ear has no trouble performing it.
Creating a seamless interface between the mechanical and the biological has become a goal for several major research facilities, with products as varied as a minimally-invasive brain electrodes and a high-fidelity MRI skullcap. However, none of these devices integrate with the body at a molecular or cellular level, so they are forced to detect them across a molecular gap. Now, a development by researchers at Lawrence Livermore National Laboratory (LLNL), Livermore, California, could eventually make such devices and many others more accurate and more effective.
Fatty Membranes Protect and Communicate
An article published in the August 18 Proceedings of the National Academy of Sciences describes how a team of researchers has devised a method for mingling biological components with electronic circuits by coating nanowires with a membrane of lipid (fat) molecules.
“Lipid membranes occupy a special place in the hierarchy of the cellular structures,” says Nipun Misra, one of the two lead authors on the study. Nipun is a graduate student at the University of California, Berkeley, and is affiliated with the Physical and Life Sciences Directorate at LLNL. “They represent important structural and protective elements of the cell that form a stable, self-healing, and virtually impenetrable barrier to ions and small molecules.”
By coating a nanowire with a lipid membrane, a “shielded wire” is born. When placed into a solution of proteins, the proteins can form ion channels in the membrane. The ion channels serve as pores that transport ions-electrically charged atoms or molecules that serve as the signaling power in biological systems-from the biological environment to the nanowire, all without chemically reacting with the nanowire. When given an electric charge from an outside source, such as a battery, the nanowires open the ion channels and selectively bring in any ionic signals the proteins are able to receive.
The end result is what LLNL calls “bionanoelectronic devices.” When turned on, these devices have direct, unmitigated connection with the biological system in which they are embedded, receiving electrical impulses the same way a muscle or nerve would. The researchers speculate that such devices could enhance neuroprosthetics, biosensing and diagnostic tools, and could even increase the efficiency of future computers.
Misra also notes that the lipid membranes serve as “nearly universal” matrices that can transport an almost unlimited range of proteins through themselves, carrying information about a huge variety of processes. Immune-system reactions, changes in blood sugar, and the appearance of cancer markers are just a few of the biological events that such devices could detect.
Misra and his colleagues consider their current research to be a first, and relatively minor step toward fully biologically integrated devices.