Computers and the Human Body
Scientists have made some recent advances in connecting computer technology with the cellular level processes of the human body. Both of these advances use the concept of the transistor to gain human control over cellular level processes. Many processes within the cell use protons, so the development of a transistor that can control the flow of protons, as opposed to the traditional transistor that controls the flow of electrons, is a crucial step in being able to implement human-directed changes in how the human body functions. Furthermore, a group of scientists at Stanford University have even used the idea of the transistor in order to control the expression of certain genes at the DNA level.
What is a transistor?
A transistor is a device that can amplify an electrical signal or act as an on-off switch . Transistors use the electron potential or voltage of transmitters to control the flow of electric current through them . Electron potential refers to the difference in charge created by an excess or lack of negatively charged electrons in certain areas . The positive and negative areas of a transistor are separated by a physical barrier, which means there is no movement of electrons from the negative to the positive area until the two areas are connected via a circuit .
A junction transistor is made up of three parts: an emitter, a base and a collector . The collector and emitter have opposite charges and lie on opposite sides of the base; however, there is no movement of electrons between collector and emitter until the base is injected with a small current . This device is particularly remarkable because only a small amount of current injected into the base is necessary for a large current to flow between collector and emitter . The two types of junction transistors are a PNP or a NPN, which refer to the pattern of semiconductors the transistor is constructed from . A P-type semiconductor material allows electrons to flow into the material and an N-type semiconductor material allows electrons to flow out of the material . In an NPN transistor, free electrons flow from the emitter to the base, which then flow to the collector . In the PNP transistor, the emitter forces electrons in the base from their positions, most of which flow into the collector .
Development of a transistor compatible with the human body
Scientists at the University of Washington recently developed a transistor that can control the flow of protons as opposed to simply the flow of electrons . The protonic transistor is made from maleic-chitosan which is a polysaccharide chitin derivative . The original compound from which is was derived is chitosan; it is a compound found in squid pen that can be collected from the crab shells and squid pen discarded as waste products by the food industry . Squid pen is a structure in squid that supports their mantle, or outer protective layer . Moreover, most derivatives are safe for the human body in the sense that they are biodegradable, physiologically inert and nontoxic [2,6].
The proton-based transistor these scientists developed is a field-effect transistor . A field-effect transistor is made up of a gate, a drain and a source terminal . In this type of transistor, a voltage is applied between the source terminal and drain so that electrons flow along a channel beginning from the source terminal and exiting through the drain . This continues as long as there is a continual supply of electrons applied to the source terminal . The gate is a P-type semiconductor; a voltage can be applied to the gate in order to control the flow of electrons along the channel . In this proton-based transistor, palladium is used at the source terminal and drain because it can form proton-conducting palladium hydride when exposed to hydrogen . Therefore, proton exchange occurs between the palladium hydride contacts (source terminal and drain) and the channel made out of maleic-chitosan nanofibers without electrolysis . In between the silicon gate at the bottom of the transistor and the palladium hydride contacts is a layer of silicon dioxide which insulates both the maleic-chitosan and palladium hydride contacts from the silicon gate .
Recently, scientists have used the concept of a transistor to create a biological device that can control the activity of RNA polymerase . RNA polymerase is responsible for making RNA from DNA; the strands of RNA transcribed from DNA are used to produce the proteins that our body uses .
This transistor is known as a "transcriptor" and uses an asymmetric transcription terminator to regulate whether or not RNA polymerase is allowed to flow along or read DNA in order to make RNA . A control signal is used to control the flipping of the terminator, which, if the control signal is present and the terminator is flipped, allows the RNA polymerase to read the DNA in one of two directions . Scientists have used these "transcriptors" to make logic gates based on Boolean logic; Boolean logic is used by computers and is a system of true and false statements that can be combined to accomplish more complex tasks . Their gates would allow researchers to detect a cell's exposure to external stimuli such as glucose .
The three parts of this "transcriptor" consist of a DNA strand, RNA polymerase, and integrase proteins that can cut and paste DNA . In the middle of the DNA strand there is a short sequence of DNA that causes RNA polymerase to detach from the DNA . However, the integrase proteins can cut this sequence of DNA and then reinsert it backwards so that the RNA polymerase does not recognize the terminator DNA sequence and continues RNA transcription . These "transcriptors" could be designed like a computer circuit within the cell so that more complex logical functions could be controlled . This novel technology could be used to directly regulate the expression of certain genes in DNA .
A transistor that can control the flow of protons is important because proton currents are used for electrical signaling rather than a current of electrons . For example, ATP oxidative phosphorylation that occurs in mitochondria uses proton transport and electrical signals in living systems are processed by controlling ionic and protonic currents . Therefore, being able to control proton currents in certain parts of the body is a direct way to affect how such processes are carried out in the body . In addition, the ability of this material to conduct protons can be used to monitor charge transport within neurons .
Furthermore, the chitin nanofibers used in this proton based transistor could provide the ideal material for nanopatterned surfaces that can be used in various ways, one of which is culturing nerve cells . The self-assembled chitin nanofibers is a valuable tool for creating a biomimetic platform that can culture nerve cells . Since the chitin nanofibers' mechanical properties can be modified to match native cell environments, they can also be used to test how certain topographical configurations affect neuron behavior .
This transistor-based technology is an innovative step toward integrating our rapidly developing computer technology with our knowledge of the human body and the human genome. Scientists are continually discovering more about the mechanisms used by the body at the cellular level. Therefore, technology that is able to communicate human control over these processes is essential to making important advances in disease treatment on the cellular level. By regulating the flow of protons, a gradient used naturally by the body, and the expression of genes, these innovations in transistor technology are forging a novel path in the area of disease treatment via some of the most basic mechanisms of the human body.
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