One of the barriers scientists have encountered when trying to link microelectronic devices with biological systems has to do with information flow. In biology, almost all activity is made possible by the transfer of molecules like glucose, epinephrine, cholesterol and insulin signaling between cells and tissues. Infecting bacteria secrete molecular toxins and attach to our skin using molecular receptors. To treat an injury or infection, we need to detect these molecules to identify the bacteria, discern their activities and determine how to respond.
Microelectronic devices don’t process information with molecules. A microelectronic device typically has silicon, gold, chemicals like boron or phosphorus and an energy source that provides electrons. By themselves, they’re poorly suited to engage in molecular communication with living cells.
Free electrons don’t exist in biological systems so there’s almost no way to connect with microelectronics. There is, however, a small class of molecules that stably shuttle electrons. These are called “redox” molecules; they can transport electrons, sort of like wire does. The difference is that in wire, the electrons can flow freely to any location within; redox molecules must undergo chemical reactions – oxidation or reduction reactions – to “handoff” electrons.
“Normal” Electricity as we use in our daily life to empowering products is of a different “nature” than the electricity used in our body. The differences are:
|Electron electricity||Biological electricity|
|Energy is based on electron flow||Energy is based on ion activity|
|Can use electrons of most materials||Is based on mainly inorganic elements|
|Can flow at all time||Depends on action potential|
|Can use a wide range of Volt / Ampere etc.||Has a small low active V / A / Ohm|
Most of the information is based on Julius Bernstein (18 December 1839 – 6 February 1917). Bernstein speculated that cells have high K+ and low Na+ concentrations and that the extracellular fluid has low K+ and high Na+ concentrations. Another discovery was the fact that that cells were highly permeable to K+ but not very permeable to other ions.
Walther Hermann Nernst, (25 June 1864 – 18 November 1941) was a German chemist who is known for his work in thermodynamics; his formulation of the Nernst heat theorem helped pave the way for the third law of thermodynamics, for which he won the 1920 Nobel Prize in Chemistry. Nernst helped establish the modern field of physical chemistry and contributed to electrochemistry, thermodynamics and solid state physics. He is also known for developing the Nernst equation in 1887.
Effects of altered extracellular concentrations of K+ on the membrane potential: (•), measured membrane potential at each of a variety of different concentrations of K+; the straight line is the potential predicted by the Nernst equation. The value of 140 in the Nernst equation is the estimated intracellular concentration of K+ for the cell used in the experiment. (Modified from Hodgkin AL, Horowicz P. J Physiol 1959; 148:127.) where Vm is the membrane potential and EK the potassium equilibrium potential.
An action potential is the brief (about one-thousandth of a second) reversal of electric polarization of the membrane of a excited cells such as nerve cell (neuron), muscle cell, endocrine cell and so on. In neurons, an action potential happens when a neuron sends information down an axon, away from the cell body. In muscle cells, for example, an action potential produces the contraction required for all movement. Action potentials in neurons are also known as “nerve impulses” or “spikes”, and the temporal sequence of action potentials generated by a neuron is called its “spike train”. A neuron that emits an action potential is often said to “fire”. Action potentials are generated by specific voltage-gated ion channels embedded in a cell’s plasma membrane.
Until today these calculations are still standing and used in modulated forms, the basic principles did not change. Cell have an action potential. Short outburst of energy transfers at which ion’s are the main short of power. These powers occur in several types which are called excitable cells, a category of the cell include neurons, muscle cells, and endocrine cells. Galvani coined the term animal electricity to describe the phenomenon. Galvani and contemporaries regarded muscle activation as resulting from an electrical fluid or substance in the nerves.