Ion signalling in eukaryotic cells is essential for numerous physiological processes, including regulation of exocytosis, contraction, gene transcription and fertilization, as well as maintenance of cell membrane potential. Ion signalling is equally important in prokaryotic cells, e.g. in osmoregulation. Ion signalling in cells may be affected by alteration of extracellular and intracellular concentration of ions. Such alterations result in intracellular concentration changes in the forms of i) rapid increase followed by a rapid decrease (termed spikes), ii) a sustained, elevated concentration, or iii) repetitive spikes that produce an oscillation of characteristic frequency and amplitude. Due to technical limitations of available methods to decipher these complex signalling pathways, very little is known about the molecular and physiological effects on cells. A limitation of certain concern is the inability of available methods to provide controlled ion fluxes to cells to be studied.
Presently, transport of ions from, to or between electrolytes, such as from a stock solution to a cell culture medium, is performed by manual or automated use of e.g. pipettes, pumps or membranes. Such techniques result in unspecific delivery of ions to a cell culture medium as such only, whereas further diffusion to cells cultured in the medium is uncontrollable and unpredictable. Furthermore, said techniques require the use of expensive equipment. Examples of present methods for transport of ions are given below.
U.S. Pat. No. 6,780,584 discloses a device for the modulation of a reaction comprising: a first buffer reservoir containing a first buffer and a first charged entity, wherein the first buffer has an initial conductance less than 1000 μS/cm; a second buffer reservoir separated from the first buffer reservoir containing a second buffer comprising a second charged entity, wherein the second charged entity has a charge opposite that of the first charged entity, the second charged entity modulates the specific reaction between the specific binding entity and the first charged entity; a conductive semi permeable matrix contained in a non-conductive support material, the conductive semi permeable matrix disposed between and fluidically connecting the first buffer reservoir and the second buffer reservoir; a first electrode linked to a power source and located in the first buffer reservoir and contacting the first buffer; and a second electrode linked to the power source and located in the second buffer reservoir and contacting the second buffer; and a specific binding entity which reacts specifically with the first charged entity and which is physically fixed on, in, or adjacent to the semi permeable matrix.
U.S. Pat. No. 5,776,325 discloses a method of inducing mono-directional transport of ions between electrolyte solutions comprising separating the electrolyte solutions with a conducting polymer membrane and creating a potential gradient across said membrane wherein the potential gradient is created by using the conducting polymer membrane as a shared working electrode.