Patent EP-0911631-A1 (EP)
Inventor: BELLON FRANCK
IPC: G01N27/447
Filed: 1991-12-12
Abstract: Assembly to deposit fluid biological samples has a porous membrane with land surfaces formed at one edge to deposit the samples on the surface of an electrophoresis plate. The apparatus to place biological samples on an electrophoresis plate has one or more flat units of a porous material with groove lands. They are cut on an extension of the plane and on the edge of a flat porous membrane, so that the section not in contact with the membrane presents the projecting lands which can be placed on the surface of the electrophoresis plate, to deposit one or more biological samples which are carried on the surfaces of the lands. The samples are deposited simultaneously in a matching alignment with the porous membrane. They are positioned at an angle to the plate surface or at right angles to it. In an Independent claim the biological samples are diffused on to the surface of the electrophoresis plate by the surfaces of the lands in simultaneous contact with the plate. Preferred Features: The porous membrane and the land units have a thickness of 50-200 mu  or 100-150 mu . The lands can be wetted, with the porous membrane or separately, by a material which can be impregnated with a liquid and fitted to the porous membrane over the area where each sample is deposited on each land. The porous membrane has a quadrilateral shape, with one edge bonded to the lands section. The end surfaces of the lands have a polygon shape such as a triangle, trapezoid, rectangle, square, disk segments or sections of an ellipse. The lands have a contact length with the gel of 1-200 mm, and they are spaced at least 0.5 mm apart. The porous membrane and the lands are of a hydrophilic material using cellulose or its derivatives or regenerated cellulose, or mixed cellulose esters, cellulose acetate, cellulose propionate or cellulose nitrate. The porous membrane can also be of a hydrophobic material The porous membrane is stiffened to maintain its shape, without contact between the membrane and the stiffener where the land surfaces deposit the samples on the electrophoresis plate, pref. using the wetting system of a sponge material which is attached to the membrane or is close to its edges. The wetting agent is a watery solution of glycerin at 0-50 vol%, or a saline solution as a plug solution of phosphate 0.15 M, triglycerin 0.15 M or a solution containing NaCl 0.15 M. The porous membrane can be a sheet of cellulose acetate, with the projecting lands at one edge, and the stiffener contains an integrated reservoir. Or the porous membrane is a sheet of paper, with a sponge material as the stiffener. The vol. of the biological sample deposited on the land surface is 0.05 x 10<->2 to 1 x 10<->2 mu l/mm per mu  thickness of the porous material with a pore level of 50-90%. The vol. of the deposited material on the electrophoresis plate is sufficient for detection of the sample components and less than the amount where the resolution would be lost for detection. The membrane contains a wetting agent, which does not degrade the sample quality, and which is sufficient to allow the sample to pass to the land surfaces without any concentration of the agent on the lands. The wetting agent can be glycerin, 1.3-butane diol, or non-charged tensides such as Triton X-100 (RTM) or Tween (RTM), in concentrations of 0.001-10.0%. The sample material is moved towards the land surfaces by a fluid flow, such as by evaporation of the biological sample fluid, or the evaporation is assisted by a flow of air at a temp. of ≤ 40 degrees C. For the sample deposit, an electrical voltage is applied to the porous membrane and the lands. The wetting fluid has a pH so that all the mols. in the sample are ionized, and have a charge of the same sign. The sign is negative, if the pH value is over the isoelectric point of the most alkaline mol. type, or positive if the pH value is lower than the most acid mol. type. An electrode is fitted to the edge of the porous membrane away from the lands, with a further pole at one end of the electrophoresis plate. The pole at the plate is positive if the sample mols. have a negative charge, and vice versa.