Process and device for separating biological particles contained in a fluid by means of filtration

Abstract

The invention relates to a method of separating biological particles from the liquid containing same for purification, analysis and optionally diagnostic purposes. The inventive method comprises at least one step involving vertical filtration through a filter having a porosity that is adapted to the type of biological particles to be separated, such that said particles are retained by the filter. The invention is characterised in that: (i) the method involves the use of a filter comprising at least one basic filtration zone, whereby each basic filtration zone has a limited surface area; and (ii) the surface area of each basic filtration zone and the number of basic filtration zones are selected as a function of the type of liquid to be filtered, the type of biological particles to be separated and the volume of liquid to be filtered.

1 . Process for separating biological particles, and the fluid that contains them, for the purposes of purification or analysis and possibly for diagnosis, comprising at least one vertical filtration stage through a filter the porosity of which is suited to the nature of the biological particles to be separated so that said biological particles are retained by the filter, wherein a filter is used comprising at least one elementary filtration area, each elementary filtration area having a limited surface, in that the surface of each elementary filtration area and the number of elementary filtration areas are chosen according to the nature of the fluid to be filtered, the nature of the biological particles to be separated and the volume of fluid to be filtered, and in that each elementary filtration area has a surface equal to that of a disk with a diameter of between 0.6 cm and 3 cm, and in that the number of elementary filtration areas is chosen so that the ratio of the volume of fluid filtered and of the filtration surface is less than 40 ml/cm 2 . 
     
     
         2 . Process according to  claim 1 , wherein each elementary filtration area has a surface equal to that of a disk having a diameter greater than or equal to 0.8 cm. 
     
     
         3 . Process according to  claim 2 , wherein the filter has pores calibrated to a size of between 3 μm and 100 μm and a pore density of between 3×10 3  and 5×10 6  pores/cm 2 . 
     
     
         4 . Process according to  claim 1 , wherein filtration is carried out by a reduction in pressure of between 0.05 bar and 1 bar with, possibly, an increase in pressure of less than 1 bar. 
     
     
         5 . Process according to  claim 1 , wherein, to carry out filtration, a filter forming a badge is used, suitable to be associated with a means of analysing filtration residues by locating the elementary filtration areas. 
     
     
         6 . Process according to  claim 5 , wherein to carry out filtration, the badge forming the filter is incorporated in a filtration module comprising at least one chamber for containing the fluid to be filtered, and that can be treated before use to sterilise it or to free it from enzymes that digest DNA, RNA or proteins. 
     
     
         7 . Process according to  claim 6 , wherein the filtration module is a single-use filtration module. 
     
     
         8 . Process according to  claim 1 , wherein the biological particles to be separated are cells. 
     
     
         9 . Process according to  claim 8 , wherein prior to filtering the fluid containing the cells, a sample of fluid for filtering is prepared from a sample of fluid containing cells such as a biological fluid or cell culture by pre-enriching it with the cells to be separated and/or by diluting it. 
     
     
         10 . Process according to  claim 8 , wherein the fluid containing the cells may be blood and in that the filter has calibrated pores of between 5 μm and 25 μm. 
     
     
         11 . Process according to  claim 1 , wherein the biological particles are fibrins, red blood cells, platelet aggregates, fibrins or tissue waste. 
     
     
         12 . Process according to  claim 11  wherein the fluid containing the biological particles is urine and in that the calibrated pores of the filter are between 8 μm and 100 μm. 
     
     
         13 . Use of the process according to  claim 1  for the detection of cells for diagnostic purposes such as tumour, foetal, endothelial, fibroblastic, muscle, nerve or monocytal cells, cell strains, organ cells, precursors or haematopoietic cells, in a biological fluid such as blood, urine, ascites, cephalorachidian fluid, milk, pleural extravasation, fluid for washing the neck of the uterus, cell suspension fluid obtained by biopsy, by a surgical method or by mouth washing, or for the detection of animal or vegetable cells. 
     
     
         14 . Filtration module for implementing the process according to  claim 1 , of the type comprising:
 a chamber block comprising at least one compartment closed at its lower portion by a base comprising at least one opening;   a filter support drawer comprising at least one hole, each hole being arranged facing an opening in the chamber block;   a filter gripped between the lower face of the chamber block and the support drawer,   
       wherein the dimensions of each opening in the base of the chamber block and the dimensions of each hole in the filter support drawer are such that each pair made up of an opening in the base of the chamber block and the associated hole in the filter support draw, define an elementary filtration area of limited surface, in that the useful volume of each compartment is proportional to the number of elementary filtration areas situated in the base of the compartment and in that the surface of the elementary filtration area is equal to that of a disk having a diameter of between 0.6 cm and 3 cm, and in that the ratio of the useful volume of each compartment to the sum of the surfaces of the openings comprising the base of the compartment is less than 40 ml/cm 2 . 
     
     
         15 . Filtration module according to  claim 14 , wherein the dimensions of at least one opening in the base of the chamber block and the dimensions of a corresponding hole in the filter support drawer are such that the surface of the corresponding elementary filtration area is greater than or equal to that of a disk 0.8 cm in diameter. 
     
     
         16 . Filtration module according to  claim 14 , wherein at least one compartment may be divided into part compartments by at least one removable separation wall, such that at least one part compartment comprises in its base at least one opening and in that the ratio of the volume of said part compartment to the sum of the surfaces of the openings comprised in the base of the part compartment is less than 40 ml/cm 2 . 
     
     
         17 . Filtration module according to  claim 1 , wherein it also comprises a grooved sealing joint arranged between the base of the chamber block and the filter, comprising at least one hole corresponding to a hole in the base of the chamber block, the hole being surrounded by at least one projecting lips. 
     
     
         18 . Filtration module according to  claim 14 , wherein it also comprises a plate joint between the filter and the filter support, comprising at least one opening facing a hole in the filter support. 
     
     
         19 . Filtration module according to  claim 14 , wherein the filter forms a badge the central portion of which comprises at least one porous area and the periphery of which forms a frame comprising means for indexing its position on the filter support. 
     
     
         20 . Filtration module according to  claim 19 , wherein the indexation means are at least two holes of different diameter designed to cooperate with studs of corresponding diameter provided on the filter supports. 
     
     
         21 . Filtration module according to  claim 14 , wherein at least a central porous portion of the filter comprises between 3×10 3  and 5×10 6  pores per cm 2  of between 3 μm and 100 μm. 
     
     
         22 . Filtration module according to  claim 14 , wherein it also comprises at least one stopper for closing the upper opening of a compartment. 
     
     
         23 . Filtration module according to  claim 14 , wherein the chamber block comprises, at its lower portion, a rim extending outwards and cooperating with at least one assembly pin allowing the filter to be gripped between the filter support Hand the chamber block, the assembly pin comprising a breakable end extending above the rim of the chamber block. 
     
     
         24 . Filtration module according to  claim 14 , wherein all its parts are made of materials suited to a sterilisation operation or designed to render them free from RNases, DNases or proteinases. 
     
     
         25 . Support block for a filtration module designed to retain a filtration module ( 1 ) according to  claim 14  on a filtration machine, comprising at least one cam that can move between an open position and a gripping position, designed to put pressure on the filter between the filter support and the chamber block. 
     
     
         26 . Support block according to  claim 25 , wherein at least one cam is designed so that, if the filtration module comprises at least one fixing pin one end of which is breakable, the end of at least one fixing pin is cut when pressure is applied to the filter by at least one cam. 
     
     
         27 . Support block according to  claim 25  wherein it forms part of a filtration machine. 
     
     
         28 . Filtration module according to  claim 14 , wherein it comprises means designed to cooperate with complementary means on a support block comprising at least one cam that can move between an open position and a gripping position, designed to put pressure on the filter between the filter support and the chamber block, so as to impose the orientation of the filtration module in relation to the support block. 
     
     
         29 . Support block according to  claim 25 , wherein it comprises means designed to cooperate with means on a filtration module, so as to index the orientation of the filtration module in relation to the support block.