A METHOD OF USING POLYPROPYLENE GLYCOL TO IMPROVE MOVEMENT AND INTERMIXTURE OF BLOOD AND OTHER FLUIDS IN CAPILLARY TUBES

Abstract: A method of neutralizing the electrostatic forces in liquids or solutions in liquid phase, preferably blood and blood solutions, respectively. The electrostatic forces primarily consist of surface tension and interrepellant forces between particles in the solution. The purpose of the invention is obtained by adding polypropylene glycol H[OCH(CH3)CH2]nOH to the liquid or solution. Polypropylene glycol possesses properties allowing it to neutralize the electrostatic forces without affecting the red blood cells.

Description: A Method of Using Polypropylene Glycol to Improve Movement and Intermixture of Blood and Other Fl uids in Capil lary Tubes . The subject invention relates to a method which improves the movement of blood and other fl uids and thei r intermixture in tubes where the surface tension is strong, and thi s without damage being done to the blood corpuscles . The invention al so al lows the use of thinner- -bore tubes or less energy-consuming pumps in continuous-flow systems without change of the character of the fl uids passing through systems of this kind. In the health service, particularly in l aboratories, capil lary tubes are often used for col lection of blood. To prevent the blood from coagulating it is customary to add double-acti ng sol utions, i .e. ant -coagul ants and thinning agents . The strong surface tension that exists in capillary tubes causes problems in achieving inter-mixture of blood and solutions added thereto. For this reason techniques such as magnetic stirring, manual and mechanic vibrating and shaking methods are used to obtain satis¬ factory degrees of intermixture. However, these methods often lead to bursting of the blood corpuscles, resulting in undesirable haemolysis, which has a detrimental effect on the subsequent analysis of the blood. Surface tension in capillary tubes may be reduced by means of various kinds of surfactants. However, surfactants too, have an hae o- lytical effect on blood corpuscles and interfer with other analysis reactants and therefore are used very sparingly. Capillary tubes are also used within the health service to carry and transport blood and other fluids in so called continuous flows. In order to separate blood samples from one patient from blood samples from other patients or from other fluids which are flow¬ ing simultaneously in the same tube these fluids are separated with the aid of gas bubbles (Fig. 1). Gas bubbles and solutions channelled through tubes of this kind are affected by the strong surface tension therein. The larger the amount of bubbles in the tubes and the longer the tube the larger the total surface tension that must be overcome. For this purpose large and energy-consuming pumps are used, e.g. peristaltically operating pumps, or el se larger-bore tubes are chosen for the purpose of reducing the effects of the surface tension. The purpose of the subject invention is: - to completely or partially block the effects of the surface tension in capi llary tubes to al l ow easy intermixture of blood and other fl uids without detrimental effects on the blood corpuscles; - to reduce the need of mechanical aids to effect the mixing; - to reduce the effects of surface tension of gas bubbles and other fluids in continuous-flow systems so that a ) the risks of undes ed haemolysis are reduced; b) thinner capillary tubes may be used; c ) less energy-consuming pumps may be used. This is achieved in accordance with the teachings of the inven- tion by adding polypropylene gycol H βCH(CH3)CH^) n to reduce the el ectrostatic forces, e. g. surface tension, in l iquids or sol utions in l iquid phase, such as blood and bl ood sol utions. . Polypropylene glycol may be added when blood is mixed with a sol ution designed to facil itate dispersion of the blood in said sol uton as claimed in cl aim 2. Polypropyleneglycil may al so be added to said l iqui d or said sol ution to reduce the surface tension thereof when the l iquid or the solution is conducted through capillary tubes as set forth in claim 3. In the performance of analyses involving sedimentation of a l i- quid, polypropylene glycol may be added to reduce the repel! ant forces existing between the particl es forming the sediment, as claimed in claim 4. A particular application is to use polypropylene glycol to facil itate the rouleaux formation of cl ustered red cells as specified in claim 5. In order to ill ustrate the invention the method described above will be expl ained in closer detail with reference to the accompanying drawings. In the drawings, Fig.l shows a continuous-flow system wherein one or several fl uids (lb, Id, le) are separated from each other by means of gas bubb¬ les (lc ) in a capil lary tube. When a tube of this kind is treated with polypropylene glycol (If) the latter will deposit on the inner face of the capillary tube (la), thus reducing the surface tension without reaction with the fluid contained in the tube. Fig. 2 shows a capillary tube (2b) which is treated on its in- side face with polypropylene glycol (2a) in accordance with the teach¬ ings of the invention ' . Fig. 3 illustrates a capillary tube (3c) to which has been added polypropylene glycol (3a) to be mixed with another fluid (3b) in¬ side the tube. The result is that the surface tension is partially or completely abolished and for this reason intermixture with any further fluid (3d) which is added to the first solution (3b) is facilitated. Fig. 4 shows the sedimentation reaction of erythrocytes forming stacked-coin clusters and surrounded by polypropylene glycol (4d) which neutralizes the repellent forces existing between the erythrocytes and between the blood corpuscle column (4e) and the plasma column' (4f), creating a flat interface (4b) between the- sedimented erythrocytes and the plasma (4a) on top thereof. By adding polypropylene glycol (PPG) which is a solution of inert character, to capillary tubes (Fig. 2) or to the fluid contained in such tubes (Fig. 3) the solution will be prevented from penetrating into and damaging the blood corpuscles, thus avoiding haemolysis or, it w ll not mix with other solutions which are added to the blood and for this reason cross reactions will be prevented. Since polypropylene glycol also has surface-tension reducing properties the intermixture of blood with other fluids is improved and the use of mechanical mixing appliances may be avoided. The same results are achieved in continuous- -flow systems, when the tube is treated with polypropylene glycol or if polypropylene glycol is added to the fluids propelled inside a tube of this kind. Thus, less energy-consuming pumps may be used. Polypropylene glycol mixed with blood to which citrate has been added to effect the er throcyte sedimentation rate test (ESR) enhances the formation of the erythrocytes in "rouleaux formation" clusters and this is due to the polypropylene glycol neutralizing the repellent for¬ ces existing between the erythrocytes which aggregate in stacked-coin clusters and which are negatively charged by nature. Consequently, the formation into stacked coin clusters is facilitated. Considering that polypropylene glycol also is instrumental in reducing surface tension the interface between sedimented erythrocytes in the ESR column and the plasma becomes flat rather than concave and consequently reading fauls are avoided (Fig. 4). The invention 'belongs to the medical technical and analytical fields wherein capillary tubes are used for mixture or transport of blood and/or other fluids. Capillary tubes are used both for blood collection and for addition to the very same tube of a further fluid. The fluids are mixed with each other with the aid of a gas bubble and repeated turning-over of the capillary tube. However, because the inertia of intermixing is considerable, mechanical means must often be used to assist in the intermixing, which easily can cause damage to the erythrocytes of the blood. Also transport and propulsion of blood or other fluid in the lengthwise direction inside the capillary tube, such as is the case in e.g. continuous-flow systems, is both difficult and energy-consuming because of the strong surface tension present in such tubes. It there- fore becomes necessary to use liquid-propulsion mechanisms which easily could damage the erythrocytes. For this reason larger-bore capillary tubes are often used to reduce the surface tension. The purpose of the subject invention is to reduce the surface tension inside capillary tubes, thereby increasing the ability of blood and other fluids to intermix or increasing their movability therein without altering the character of either the blood or the other fluids. This problem is solved in that to the capillary tube or to the fluids contained in the tube is added- polypropylene glycol which redu- ces the surface tension and the electro-static forces. Fluids there¬ fore flow more easily through the tube and use much less energy while at the same time the intermixing is effected more rapidly and more efficiently. In analytical methods according to which fluids contained in a capillary tube are sedimented so that an interface is formed between the sediment and the layer on top, this interface wil l become fl at on account of the surface-tension reducing and the el ectrostatically repell ant effects of polypropylene glycol . In addition, the polypropy¬ lene glycol wil l act as a foam-reducing agent. The invention is pri arly intended for use within the medical technology and analytical field or in any other technology wherein capill ary tubes are used for mixing fluids insi de such tubes or to transport fl uids through such tubes without al teration of the character of the fluids, such as is the case in e.g. dispensing devices, through- -flow analytical devices, flow cuvettes, infusion or transfusion units or in capi llary analysis tubes for laboratory uses. The expert in the fiel d readily understands that the appl ica¬ tions referred to above may be varied in many ways within the scope of the appended cl aims.

Claims: C l a i s 1. A method of reducing the electrostatic forces e.g. the sur¬ face tension, in liquids or solutions in liquid phase, preferably blood and blood solutions, respectively, c h a r a c t e r z e d by the addition of polypropylene glycol H|θCH(CH3)CH2)nOH to the liquid or the solution. 2. The method as claimed in claim ^ c h a ra c t e r i¬ z e d therein that polypropylene glycol is added when blood is mixed with asolution designed to facilitate dispersion of the blood in said solution. 3. The method claimed in claim 1, c h a r a c t e r i z e d therein that polypropylene glycol is added to said liquid or said solu¬ tion to reduce the surface tension thereof when the liquid or the solu¬ tion is conducted through capillary tubes. 4. The method as claimed in claim 1, c h a r a ct e r i¬ z e d therein that in the performance of analyses involving sedimenta¬ tion of a liquid polypropylene glycol is added to reduce the repel! ant forces existing between the particles forming the sediment. 5. The method as claimed in claim 4, c h a r a c t e r i- z e d by adding polypropylene glycol to a solution containing red blood cells to neutralize the repel! ant forces existing between these cells and to facilitate the formation of rouleaux consisting of clus¬ tered red blood cells.

Inventors: FELE KARL, LINDBERG STELLAN, FELE, KARL, LINDBERG, STELLAN
Applicants: BIOLABIMEX AB
Application year: 1985
Main classification: G01N1
IPC codes: G01N1, G01N15, G01N33