Vertical Reaction Vessel

The invention relates to mechanical structures for vertical reaction vessels. More specifically, the invention relates to apparatus and methods for uniformly distributing fluid through a reaction vessel and for maintaining the viability of a reaction medium contained in the reaction vessel.

The advance of medical technology has permitted the development of monoclonal antibodies which have been designed with a high degree of affinity for specific cell tissue. These antibodies can be conjugated ("tagged") with radioactive isotopes for the visualization of tissues for which the antibodies are specific. For example, cancer tissue-specific monoclonal antibodies can be conjugated with radioactive isotopes to facilitate imaging of soft tissue turmors which would otherwise be difficult to image with conventional X-ray techniques. In addition, these antibodies can be tagged with radioactive material for the treatment of cancer. This form of chemotherapy is advantageous in that the radioactive material is delivered directly to the site of the tumor through the bloodstream.

Prior to introduction of the above-described site-specific medicine into the human body, the conjugated antibody must be isolated from a reaction solution containing: the desired antibody conjugated with the radioactive material; unbound antibody; unbound radioactive material; and other impurities. Each of these items (other than the desired conjugated antibody) exists as ions in the solution. Thus, the desired, conjugated antibody is typically isolated by passing the reaction solution through an ion-exchange column.

A conventional, prior art, ion-exchange column is identified by reference numeral 10 in FIG. 2. The ion-exchange column has a fluid inlet 12 for introduction of the reaction solution from which the conjugated antibody is to be isolated. The isolated, conjugated antibody exits the ion-exchange column through a fluid outlet 14. The ion-exchange column contains an ion-exchange resin 16 which has an affinity for the anionic, unconjugated radioactive material so as to retain this undesirable material in the ion-exchange column while allowing the uncharged, conjugated antibody to pass therethrough. During this process, other, undesirable anions are retained in the column (during this reaction, the ion-exchange resin gives up a harmless anion, such as chlorine, which exits the fluid outlet 14 with the isolated, conjugated antibody).

The ion-exchange resin 16 typically comprises a polymer material which binds quaternary amino ethyl crystals (such as QAE-Sephadex) together. Prior to introduction of the reaction solution into the fluid inlet 12, the ion-exchange resin 16 is hydrated with a buffer solution. The buffer solution maintains a relatively narrow pH range within the ion-exchange column during passage of the reaction solution therethrough.

Without the buffer solution, the ion-exchange resin was the consistency of a tacky powder. Upon introduction of the buffer solution into the fluid inlet 12, the ion-exchange resin assumes the consistency of a slurry. To prevent the partially liquefied ion-exchange resin from passing through the fluid outlet 14 during operation of the column, and to prevent the tacky, unhydrated ion-exchange resin from falling out the fluid inlet 12 during storage of the ion-exchange column, hard fibrous inserts or "frits" 18, 20 are positioned adjacent to the fluid inlet 12 and fluid outlet 14, respectively.

The insert 20 adjacent to the outlet 14 also traps fine particles which result from degradation of the ion-exchange resin itself. The ion-exchange resin is in the form of a crystalline solid before hydration, and is in the form of a crystalline solid in solution when hydrated. The solid particles of the ion-exchange resin are relatively fragile and swell or contract by osmotic action according to the pH of the buffer solution introduced through the fluid inlet 12. It is highly desirable for all of the solution entering the fluid inlet 12 to fully contact the ion-exchange resin 16 before leaving the fluid outlet 14. Therefore, the ion-exchange resin is relatively tightly packed into the ion-exchange column between the hard inserts 18,20 to minimize the formation of voids and fluid channels in the reaction medium during operation of the ion-exchange column. As a consequence of this tight packaging and the repeated expansion of the crystals against the hard inserts 18, 20, the crystals begin to fracture and form fine particles ("fines"). These "fines" are trapped in the insert 20 and do not exit the fluid outlet 14. The insert 20 may eventually become clogged with these fine particles diminishing the efficacy of the column even though the ion exchange medium remains functional. In addition, undesirable voids are formed in the ion exchange resin when the resin contracts. Therefore, a need exists for a vertical reaction vessel which can accommodate volumetric changes of an ion-exchange resin contained therein.

In addition to the inability of the prior art ion-exchange column to compensate for volumetric changes in the ion-exchange resin, fluid flow distribution irregularities are associated with this device. As shown in FIG. 2, the fluid inlet 12 and fluid outlet 14 are provided with conventional Luer locks 22 and 24, respectively, having internal diameters 26, 28 which are limited by the outer diameter of a standard Luer lock. The diameter 30 and length 32 of a reaction chamber 34 containing the ion-exchange resin 16 are determined by the desired flow rate of the reaction solution through the ion-exchange column.

As is often the case, the diameter 30 of the reaction chamber 34 is significantly larger than the inner diameters 26, 28 of the fluid inlet and outlet to accommodate a desired flow rate through the ion-exchange resin 16. The reaction solution tends to form a conical fluid distribution 36, as shown in FIG. 2, which does not provide a desired, uniform fluid flow across the entire cross-sectional area of the reaction chamber. A uniform fluid flow is necessary to provide a uniform exposure for all of the reaction fluid flowing through the column. In the conical distribution 36 shown in FIG. 2, the fluid on the outside of the conical distribution has a longer travel path through the ion-exchange resin 16 and a greater period of exposure to the ion-exchange resin than does fluid passing through the center of the distribution. In addition, circled areas 38 and 40 of the ion-exchange resin receive little, if any, fluid flow and thus do not react with the reaction solution. Therefore, a need exists for a vertical reaction vessel which promotes a uniform fluid flow throughout the entire cross section of the ion-exchange resin.

It is an object of the present invention to provide a vertical reaction vessel which accommodates volumetric changes in a reaction medium contained in a reaction chamber.

It is also an object of the present invention to achieve the above object while providing for a uniform fluid flow through the reaction chamber.

The invention achieves these objects, and other objects and advantages which will become apparent from the description which follows, by providing a vertical reaction vessel with manifold distribution chambers above and below the reaction medium and resilient inserts which expand and contract to accommodate volumetric changes in the reaction medium.

A preferred embodiment of the invention includes an ion-exchange column having a body which partially confines a reaction medium in a reaction chamber. The body has a fluid inlet and a fluid outlet substantially smaller in cross-sectional area than the reaction chamber. Adjacent to the fluid inlet and fluid outlet are manifold fluid distribution chambers which distribute fluid from the fluid inlet and to the fluid outlet throughout the entire cross section of the reaction chamber. Resilient membranes, adjacent to the manifold fluid distribution chambers, prevent the reaction medium from exiting the body through either the fluid inlet or fluid outlet. The resilient membranes expand when hydrated and have sufficient reserve expansion capacity to fill up any gaps or voids which form when the reaction medium contracts. The resilient membranes also have sufficient resiliency to cushion the reaction medium when the reaction medium expands.

The invention also comprises a method for compensating for volumetric changes in a reaction medium and a method for distributing a solution across the entire cross-sectional area of a reaction medium.

FIG. 1 is a sectional, elevational view of an ion-exchange column employing the manifold distribution chambers and resilient membranes of the present invention.

FIG. 2 is a partial, sectional, elevational view of a prior art ion-exchange column.

FIGS. 3a through 3c are schematic representations of the resilient membranes of the present invention. FIG. 3a shows the thickness of the membrane when unhydrated. FIG. 3b shows the thickness of the membrane when hydrated. FIG. 3c shows the hydrated thickness of the resilient membrane when positioned between the fluid distribution manifold and the ion-exchange resin in the ion-exchange column.

FIG. 4 is a sectional view taken along line 4--4 of FIG. 1.

FIG. 5 is an enlarged, sectional, isometric view of the manifold distribution chamber adjacent to the inlet.

FIG. 6 is an enlarged, sectional, elevational view of the inlet end of the ion-exchange column.

A preferred embodiment of an ion-exchange column in accordance with the present invention is generally indicated at reference numeral 50 in FIG. 1. The column has a hollow cylindrical body 52 which defines a receptacle 54 for a reaction medium 56. The column has a fluid inlet 58 and a fluid outlet 60 at opposing ends thereof. The fluid inlet and fluid outlet have female 62 and male 64 Luer locks of the conventional design.

The reaction medium 56 can be any type of reaction medium. However, the preferred embodiment of the invention is most advantageously designed for use with an ion-exchange medium, such as quaternary amino ethyl Sephadex (QAE-Sephadex) or a diethyl aminoethyl Sephadex (DEAE-Sephadex) electrolyte. These materials have the consistency of tacky crystals when dry and of a slurry when hydrated with a buffer solution. This reaction medium is effective in removing electrically charged impurities from a reaction solution (e.g., sodium pertechnetate, technetium dioxide and the hydrolyzed--i.e., carboxylate--form of chelate). All of these impurities exist as anions and are retained on the positively charged (cation) quaternary of the ion-exchange column. The anion of the reaction medium is then expelled through the fluid outlet with any uncharged material, which is thereby isolated from the reaction solution.

As shown in FIG. 1, a reaction solution containing an electrically neutral antibody conjugate of interest and the negatively charged impurities is introduced into the fluid inlet 58 by a syringe 70. Prior to introduction of the reaction fluid into the ion-exchange column 50, a buffer solution is introduced into the reaction medium 56 through the fluid inlet 58 to hydrolyze the reaction medium. As is well known, the individual crystals of the reaction medium expand or contract through osmotic action according to the pH of the buffer solution. To prevent the crystals from fracturing and to prevent the reaction medium from falling out through the fluid inlet and fluid outlets when the reaction medium is dry, resilient membranes 76, 78 are positioned adjacent inlet and outlet ends 80, 82 containing the reaction medium therebetween.

As shown in FIG. 3a, the reaction medium has an unhydrolyzed thickness of approximately 0.090 inch. When hydrolyzed, such as with a buffer solution, the medium will expand to a thickness of approximately 0.150 inch, if unrestrained. As shown in FIGS. 3c and 5, the reaction medium is, however, constrained between radially extending fins 90 and the reaction medium 56 so that in areas 92 between the fins the resilient membrane 76 expands to a thickness of approximately 0.110 inch. At the position of the fins 90, the resilient membrane is compressed to a lesser thickness. Thus, the resilient membrane has the capacity to expand towards the reaction medium a distance of approximately 0.040 inch at either end of the reaction chamber 54 to compensate for contraction of the ion-exchange resin if the pH of the buffer solution is relatively large. Conversely, the resilient membranes have the capability to compress approximately 0.020 inch at each end of the reaction chamber when the ion-exchange resin 16 expands if the pH of the buffer solution is low. Thus, fragmentation of the reaction medium is avoided and formation of fines which would tend to clog the resilient membrane 78 near the outlet end 82 of the ion-exchange column, is discouraged.

The resilient nature of the resilient membranes 76,78 is also effective in providing a radial seating force against the receptacle 54 which holds the membranes in place during wet sterilization procedure.

The fluid inlet 58 and fluid outlet 60 have respective inner diameters 84, 86 which are limited by the standard outer dimensions of the conventional Luer locks. The reaction receptacle 54 has a substantially constant diameter which is significantly larger than these inner diameters so as to provide a satisfactory flow rate of reaction solution through the ion-exchange column. A flow rate of 10 milliliters solution per minute is considered acceptable.

To promote a uniform distribution of fluid from the fluid inlet to the fluid outlet across the entire cross section of the reaction medium, the inlet and outlet ends 80, 82 of the ion-exchange column are provided with the radially extending fins 90. As shown in FIGS. 5 and 6, the fins cooperate with the resilient membrane 76, 78 to form manifold distribution chambers for the reaction fluid.

The resilient membranes 76, 78 provide a relatively high resistance to fluid flow in the direction of the axis 100 of the ion-exchange column 50. As shown in FIGS. 4 and 5, the fins 90 extend radially from the fluid inlet 58 and fluid outlet 60 and have a height 110 sufficient to provide a gap 112 between ends of the reaction chambers 80, 82 and the resilient membranes 76, 78 so as to form radial fluid passageways therebetween. These passageways extend from the fluid inlet to the perimeter of the reaction chamber at the inlet end of the ion-exchange column, and from the perimeter of the reaction chamber to the fluid outlet at the outlet end of the ion-exchange column. The fluid passageways have a relatively low resistance to fluid flow in the radial direction as compared to fluid flow through the resilient membranes in the axial direction. Thus, the passageways cooperate with the resilient membranes to act as fluid distribution manifolds. The manifold adjacent the inlet end 80 of the ion-exchange column 50 distributes fluid evenly across the entire cross section of the reaction chamber when the reaction fluid enters the fluid inlet. The manifold adjacent to the outlet end 82 of the ion-exchange column collects fluid from the entire cross section of the reaction chamber before the fluid exits the fluid outlet.

Any suitably porous, resilient membrane exhibiting the characteristics shown in FIGS. 3a through 3c is suitable for use as the resilient membranes 76, 78 in the ion-exchange column 50 of the present invention. The preferred material is a rolled and pressed cellulose depth filter; and appropriate item is grade 01AP cellulose manufactured by Cuno, Inc., Meriden, Conn.

Other versions and embodiments of the invention are contemplated. For example, as shown in FIG. 5, the fluid passageways generally indicated at reference numeral 114 are defined by the radial pattern of the fins 90 and the swollen shape of the resilient membrane 76. Other fluid passageway shapes are possible which can also achieve uniform fluid distribution over the cross-sectional area of the reaction chamber. Therefore, the invention is not to be limited by the above description but is to be determined in scope by the claims which follow.