Patent Number: 055641040
Section: summary

FIELD OF THE INVENTION This invention relates to the processing of liquid radioactive waste containing radioactively labeled biological molecules. More specifically, this invention relates to the use of solid phase binders to remove radioactively labeled biological molecules from liquid radioactive waste solutions. BACKGROUND OF THE INVENTION There is widespread use of radioactively labeled biological molecules in research, medicine, industry and for environmental testing. For example, a variety of assays employing radiolabled biological molecules are used in biological research and medicine. For instance, there are many different types of immunoassays used in clinical laboratories and in research. There are also a many clinical assays and research procedures using radioactively labeled nucleic acids. A number of different isotopes are used in these different applications including .sup.14 C, .sup.3 H, .sup.125 I, .sup.131 I, .sup.32 P and .sup.57 Co. Many of the assays using radioactively labeled biological molecules generate relatively large volumes of low level radioactive waste, which then become a disposal problem. For example, in a typical radioimmunoassay procedure, small amounts of radioactively-labeled material are dispersed into liters of aqueous or organic solutions. These solutions often contain relatively low levels of radioactivity, but nonetheless must be disposed of as radioactive waste according to federal and state regulations. Disposal of large volumes of low level radioactive liquid waste generated by radioimmunoassays and other procedures is particularly expensive and difficult. Transportation of radioactive waste materials to federal waste disposal sites has become increasingly difficult and expensive. Disposal of low level liquid radioactive waste by transportation to radioactive waste disposal sites is also an inefficient use of space at these sites. Therefore, most institutions try to reduce or eliminate disposal of radioactive waste by this method. An additional method of radioactive waste disposal involves storing the radioactive waste material on site until the material is no longer radioactive. Fortunately, some of the most commonly used radioisotopes, such as .sup.125 I and .sup.57 Co, have relatively short halflives. Because of this, some institutions store radioactive waste containing such isotopes until the waste is no longer radioactive, and then dispose of the waste as nonradioactive material. However, it is difficult to store large volumes of low level radioactive liquid waste for a period of months or years. There is a need for methods to remove the radioactively labeled biological molecules in concentrated form from liquid radioactive waste solutions. If this can be accomplished, the concentrated radioactively labeled biological molecules can then more feasibly be stored on site until the radioactivity decays and the waste becomes nonradioactive. Alternatively, the amount of radioactive waste material that must be transported to a radioactive waste disposal site can be dramatically reduced. In either case, the expense associated with liquid radioactive waste disposal can be markedly decreased. SUMMARY OF THE INVENTION This invention provides for methods of removing radioactively labeled biological molecules from liquid radioactive waste solutions. The liquid radioactive waste solution is contacted with a solid phase binder to form a solid phase binder:radioactively labeled biological molecule complex, which is then separated from the liquid radioactive waste solution. The radioactively labeled biological molecule can be labeled with a gamma emitting radioisotope such as .sup.125 I or .sup.57 Co. Examples of .sup.125 I-labeled biological molecules include .sup.125 I thyroxine and .sup.125 I folate. .sup.57 Co vitamin B12 is an example of a .sup.57 Co-labeled biological molecule. More than one radioactively labeled biological molecule can be removed from a liquid radioactive waste solution, by more than one solid phase binder. A variety of different solid phase binders can be added to a liquid radioactive waste solution to form the solid phase binder:radioactively labeled biological molecule complex. For example, the solid phase binder can be a solid phase adsorbent, such as talc, glass wool, glass beads or a charcoal adsorbent. As an additional example, the solid phase binder can be a solid phase immunochemical binder. Preferably, the solid phase immunochemical binder is an antibody attached to a solid phase. An antibody in liquid phase can be added to a liquid radioactive waste solution to bind to a radioactively labeled biological molecule. The liquid phase antibody is then bound by a solid phase immunochemical binder to form the solid phase binder:radioactively labeled biological molecule complex. The solid phase binder:radioactively labeled biological molecule complex can be removed from the liquid radioactive waste solution in a variety of ways. For example, the solid phase binder can be present in a column and the liquid radioactive waste solution can be passed through the column. The solid phase binder in the column can be, for example, a mixture of celite and charcoal or a polymer resin containing adsorbent particles, such as adsorbent charcoal particles. The column solid phase binder can also be an immunochemical binder, such an antibody attached to a glass bead. This invention further provides for methods of removing radioactively labeled biological molecules from liquid radioactive waste solutions by contacting a magnetizable particle binder with a liquid radioactive waste solution to form a magnetizable particle binder:radioactively labeled biological molecule complex. The complex is then separated from the liquid radioactive waste solution. For instance, the magnetizable particle binder can be adsorbent particles, such as charcoal adsorbent particles, attached to a magnetizable polymer, such as a magnetizable polyacrylamide gel. For example, charcoal particles can be entrapped in a magnetizable polyacrylamide gel to form a magnetizable particle binder. This magnetizable particle binder can be used, for example, to remove .sup.125 I folate and .sup.57 Co vitamin B12 from a liquid radioactive waste solution. The magnetizable particle binder can also be, for example, a magnetizable particle immunochemical binder, such as an antibody attached to a magnetizable polymer. An antibody in liquid phase can also be added to a liquid radioactive waste solution to bind to a radioactively labeled biological molecule. The liquid phase antibody is then bound by a magnetizable particle immunochemical binder to form the magnetizable particle binder:radioactively labeled biological molecule complex. For example, a mouse antithyroxine antibody can be added in liquid phase to a liquid radioactive waste solution to bind .sup.125 I thyroxine. The liquid phase antibody is then bound with a magnetizable particle binder containing a sheep antimouse antibody, in order to remove the .sup.125 I thyroxine from the liquid radioactive waste solution.