Boronation of antibodies with mercaptoundecahydro-closo-dodecaborate(2-) anion for potential use in boron neutron capture therapy

Abstract

The anionic polyhedral borane derivative, mercaptoundecahydro-closo-dodecaborate(2-), has been evaluated as a boronating agent for antibodies. The objective of the studies was the selective delivery of boron to neoplasms for neutron capture therapy. Incubation of a large excess of this anion with the polyclonal antibody antithymocyte globulin (ATG) resulted in the incorporation of 9–13 mol of the anion per mol of antibody. The extent of boron incorporation into the protein was measured either by tritium-labeled B 12H 11SH 2− or by direct boron determination with neutron activation anlaysis. The nature of the covalent linkage of the anion to the antibody appeared to involve the formation of a new disulfide bond by a thiol-disulfide exchange. The number of boron atoms incorporated into antibodies by this method appeared to be inadequate for neutron capture therapy. However, such boronated antibodies may have potential for the detection of molecules of biologic interest by means of electron energy loss spectroscopy.