RESUMO
As an intermediate half-life positron emitter (86)Y is an attractive radioisotope for positron emission tomography (PET) studies, particularly for patient specific dosimetry planning of (90)Y-based radiotherapy procedures. It can be conveniently produced by a small-sized cyclotron via the (86)Sr(p,n)(86)Y nuclear reaction. The optimization of the electrochemical separation of (86)Y from the target material and its purification was done by modeling the whole production cycle using (90)Y. The radionuclide was isolated using four electrodes in two electrolytic steps. In the first step two Pt plate anodes and a Pt Winkler cathode were used and the electro-deposition yield was determined in constant current mode of operation. In addition, the influence of pH on the efficiency of this first step was investigated. The second electrolysis, with Winkler electrode as anode and a Pt wire as cathode, was also performed in constant current mode of operation. The kinetics of recovery of the deposited activity on the Pt wire was investigated in acidic solutions. The optimized electrochemical method was then applied for (86)Y separation and purification. This modified procedure was proved to be faster and simpler than the previously proposed electrochemical techniques and is more convenient for automation of the routine production of (86)Y.
RESUMO
We investigated the effects of the alpha-particle emitters (149)Tb and (213)Bi coupled to a tumor-specific antibody targeting the mutated delta 9 E-cadherin (d9 E-Cad) on single cells and cell pellets. The d9 mutation of the adhesion molecule E-cadherin is found in 10% of diffuse-type gastric cancers and is not expressed in normal tissue. Human breast cancer cells (MDA-MB-435S) transfected with d9 E-Cad or the wild-type E-cadherin gene were used to study the effects of anti-d9 E-Cad MAb coupled to (149)Tb and (213)Bi ((149)Tb-d9 MAb and (213)Bi-d9 MAb). The density of binding sites determined on transfected MDA tumor cells by Scatchard analysis and flow cytometry varied from 4 x 10(4) to 6 x 10(4) antigens per cell. Internalization of radioimmunoconjugates by cells expressing d9 E-Cad was less than 10% of bound antibody within 240 min. The effect of the radioimmunoconjugates on cell suspensions and cell pellets was quantified by [(3)H]thymidine incorporation, and the dose to the cell nuclei was determined using microdosimetric calculations. (149)Tb and (213)Bi immunoconjugates affected cells in suspension similarly. Significant differences in the proliferation capacity of d9 E-cadherin- and wild-type E-cadherin-expressing cells were observed at activity concentrations around 185 kBq/ml, corresponding to antibody concentrations between 200 ng/ml and 1000 ng/ml. Proliferation after incubation with (213)Bi-d9 MAb was 50% greater in pelleted wild-type E-Cad-expressing cells compared to wild-type E-Cad cells in suspension. In contrast, the proliferation of pelleted d9 E-Cad cells was similar to that of d9 E-Cad cells in suspension. For (149)Tb-d9 MAb, no significant difference was found between pelleted cells and cells in suspension for low activity concentrations. However, at high activity concentrations, (149)Tb-d9 MAb had only a small effect on pelleted cells. These in vitro studies demonstrate different effects of (149)Tb and (213)Bi conjugated to a tumor-specific antibody toward single cells and tumor cell pellets. Microdosimetric simulation of single cell survival after alpha-particle irradiation modeled the experimental results with reasonable accuracy.
