[Remote controlled drug release in the alimentary tract by local power deposition in alternating magnetic fields]. / Remote controlled drug release in the alimentary tract by local power deposition in alternating magnetic fields.

Remote controlled release of agents in the alimentary tract is an important task of gastroenterology and pharmacy. We investigated two different methods of drug release by heating locally restricted parts in medical capsules: hysteresis losses of magnetite powder and eddy current losses of metals in alternating magnetic fields. The comparison of our experimental results with theoretically derived expectations show that both methods are suitable techniques if special technical conditions are met. In order to demonstrate the feasibility of simple constructions, we used a gelatin capsule, consisting of two parts which were kept together by a belt of wax and a small copper coil. This capsule was placed in water and the belt was heated in an alternating magnetic field until melting and releasing a test fluid after about 60 s.

A novel method for real-time magnetic marker monitoring in the gastrointestinal tract.

In internal medicine, a simple method for the functional examination of the gastrointestinal tract without the risk of radiation exposure is required. We describe a novel principle based on the monitoring of magnetic markers which meets these demands. Our method employs a special permanent magnet which is repeatedly aligned by a vertically oriented pulsed magnetic field. Due to this alignment, the marker position can be derived from the stray field components measured by commercial field sensors. Our method was evaluated by means of a 3D intestinal phantom. The monitoring procedure yielded the time course of the marker position as a 3D plot either in real-time or as a time-lapse movie. The spatial resolution, expressed by the mean square deviation, was better than 10 mm and is thus sufficiently high to distinguish between adjacent loops of the gut. The temporal resolution, i.e. the minimum time between two successive measurements, was about 1 s. The presented method has very moderate technical demands and allows us to monitor magnetic markers in real-time. The technique may be useful with respect to functional examination of the gastrointestinal tract. In pharmaceutical research, our method offers the opportunity for remote drug release at any position of the gut.

Model experiments for immunomagnetic elimination of leukemic cells from human bone marrow. Presentation of a novel magnetic separation system.

Optimal conditions for removing leukemic cells from human bone marrow with monoclonal antibodies (mAb) and magnetic immunobeads were investigated. Monodisperse 3 microns polystyrene microspheres containing magnetite were coated with affinity-purified rabbit antimouse IgG at 4 degrees C, pH 9.6 for 18 h. SKW-3 cells (T-CLL cell line) were marked with the supravital DNA stain Hoechst 33342, seeded into normal human bone marrow, and then incubated with the mAb CD1, CD6, and CD8 at 4 degrees C for 30 min. In preliminary experiments REH cells (cALL cells) and mouse anti-REH cell antibodies were used to find the most favorable conditions for the binding of magnetic beads to tumor cells. Optimal formation of cell-bead rosettes was achieved by rotating beads and tumor cells together at room temperature at a concentration of 1 x 10(7) cells/ml, a bead: tumor cell ratio of 100:1 and an incubation time of one hour. The novel magnetic separation apparatus consists of three polystyrene chambers connected by silicone rubber tubing. The chambers contain four steel inserts each equipped with 32 nickel wires, which are magnetized by permanent magnets in such a way that the inhomogeneous high gradient magnetic field could be established within the cell suspension containing the cells to be depleted. The fluid flow was established by a peristaltic pump. At a flow rate of 1.5 ml/min and a field strength of 160 kA/m, no beads could be detected in the purged marrow. A cocktail of the three mAb was more effective than any single antibody in forming bead-cell rosettes. Two sequential purging cycles were superior to one. The marrow recovered was highly viable as assessed by trypan blue dye exclusion and by growth of CFU-GM.