In vitro and in vivo visualization and trapping of fluorescent magnetic microcapsules in a blood stream
At last few decades polyelectrolyte microcapsules were shown as promising candidates for targeted delivery and remote controlled release of encapsulated drugs. The main benefits of polyelectrolyte microcapsules comparing to other delivery systems are high loading capacity and adjustability of physical and chemical properties. Typical capsules size is in a micrometer range that allows an effective loading of various compounds in capsules cavity. Capsules are prepared by stepwise deposition of charged species so that different polymers and inorganic nanoparticles can be used as building blocks bringing the functional properties and responsibility to external stimuli. However, to put into practice the capsules as a targeted delivery system one should realize their behavior in a body and have the ability to localize the capsules in the desired area. A number of publications shows that incorporation of magnetic nanoparticles into capsules shell makes them sensitive to external magnetic field. From this point, the non-uniform magnetic field seems to be perspective for accumulation of magnetic microcapsules, for instance, injected in a blood vessel feeding a tumor. Thus, it is essential to design the capsules so as to distinguish them from the whole blood environment as well as to be able to trap them via gradient of magnetic field.
In this work we would like to report about our results on in vitro and in vivo trapping of fluorescent magnetic microcapsules in a whole blood stream. The first part of this work was devoted to optimization of capsules composition in order to detect florescence in a blood. Afterwards, we designed an experimental setup combining a microscope, laser, fluorescent camera and electromagnet. This setup allowed to carry out the realtime observation of the capsules in a blood stream. The next step was in vitro trapping of the capsules moving in a blood stream through an artificial glass vessel (Figure 1). Finally, we trapped the capsules in vivo in a rat mesentery blood vessel. We found out that the capsules can be effectively stopped by non-uniform magnetic field applied upstream from the injection place (Figure 2). We believe, that this approach is perspective for development of targeted delivery systems and can be promising for further cancer therapy.
Figure 1. In vitro trapping of fluorescent magnetic microcapsules in a whole blood stream in a glass vessel.
Figure 2. Image of rat mesentery blood vessel in a blue-LED light (1,56 W) before microcapsules injection (a); Fluorescent image of blood vessel with microcapsules trapped by magnetic field. The fluorescence was excited by green 532 nm laser (20 mW) (b); Merged image of the blood vessel with the trapped microcapsules in a blue (LED) and green (laser) light (c).