Polyelectrolyte Microcapsules for controlled cargo-release and sensing applications in living cells
Topic of the presented work is the preparation of multifunctional polymer microcapsules for biological and biomedical applications. The fabrication of such capsules is based on the layered adsorption of oppositely charged polymers, the so-called polyelectrolytes, onto charged templates (layer-by-lay...
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|Summary:||Topic of the presented work is the preparation of multifunctional polymer microcapsules for biological and biomedical applications. The fabrication of such capsules is based on the layered adsorption of oppositely charged polymers, the so-called polyelectrolytes, onto charged templates (layer-by-layer assembly). As spherical base for the capsules porous calcium carbonate particles have been used. In addition to molecules that were encapsulated into the final polymer capsules further properties such as fluorescence, paramagnetic behavior or the ability to convert light energy into heat were embedded into the polymer shell by implementing nanoparticles. These functional groups were crucial for the realization of the experimental demands on the microsystems. In addition to the functionalization of the shell an efficient filling of the capsules with a multitude of different molecules was one of the major developments. Besides a coprecipitation method (pre-filling of the templates), a post-loading technique as well as the enrichment of the capsules with amphiphilic polymer micelles were used for loading the capsules. This last approach even allowed for filling both, hydrophilic and hydrophobic molecules into the the polymer microcapsules. The prepared materials were observed via absorbance or fluorescence spectroscopy or electron- and optical microscopy, the capsules were tested specifically for their intended applications. Here, special emphasis was placed on the intracellular release of the encaged cargo materials. Numerous experiments were performed to test the release of the cargo molecules within living cells. The efficient release via external laser-triggered heating was proven and improved by variation of gold-nanoparticle concentration attached to the polymer shells. In addition, the released content distributed into the cells, was observed to react after its liberation. Reactive substances, which have been separately encapsulated could successfully be released intracellularly and the occurring reactions were detected. Furthermore, nucleic acid chains (mRNA) could be encapsulated and successfully be released within cells. The cellular production of the RNA-encoded proteins was demonstrated. Another aim of the study was the targeted delivery of capsules to a desired place. In a flow chaannel, the flow of blood in living organisms was simulated. Capsules modified with ironoxide nanoparticles could be deposited selectively on a cell layer with the help of magnetic field gradients. This enabled for deposition of capsules on a large scale area as well as on on small, sub-millimeter patterns. Additionally to the release of materials and controlled deposition of capsules, the presented work is also studying the possible use of microcapsules as sensors for the composition of the environmental solution. These sensor properties were tested on the basis of ion-selective fluorescent dyes in the extracellular as well as in the intracellular space. In summary, the presented polymer microcapsules were proven as an advanced and versatile approach towards bio-medical requirements for drug delivery and sensing applications.|