Stimulus-Sensitive Theranostic Delivery Systems Based on Microcapsules Encoded with Quantum Dots and Magnetic Nanoparticles.

Fluorescent semiconductor nanocrystals, known as quantum dots (QDs), and magnetic nanoparticles (MNPs) are extensively studied perspective tools for optical (fluorescence) and magnetic resonance imaging techniques. The unique optical properties, high photostability, and bright luminescence of QDs make them more promising fluorophores than the classical organic dyes. Encoding polyelectrolyte microcapsules with QDs and MNPs ensures their sensitivity to both photoexcitation and magnetic field. This chapter presents the protocol for obtaining a stimulus-sensitive delivery system based on QD- and MNP-encoded polyelectrolyte microcapsules by means of layer-by-layer self-assembly. The resultant fluorescent magnetic polyelectrolyte microcapsules are 3.4-5.5 μm in size, have a hollow structure, and are brightly fluorescent to be detected with the standard imaging equipment. Polyelectrolyte microcapsule surface bears functional groups for subsequent functionalization with vector capture molecules. The polyelectrolyte microcapsules containing combination of QDs and MNPs are advanced visualization tools, since they can be sorted in a magnetic field and at the same time are suitable for fluorescent imaging what can be applied within a wide range of diagnostic and therapeutic protocols.