In this review we provide an overview of the recent progress in designing composite polymer capsules based on the Layer-by-Layer (LbL) technology demonstrated so far in material science, focusing on their potential applications in medicine, drug delivery and catalysis. The benefits and limits of current systems are discussed and the perspectives on emerging strategies for designing novel classes of therapeutic vehicles are highlighted.

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Release me: polyelectrolyte capsules with different cargo in their cavities and plasmonic and magnetic nanoparticles in their walls were synthesized. Enzymatic reactions were triggered inside cells by light-mediated opening of two individual capsules containing either an enzyme or its substrate, by using photothermal heating. Furthermore, this technique allows controlled release of mRNA from capsules, thereby resulting in synthesis of green fluorescent protein (GFP).

Multiplexed detection of analytes is a challenge for numerous medical and biochemical applications. Many fluorescent particulate devices are being developed as ratiometric optical sensors to measure the concentration of intracellular analytes. The response of these sensors is based on changes of the emission intensity of analyte-sensitive probes, entrapped into the carrier system, which depends on the concentration of a specific analyte. However, there are a series of technical limits that prevent their use for quantitative detection of several analytes in parallel (e.g., emission crosstalk between different sensor molecules). Here we demonstrate that double-wall barcoded sensor capsules can be used for multiplexed analysis of proton, sodium, and potassium ions. The sensor detection methodology is based on porous microcapsules which carry ion-sensitive probes in their inner cavity for ion detection and a unique QD barcode in their outermost wall as tag for identification of individual sensors. The engineering of QD barcodes to capsules walls represents a promising strategy for optical multianalyte determination.

Degradable and light-addressable silica capsules have been prepared on the basis of CaCO 3 template particles. It was possible to load these capsules with an array of molecules such as anticancer drugs (doxorubicin), proteins (bovine serum albumin), and nucleic acids (mRNA encoding green fluorescent protein). In vitro degradation and release of these molecules was demonstrated and quantitatively compared with several kinds of polyelectrolyte multilayer capsules as examples of other delivery vehicles. The data suggests hydrolysis as a mechanism involved in intracellular degradation of silica capsules. Photothermal heating (by integrating plasmonic nanoparticles in the silica shell) was further used to induce remote molecular release.