BackgroundDrug delivery systems (DDS) and their interaction with cells are a controversial topic in the development of therapeutic concepts and approaches. On one hand, DDS are very useful for protected and targeted transport of defined dosages of active agents. On the other hand, their physicochemical properties such as material, size, shape, charge, or stiffness have a huge impact on cellular uptake and intracellular processing. Additionally, even identical DDS can undergo a completely diverse interaction with different cell types. However, quite often in in vitro DDS/cell interaction experiments, those aspects are not considered and DDS and cells are randomly chosen.Methods and resultsHence, our investigations provide an insight into layer-by-layer designed microcarriers with modifications of only some of the most important parameters (surface charge, stiffness, and applied microcarrier/cell ratio) and their influence on cellular uptake and viability. We also considered the interaction of these differently equipped DDS with several cell types and investigated professional phagocytes (neutrophil granulocytes; macrophages) as well as non-professional phagocytes (epithelial cells) under comparable conditions. We found that even small modifications such as layer-by-layer (LbL)-microcarriers with positive or negative surface charge, or LbL-microcarriers with solid core or as hollow capsules but equipped with the same surface properties, show significant differences in interaction and viability, and several cell types react very differently to the offered DDS.ConclusionAs a consequence, the properties of the DDS have to be carefully chosen with respect to the addressed cell type with the aim to efficiently transport a desired agent.

Recent progress in DNA nanotechnology allows the fabrication of 3D structures that can be loaded with a large variety of molecular cargos and even be responsive to external stimuli. This makes the use of DNA nanostructures a promising approach for applications in nanomedicine and drug delivery. However, their low stability in the extra-and intracellular environment as well as low cellular uptake rates and release rates from endosomes into the cytoplasm hamper the efficient and targeted use of DNA nanostructures in medical applications. Here, such major obstacles are overcome by integrating DNA origami nanostructures into superordinated layer-by-layer based microparticles made from biopolymers. The modular assembly of the polymer layer allows a high-density incorporation of the DNA structures at different depth. This enables controllable protection of the DNA nanostructures over extended durations in a broad range of extra-and intracellular conditions without compromising the cell viability. Furthermore, by producing protein-complexed DNA nanostructures it is demonstrated that molecular cargo can be conveniently integrated into the developed hybrid system. This work provides the basis for a new multistage carrier system allowing for an efficient and protected transport of active agents inside responsive DNA nanostructures.

Nano- and microcarriers as vehicles for active agents are additionally equipped with specific agents to prevent endolysosomal acidification in order to support them to reach their target in a defined, specific, and protected way.

The efficient application of smart drug-delivery systems requires further improvement of their cellular uptake and in particular their release from endolysosomal compartments into the cytoplasm of target cells. The usage of virus proteins allows for such developments, as viruses have evolved efficient entry mechanisms into the cell, mediated by their fusion proteins. In our investigations, the transferability of the glycoprotein G which is a fusion protein of the vesicular stomatitis virus (VSV-G) onto the surface of a layer-by-layer (LbL) designed microcarrier was investigated. The assembly of VSV-G as a reversible viral fusion protein onto LbL microcarriers indeed induced an enhanced uptake rate on Vero cells as well as a fast and efficient release of the intact carriers from endolysosomes into the cytoplasm. Additionally, neither virus-associated effects on cellular viability nor activation of an interferon response were detected. Our study emphasizes the suitability of VSV-G as an efficient surface functionalization of drug-delivery systems.

Conventional therapies for chronic inflammation with high dose application of active agents are often accompanied with severe side effects so that other therapeutical strategies shall be developed to be less physically demanding but still highly efficient. Locally applied Layer‐by‐Layer (LbL) microcarriers transporting a low, but efficient dosage of active agents directly into the inflamed tissue offer a gentle therapy option. Here, the inhibition of highly degradative enzyme human neutrophile elastase (HNE) is adressed, which is produced and secreted by neutrophile granulocytes (PMNs) in the progress of inflammation. The protected transport and release of its natural inhibitor α1‐antitrypsin (AT) as a constituent of the microcarrier's biopolymer multilayer allows for an efficient inhibition of extra‐ and intracellular elastase. The HOCl scavenger molecule cefoperazone, which preserves AT activity, as an additional multilayer constituent induces a much higher efficacy of the inhibitor. The successful assembly of both agents in different layers of the multilayer and the subsequent HNE inhibition in PMNs is investigated. The parallel application of cefoperazone leads to an enhanced inhibitory effect even with reduced AT amount and reduced carrier:cell ratio. It is demonstrated that the modular assembly strategy of LbL carriers allows for efficient synergistic effect of active agents in inflammatory process.