Enhanced cytoplasmic release of drug delivery systems: chloroquine as a multilayer and template constituent of layer-by-layer microcarriers.

Nano- and microcarriers as vehicles for active agents are applied to support them to reach their target in a defined, specific, and protected way. This implies not only a safe transport of agents towards the desired cell type or tissue but also the intracellular processing of the carrier: in particular, release of the incorporated carriers into the cytoplasm is a prerequisite for the successful subsequent delivery of most active agents and is often impeded by endolysosomal degenerative enzymes. We address this issue by using the layer-by-layer strategy of carrier assembly offering the opportunity to independently integrate and carry active agents but also specific agents preventing endolysosomal acidification. The weak base chloroquine (CQ) was investigated as a multilayer, template and capsule constituent regarding its ability to delay endolysosomal acidification and prolong the tolerable time frame in endolysosomes, which allows the carrier to finally escape into the cytoplasm. As a model and reporter active agent, plasmid encoding enhanced green fluorescent protein was used as a multilayer-assembly component to illustrate the cytoplasmic release of the intact carrier by final expression of the green fluorescent protein. Integrating CQ into the carrier, GFP expression could be strongly increased and a transfection efficiency of up to 20% could be obtained. This represents a very high transfection rate for a drug delivery system reached by only one additional reagent that has no further influence on the activity of the transported drug and cell viability, offering a significantly enhanced delivery efficiency.