In nature there are various specific reactions for which highly selective detection or support is required to preserve their bio-specificity or/and functionality. In this respect, mimics of cell membranes and bio-compartments are essential for developing tailored applications in therapeutic diagnostics. Being inspired by nature, we present here biomimetic nanocompartments with ion-selective membrane permeability engineered by insertion of ionomycin into polymersomes with sizes less than 250 nm. As a marker to assess the proper insertion and functionality of ionomycin inside the synthetic membrane, we used a Ca²⁺-sensitive dye encapsulated inside the polymersome cavity prior to inserting the biopore. The calcium sensitive dye, ionomycin, and Ca²⁺ did not influence the architecture and the size of polymersomes. Successful ionomycin functionality inside the synthetic membrane with a thickness of 10.7 nm was established by a combination of fluorescence spectroscopy and stopped-flow spectroscopy. Polymersomes equipped with ion selective membranes are ideal candidates for the development of medical applications, such as cellular ion nanosensors or nanoreactors in which ion exchange is required to support in situ reactions.

A promising approach for addressing a range of diseases lies in the delivery of functional biomacromolecules such as nucleic acids or proteins to cells. Polymers, peptides and the different shapes accessible through self-assembly of polymeric and peptidic amphiphiles have been widely explored as carriers and as containers for reactions on the nanoscale. These building blocks are particularly interesting, because several essential parameters such as physical characteristics, conditions for degradation or biocompatibility can be tuned to suit specific requirements. In this review, different three-dimensional architectures ranging from dendrimers and hyperbranched molecules to micelles, vesicles and nanoparticles assembled from synthetic polymers and peptides are discussed. It is focused on their function as a carrier for biologically active macromolecules, highlighting seminal examples from the current literature and pointing out the remaining and upcoming challenges in this important area of research.