Layer-by-Layer-Assembled Capsule Size Affects the Efficiency of Packaging and Delivery of Different Genetic Cargo

The lack of an efficient and versatile intracellular nucleic acids delivery platform impedes the clinical implementation of gene therapy. Advances in layer-by-layer (LbL) technology have led to the production of LbL polymer capsules, a promising universal delivery tool. The biocompatibility, sufficient packaging capacity, safety, low cost, and high variability of structure and composition of the LbL capsules make it possible to meet the requirements for clinical-grade nonviral gene transfer. Here, the possibility of polymeric LbL capsules of different sizes (micrometer and sub-micrometer-sized) to serve as universal nonviral carriers for messenger RNA (mRNA) and small interfering RNA (siRNA) is considered. In particular, the internalization of capsules into human mesenchymal stem cells (hMSCs, as an example of adult primary stem cells), capsule uptake, and intracellular delivery of mRNA and siRNA is studied. Importantly, the use of micrometer- or sub-micrometer-sized polymer capsules (MicCaps and SubCaps) allows the mRNA or siRNA to be packaged and transferred into hMSCs with high efficiency. While the uptake efficiency is comparable between MicCaps and SubCaps, the latter are significantly more efficient than MicCap when transferring siRNAs. These results demonstrate the potential of the LbL capsules as a universal gene delivery platform, which can be tuned according to the properties of genetic cargo.