Nanogel hybrid assembly for exosome intracellular delivery: effects on endocytosis and fusion by exosome surface polymer engineering

Surface polymer engineering was applied with a carrier of exosomes, namely, the amphiphilic cationic CHP (cCHP) nanogel, to improve the delivery of exosome content by forming complexes with the exosomes. Mouse macrophage cells were used to produce the exosomes, which were then mixed with the cCHP nanogel to form a hybrid. Transmission electron microscopy revealed that the surface of each exosome was coated with cCHP nanogel particles. Flow cytometry also showed a significant uptake of this exosome/nanogel hybrid by HeLa cells, with the main mechanism behind this internalization being endocytosis. A range of different molecules that inhibit different types of endocytosis were also applied to determine the particular pathway involved, with a caveolae-mediated endocytosis inhibitor being revealed to markedly affect the hybrid uptake. Next, we evaluated the fate of the internalized hybrid using fluorescent labeling, with the results suggesting fusion between endosomes and exosomes. Finally, revealing the functional efficacy of this approach, we showed that the nanogel system could successfully deliver functional exosomes into cells, as indicated by its ability to induce neuron-like differentiation in the recipient cells. Overall, our findings show the potential of using this hybrid nanocarrier system for transporting various contents in exosomes and ensuring their effective delivery in a functionally intact state.