Intracellular controlled release of molecular beacon prolongs the time period of mRNA visualization.

The objective of this study is to prepare cationized gelatin nanospheres (cGNS) incorporating molecular beacon (MB) and a cationized gelatin-MB complex, and evaluate the time period of mRNA visualization. The cGNS with different degradabilities were prepared to incorporate MB. There was no difference in the apparent size and zeta potential between the cGNS incorporating MB and the complex, while the MB release from the complex was faster than that from the cGNS. When mouse mesenchymal stem cells were incubated with the complex and cGNS, the amount of MB internalized into cells and cytotoxicity of complex was higher than those of cGNS. However, in the amount range of non-cytotoxicity, the amount of MB internalized was at a similar level among them. The intracellular fluorescence of cGNS was observed over 14 days, whereas that of complex disappeared within 5 days. Moreover, the time period of cGNS remaining in the cells prolonged with the increase of glutaraldehyde amount used in cGNS preparation. As the result, it is likely that the intracellular fluorescence was retained at a high level for longer time periods. It is concluded that the intracellular controlled release of MB is a promising to achieve the long-term and continuous visualization of mRNA.