Development of Nanoflare Nanosensors for Monitoring Cellular Insulin mRNA in Beta Cells and Islets

This article introduces the development of Nanoflare (NF) nanosensors for detecting and monitoring cellular insulin mRNA in the culturing of beta cells and islets. These probes are designed using the classic spherical nucleic acid (SNA) technology, consisting of densely packed and highly oriented oligonucleotide sequences on gold nanoparticles. Each oligonucleotide is hybridized to a flare strand bearing a distinct fluorophore label, with all sequences complementary to the target strand. We designed the recognition strand targeting insulin mRNA (Ins2, the ortholog of the human insulin gene). When the target strand is introduced, the fluorescence intensity of the In2-NF solution increases more than 24-fold. A linear correlation was observed between the fluorescence signal and the concentration of the target strand in the range of 0.01–0.1 µm (R² = 0.9997). Finally, the In2-NF sensors were applied to monitor the cellular expression of insulin mRNA in MIN6 cells (2D culture), MIN6 cell spheroids (3D culture), and rat islets. In the MIN6 cell experiment, NF signals were also correlated with qPCR results. All the results suggest that SNA-based In2-NFs are capable of optical detection of intracellular insulin mRNA.