Evaluation of respiratory and secretory activities of multicellular spheroids via electrochemiluminescence imaging

Multicellular spheroids are considered biologically and pathophysiologically relevant models in modern in vitro studies; therefore, monitoring their cellular activities is highly significant in both fundamental and translational research. However, only a few analytical techniques enable the tracking of the activities of spheroids without labeling. Electrochemiluminescence (ECL) is a luminescence generated under an electrochemical reaction on an electrode; hence, it can potentially display adhesive molecules, which hinder the electrochemical reaction, on the electrode. Here we report an ECL system that can display the secreted molecules of spheroids that adhere to the electrode. In this study, the electrode, after the removal of the spheroid, was particularly investigated. The cellular membrane components and secreted molecules from a single spheroid were observed to adhere either firmly or softly on the electrode and displayed a strong or weak hindrance of the ECL, respectively. These negative imprints of the ECL corresponded to the viability of spheroids and could be utilized to evaluate their cellular activity. Finally, using this system, the unique alteration of cellular activity (respiratory and secretory) of a spheroid upon treatment with rotenone, a common respiratory activity inhibitor, was tracked. We believe this method may offer facile imaging for the evaluation of the secretory activity of multicellular spheroids.

Automated summary

Multicellular spheroids are important models in vitro for studying biological and pathological processes. Monitoring their cellular activities without labeling is challenging, but electrochemiluminescence (ECL) has the potential to track the activities of spheroids by displaying secreted molecules adhering to an electrode.