Study of a miniaturizable system for optical sensing application to human cells

Conventional approaches to human intracellular optical sensing, generally, require dedicated laboratories with bulky detection systems. They are performed by cell labeling procedures based on the use of fluorophores that are, mostly, phototoxic, invasive, bleached in case of prolonged light exposures, which require carriers and/or structural modifications for the cellular uptake. These issues, together with the sensitivity of the eukaryotic cell model, could be problematic towards the development of a robust sensing system suitable for biomedical screening. In this work, we studied a sensing system resulting from the combination of the commercial tris(2,2'bipyridyl)ruthenium(II) fluorophore, for cell labeling, with a potentially miniaturizable optical system composed by a laser source and a photomultiplier tube, for the fluorescence analysis. We used the human dermal fibroblasts (HDF) as a cell model for the characterization of the proposed approach together with MTT assays, to validate the cells viability after treatments, and fluorescence and confocal laser scanning microscopy, to confirm the labeling. We investigated the versatility of this carrier-free labeling method with other cell models by using human colon adenocarcinoma (LoVo) cells, performing the cellular uptake and testing the cytotoxicity of Ru(bpy) 32+ , as a possible application in biomedical diagnostics.