Nanometre-sized materials are widely used in biomedicine for applications including fluorescent probes as in vitro and in vivo bimolecular tags, drug carriers and contrast agents. In particular, recent research has highlighted the possibility of using mesoporous silica nanoparticles loaded with fluorescent chemicals as optically efficient alternatives to fluorescent dyes for in vivo medical diagnostic applications.

Traditional cell imaging technologies utilize organic fluorophores, which have drawbacks due to their non-specific accumulation inside cells and the photobleaching of the dyes.

Now, researchers at the Bio-Nano Electronics Research Centre at Toyo University, Japan, report that highly photostable silica nanoparticles loaded with the fluorescent tracer, FITC (fluorescein isothiocyanate) act as efficient cell labels for so-called theragnostic applications, where the nanomaterials are used for both the diagnosis and treatment of diseases such as cancer.

The researchers produced silica nanoparticles of 30 nm~100 nm in diameter and loaded them with fluorescein dye emitting green light by template-directed synthesis and oil in water microemulsion. Experiments focused on the effect of silica particle size on the uptake and internalization by Human Umbilical Vein Endothelial Cells (HUVEC) cell line and the optical photo-stability of the fluorescent particles inside live cells.

The silica nanoparticles showed excellent biocompatability and high photostablity inside live cells for longer periods of time than the fluorescent dye alone. Notably, this is the first report on the use of 30 nm fluorescent silica nanoparticles as efficient endothelial tags, with the possibility of directed diagnostic targeting with functionalized surfaces.

The researchers state that the silica nanoparticles "may enable highly accurate therapeutic delivery and diagnostic imaging".

The work is reported in Journal of fluorescence.