Fluorescent nanoparticles for quantitative uptake studies

Nanocarriers, such as those made of polymer nanoparticles, are promising drug delivery vehicles. Thanks to a process called emulsion free radical polymerization, researchers in Italy have now succeeded in quantifying the amount of nanoparticles that enter the cell cytoplasm. The…

Nanocarriers, such as those made of polymer nanoparticles, are promising drug delivery vehicles. Thanks to a process called emulsion free radical polymerization, researchers in Italy have now succeeded in quantifying the amount of nanoparticles that enter the cell cytoplasm. The findings from the new study will be important for developing more efficient anti-cancer therapies.

Fluorescent nanoparticles made of a biocompatible polymer linked to rhodamine

The team, led by Massimo Morbidelli of the ETH Zurich in Switzerland and Davide Moscatelli of the Politecnico di Milano in Italy, together with colleagues at the Mario Negri Institute for Pharmacological Research in Milano looked at how emulsion free radical polymerization – which is routinely employed to synthesize polymer nanoparticles – can be successfully applied to the biomedical field.

The researchers succeeded in optimizing a novel procedure that allowed them to quantitatively assess the amount of nanoparticles taken up by the cell cytoplasm. The technique relies on flow cytometry and plate fluorimetry, and also measures the number of cells. The method exploits polymer nanoparticles functionalized with a fluorescent dye (Rhodamine B).

PhD student Raffaele Ferrari at the Politecnico di Milano synthesized biocompatible polymethylmethacrylate-based nanoparticles covalently bound to RhB to avoid dye diffusion from the nanocarriers. By changing the process parameters, different carriers with tuneable size, charge, and amount of dye were produced. These materials were employed in in vitro experiments.

Team members Monica Lupi and Paolo Ubezio from Mario Negri obtained a reproducible linear relationship for each type of polymeric nanoparticle – between the number of nanoparticles, the molecules of RhB per nanoparticle and the relative fluorescence detected by a microplate reader. The researchers were then able to correlate results from plate fluorimetry measurements and measured the average cell fluorescence using flow cytometery by evaluating the number of nanoparticles internalized in individual cells.

The researchers presented their results in the journal Nanotechnology.