NCCR Bio-Inspired Materials researchers at the University of Fribourg have highlighted the need to apply complementary analysis methods to study nanoparticle behavior inside cells, pointing to shortfalls in some techniques. In a recent study published in the journal Angewandte Chemie International, PhD student Ana Milosevic and her colleagues at the Adolphe Merkle Institute investigated the fate of fluorescently encoded gold nanoparticles (AuNPs) after cellular uptake, potential particle aggregation, and the integrity of the surrounding polymer layer into which a fluorophore was integrated. The research, among the first of its kind, focused in particular on digestive organelles known as lysosomes, an acidic and confined space in cells where most of the observed nanoparticles accumulate after uptake.

Results showed that the strong salt content and low pH environment of the lysosomes strongly affected the stability and integrity of negatively-charged polymer-grafted AuNPs. This led to aggregation, and conformational changes of the polymer followed by a loss of the fluorescence property of the fluorophore. The study highlights both the changes to the nanoparticles caused by the specific environment in the lysosomes, as well as the uncertainty of relying only on fluorescence techniques. The article’s authors say that this is significant, because this project not only proves the need to use multiple complementary analysis methods, but also gives insight into nanoparticle fate within cells. They especially emphasize the importance of investigating more thoroughly the effects of a specific biological environment on all the components that researchers rely on to detect a nanoparticle, such as fluorescence.

Article:

Milosevic, A. M., Rodriguez-Lorenzo, L., Balog, S., Monnier, C. A., Petri-Fink, A. and Rothen-Rutishauser, B. (2017), Assessing the Stability of Fluorescently Encoded Nanoparticles in Lysosomes by using Complementary Methods. Angew. Chem. Int. Ed.. doi:10.1002/anie.201705422