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Failure to launch: nano toxicity studies may be affected by nanoparticles staying behind in syringes

A new study has shown that a significant fraction of nanoparticles tested in the toxicity studies of nanoparticles and to develop nanomedicines, may remain in the plastic syringes used to dose the nanoparticles. This has implications on the reliability and reproducibility of the studies and on efforts to reduce animal testing.

Helsinki, 25 November 2019 – The scientists in this study radiolabelled a variety of different nanoparticles, loaded suspensions of particles into different plastic syringes, and then measured the radioactivity left behind after emptying the nanoparticle suspension from the syringe. This gave a simple way to measure the fraction of nanoparticles that remained stuck inside the syringe. In the worst case, up to 79.1% of the particles remained.

The study also found variability in the amounts remaining behind depending on the types of particles and syringes used. The researchers propose checks to find out the correct combination of syringe and nanoparticle that should be used to minimise the problem. The study did not identify the root causes of the high variability between the different nanoparticles and syringe types used.

Although a similar problem exists in the field of nuclear medicine, this is the first study of its kind to demonstrate it for nano particles. The results can have implications for the performance of toxicity studies on nanoparticles, the development of new nanomedicines and for animal welfare.

Studies used to develop nanomedicines, as well as some toxicology studies can be both costly and time consuming, and uncertainty regarding the fraction of nanoparticles remaining behind in syringes, instead of reaching the test animals, may compromise the interpretation of their results.