21 September 2010

Uncertainties surrounding nanoparticles aimed for medical use

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Nanomedicine holds a lot of promise, but many questions remain before nanoparticles (NPs) can be widely used in this field. Reports revealed adverse effects in different models, but the effects in humans are unclear

Researchers are trying to find out more about the relationship between different NPs’ shapes, sizes and surface chemistries and how they behave in the human body. They also need to know what happens to NPs which deliver drugs after the mission is completed. Jie Lu and colleagues at the University of California have studied mesoporous silica nanoparticles (MSNs) delivering chemotherapeutic drugs to tumors in mice. The concentration of Si was quantified in each organ to investigate NP distribution. MSNs were conjugated to folic acid to allow targeting to cancer cells and compared to nontargeting MSNs. The researchers found more-significant accumulation in tumors in comparison with other organ when using the folic-acid modified NPs. At 4, 24 and 48 hours after injection the Si concentration in tumors were about 65, 170 and 90 ng mg-1 respectively, compared to 3-18 ng mg-1 in other organs within 48 hours. More than 94 percent of MSNs were excreted within four days after injection, which is quickly according to the researchers.

Marie Sønnegaard Poulsen at the University of Copenhagen has worked on the EU-project Nanotest, developing alternative testing strategies for NP risk assessment. She knows about NPs’ potential harmful effects seen in models. “In the field of nanotoxicology and placental transport, studies have shown that some nanoparticles can cross the placental barrier and thereby have the potential to interfere with the development of the fetus. It has also been shown that some nanoparticles can cause indirect DNA damage across a cellular barrier. This means the developing fetus might be damaged by nanoparticles in the maternal circulation, even though they are not able to cross the placental barrier. It has also been demonstrated that nanoparticles can circumvent the blood brain barrier by neuronal translocation to affect the brain.”

Last year Bengt Fadeel and Alfonso Garcia-Bennett at Karolinska Institutet and The Ångström Laboratory in Sweden published a report about toxicological properties of NPs manufactured for biomedical applications. They highlight that it is uncertain if these NPs could cause harm in the human body, but this does not imply all NPs should be considered dangerous. Better standardization of in vitro and in vivo assays is needed to determine more possible adverse effects.


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