Small and sensitive nanoparticles

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Putting individual nanoparticles inside micelles could make improved contrast agents for imaging in the body

A new highly sensitive nanoparticle contrast agent for imaging in the body stays in the bloodstream longer and is better at targeting tumours than other nanoparticle contrast agents, say Chinese scientists.

Xintao Shuai from Sun Yat-Sen University, Guangzhou,and colleagues encapsulated individual - or nonclustered - superparamagnetic iron oxide nanoparticles inside micelles composed of folate and a polymer.

The team injected the nanoparticles into the veins of mice tails and followed their progress with magnetic resonance imaging (MRI). They found that the micelles increased the nanoparticles’ ability to show the bright and dark contrast between healthy and diseased tissue. The nanoparticles stayed in the bloodstream longer than larger nanoparticles because it took longer for them to accumulate in the liver. By introducing folate, the nanoparticles’ ability to target tumour cells was also increased.

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The smaller nanoparticles stay in the bloodstream longer because they don’t accumulate in the liver as quickly as larger nanoparticles

Similar imaging agents are made from clusters of nanoparticles inside micelles, but clusters are larger, limiting their use. As Shuai’s micelles encapsulate the nanoparticles individually, they are smaller and more versatile.

’Effective tumour imaging requires a tumour-specific and highly sensitive MRI contrast agent,’ explains Shaui. ’Such an MRI agent must combine high MRI sensitivity, long blood circulation and tumour specificity. We believe that these features are equally important and should be combined into one system.’

’Compared with other systems, this system is useful for imaging non-liver tumors,’ says Youqing Shen, an expert in biomaterials from Zejiang University, China. ’Currently there are no such highly sensitive MRI contrast agents for non-liver tumour detection.’

Shuai says the next step for these encapsulated nanoparticles is to achieve an even higher sensitivity and to carry out preclinical studies, including studies on the pharmokinetics and long term in vivo toxicity. One future challenge will be to extend this strategy to the detection of other tumours with different biomarkers, he adds.

Rachel Cooper