Magnetic nanosprings might be the key for drug delivery agents

Materials World magazine
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19 Dec 2018

Creating nanorobots, nanosensors and targeted drug delivery agents for anticancer therapy could be easier in the future with the development of nanosprings with magnetic properties. Idha Valeur reports.

Nanosprings are uncommon objects that were discovered a little more than a decade ago. But their magnetic properties had not been studied until scientists from the Far Eastern Federal University (FEFU), Russia, and Korea University created cobalt (Co) and cobalt-iron (CoFe) nanosprings with magnetic properties and long-lasting elasticity.

Alexander Samardak, Associate Professor of the Department of Computer Systems, part of the School of Natural Sciences at FEFU, explained to Materials World that magnetic nanosprings can be driven by a rotating magnetic field due to translation-rotation coupling. ‘It allows them behave in a fluid medium, as swimmers propagating inside a human body,’ he said. ‘Nanosprings, in contradistinction to cylindrical nanowires or spherical nanoparticles, have an inner volume, which can be functionalised with proteins or peptides or filled by drugs to be delivered and released in defined places of a human body.

‘It is very important that free magnetic nanosprings placed in a fluid do not interact with each other as nanoparticles or nanowires forming agglomerates, because of very small stray fields induced by their helical shape.’

Samardak explained that the nanosprings are not particularly small. They have a wire width of 50nm. This size allows for 200 cobalt atoms to be placed in the chain within the space, while the outer diameter of coils is 200nm. ‘Inside each nanospring we have a cavity with the diameter of 50nm. The length of nanosprings can be between hundreds nanometres to a few micrometres. Thus, nanosprings have an inner volume, high enough to accommodate drugs or any other molecular complexes, like proteins or peptides,’ he said.

By using high-resolution transmission electron microscopy and magnetic force microscopy, both of which offer an atomic-scale resolution, the researchers were able to study the nanosprings. Powerful micromagnetic simulation has also helped them to better understand the details of the magnetic behaviour.

The team has completed the first stage of the fundamental study of structural and magnetic properties of Co and CoFe nanosprings. They believe their findings will be useful for other applications in the field of magnetic field-driven devices.

‘We now understand the mechanisms of magnetisation reversal of nanosprings,’ Samardak said. ‘Due to the helical geometry, these mechanisms are complex and different from other shaped nanoparticles. It means that for field-driven control we have to consider these mechanisms in order to optimise and to enhance effectiveness of nanosprings propagating on a surface or moving in a fluid.’

Anticancer therapy plans

One possible application for the nanosprings is as drug delivery agents.

‘There are different ways to use magnetic nanoparticles for anticancer therapy,’ he said. ‘The most common is to use mechanical destruction of cancer cells by bioactivated magnetic nanoparticles like nanodiscs or nanorods. They stick to a cell membrane and move under applied magnetic field, resulting in killing of cancer cells.’

He believes the method can achieve up to 70–80% success in destroying cancer cells. Killing up to 100% of the cancer cells while preserving living cells can be achieved by using nanocargos, such as nanosprings to deliver anti-cancer drugs to a tumour.

A radically different way is to use nanocargos like nanosprings to deliver anti-cancer drugs to a tumour and to kill up to 100% of infected cells while preserving living cells.

The device itself has not yet been developed, but Samardak explained that any such device would be based on functionalisation with proteins or peptides and magnetic propulsion to match the specific organ or tissue.

Although the research is promising, Samardak confirmed ‘there is still a long way for implementation of nanosprings in real applications. We plan to continue our study to be closer to practical realisation of functional devices. At the beginning, we have to test Co and CoFe nanosprings’ toxicity and biocompatibility. After that, we will be able to study the cargo’s properties’.