Macroporous ferrogel squeezes medicines into a sore spot
A new form of drug and cell delivery – "magnetic sponge"
NanoNewsNetEngineers at Harvard University and Duke University have developed a "magnetic sponge" implantable in the body, from which cells, drugs or other substances can be "squeezed" by simply holding a magnet over it.
The new material, called macroporous ferrogel, can be compressed up to 70 percent by a magnetic field. Reversible compression quickly removes drugs or cells and proteins embedded in the gel from the gel.
Although porous biomaterials are already used as scaffolds in tissue regeneration and cell therapy, they are mostly passive in relation to the drugs contained in them. The diffusion of molecules and the migration of cells occur independently and independently of such materials. In contrast, the new delivery vehicle can be controlled by external signals, releasing the cells and drugs contained in them on demand.
Macroporous ferrogel contains iron nanoparticles that respond to the influence of a magnetic field. It is equally important that the pore size of the new ferrogel is much larger than that of existing analogues.
"Larger pores allow us to use drugs with larger molecules, such as proteins, and cells, as well as achieve more significant compression of the gel in the presence of a magnetic field," explains Xianhe Zhao, associate professor of mechanical engineering and materials science at the Pratt School of Engineering at Duke University. Zhao did most of his work as a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences in the laboratory of bioengineering professor David Mooney.
"When the ferrogel is frozen, the water inside it crystallizes and partially damages the gel," Zhao explains. "And after defrosting, a "hole" remains. By changing the temperature and duration of freezing, we can adjust the pore size. Unlike conventional wireframes, our ferrogel allows you to actively control the process of removing what needs to be removed. For example, the size of the pores or the level of magnetism depends on the processing of the ferrogel, and we can change them."
On the left – ferrogel after freezing at -20°, on the right – at -80° (VM)
The scientists tested their ferrogels loaded with human and mouse cells on animal models and were satisfied with how they respond to magnetic field stimulation.
"To our knowledge, this is the first demonstration of the use of such porous ferrogels for controlled cell delivery," says Mooney. "More broadly, this is the first demonstration of cell isolation from porous scaffolds on demand, which could promote the widespread use of such materials in tissue regeneration and other types of cell therapy."
Living cells can be injected into ferrogels, which will multiply for many years, the scientist claims.
"Although this study focuses on the ability to deliver drugs and cells on command, we expect that due to the large and rapid volume change under the influence of a magnetic field, such ferrogels will have much wider applications, including use as actuators and sensors in biomedicine and other fields," Mooney believes.
Ferrogels are made of biodegradable material, so they do not need to be removed from the body, scientists specify.
The results of the work are published online in the Proceedings of the National Academy of Sciences: Xuanhe Zhao et al., Active scaffolds for on-demand drug and cell delivery.
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16.12.2010