If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Tissue Engineering

Magnetic bone scaffolds can help speed bone cell growth

Remotely activated bone scaffolds can mimic the effects of patient movement and may someday help bone regeneration

by Lakshmi Supriya, special to C&EN
December 18, 2019


Scanning electron microscopy images showing a magnetic scaffold interior and surface with growth of bone cells.
Credit: ACS Appl. Mater. Interfaces
Scanning electron micrographs show the growth of bone cells on the interior (left) and on the surface (right) of a magnetically stimulated polymeric scaffold with 80 µm pores.

Treatments that require reconstructing bone often involve growing new bone tissue on scaffolds that support the developing cells. A new study reports a scaffold that is not only similar to bone physically but can also respond to an outside magnetic stimulus, which could help bone cells grow almost twice as fast (ACS Appl. Mater. Interfaces 2019, DOI: 10.1021/acsami.9b14001).

Common bone scaffolds only provide a passive structure that supports new cell growth. The new scaffolds are different, says study coauthor Margarida M. Fernandes of the University of Minho, because they can transmit magnetic and mechanical stimuli to the bone cells, which boost cell proliferation rates.

This is similar to what happens in bones. Bone is a piezoelectric material: it can generate an electric charge when it is deformed, for example, while walking. Using this idea, Fernandes and her team created a polymeric scaffold that mimics the porous microstructure and piezoelectric characteristics of bone and added magnetic nanoparticles to it. The researchers first made a template by stacking a few layers of nylon with 85–145 µm sized pores on top of each other. Then they immersed the template in a dispersion of poly(vinylidene fluoride) (PVDF), a piezoelectric polymer, and cobalt ferrite nanoparticles. Dissolving away the nylon template with acid left behind a porous PVDF scaffold embedded with magnetic nanoparticles. The team could make scaffolds with different pore sizes by changing the pore size of the nylon templates.

Applying a magnetic field to the scaffold causes the magnetic nanoparticles to change their shape, which in turn applies a mechanical pressure to the scaffold. “This effect imitates the action of walking,” Fernandes says.

To test bone growth, the researchers placed bone precursor cells called preosteoblasts on the scaffolds and applied a magnetic field intermittently for up to 72 hours to mimic mechanical stimulations in the human body. Starting with about 15,000 cells, after 24 h the team found almost double the number of initial cells growing on scaffolds with magnetic stimulation compared with only 50% more cells without stimulation. In addition, the pore size of the scaffolds affected the growth rate, with a pore size of about 80 µm showing the highest rate of growth. PVDF is biocompatible, although the nanoparticles are not. The researchers found that the nanoparticles did not leach out of the scaffolds even after 7 days of immersion in a solvent and think this may be safe for clinical use.

“Given the growing realization that biophysical forces are important in biology, the results are not completely unexpected,” says Kaushik Chatterjee of the Indian Institute of Science, who studies tissue engineering and was not involved in the study. “But the extent to which the cells responded differently to the physical stimulation is impressive.” Testing the scaffolds in animal models, however, will be needed to prove their usefulness and safety.



This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.