Schematic representation of the synthesis and function of Cu-containing MBG nanoparticles in bone repair.
Schematic representation of the synthesis and function of Cu-containing MBG nanoparticles in bone repair.

Researchers have synthesized copper-containing bioglass nanoparticles that boost bone repair by providing the right conditions for new growth while suppressing bacterial infections [Bari et al., Acta Biomaterialia (2017), doi: 10.1016/j.actbio.2017.04.012].

Conventional treatments for bone defects arising from conditions such as osteoporosis or trauma like fractures can be ineffective, especially if there is infection. But mesoporous bioactive glass (MBG) nanoparticles, developed by Chiara Vitale-Brovarone, Sonia Fiorilli, and colleagues at Politecnico di Torino, Livia Visai at University of Pavia, and Maria Vallet-Regí at Universidad Complutense de Madrid, take a multifunctional role.

The copper-containing MBGs simultaneously promote new bone growth (osteostimulation), have an antibacterial effect, and can induce the formation of blood vessels (proangiogenic).

The researchers used a one-pot, ultrasound-assisted sol-gel method, which relies on a template agent, to assemble a regular nanoporous structure in a bioactive glass.

“This is the first study using the templated sol-gel method to produce MBG nanoparticles containing copper ions,” says Vitale-Brovarone.

The uniformly spherical nanoparticles, around 200 nm in diameter, have a very high specific surface area (over 500 m2/g) and nanopores approximately 2.6 nm in diameter. By varying the copper content, glass composition, surface area, and nanopore size, the release of the copper ions – and, therefore, the biological response – can be tailored and optimized.

“Copper-MBG nanoparticles and their ionic dissolution extracts exhibit important antibacterial effect against three different bacteria strains, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and the ability to inhibit and disperse the biofilm produced by bacteria,” reports Vitale-Brovarone.

Biofilms, which can colonize medical devices and cause persistent infections, can be particularly resilient to antibiotics. The ability to counteract biofilms makes the MBG nanoparticles particularly attractive.

“Compared with scaffolds based on MBGs, whose application is still limited by the poor mechanical properties of the final meso-macroporous structure, MBG nanoparticles are versatile, characterized by multifunctional biological properties and drug-loading ability,” points out Vitale-Brovarone.

The MBG nanoparticles can be coated with stimuli responsive agents and delivered directly to the site of damage or infection. Alternatively, nanoparticles could be dispersed in an organic matrix and implanted into the body to produce collagen-based composites that induce bone remodeling.

The researchers believe the nanoparticle offer a promising approach to the prevention of infection and stimulation of bone regeneration. Different ions could also be introduced into the MBG mixture to improve osteostimulation and reduce the activity of osteoclasts related to osteoporosis.

“The main challenge is the perfect tuning of the ion release kinetics, which should match clinical needs (time of the delivery, concentrations, time and so on),” says Fiorilli.

The researchers are now working on developing a complete medical device for bone and wound applications1 and osteoporosis2.

Further information:

1. European Commission funded project H2020-MOZART.

2. European Commission funded project ERC-BOOST.