Schematic representation of synthesis procedures for (A) MBG-xAg powder materials and (B) SC-MBG-xAg scaffolds.
Transmission electron microscope image and (inset) photograph of MBG-AgNP scaffold showing antibacterial activity.Researchers have developed a new scaffold material for supporting bone regeneration and repair after disease or trauma that can also reduce incidence of infection [Sánchez-Salcedo et al., Acta Biomaterialia 155 (2023) 654-666, https://doi.org/10.1016/j.actbio.2022.10.045 ].
When bone is damaged tissue engineering represents a powerful approach to encourage repair and regrowth on the cellular level. Three-dimensional (3D) scaffolds based on biocompatible polymeric or ceramic materials with interconnected, hierarchical porous structures provide templates for regrowing and proliferating cells. But the implanted scaffolds are treated as ‘foreign’ objects by the body’s immune system and can become colonized by bacteria, leading to infection. Bacterial infections are one of the major complications associated with bone tissue engineering and implants, typically requiring additional surgery and systemic antibiotics to treat, resulting in long hospital stays for patients.
To get around this issue by giving scaffolds inherent antibacterial properties, the team from Universidad Complutense de Madrid and CIBER de Bioingeniería, Biomateriales y Nanomedicina incorporated silver nanoparticles (AgNPs), which have well-recognized antibacterial properties, into their scaffold matrix.
“The dual scaffolds are biocompatible and deliver active doses of silver capable of combating bone infections, which represent one of the most serious complications associated with surgical treatments of bone diseases and fractures,” says María Vallet-Regí, who led the work.
The researchers used an innovative one-pot sol-gel method to produce mesoporous bioactive glass (MBG) matrices based on SiO2-CaO-P2O5 doped with the metallic AgNPs and combined this with rapid prototyping (RP), which creates structures with ultra-large microporosity based on computer-aided design. The single-step sol-gel route induces the spontaneous reduction of Ag salts into nanoparticles, which are incorporated uniformly throughout the matrix. Once implanted into the body, the AgNPs are released as the MBG matrices dissolve, preventing the buildup of Gram positive and negative bacteria.
“Our in vitro antimicrobial assays show that Staphylococcus aureus and Escherichia coli growth inhibition and biofilm reduction are directly related to the increased presence of AgNPs in the MBG matrices,” Vallet-Regí explains.
Moreover, only small amounts of AgNPs are needed to produce an antimicrobial effect, which appear to have no impact on the viability of regrowing bone tissue cells. The new bioceramic scaffold material, therefore, provides a level of bioactivity sufficient to support the repair and regeneration of bone tissue while suppressing the risk of infection by releasing antibacterial AgNPs. While the material has been studied in vitro, in vivo studies are now needed to corroborate the researchers’ initial findings, Vallet-Regí points out.