Bone implants are commonly used in medicine. Materials for these implants need to promote bone growth (osteogenesis) to fuse with the surrounding bone. They also need antibacterial properties to prevent infections. Antibiotics can be integrated into the materials to achieve the latter, but there is a risk of antibiotic resistance. Metal nanoparticles could be an alternative antimicrobial coating, but this could affect osteogenesis.

Xingjie Zan, Wenzhou Medical University and Wenzhou Institute of Biomaterials and Engineering, China, Yifu Guan, China Medical University, Shenyang, and colleagues have developed an ultrathin coating for bone implants that promotes osteogenesis and kills bacteria. The team used a layer-by-layer deposition to create the film from alternating layers of graphene oxide (GO) and lysozyme (Lys). The substrate was simply dipped first into a GO solution and then in a Lys solution. The process was repeated eight times to give a coating several tens of nanometers thick.

GO can promote the adhesion and growth of bone cells and is biocompatible in low concentrations. Lys is an enzyme that can cleave certain bonds that occur in bacterial walls and, thus, has strong antimicrobial properties. The negatively charged GO would not adhere well to implants on its own, but interactions with the positively charged Lys lead to a stable film.

According to the researchers, the film is active against Staphylococcus aureus and Escherichia coli. The team used dental pulp stem cells (DPSCs) to show that the material also enhances osteogenesis.

• https://doi.org/10.1021/acs.langmuir.9b00035″>Graphene Oxide and Lysozyme Ultrathin Films with Strong Antibacterial and Enhanced Osteogenesis,
  Meng Li, Huaqiong Li, Qiongxi Pan, Chenyuan Gao, Yingying Wang, Shuoshuo Yang, Xingjie Zan, Yifu Guan,
  Langmuir 2019.
  https://doi.org/10.1021/acs.langmuir.9b00035