Abstract: BACKGROUND: Periprosthetic joint infection is the most common cause of early failure after total knee replacement. The current methods of preventing periprosthetic joint infection by improving the surface of the prosthesis have limitations to varying degrees.
OBJECTIVE: To construct a coating material that can stably improve the surface of the implant, prevent the initial floating bacterial infection of periprosthetic infection, and regulate the bone transfer function around the implant.
METHODS: (1) Material preparation: YGF polypeptide (which promotes bone formation), LL-37 polypeptide (with antibacterial properties) and YGF+LL-37 composite peptide were prepared by Fmoc solid phase peptide synthesis technology. The titanium-based materials were immersed in the three polypeptide solutions for 2 hours to obtain YGF coating, LL-37 coating and composite peptide coating coated titanium sheets. (2) In vitro experiment: Uncoated titanium sheets and coated titanium sheets were co-cultured with Escherichia coli (or Staphylococcus aureus) and the colonies were counted by plate method. MC3T3 cells were inoculated on the surface of uncoated titanium sheet and coated titanium sheet, respectively. Alizarin red staining was used to observe the calcium salt deposition on the surface of the material. Western blot assay was used to detect the protein expression of RUNX2, osteocalcin, osteopontin, and bone morphogenetic protein 2. (3) Animal experiment: 24 SD rats were randomly divided into three groups: the blank group (n=8) was implanted with uncoated titanium nails in the femoral medullary canal; the control group (n=8) was implanted with uncoated titanium nails in the femoral medullary canal + intra-articular injection of Staphylococcus aureus suspension; the experimental group (n=8) was implanted with composite peptide coated titanium nails in the femoral medullary canal + intra-articular injection of Staphylococcus aureus suspension. After 5 weeks of implantation, micro-CT examination, hematoxylin-eosin staining and immunohistochemical staining of femur specimens were performed.
RESULTS AND CONCLUSION: (1) In vitro experiment: Compared with uncoated titanium sheet and YGF coated titanium sheet, LL-37 coated and composite peptide coated titanium sheet could significantly inhibit the growth and reproduction of Escherichia coli and Staphylococcus aureus. Compared with uncoated titanium sheets and LL-37-coated titanium sheets, YGF-coated and composite peptide-coated titanium sheets could promote calcium salt deposition in osteoblasts and increase the protein expression of RUNX2, osteocalcin, osteopontin and bone morphogenetic protein 2. (2) Animal experiment: Micro-CT test showed that the control group had less bone mass than the blank group and the experimental group. Hematoxylin-eosin staining showed that there was a large amount of fibrous tissue around the nail channel in the control group, only a small amount of tissue fibrosis around the nail channel in the blank group, and only a small amount of tissue fibrosis around the nail channel in the experimental group. Immunohistochemical staining showed that the protein expression of interleukin 1β and tumor necrosis factor α in the control group was higher than that in the blank group and the experimental group, and the expression of osteocalcin, RUNX2 and osteopontin in the experimental group was higher than that in the blank group and the control group. (3) The results show that the titanium-based material coated with YGF+LL-37 composite peptide coating has good antibacterial ability and can promote bone transfer around the implant

Key words: periprosthetic joint infection, biopeptide coating, antimicrobial peptide, bone transfer, polypeptide, bone integration, engineered bone material