关键词: 3D打印, 组织工程, 载药支架, 盐酸米诺环素, 种植体周围炎, 同轴支架, 单轴支架

Abstract: BACKGROUND: Due to the unstable drug release rate of uniaxial bone scaffolds, multi-structure composite printing methods have been sought in and outside China in recent years. Currently, coaxial drug-loaded bone scaffolds, which combine drug-loaded sustained release system with bone transplantation and repair technology, not only replace the defective bone after implantation, but also release drugs slowly, providing a microenvironment conducive to bone formation at the implant site. 
OBJECTIVE: To explore and assess the in vitro antibacterial properties of uniaxial and coaxial minocycline hydrochloride bone scaffolds. 
METHODS: Rapid prototyping technology was used to prepare uniaxial hydroxyapatite/silk fibroin-polyvinyl alcohol scaffold, uniaxial hydroxyapatite/silk fibroin-polyvinyl alcohol scaffold, coaxial hydroxyapatite/silk fibroin-polyvinyl alcohol scaffold, and coaxial hydroxyapatite/silk fibroin-polyvinyl alcohol scaffold, respectively, which were named S1, S2, T1 and T2. The morphology, porosity, degradation performance, in vitro sustained-release performance and cytotoxicity of scaffolds were characterized. Four kinds of bone scaffolds were immersed in PBS to prepare the extracts at different time points (1, 3, 5, 7, 14, 21, and 28 days). The qualitative filter paper was placed into the extract for 24 hours. The filter paper was co-cultured with Porphyromonas gingivalis and Fusobacterium nucleatum for 72 hours. The bacteriostatic effect of four groups of scaffolds was detected by the agar diffusion method.
RESULTS AND CONCLUSION: (1) Scaffold characterization: Four groups of scaffolds were well formed. The surface of micro-wires in the S1 and S2 groups was dense and smooth, and the surface of micro-wires in the T1 and T2 groups was rough. Porosity was between 40%-47% and met the requirements of bone scaffolds. Compared with the S2 group, sustained release time was longer in the T2 group. The sustained release concentration of the drug was between 1-10 µg/mL for a long time, which was more conducive to bacteriostasis and osteogenesis. After 10 weeks of immersion in PBS in vitro, the degradation rate of the coaxial printed bone scaffold was faster than that of the corresponding uniaxial printed bone scaffold, and the degradation rate of the coaxial loaded bone scaffold was lower than that of the coaxial non-loaded bone scaffold. The four groups of scaffold extracts were co-cultured with osteoblasts respectively. CCK-8 assay displayed that the cell proliferation rate was greater than 75%, which met the requirements of biocompatibility. (2) In vitro antibacterial effect: S1 and T1 did not have antibacterial activity. S2 and T2 had an obvious antibacterial effect. Under the extraction solution on day 28, the diameter of Porphyromonas gingivalis and Fusobacterium nucleatum inhibition zone in the S2 group was smaller than that in the T2 group (P < 0.05). (3) These findings exhibit that hydroxyapatite/silk fibroin-polyvinyl alcohol scaffolds with coaxial minocycline have good physical properties and bacteriostatic properties.

Key words: 3D printing, tissue engineering, drug-loaded scaffold, minocycline hydrochloride, peri-implantitis, coaxial scaffold, uniaxial scaffold