Yi Sun

The aim of this study is to explore the therapeutic effects of Mg-Sr-Ca containing bioactive glass nanoparticles sodium alginate hydrogel modified mineralized collagen scaffold (Mg-Sr-Ca-BGNs-SA-MC) on the repair of osteoporotic bone defect. During the study, Mg-Sr-Ca containing bioactive glass nanoparticles (Mg-Sr-Ca-BGNs) were synthesized using the sol-gel method, and the Mg-Sr-Ca-BGNs-SA-MC scaffold was synthesized by a simple method. The Mg-Sr-Ca-BGNs and the Mg-Sr-Ca-BGNs-SA-MC scaffold were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The elements of Mg, Sr, Ca and Si were effectively integrated into Mg-Sr-Ca-BGNs. SEM analysis revealed the presence of Mg-Sr-Ca-BGNs on the scaffold’s surface. Furthermore, the cytotoxicity of the scaffolds were assessed using a live/dead assay. The result of the live/dead assay demonstrated that the scaffold materials were non-toxic to cell growth. More importantly, the in vivo study indicated that implanted scaffold promoted tissue regeneration and integration with newly formed bone. Overall, the Mg-Sr-Ca-BGNs-SA-MC scaffold is suitable for guided bone regeneration and beneficial to repair of osteoporotic bone defects.

Magnesium containing bioactive glass nanoparticles modified gelatin scaffolds (MBGNs/Gel scaffolds) have shown recently the potential for bone regeneration due to its good biocompatibility, bioresorbability and bioactivity. Nevertheless, its use is limited by its complicated manufacturing process and a relatively expensive price. In this study, MBGNs were prepared by sol–gel process. The MBGNs/Gel was synthesized by a simple immersion method. SEM, transmission electron microscopy and dynamic light scattering analysis showed that the particles had spherical morphology with mean particle size of 100 nm. The MBGNs/Gel scaffolds were observed by SEM. The scaffolds showed connected pore structure with pore size ranging from 100 to 300 μm. SEM images with high magnification showed the existence of MBGNs on the surface of micro-pores. The ion release results revealed the release of Mg, Ca and Si elements from the MBGNs. MTT assay and cytotoxicity studies indicated that, the scaffolds provide a suitable ion related micro-environment for cell attachment and spreading. The Reverse Transcription-Polymerase Chain Reaction (RT-PCR) results showed the scaffolds could promote the osteogenesis of MC3T3-E1. The in vivo study also showed higher amount of new bone and trabecular bone which indicated excellent bone induction and conduction property of modified scaffolds. So, the developed MBGNs/Gel scaffolds are a potential candidate for bone regeneration applications.

To explore the optimal combination of Mg²⁺, Sr²⁺ and mineralized collagen (nHAC) with two different proportions of hydroxyapatite (HA) and collagen (COL) on differentiation of MC3T3-E1 and the underlying mechanism, as well as achieve bone osseointegration. MC3T3-E1 cells were cultured in a complete medium with Mg²⁺ at the concentration of 0, 4, 8, 12, 16, 20 mmol/L, Sr²⁺ at the concentration of 0, 3, 6, 12 mmol/L, and the impregnation solution of 3:7 and 5:5nHAC. The differentiation of MC3T3-E1 was measured by expression of osteogenic genes and proteins including Runx-2, BMP-2 and OCN and determined the activation of PI3K/AKT/GSK3β/β-catenin signaling pathway in 12 mmol/LMg ^{2 +}+3 mmol/LSr ^{2 +}+3:7nHAC group. Osteoporosis was induced in 18 female rats by means of ovariectomy, the implants were immersed in 60 mmol/LMg ^{2 +}+15 mmol/LSr ^{2 +}+3:7nHAC impregnation solution and implanted into the mesial alveolar fossa for immediate implantation. The osseointegration of the implants was observed by Confocal laser scanning microscopy (CLSM) and histology at 4 and 8 weeks. The groups cultured with 12 mmol/LMg ^{2 +}, 3 mmol/LSr ^{2 +} and 3:7nHAC impregnation solution showed the osteogenic genes and proteins were significantly higher respectively (P < 0.05), as well as p-Akt, p-GSK3β and β-catenin proteins (P < 0.05). CLSM and histology showed that the implant surface was surrounded by thick lamellar bone plate, and the trabecular bone were dense and continuous in the impregnation solution. These results found that magnesium and strontium ion-loaded mineralized collagen play an critical role in up-regulating the cells activity through PI3K/AKT/GSK3β/β-catenin signaling pathway and could be promote the formation of osseointegration.

This study was aimed at assessing the effects of the porous mineralized collagen plug with or without the bilayer mineralized collagen-guided bone regeneration membrane on alveolar ridge preservation in dogs. The third premolars in the bilateral maxilla of mongrel dogs (N = 12) were extracted. Twenty-four alveolar sockets were thus randomly divided into three groups: membrane + collagen plug (MP, n = 8), nonmembrane + collagen plug (NP, n = 8) and blank group without any implantation (BG, n = 8). Radiographic assessment was carried out immediately and in the 2nd, 6th, and 12th week after surgery. The bone-repairing effects of the two grafts were respectively evaluated by clinical observation, X-ray micro-computed tomography examination, and histological analysis in the 8th and 12th week after surgery. Three groups presented excellent osseointegration without any inflammation or dehiscence. X-ray micro-computed tomography and histological assessment indicated that the ratios of new bone formation of MP group were significantly higher than those of NP group and BG group in the 8th and 12th week after surgery (P < 0.05). As a result, the porous mineralized collagen plug with or without the bilayer mineralized collagen-guided bone regeneration membrane could reduce the absorption of alveolar ridge compared to BG group, and the combined use of porous mineralized collagen plug and bilayer mineralized collagen-guided bone regeneration could further improve the activity of bone regeneration.