ABSTRACT
Objective:To investigate the physicochemical and biological properties of different magnesium modified calcium phosphate bone cements.Methods:The different magnesium modified calcium phosphate bone cements were divided into magnesium citrate, magnesium lactate, magnesium malate, magnesium phosphate and magnesium glycinate groups, each of which was added with different magnesium agents in the proportion of 0%, 1%, 3% and 5% of the total weight of calcium phosphate bone cements. The initial and final setting time, injectability, anti-collapse performance and compressive strength of different magnesium modified calcium phosphate bone cements were tested. Furthermore, the screened bone cement extracts were used to culture with third generation osteoblasts. Bioactivity assays were performed using the Cell Proliferation and Toxicity Assay Kit (CCK-8). Alkaline phosphatase (ALP) staining and Alizarin Red S (ARS) staining were performed on osteoblasts to observe the osteogenic activity of magnesium malate modified calcium phosphate bone cements.Results:The addition of different proportions of different magnesium agents led to the shortening of the initial and final setting time of modified calcium phosphate bone cements. Moreover, the final setting time of 5% magnesium malate modified calcium phosphate bone cements was the shortest (<40 minutes), which was significantly shorter compared with other magnesium agents in the same proportion (all P<0.05). With the addition of different magnesium agents in different proportions, the injectability of bone cements was gradually increased, and the injectability of 5% magnesium malate calcium phosphate bone cements reached the highest for (87.3±1.9)%, which was significantly increased compared with other magnesium agents in the same proportion (all P<0.05). The anti-collapse performance of bone cements was decreased with the addition of different magnesium agents in different proportions. Magnesium citrate, magnesium phosphate and magnesium glycinate modified calcium phosphate bone cements could not resist the flushing of deionized water. In particular, magnesium malate modified calcium phosphate bone cements had the best anti-collapse performance, with the maximum weight loss rate for only (9.8±2.3)% after 30 minutes of deionized water flushing, which was better than the rest of the groups (all P<0.05). The compressive strength of magnesium lactate and magnesium phosphate modified calcium phosphate bone cements showed a decrease compared with original calcium phosphate bone cements, while the compressive strength of magnesium citrate and magnesium malate modified calcium phosphate bone cements was significantly increased compared with original calcium phosphate bone cements, of which 3% magnesium malate modified calcium phosphate bone cements had the greatest compressive strength of (6.2±0.2)MPa, significantly higher than the rest of the groups (all P<0.05). The sieve test yielded magnesium malate modified calcium phosphate bone cement, which had a weight loss of (27.0±0.9)% at 35 days in vitro. The release of magnesium ions was increased with increasing magnesium malate dose in the in vitro environment of magnesium malate modified calcium phosphate bone cements in different ratios. A stable magnesium ion release was achieved within 35 days.Also, the pro-proliferative and osteogenic effects of modified calcium phosphate bone cements on osteoblasts were more obvious with increase of magnesium malate dose. For 5% magnesium malate modified calcium phosphate bone cements, the cell number, ALP staining area ratio and calcium nodule area ratio were significantly increased compared with the groups in the proportion of 0% and 1% magnesium malate (all P<0.05). Conclusions:Among magnesium citrate, magnesium lactate, magnesium malate, magnesium phosphate and magnesium glycinate modified calcium phosphate bone cements, magnesium malate modified calcium phosphate bone cements have relatively suitable setting time, excellent anti-collapse performance and mechanical strength. Meanwhile, 5% magnesium malate modified calcium phosphate bone cements have better biological activity among different ratios of magnesium malate modified calcium phosphate bone cements, suggesting a potential value for clinical application.
ABSTRACT
Objective:To explore the effect of calcium phosphate cement（CPC）scaffold loaded with emodin（EMO）on osteogenic activity of osteoblasts.Methods:The bone cement scaffold was prepared by mixing EMO powder and CPC powder（ratio 1∶9），adding citric acid and then was poured into polytetrafluoroethylene mold（EMO-CPC group）. A dose of 0.36 g CPC powder was mixed with citric acid and injected into the polytetrafluoroethylene mold（CPC group）. General morphology，setting time（initial setting time and final setting time），injection rate and compressive strength of stents were compared between the two groups. Primary osteoblasts were extracted and co-cultured with two sets of scaffolds. After co-culture for 3 days，their characterization was observed by scanning electron microscopy. Live/dead cell staining and 3-（4,5-dimethylthiazole-2）-2,5-diphenyltetrazolium bromide（MTT）colorimetric method were used to detect cell viability，toxicity and proliferation activity of scaffolds. Two sets of scaffolds were stained with immunofluorescence for osteopontin（OPN），and protein expression was observed under an inverted fluorescence microscope. After co-culture for 7 days，tetrazolium nitro blue/5-bromo-4-chloro- 3-indolyl-phosphate（NBT/BCIP）staining method was used for alkaline phosphatase（ALP）staining. After co-culture for 14 days，two sets of scaffolds were stained with Alizarin Red to detect their osteogenic activity.Results:Two sets of stents showed relatively smooth and flat topography under the scanning electron microscope. There were no significant differences in initial setting time，final setting time，injection rate and compressive strength of stents between two groups（ P > 0.05）. After co-culture for 3 days，the osteoblast clusters were adhered to the surface of the EMO-CPC scaffold，with good shape. Viable cell rate reached（98.2 ± 0.1）% in EMO-CPC group and（90.2% ± 0.1）% in CPC group（ P <0.05）. Cell proliferation activity in EMO-CPC group was stronger than that in CPC group（ P < 0.05）. OPN-specific staining showed that EMO-CPC group had stronger OPN protein fluorescence expression compared to CPC group. After co-culture for 7 days，expression of ALP in EMO-CPC group was higher than that in CPC group. After co-culture for 14 days，staining intensity of Alizarin Red in EMO-CPC group was more significant than that in CPC group. Conclusions:The EMO-CPC scaffold can provide a suitable environment for the growth of osteoblasts for it has better biocompatibility，cell proliferation and osteogenic activity than the CPC scaffold.