Effect of pH on the chelation between strontium ions and decellularized small intestinal submucosal sponge scaffolds / 北京大学学报(医学版)

OBJECTIVE@#To investigate the preparation of decellularized small intestinal submucosa (dSIS) sponge scaffolds with chelated strontium (Sr) ions at different pH values, and to select the appropriate pH values for synthesizing Sr/dSIS scaffolds using the physicochemical properties and biocompatibility of the scaffolds as evaluation indexes.@*METHODS@#(1) Sr/dSIS scaffolds preparation and grouping: After mixing dSIS solution and strontium chloride solution in equal volumes, adjusting pH of the solution to 3, 5, 7, and 9 respectively, porous scaffolds were prepared by freeze-drying method after full reaction at 37℃, which were named Sr/dSIS-3, -5, -7, and -9 respectively, and the dSIS scaffolds were used as the control group. (2) Physicochemical property evaluation: The bulk morphology of the scaffolds was observed in each group, the microscopic morphology analyzed by scanning electron microscopy, and the porosity and pore size determined, the surface elements analyzed by energy spectroscopy, the structure of functional groups analyzed by infrared spectroscopy, the chelation rate determined by atomic spectrophotometry, the water absorption rate detected by using specific gravity method, and the compression strength evaluated by universal mechanical testing machine.(3) Biocompatibility evaluation: The cytotoxicity and proliferative effect to bone mesenchymal stem cells (BMSCs) of each group were evaluated by Calcein-AM/PI double staining method.@*RESULTS@#Scanning electron microscopy showed that the scaffolds of each group had an interconnected three-dimensional porous structure with no statistical difference in pore size and porosity. Energy spectrum analysis showed that strontium could be detected in Sr/dSIS-5, -7 and -9 groups, and strontium was uniformly distributed in the scaffolds. Functional group analysis further supported the formation of chelates in the Sr/dSIS-5, -7 and -9 groups. Chelation rate analysis showed that the Sr/dSIS-7 group had the highest strontium chelation rate, which was statistically different from the other groups (P < 0.05). The scaffolds in all the groups had good water absorption. The scaffolds in Sr/dSIS-5, -7 and -9 groups showed significantly improved mechanical properties compared with the control group (P < 0.05). The scaffolds in all the groups had good biocompatibility, and the Sr/dSIS-7 group showed the best proliferation of BMSCs.@*CONCLUSION@#When pH was 7, the Sr/dSIS scaffolds showed the highest strontium chelation rate and the best proliferation effect of BMSCs, which was the ideal pH value for the preparation of the Sr/dSIS scaffolds.

Genetic substructure analysis of three isolated populations in southwest China.

Southwest China is home to numerous ethnic minorities, as well as many geographically and genetically isolated groups. However, the genetic substructure of these ethnic groups, especially the paternal genetic structure between groups, has not been comprehensively analyzed. In this study, we used Y chromosome capture and Illumina sequencing technologies to investigate the paternal genetic structure of three isolated groups of male unrelated individuals, including Baima in Pingwu, Sichuan Province, Muya in Shimian, Sichuan Province, and Kongge in Jinghong, Yunnan Province. We calculated the frequencies of related haplogroups by the fixed-point compound amplification method and direct counting method, and used the Past3.0 software to perform principal component analysis to draw a population clustering tree. we observed that Kongge had 3 Y chromosome haplogroups, Baima had 4 Y chromosome haplogroups, and Muya had 5 Y chromosome haplogroups. The results showed that Kongge was most closely related to the Wa, and the Y chromosome types of the Baima and Muya were mainly concentrated in the D haplogroup and its lower reaches. It has the closest relationship with the Tibetans in Qamdo and Nyingchi. The study on the genetic structure of different ethnic groups has enriched the genetic relationship of isolated populations and provided a new perspective for understanding Chinese ethnic groups.