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.

Alveolar bone repair with strontium- containing nanostructured carbonated hydroxyapatite

ABSTRACT Objective: This study aimed to evaluate bone repair in rat dental sockets after implanting nanostructured carbonated hydroxyapatite/sodium alginate (CHA) and nanostructured carbonated hydroxyapatite/sodium alginate containing 5% strontium microspheres (SrCHA) as bone substitute materials. Methods: Twenty male Wistar rats were randomly divided into two experimental groups: CHA and SrCHA (n=5/period/group). After one and 6 weeks of extraction of the right maxillary central incisor and biomaterial implantation, 5 μm bone blocks were obtained for histomorphometric evaluation. The parameters evaluated were remaining biomaterial, loose connective tissue and newly formed bone in a standard area. Statistical analysis was performed by Mann-Withney and and Wilcoxon tests at 95% level of significance. Results: The histomorphometric results showed that the microspheres showed similar fragmentation and bio-absorbation (p>0.05). We observed the formation of new bones in both groups during the same experimental periods; however, the new bone formation differed significantly between the weeks 1 and 6 (p=0.0039) in both groups. Conclusion: The CHA and SrCHA biomaterials were biocompatible, osteoconductive and bioabsorbable, indicating their great potential for clinical use as bone substitutes.

Histomorphometric evaluation of strontium-containing nanostructured hydroxyapatite as bone substitute in sheep

Abstract The aim of this study is to evaluate the biocompatibility and osteoconductivity in surgical defects of sheep tibias filled with 1% strontium-containing nanostructured hydroxyapatite microspheres (SrHA), stoichiometric hydroxyapatite without strontium microspheres (HA), or blood clots. Santa Ines sheep were subjected to three perforations on the medial side of the left tibia. The biomaterials were characterized by X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) before implantation and by X-Ray Microfluorescence (µFRX) and Scanning Electron Microscopy (SEM) after sheep tibias implantation. Surgical defects were filled with blood clots (control), SrHA (Group 1) or HA (Group 2). After 30 days, 5-µm bone blocks were obtained for histological evaluation, and the blocks obtained from 1 animal were embedded in methylmethacrylate for undecalcified sections. Mononuclear inflammatory infiltrate remained mild in all experimental groups. Giant cells were observed surrounding biomaterials particles of both groups and areas of bone formation were detected in close contact with biomaterials. All groups showed newly formed bone from the periphery to the center of the defects, which the control, HA and SrHA presented 36.4% (± 21.8), 31.2% (± 14.7) and 26.2% (± 12.9) of newly formed bone density, respectively, not presenting statistical differences. In addition, the connective tissue density did not show any significant between groups. The SrHA showing a higher volume density of biomaterial (51.2 ± 14.1) present in the defect compared to HA (32.6 ± 8.5) after 30 days (p = 0.03). Microspheres containing 1% SrHA or HA can be considered biocompatible, have osteoconductive properties and may be useful biomaterials for clinical applications.

Effects of calcium, strontium, and barium on isolated phrenic nerve-diaphragm preparation of rat and their interactions with diltiazem and nifedipine.

Calcium (Ca2+), strontium (Sr2+), and barium (Ba2+) are expected to exert similar chemical and pharmacological effects. The effects of barium, strontium and calcium were studied on the contractions of rat phrenic nerve-diaphragm preparations, following electrical stimulation and their interactions with nifedipine (nif) and diltiazem (DZM) were also studied. Low doses of strontium chloride (SrCl2), barium chloride (BaCl2) and calcium chloride (CaCl2) were able to increase the force of contraction of the rat diaphragm when actively stimulated. Diltiazem inhibited the stimulant effects of Sr2+, Ba2+, and Ca2+. On the other hand, nifedipine blocked the effects of Sr2+ and Ca2+ but potentiated the effects of Ba2+. Strontium, barium, and calcium restored the contractility of the muscle following electrical stimulation when the tissue was in biological fluid absolutely depleted of calcium. These findings suggest that Sr2+ and Ba2+ may be able to substitute Ca2+ in the rat diaphragm for its contractions and nifedipine and diltiazem may follow different mechanisms of actions or channels in their blocking effects.

Effects of molybdenum, strontium and their combination on dental caries in the rat

The effect of Sr and Mo alone or in combination on dental caries has not extensively evaluated and still a subject of controversy. To investigate this effect, rats were given weaning 50 ppm Sr and 1 ppm Mo alone or in combination via the drinking water. The control group was given distilled water. The rats fed a formulated cariogenic diet from 21 to 71 days of age, were killed and the first, second and third molars were evaluated for carious lesions. Strontium and molybdenum or their combination decreased the number and the extent of enamel and dentin caries of molars erupted at the time of the elements administration. For third molars where the elements were given before and after its eruption, Sr and its combination with Mo decreased the caries. However, the Mo alone did not produce significant caries reduction. The results demonstrate that Sr and Sr + Mo combination has a pre- and post-eruptive cariostatic effect whereas Mo has a post- eruptive effect only. Also, it demonstrates that the Sr and Mo did not have synergistic effects

Mechanisms underlying post-rest potentiation in isolated left rat atria

En la aurícula izquierda aislada de rata se estudió la influencia de períodos de reposo sobre la fuerza desarrollada por el primer latido post-pausa (PRB). En condiciones controles la fuerza desarrollada por el PRB aumentó con la prolongación del período de reposo hasta los 20 s. Con intervalos más largos, el incremento de la fuerza del PRB disminuyó progresivamente. En presencia de cafeína (1 y 4 mM más alta [Ca]), iguales intervenciones produjeron una caída monótona del PRB en función de la longitud del intervalo de reposo. Cuando el calcio extracelular fue reemplazado por estroncio, la curva de tensión desarrollada por el PRB vs. el intervalo de reposo aumentó con una pendiente menor que la curva control y alcanzó el máximo a los 60 s. A niveles de saturación de la [Ca], la tensión desarrollada por el PRB no varió hasta los 20 s de pausa y, a continuación, sólo se observó una fase descendente. La curva obtenida a 0.5 mM de Ca extracelular fue similar a la control. Los resultados obtenidos en presencia de cafeína y estroncio sugieren que, en aurícula de rata, la potenciación post-reposo seria dependiente de la liberación de Ca de almacenes intracelulares y son coherentes con la hipótesis que propone que la prolongación del período de reposo provee un mayor intervalo para la transferencia de Ca de los sitios de captación a los de liberación en el retículo sarcoplasmático

Magnesium and octylguanidinium inhibition of monovalent cation translocation in mitochondria

Nosotros hemos estudiado los efectos inhibitorios de varios cationes (OG+, Mg2+, Ca2+, Ba2+, Mn2+, La3+) sobre las vías"uniport" y de intercambio para el Na+ y el K+ en mitocondrias de hígado de rata. El hinchamiento de las mitocondrias suspendidas en acetato de sodio o de potasio indica que: 1. El influjo pasivo de Na+ a mitocondrias inhibidas no se ve afectado por OG+ (en el rango micromolar), y concentraciones milimolares de cationes polivalentes sólo inducen una inhibición pobre, siendo la secuencia La3+>Mn2+>Ca2+>Mg2+>Sr2+ = 0. 2. El influjo activo de sodio se inhibe en un 50% con Mg2+ 60 micronM o con OG+ 90 micronM. El La3+, Mn2+, Ca2+ y Sr2+ también inhiben el influjo de sodio (rango milimolar). Se necesitan 10 mM de Mg2+ o 35 micronM de OG+ para inhibir en un 50% el influjo activo de potasio. 3. La salida de cationes alcalinos de mitocondrias parcialmente hinchadas e inhibidas se bloquea en un 50% con 2 mM de Mg2+ o 105 micronM OG+ siempre que el sodio sea el principal catión permeable de la solución. Se necesitan 3 mM de Mg2+ o 38 micronM de OG+ para inhibir en un 50% a las mitocondrias suspendidas en acetato de potasio. 4. La salida de cationes alcalinos de mitocondrias activas parcialmente hinchadas suspendidas en acetato de sodio se ve favorecida por concentraciones superiores a 0.1-0.2 Mg2+ o 50-100 micronM OG+. Estos datos se ajustan a un mecanismo que involucra a un translocador que introduce Na+ en un proceso dependiente de energía y que es sensible a Mg2+ y OG+ y un intercambiador catión/H+, insensible a Mg2+ y OG+, que trabajan en balance dinámico