Human Periodontal Ligament Stem Cell and Umbilical Vein Endothelial Cell Co-Culture to Prevascularize Scaffolds for Angiogenic and Osteogenic Tissue Engineering

(1) Background: Vascularization remains a critical challenge in bone tissue engineering. The objective of this study was to prevascularize calcium phosphate cement (CPC) scaffold by co-culturing human periodontal ligament stem cells (hPDLSCs) and human umbilical vein endothelial cells (hUVECs) for the first time; (2) Methods: hPDLSCs and/or hUVECs were seeded on CPC scaffolds. Three groups were tested: (i) hUVEC group (hUVECs on CPC); (ii) hPDLSC group (hPDLSCs on CPC); (iii) co-culture group (hPDLSCs + hUVECs on CPC). Osteogenic differentiation, bone mineral synthesis, and microcapillary-like structures were evaluated; (3) Results: Angiogenic gene expressions of co-culture group were 6–9 fold those of monoculture. vWF expression of co-culture group was 3 times lower than hUVEC-monoculture group. Osteogenic expressions of co-culture group were 2–3 folds those of the hPDLSC-monoculture group. ALP activity and bone mineral synthesis of co-culture were much higher than hPDLSC-monoculture group. Co-culture group formed capillary-like structures at 14–21 days. Vessel length and junction numbers increased with time; (4) Conclusions: The hUVECs + hPDLSCs co-culture on CPC scaffold achieved excellent osteogenic and angiogenic capability in vitro for the first time, generating prevascularized networks. The hPDLSCs + hUVECs co-culture had much better osteogenesis and angiogenesis than monoculture. CPC scaffolds prevacularized via hPDLSCs + hUVECs are promising for dental, craniofacial, and orthopedic applications.

Biomineralization of Magnetosomes: Billion-Year Evolution Shaping Modern Nanotools

Biomineralization in the microbial realm usually gives origin to finely structured inorganic nanomaterials. Perhaps, one of the most elegant bioinorganic processes found in nature is the iron biomineralization into magnetosomes, which is performed by magnetotactic bacteria. A magnetosome gene cluster within the bacterial genome precisely regulates the mineral synthesis. The spread and evolution of this ability among bacteria are thought to be a 2,7-billion-year process mediated by horizontal gene transfers. The produced magnetite or greigite nanocrystals coated by a biological membrane have a narrow diameter dispersibility, a highly precise morphology, and a permanent magnetic dipole due to the molecular level control. Approaches inspired by this bacterial biomineralization mechanism can imitate some of the biogenic nanomagnets characteristics in the chemical synthesis of iron oxide nanoparticles. Thus, this chapter will give a concise overview of magnetosome synthesis’s main steps, some hypotheses about the evolution of magnetosomes’ biomineralization, and approaches used to mimic this biological phenomenon in vitro.

Rainfall as the major driver of plant Si availability in gibbsitic Andosols

<p>The amount of water available to leach solutes from soil is one of the major features determining mineral weathering, secondary mineral synthesis and soil properties. The occurrence of gibbsite in soils denotes strong desilication.</p><p>Here, we quantify the reservoirs of bioavailable Si and phytolithic Si in wet tropical Andosols rich in gibbsite along a topoclimosequence where mean annual rainfall (MAR) increases from 2650 to 4400 mm with increasing altitude (65-375m above sea level) in Basse-Terre, Guadeloupe. We assessed bioavailable Si through CaCl<sub>2</sub> extraction in soil and the pool of soil phytoliths through Na<sub>2</sub>CO<sub>3</sub> extraction and heavy liquid (hl) separation (followed by XRD quantification). The Na<sub>2</sub>CO<sub>3</sub> extraction was performed on both the bulk soil and oxalate–treated soil (ox-Na<sub>2</sub>CO<sub>3</sub>) cleared of its amorphous aluminosilicates.</p><p>The Andosols have reached an advanced weathering stage. Their secondary products included (Al, Fe)-humus complexes, ferrihydrite, gibbsite and aluminous allophanic substances. The contents of organic C, metal-humus, ferrihydrite and gibbsite increased in wettest conditions (>3000mm) whereas allophane content concomitantly decreased. Ox-Na<sub>2</sub>CO<sub>3</sub> Si (2-7 g kg<sup>-1</sup>) contents were below hl Si contents (2-22 g kg<sup>-1</sup>), and were negatively correlated to each other (r = -0.88) suggesting the occurrence of two pools of phytoliths: (i) free and fresh phytoliths, (ii) aged phytoliths entrapped in soil aggregates. Yet, bioavailable Si content in soil decreased from 63 to 12 mg kg<sup>-1</sup> with increasing MAR (r = -0.92), and was strongly correlated (r = +0.95) to that of phytolithic Si as assessed after ox-Na<sub>2</sub>CO<sub>3</sub> extraction. The Si/Al ratio of the ox-Na<sub>2</sub>CO<sub>3</sub> extract regularly decreased from 1.06 to 0.37 with increasing MAR, hence corroborating strongest desilication in wettest conditions. In these highly leached, gibbsitic Andosols, rainfall is thus the major driver of plant Si availability.</p>

Numerical simulation of orthosilicic acid polycondensation and silica particles formation inhydrothermal solutions

Numerical simulation of the process of polycondensation of orthosilicic acid and colloid silica particles growth under different physical and chemical conditions was done: temperature, pH, ionic strength and other. Calculated dependences of orthosilicic acid concentration and mean radius of silica particles versus time, graphs of particles dimensions distributions were received. Results of calculations were compared with experimental data. Research is important for to make clear role of colloid silica on hydrothermal mineral formation and for industrial extraction and utilization of silica, and also for mineral synthesis.