Effects of perfusion and cyclic compression on in vitro tissue engineered meniscus implants.

PURPOSE: The purpose of this study was to investigate the influence of continuous perfusion and mechanical stimulation on bone marrow stromal cells seeded on a collagen meniscus implant. METHODS: Bone marrow aspirates from 6 donors were amplified in vitro. 10(6) human BMSC were distributed on a collagen meniscus implant. Scaffolds were cultured under static conditions (control) or placed into a bioreactor system where continuous perfusion (10 ml/min) or perfusion and mechanical stimulation (8 h of 10% cyclic compression at 0.5 Hz) were administered daily. After 24 h, 7 and 14 days, cell proliferation, synthesis of procollagen I and III peptide (PIP, PIIIP), histology, and the equilibrium modulus of the constructs were analyzed. RESULTS: Proliferation demonstrated a significant increase over time in all groups (p < 0.001). PIP synthesis was found to increase from 0.1 ± 0.0 U/ml/g protein after 24 h to 2.0 ± 0.5 (perfusion), 3.8 ± 0.3 (mechanical stimulation), and 1.8 ± 0.2 U/ml/g protein (static control, lower than perfusion and mechanical stimulation, p < 0.05). These differences were also evident after 2 weeks (2.7 ± 0.3, 4.0 ± 0.6, and 1.8 ± 0.2 U/ml/g protein, p < 0.01); PIIIP synthesis was found to increase from 0.1 ± 0.0 U/ml/g protein after 24 h to 2.9 ± 0.7 (perfusion), 3.1 ± 0.9 (mechanical stimulation), and 1.6 ± 0.3 U/ml/g protein (controls) after 1 week and remained significantly elevated under the influence of perfusion and mechanical stimulation (p < 0.01) after 2 weeks. Mechanical stimulation increased the equilibrium modulus more than static culture and perfusion after 2 weeks (24.7 ± 7.6; 12.3 ± 3.7; 15.4 ± 2.6 kPa; p < 0.02). CONCLUSION: Biomechanical stimulation and perfusion have impact on collagen scaffolds seeded with BMSCs. Cell proliferation can be enhanced using continuous perfusion and differentiation is fostered by mechanical stimulation.

N(2)-BET specific surface area of bentonites.

The specific surface areas (SSA(N2BET)) of 36 different bentonites had larger values for Ca(2+)/Mg(2+) bentonites than for Na(+) bentonites. This trend could not be explained by the different d(001) values nor by the different microstructures. The investigation of Cu-triene-exchanged smectites, which on drying at 105 degrees C still had a d(001) value accounting for approximately 13A, proved that the SSA(N2BET) of low-charged smectites increased more than that of high-charged smectites. This could be explained by: (i) more space between the permanent charge sites in the case of low-charged smectites and (ii) the fact that the layers of Cu-triene smectites do not collapse at 105 degrees C. In contrast the SSA(N2BET) of Ca(2+)-exchanged bentonites could not be related to the layer charge density (LCD) as in the case of the Cu-triene-exchanged bentonites which is probably due to the varying number of collapsed layers. In conclusion, the SSA(N2BET) of bentonites which is known to be largely variable is probably determined by microporosity resulting from the quasi-crystalline overlap region and accessible areas of the interlayer. The number of layers per stack and the microstructure are supposed to play a subordinate role. The larger SSA(N2BET) of Ca/Mg bentonites compared to Na bentonites probably can be explained by the larger space between the charges in the case of the presence of divalent cations.

Incorporation of Eu(III) into hydrotalcite: a TRLFS and EXAFS study.

The behavior of radionuclides in the environment (geo-, hydro-, and biosphere) is determined by interface reactions like adsorption, ion exchange, and incorporation processes. Presently, operational gross parameters for the distribution between solution and minerals are available. For predictive modeling of the radionuclide mobility in such systems, however, individual reactions and processes need to be localized, characterized, and quantified. A prerequisite for localization and clarification of the concerned processes is the use of modern advanced analytical and speciation methods, especially spectroscopy. In this study, Eu(III) was chosen as an analogue for trivalent actinides to identify the different species that occur by the Ln(III)/hydrotalcite interaction. Therefore, Eu(III) doped Mg-Al-Cl-hydrotalcite was synthesized and investigated by TRLFS, EXAFS, and XRD measurements. Two different Eu/hydrotalcite species were obtained. The minor part of the lanthanide is found to be inner-sphere sorbed onto the mineral surface, while the dominating Eu/hydrotalcite species consists of Eu(III) that is incorporated into the hydrotalcite lattice. Both Eu/hydrotalcite species have been characterized by their fluorescence emission spectra and lifetimes. Structural parameters of the incorporated Eu(III) species determined by EXAFS indicate a coordination number of 6.6 +/- 1.3 and distances of 2.41 +/- 0.02 A for the first Eu-OH shell.