Cytocompatibility of a free machining titanium alloy containing lanthanum

Biocompatibility and degradation of the open-pored magnesium scaffolds LAE442 and La2

Porous magnesium implants are of particular interest for application as resorbable bone substitutes, due to their mechanical strength and a Young's modulus similar to bone. The objective of the present study was to compare the biocompatibility, bone and tissue ingrowth, and the degradation behaviour of scaffolds made from the magnesium alloys LAE442 (n= 40) and Mg-La2 (n= 40)in vivo. For this purpose, cylindrical magnesium scaffolds (diameter 4 mm, length 5 mm) with defined, interconnecting pores were produced by investment casting and coated with MgF₂. The scaffolds were inserted into the cancellous part of the greater trochanter ossis femoris of rabbits. After implantation periods of 6, 12, 24 and 36 weeks, the bone-scaffold compounds were evaluated usingex vivo µCT80 images, histological examinations and energy dispersive x-ray spectroscopy analysis. The La2 scaffolds showed inhomogeneous and rapid degradation, with inferior osseointegration as compared to LAE442. For the early observation times, no bone and tissue could be observed in the pores of La2. Furthermore, the excessive amount of foreign body cells and fibrous capsule formation indicates insufficient biocompatibility of the La2 scaffolds. In contrast, the LAE442 scaffolds showed slow degradation and better osseointegration. Good vascularization, a moderate cellular response, bone and osteoid-like bone matrix at all implantation periods were observed in the pores of LAE442. In summary, porous LAE442 showed promise as a degradable scaffold for bone defect repair, based on its degradation behaviour and biocompatibility. However, further studies are needed to show it would have the necessary mechanical properties required over time for weight-bearing bone defects.

Soft Hydrogel Zwitterionic Coatings Minimize Fibroblast and Macrophage Adhesion on Polyimide Substrates

Minimizing the foreign body reaction to polyimide-based implanted devices plays a pivotal role in several biomedical applications. In this work, we propose materials exhibiting nonbiofouling properties and a Young's modulus reflecting that of soft human tissues. We describe the synthesis, characterization, and in vitro validation of poly(carboxybetaine) hydrogel coatings covalently attached to polyimide substrates via a photolabile 4-azidophenyl group, incorporated in poly(carboxybetaine) chains at two concentrations of 1.6 and 3.1 mol %. The presence of coatings was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy. White light interferometry was used to evaluate the coating continuity and thickness (between 3 and 6 μm under dry conditions). Confocal laser scanning microscopy allowed us to quantify the thickness of the swollen hydrogel coatings that ranged between 13 and 32 μm. The different hydrogel formulations resulted in stiffness values ranging from 2 to 19 kPa and led to different fibroblast and macrophage responses in vitro. Both cell types showed a minimum adhesion on the softest hydrogel type. In addition, both the overall macrophage activation and cytotoxicity were observed to be negligible for all of the tested material formulations. These results are a promising starting point toward future advanced implantable systems. In particular, such technology paves the way for novel neural interfaces able to minimize the fibrotic reaction, once implanted in vivo, and to maximize their long-term stability and functionality.

Extended culture of macrophages from different sources and maturation results in a common M2 phenotype

Inflammatory responses to biomaterials heavily influence the environment surrounding implanted devices, often producing foreign-body reactions. The macrophage is a key immunomodulatory cell type consistently associated with implanted biomaterials and routinely used in short-term in vitro cell studies of biomaterials aiming to reproduce host responses. Inconsistencies within these studies, including differently sourced cells, different durations of culture, and assessment of different activation markers, lead to many conflicting results in vitro that confound consistency and conclusions. We hypothesize that different experimentally popular monocyte-macrophage cell types have intrinsic in vitro culture-specific differences that yield conflicting results. Recent studies demonstrate changes in cultured macrophage cytokine expression over time, leading to the hypothesis that changes in macrophage phenotype also occur in response to extended culture. Here, macrophage cells of different transformed and primary-derived origins were cultured for 21 days on model polymer biomaterials. Cell type-based differences in morphology and cytokine/chemokine expression as well as changes in cell surface biomarkers associated with differentiation stage, activation state, and adhesion were compared. Results reflect consistent macrophage development toward an M2 phenotype via up-regulation of the macrophage mannose receptor for all cell types following 21-day extended culture. Significantly, implanted biomaterials experiencing the foreign-body response and encapsulation in vivo often elicit a shift toward an analogous M2 macrophage phenotype. In vitro "default" of macrophage cultures, regardless of lineage, to this M2 state in the presence of biomaterials at long culture periods is not recognized, but has important implications to in vitro modeling of in vivo host response.

Lanthanum breaks the balance between osteogenesis and adipogenesis of mesenchymal stem cells through phosphorylation of Smad1/5/8

La breaks the balance between osteogenesis and adipogenesis of MSCs through phosphorylating Smad1/5/8 to activate the BMP signaling pathway.

The role of chemical interactions between thorium, cerium, and lanthanum in lymphocyte toxicity

Thorium, cerium, and lanthanum are metals present in several types of minerals, the most common of which is monazite. Cerium and lanthanum are elements in the lanthanides series. Thorium, an actinide metal, is a hazardous element due to its radioactive characteristics. There is a lack of information describing the possible chemical interactions among these elements and the effects they may have on humans. Toxicological analyses were performed using cell viability, cell death, and DNA damage assays. Chemical interactions were evaluated based on the Loewe additivity model. The results indicate that thorium and cerium individually have no toxic effects on lymphocytes. However, thorium associated with lanthanum increases the toxicity of this element, thereby reducing the viability of lymphocytes at low concentrations of metals in the mixture.