A novel BSA immobilizing manner on modified titanium surface ameliorates osteoblast performance

Characteristics and mechanism of phosphate removal by lanthanum modified bentonite in the presence of dissolved organic matter

Lanthanum modified bentonite (LMB) is a widely used adsorbent for removing inorganic phosphorus from polluted water to prevent eutrophication. However, its efficiency can be affected by various environmental factors, including dissolved organic matter (DOM), which is still unclear. In this study, we systematically explored the influence of model DOMs, including HA, bovine serum albumin (BSA), and sodium alginate (SA), on phosphate adsorption by LMB, as well as to elucidate the underlying adsorption mechanisms. Our results showed that only HA had a significant effect on phosphate adsorption by LMB, causing inhibition. When three DOMs were mixed with phosphate in different proportions and DOM was mainly HA, the performance of phosphate adsorption on LMB became worse, while BSA can slightly offset this impact. The kinetics of HA and phosphate adsorption on LMB followed the pseudo-second-order kinetic model, and isotherms fitted the Langmuir model, with a maximum adsorption capacity of 5.7 mg g-1 for P and 12 mg g-1 for HA. However, when HA and phosphate were mixed based on their Qm, a C/P molar ratio of 5.35, LMB preferentially adsorbed phosphate. HA invasion was also disadvantageous for phosphate removal by LMB, in which P adsorption was less efficient at low-concentrations. However, during co-adsorption the adsorption capacity for HA was higher. With a secondary addition of higher levels of P, both pollutants were adsorbed more effectively. In the natural water experiment, phosphate concentration decreased with increasing shaking time, while the UV254 value showed a downward trend, indicating that LMB also adsorbed HA. Characterization results showed that La and phosphate formed LaPO4 precipitation, forming La-O-P inner-sphere complexes as the main mechanism of phosphate removal by LMB. La and HA formed La-HA complexes, with O-CO bonds from HA competing for lanthanum with phosphate. Despite HA obstructing pores from adsorbent, LMB still maintained a good binding ability with phosphate. It may form La-P-HA ternary complexes during adsorption to keep HA adsorption amount.

The Action of Angiocrine Molecules Sourced from Mechanotransduction-Related Endothelial Cell Partially Explain the Successful of Titanium in Osseointegration

Since Branemark's findings, titanium-based alloys have been widely used in implantology. However, their success in dental implants is not known when considering the heterogenicity of housing cells surrounding the peri-implant microenvironment. Additionally, they are expected to recapitulate the physiological coupling between endothelial cells and osteoblasts during appositional bone growth during osseointegration. To investigate whether this crosstalk was happening in this context, we considered the mechanotransduction-related endothelial cell signaling underlying laminar shear stress (up to 3 days), and this angiocrine factor-enriched medium was harvested further to use exposing pre-osteoblasts (pOb) for up to 7 days in vitro. Two titanium surfaces were considered, as follows: double acid etching treatment (w_DAE) and machined surfaces (wo_DAE). These surfaces were used to conditionate the cell culture medium as recommended by ISO10993-5:2016, and this titanium-enriched medium was later used to expose ECs. First, our data showed that there is a difference between the surfaces in releasing Ti molecules to the medium, providing very dynamic surfaces, where the w_DAE was around 25% higher (4 ng/mL) in comparison to the wo_DAE (3 ng/mL). Importantly, the ECs took up some of this titanium content for up to 3 days in culture. However, when this conditioned medium was used to expose pOb for up to 7 days, considering the angiocrine factors released from ECs, the concentration of Ti was lesser than previously reported, reaching around 1 ng/mL and 2 ng/mL, respectively. Thereafter, pOb exposed to this angiocrine factor-enriched medium presented a significant difference when considering the mechanosignaling subjected to the ECs. Shear-stressed ECs showed adequate crosstalk with osteoblasts, stimulating the higher expression of the Runx2 gene and driving higher expressions of Alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin. Mechanotransduction-related endothelial cell signaling as a source of angiocrine molecules also stimulated the higher expression of the Col3A1 gene in osteoblasts, which suggests it is a relevant protagonist during trabecular bone growth. In fact, we investigated ECM remodeling by first evaluating the expression of genes related to it, and our data showed a higher expression of matrix metalloproteinase (MMP) 2 and MMP9 in response to mechanosignaling-based angiocrine molecules, independent of considering w_DAE or the wo_DAE, and this profile reflected on the MMP2 and MMP9 activities evaluated via gelatin-based zymography. Complimentarily, the ECM remodeling seemed to be a very regulated mechanism in mature osteoblasts during the mineralization process once both TIMP metallopeptidase inhibitor 1 and 2 (TIMP1 and TIMP2, respectively) genes were significantly higher in response to mechanotransduction-related endothelial cell signaling as a source of angiocrine molecules. Altogether, our data show the relevance of mechanosignaling in favoring ECs' release of bioactive factors peri-implant, which is responsible for creating an osteogenic microenvironment able to drive osteoblast differentiation and modulate ECM remodeling. Taking this into account, it seems that mechanotransduction-based angiocrine molecules explain the successful use of titanium during osseointegration.

Titanium-Enriched Medium Promotes Environment-Induced Epigenetic Machinery Changes in Human Endothelial Cells

It is important to understand whether endothelial cells are epigenetically affected by titanium-enriched media when angiogenesis is required during bone development and it is expected to be recapitulated during osseointegration of biomaterials. To better address this issue, titanium-enriched medium was obtained from incubation of titanium discs for up to 24 h as recommended by ISO 10993-5:2016, and further used to expose human umbilical vein endothelial cells (HUVECs) for up to 72 h, when the samples were properly harvested to allow molecular analysis and epigenetics. In general, our data show an important repertoire of epigenetic players in endothelial cells responding to titanium, reinforcing protein related to the metabolism of acetyl and methyl groups, as follows: Histone deacetylases (HDACs) and NAD-dependent deacetylase sirtuin-1 (Sirt1), DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) methylcytosine dioxygenases, which in conjunction culminate in driving chromatin condensation and the methylation profile of DNA strands, respectively. Taking our data into consideration, HDAC6 emerges as important player of this environment-induced epigenetic mechanism in endothelial cells, while Sirt1 is required in response to stimulation of reactive oxygen species (ROS) production, as its modulation is relevant to vasculature surrounding implanted devices. Collectively, all these findings support the hypothesis that titanium keeps the surrounding microenvironment dynamically active and so affects the performance of endothelial cells by modulating epigenetics. Specifically, this study shows the relevance of HDAC6 as a player in this process, possibly correlated with the cytoskeleton rearrangement of those cells. Furthermore, as those enzymes are druggable, it opens new perspectives to consider the use of small molecules to modulate their activities as a biotechnological tool in order to improve angiogenesis and accelerate bone growth with benefits of a fast recovery time for patients.

Robust Transparent Titanium Dioxide Coating Based on the AACVD Process for Anticorrosion Marine Exploration

Transparent and robust titanium dioxide (TiO₂) coatings were prepared by the facile aerosol-assisted chemical vapor deposition (AACVD) method. The effects of deposition temperature and precursor concentration on the crystal growth and optical properties of TiO₂ coating were investigated. It is found that the obtained TiO₂ coating has strong adhesion to the substrate, which can effectively avoid mechanical scratches and wear by sharp objects, adhesive tape and steel wool. Besides, in the marine corrosion protection test, both the open circuit potential and electrochemical impedance of TiO₂ coating immersed in artificial seawater for different times are greater than those of the bare S420 steel substrate. Particularly, the high-frequency phase angle of the TiO₂ coating increases, and the impedance value at low frequency of 0.10 Hz is about 2 orders of magnitude higher than that of the bare S420 substrate. In addition, the significant decrease of corrosion products on the surface further proves that the deposited TiO₂ coating exhibits better corrosion inhibition and excellent anticorrosion properties, which is expected in application of the surface coating protection of the marine exploration lens.

Revisiting the hydroxylation phenomenon of SiO2: a study through "hard-hard" and "soft-soft" interactions

Surface hydroxylation has been extensively studied over the years for a variety of applications, and studies involving hydroxylation of different silica surfaces are still carried out due to the interesting properties obtained from those modified surfaces. Although a number of theoretical studies have been employed to evaluate details on the hydroxylation phenomenon on silica (SiO₂) surfaces, most of these studies are based on computationally expensive models commonly based on extended systems. In order to circumvent such an aspect, here we present a low-cost theoretical study on the SiO₂ hydroxylation process aiming to evaluate aspects associated with water-SiO₂ interaction. Details about local reactivity, chemical softness, and electrostatic potential were evaluated for SiO₂ model substrates in the framework of the density functional theory (DFT) using a molecular approach. The obtained results from this new and promising approach were validated and complemented by fully atomistic reactive molecular dynamics (FARMD) simulations. Furthermore, the implemented approach proves to be a powerful tool that is not restricted to the study of hydroxylation, opening a promising route for low computational cost to analyze passivation and anchoring processes on a variety of oxide surfaces.

Metabolic effects of CoCr-enriched medium on shear-stressed endothelial cell and osteoblasts: A possible mechanism involving a hypoxic condition on bone healing

Cobalt-chromium (CoCr)-based alloys have emerged as an interesting biomaterial within biomedical field, mainly considering their biocompatibility, resistance to corrosion and absence of magnetism; however, its effect on cell metabolism is barely known and this prompted us better evaluating whether CoCr-enriched medium affects the metabolism of both osteoblast and endothelial cells, and also if there is a coupling between them. This is also considered here the already-known effect of Cobalt (Co) as a hypoxic element. Firstly, discs of CoCr [subjecting (W) or not (Wo) to dual acid-etched (DAE)] were incubated into FBS-free cell culture medium up to 24 h (37 °C). This CoCr-enriched medium was further used to treat shear-stressed endothelial cells cultures up to 72 h. Thereafter, the conditioned medium containing metabolites of shear-stressed endothelial cells in response to CoCr-enriched medium was further used to subject osteoblast's cultures, when the samples were properly harvested to allow the analysis of the molecular issues. Our data shows that CoCr-enriched medium contains 1.5 ng-2.0 ng/mL of Co, which was captured by endothelial cells and osteoblasts in about 30% in amount and it seems modulate their metabolic pathways: shear-stressed endothelial cells expressed higher profile of HIF1α, VEGF and nNOS genes, while their global profile of protein carbonylation was lower than the control cultures, suggesting lower oxidative stress commitment. Additionally, osteoblasts responding to metabolites of CoCr-challenged endothelial cells show dynamic expression of marker genes in osteogenic differentiation, with alkaline phosphatase (ALP), osteocalcin, and bone sialoprotein (BSP) genes being significantly increased. Additionally, tensional shear-stress forces decrease the stimulus for ColA1gene expression in osteoblasts responding to endothelial cells metabolites, as well as modifying the extracellular matrix remodeling related genes. Analyzing the activities of matrix metalloproteinases (MMPs), the data shows that shear-stressed endothelial cells metabolites increase the activities of both MMP9 and MMP2 in osteoblasts. Altogether, our data shows for the first time that shear-stressed endothelial metabolites responding to CoCr discs contribute to osteogenic phenotype in vitro, and this predicts an active crosstalk between angiogenesis and osteogenesis during osseointegration of CoCr alloy and bone healing, maybe guided by the Co-induced hypoxic condition.

The molecular pathway triggered by zirconia in endothelial cells involves epigenetic control

The requirement to achieve natural looking restorations is one of the most challenging aspects in dentistry. Although zirconia has provided new opportunities for achieving superior aesthetics and physicochemical outcomes, very little has been achieved for its cellular and molecular performance, especially considering angiogenesis and osteogenesis. As angiogenesis is a secondary event and concomitant to osteogenesis, an indirect effect of dental implant on endothelial cells could be the release of active molecules such as those already reported affecting osteoblasts. To better address this issue, we challenged human endothelial cells (HUVECs) with zirconia-conditioned medium up to 72 h to allow analysis specific gene expression and protein pattern of mediators of epigenetic machinery in full. Our data shows involvement of zirconia in triggering intracellular signaling through MAPK-ERK activation, leading the signal to activate histone deacetylase HDAC6 likely with concomitant well-modulated DNA methylation profile by DNMTs and TETs. These signaling pathways seem to culminate in cytoskeleton rearrangement of endothelial cells, an important prerequisite to cell migration expected in angiogenesis. Collectively, this study demonstrates for the first time epigenetic-related molecular mechanism involved in endothelial cells responding to zirconia, revealing a repertoire of signaling molecules capable of executing the reprogramming process of gene expression, which are necessary to drive cell proliferation, migration, and consequently angiogenesis. This set of data can further studies using gene editing approaches to better elucidate functional roles.

PI3K/AKT signaling drives titanium-induced angiogenic stimulus

Although osseointegration and clinical success of titanium (Ti)-implanted materials depend on neovascularization in the reactional peri-implant tissue, very little has been achieved considering the Ti-molecules release on the behavior of endothelial cells. To address this issue, we challenged endothelial cells (HUVECs) with Ti-enriched medium obtained from two types of commercial titanium surfaces [presenting or not dual-acid etching (DAE)] up to 72 h to allow molecular machinery analysis. Our data show that the Ti-enriched medium provokes significant stimulus of angiogenesis-related machinery in endothelial cells by upexpressing VEGFR1, VEGFR2, VEGF, eNOS, and iNOS genes, while the PI3K/Akt signaling pathway was also significantly enhanced. As PI3K/AKT signaling was related to angiogenesis in response to vascular endothelial growth factor (VEGF), we addressed the importance of PI3K/Akt upon Ti-enriched medium responses by concomitantly treating the cells with wortmannin, a well-known PI3K inhibitor. Wortmannin suppressed the angiogenic factors, because VEGF, VEGFR1, and eNOS genes were downregulated in those cells, highlighting the importance of PI3K/AKT signaling on driving angiogenic phenotype and angiogenesis performance within the peri-implant tissue reaction. In conjunction, these data reinforce that titanium-implantable devices modify the metabolism of surrounding cells, such as endothelial cells, probably coupling osteogenesis and angiogenesis processes in peri-implant tissue and then contributing to successfully osseointegration of biomedical titanium-based devices.