However, the concentrations of IGF-1 and Gla-osteocalcin supernatants, which characterize the propensity to differentiate into osteoblasts, were slightly higher than that of cells exposed to Al2O3 substrates, as seen in Figure 3a,c. osteoblastogenic effects on different biomaterial substrates. Raman spectroscopy 1. Introduction It is well established that bioceramics could be bioactive in terms of both osteoblastogenesis and osteoinductivity [1]. However, to acquire conclusive evidences that osteoinductive bioceramics can provide a valid alternative to autologous bone and osteogenic growth factors, a complete Araloside V understanding of the chemical mechanisms behind the conversation between cells and the bioceramic surface is needed. In this context, we notice that, within the field of biomaterials, it is common to classify oxide (e.g., alumina) and non-oxide ceramics (e.g., silicon nitride) as fully bioinert materials while only synthetic apatites and calcium phosphates are considered to be bioactive [1,2,3]. We shall instead provide clear evidence that those oxide and non-oxide ceramics are not bioinert. Conversely, they may be either supportive (bioactive) or detrimental to differentiation and metabolism of mesenchymal progenitor cells. After an initial proposal of osteoinductivity for calcium phosphate made up of biomaterials [4,5], only one study has proposed osteoinductivity for alumina ceramics [6]; however, several studies have favored titanium as an osteoinductive substrate [7,8]. Recent and studies [9,10] have indicated that silicon nitride, a non-oxide bioceramic previously considered to be fully bioinert [1], is usually instead a formidable stimulator of osteoblastogenesis and osteoinductivity. The mechanisms of osteoinduction by the above biomaterials have been phenomenologically covered by the above publications, but the fundamental chemistry driving osteoblastogenesis and the successive bone formation needs additional elucidation. For more than 50 years bone biologists have embarked on efforts to understand the dynamic processes of differentiation and energetics of bone cells. However, the initial investigations of substrate utilization by bone cells were mainly focused on finely tuning the culture conditions for supporting collagen and mineral production [11]. Later, the focus shifted to hormonal regulation [12]. Currently, the search targets the role of substrates in anabolic treatments for osteoporosis and the enhancement of the work of the osteoblast through ionic alteration of osteoblast Araloside V metabolism [13,14]. In this study, we re-examine and compare the surface chemistries of alumina, silicon nitride, and Ti6Al4V titanium alloy in this latter optics. Oxide and non-oxide bioceramics were selected for this investigation because they are presently used in joint arthroplasty and spine arthrodesis, respectively. Both bioceramics are considered as Mouse monoclonal to XRCC5 innovative choices with respect to titanium alloy, which is usually widely used in both the above applications. For this latter reason, we selected the Ti6Al4V alloy as the most appropriate substrate for comparative purpose. The focus of this paper is around the ionic exchange at the interface between mesenchymal cells and different substrates. The aim of this study is usually to clarify which off-stoichiometric reactions take place at the biomolecular interface of bioceramics and how they differ between alumina (Al2O3) and silicon nitride (Si3N4) bioceramic substrates, demonstrating how the former stresses the cells in a similar way as titanium alloy, while the latter supports cell metabolism and bone formation. 2. Results 2.1. Substrate Surface Modifications in Aqueous Environment The experiments described in this section challenge the notion that alumina oxide and silicon nitride non-oxide bioceramics remain completely inert in an aqueous environment. The substrate samples used in this study had surfaces with comparable average values of roughness: 0.32 0.02, 0.10 0.01, and 0.29 0.04, for Si3N4, Al2O3, and Ti6Al4V alloy substrates, respectively. Physique 1aCc show the variations of X-ray photoelectron spectroscopy (XPS) Si2p core spectrum of silicon nitride, O1s core spectrum of Ti6Al4V alloy, and Al2p core spectrum of alumina with time in water vapor environment, respectively. The core spectra in the respective sections, which compare the as-received and 24 h-exposed surfaces, were deconvoluted into peak components representing the respective bonds, as shown by the labels of the physique [15,16,17,18,19,20]. The plots around the left side of each section give the trends with time of the population of individual bond components in terms of elemental fractions. Open in a separate window Physique 1 X-ray photoelectron spectroscopy (XPS) analyses of the investigated substrates before (left) and after (center) accelerated assessments in water vapor environment, and plots summarizing elemental fraction results at different autoclaving times Araloside V (right): (a) Si2p core spectrum of silicon nitride; (b) O1s core spectrum of Ti6Al4V alloy; and (c) Al2p core.