19
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Bioactive Glass-Ceramic Foam Scaffolds from ‘Inorganic Gel Casting’ and Sinter-Crystallization

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Highly porous bioactive glass-ceramic scaffolds were effectively fabricated by an inorganic gel casting technique, based on alkali activation and gelification, followed by viscous flow sintering. Glass powders, already known to yield a bioactive sintered glass-ceramic (CEL2) were dispersed in an alkaline solution, with partial dissolution of glass powders. The obtained glass suspensions underwent progressive hardening, by curing at low temperature (40 °C), owing to the formation of a C–S–H (calcium silicate hydrate) gel. As successful direct foaming was achieved by vigorous mechanical stirring of gelified suspensions, comprising also a surfactant. The developed cellular structures were later heat-treated at 900–1000 °C, to form CEL2 glass-ceramic foams, featuring an abundant total porosity (from 60% to 80%) and well-interconnected macro- and micro-sized cells. The developed foams possessed a compressive strength from 2.5 to 5 MPa, which is in the range of human trabecular bone strength. Therefore, CEL2 glass-ceramics can be proposed for bone substitutions.

          Related collections

          Most cited references32

          • Record: found
          • Abstract: not found
          • Article: not found

          Biomedical applications of polymer-composite materials: a review

            Bookmark
            • Record: found
            • Abstract: not found
            • Article: not found

            Geopolymers and other alkali activated materials: why, how, and what?

              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Acidosis inhibits bone formation by osteoblasts in vitro by preventing mineralization.

              The negative effect of acidosis on the skeleton has been known for almost a century. Bone mineral serves an important pathophysiologic role as a reserve of hydroxyl ions to buffer systemic protons if the kidneys and lungs are unable to maintain acid-base balance within narrow physiologic limits. Extracellular hydrogen ions are now thought to be the primary activation signal for osteoclastic bone resorption, and osteoclasts are very sensitive to small changes in pH within the pathophysiologic range. Herein, we investigated the effects of acidosis on osteoblast function by using mineralized bone nodule-forming primary osteoblast cultures. Osteoblasts harvested from neonatal rat calvariae were cultured up to 21 days in serum-containing medium, with ascorbate, beta-glycerophosphate and dexamethasone. pH was manipulated by addition of 5 to 30 mmol/L HCl and monitored by blood gas analyzer. Abundant, matrix-containing mineralized nodules formed in osteoblast cultures at pH 7.4, but acidification progressively reduced mineralization of bone nodules, with complete abolition at pH 6.9. Osteoblast proliferation and collagen synthesis, assessed by 3H-thymidine and 3H-proline incorporation, respectively, were unaffected by pH in the range 7.4 to 6.9; no effect of acidification on collagen ultrastructure and organization was evident. The apoptosis rate of osteoblasts, assessed by the enrichment of nucleosomes in cell lysates, was also unaffected by pH within this range. However, osteoblast alkaline phosphatase activity, which peaked strongly near pH 7.4, was reduced eight-fold at pH 6.9. Reducing pH to 6.9 also downregulated messenger ribonucleic acid (mRNA) for alkaline phosphatase, but upregulated mRNA for matrix Gla protein, an inhibitor of mineralization. The same pH reduction is associated with two-and four-fold increases in Ca2+ and PO4(3-) solubility for hydroxyapatite, respectively. Our results show that acidosis exerts a selective, inhibitory action on matrix mineralization that is reciprocal with the osteoclast activation response. Thus, in uncorrected acidosis, the deposition of alkaline mineral in bone by osteoblasts is reduced, and osteoclast resorptive activity is increased in order to maximize the availability of hydroxyl ions in solution to buffer protons.
                Bookmark

                Author and article information

                Journal
                Materials (Basel)
                Materials (Basel)
                materials
                Materials
                MDPI
                1996-1944
                27 February 2018
                March 2018
                : 11
                : 3
                : 349
                Affiliations
                [1 ]Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padova, Italy; hamada.elsayed@ 123456unipd.it (H.E.); acacio.rinconromero@ 123456unipd.it (A.R.R.)
                [2 ]Ceramics Department, National Research Centre, El-Bohous Street, Cairo 12622, Egypt
                [3 ]Dipartimento Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino, Italy; giulia.molino@ 123456polito.it (G.M.); chiara.vitale@ 123456polito.it (C.V.B.)
                Author notes
                [* ]Correspondence: enrico.bernardo@ 123456unipd.it ; Tel.: +39-049-827-5510; Fax: +39-049-827-5505
                Author information
                https://orcid.org/0000-0002-9818-4498
                https://orcid.org/0000-0003-0350-8304
                https://orcid.org/0000-0003-4934-4405
                Article
                materials-11-00349
                10.3390/ma11030349
                5872928
                29495498
                5b406c52-f45a-42f7-9550-d369ea34db69
                © 2018 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 11 January 2018
                : 24 February 2018
                Categories
                Article

                cel2 glass,glass-ceramics,alkali activation,gel casting
                cel2 glass, glass-ceramics, alkali activation, gel casting

                Comments

                Comment on this article