Growth and differentiation of human bone marrow osteoprogenitors on novel calcium phosphate cements.

Materials that augment bone cell proliferation and osteogenic activity have important therapeutic implications for bone regeneration and for use in skeletal reconstruction and joint replacement. We have studied the growth and interactions of human bone marrow cells on a variety of new cement composites in vitro. These cement materials are composed of calcium-deficient hydroxyapatites, carbonated apatite and amorphous calcium phosphate. Cell proliferation was significantly reduced and cell differentiation increased in the presence of these cements compared with cells cultured on tissue culture plastic. Alkaline phosphatase, one of the markers of the osteoblast phenotype, was dramatically stimulated by 3 of the 4 cements examined between day 4 and day 10, above levels observed following culture of human osteoblasts on plastic alone. Photomicroscopic examination demonstrated growth and close integration of bone marrow cells and 3 of the composites. Longer term marrow cultures (15 day) on the cements confirmed the stimulation of cell differentiation over proliferation. From these studies, enhanced osteoblastic differentiation was observed on a 70% carbonated apatite, which has a composition similar to bone mineral, whereas, cell toxicity was observed on cells grown on amorphous calcium phosphate. This in vitro culture system demonstrates the use of human bone marrow cells for the potential evaluation of new biomaterials and the development of a novel carbonated apatite that may be of potential use in orthopaedic implants

Characterization of a novel calcium phosphate/sulphate bone cement

Apatitic cements have shown excellent biocompatibility and adequate mechanical properties but have slow resorption in the human body. To assure that new bone tissue grows into the bone defect, a certain porosity is necessary although hard to achieve in injectable cements with suitable mechanical properties. An attempt was made by mixing alpha-tricalcium phosphate (alpha-TCP), calcium sulphate hemihydrate (CSH) and an aqueous solution containing 2.5 wt% of Na2HPO4. The aim was to obtain a material containing two phases: a) one apatitic phase (calcium-deficient hydroxyapatite; CDHA) and b) one resorbable phase (calcium sulphate dihydrate; CSD). alpha-TCP and CSH mixtures were produced at relative intervals of 20 wt%. The liquid-to-powder (L/P) ratio to obtain a paste was 0.32 mLg(-1). The highest compressive strength (34 MPa) was obtained for the pure alpha-TCP sample. The strength was, in a first approximation, directly correlated to the weight proportions of the powders. X-ray diffraction analysis showed that the relative intensity for CDHA increased linearly, and the one for CSD decreased exponentially, when the amount of alpha-TCP increased. Thus, CSH ceased to transform to CSD when the amount of alpha-TCP increased. Observations in environmental scanning electron microscopy confirmed the X-ray diffraction results. CSH-crystals (100 mum) were embedded in the HA-matrix permitting gradual porosity in the material when resorbed

Microstructure analysis of novel resorbable calcium phosphate/sulphate bone cements

This paper presents a new method to obtain porosity in apatitic cements, by mixing a-tricalcium phosphate (alpha-TCP) with calcium sulphate hemihydrate. The material was characterized by X-ray diffraction and observations in Electron Microscopy. The results show that crystals of calcium sulphate stayed embedded in the hydroxyapatite formed from a-TCP. By dissolution of these crystals porosity could be obtained where new bone tissue could grow in and resorb the cement

Fast-degrading PLA/ORMOGLASS fibrous composite scaffold leads to a calcium-rich angiogenic environment

Nadège Sachot,1,2 Agata Roguska,3 Josep Anton Planell,1,2 Malgorzata Lewandowska,3 Elisabeth Engel,1,2,4 Oscar Castaño1,2,5,6 1Biomaterials for Regenerative Therapies, Institute for Bioengineering of Catalonia (IBEC), Barcelona, 2CIBER en Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza, Spain; 3Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw, Poland; 4Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya (UPC), 5Department of Materials Science and Physical Chemistry, Universitat de Barcelona (UB), 6Department of Engineerings: Electronics, Universitat de Barcelona, Barcelona, Spain Abstract: The success of scaffold implantation in acellular tissue engineering approaches relies on the ability of the material to interact properly with the biological environment. This behavior mainly depends on the design of the graft surface and, more precisely, on its capacity to biodegrade in a well-defined manner (nature of ions released, surface-to-volume ratio, dissolution profile of this release, rate of material resorption, and preservation of mechanical properties). The assessment of the biological behavior of temporary templates is therefore very important in tissue engineering, especially for composites, which usually exhibit complicated degradation behavior. Here, blended polylactic acid (PLA) calcium phosphate ORMOGLASS (organically modified glass) nanofibrous mats have been incubated up to 4 weeks in physiological simulated conditions, and their morphological, topographical, and chemical changes have been investigated. The results showed that a significant loss of inorganic phase occurred at the beginning of the immersion and the ORMOGLASS maintained a stable composition afterward throughout the degradation period. As a whole, the nanostructured scaffolds underwent fast and heterogeneous degradation. This study reveals that an angiogenic calcium-rich environment can be achieved through fast-degrading ORMOGLASS/PLA blended fibers, which seems to be an excellent alternative for guided bone regeneration. Keywords: electrospinning, fast degradation, ORMOGLASSES, angiogenesis, nanofibers, calcium release&nbsp