Dimensions of elongated mineral particles: a study of more than 570 fibers from more than 90 cases with implications for pathogenicity and classification as asbestiform vs. cleavage fragments.

Asbestos is well-recognized as the cause of a variety of disorders of the respiratory tract, including neoplastic as well as non-neoplastic conditions. Fiber dimensions and biopersistence are important determinants of the pathologic response, and analytical electron microscopy is a powerful technique for determining the fiber content of lung tissue samples. For decades our laboratory has examined lung tissue samples counting fibers measuring 5 µm or greater in length. More recent observations have indicated that fibers 10 µm or greater in length are pathogenic, and that a length of 10 µm and diameter less than 1.0 µm are useful features for distinguishing asbestiform fibers from cleavage fragments. We examined more than 570 fibers from more than 90 cases to determine the dimensions of fibers that might be classified as asbestos. The vast majority of fibers classified as amosite or crocidolite met the criteria for length greater than 10 µm and diameter less than 1.0 µm. However, a significant proportion of fibers classified as tremolite, actinolite, or anthophyllite did not meet these criteria. These findings have important implications for the identification and classification of elongated mineral particles, both in terms of pathogenicity as well as classification as asbestiform vs. cleavage fragments.

Investigation of applying chitosan coating on antibacterial and biocompatibility properties of bredigite/titanium dioxide composite scaffolds.

In this study by considering the advantages of bredigite (Br) and titanium dioxide (TiO2) bioceramics, composite scaffolds of bredigite/titanium dioxide were prepared by the gelcasting method, then, to improve the mechanical, biological and antibacterial properties, scaffolds were coated with chitosan (Ch) polymer phase. The phase structure, fundamental groups, chemical composition, and elemental distribution analysis, morphology and the form of porosity were respectively characterized by XRD, FTIR, EDS, and SEM. Mechanical properties and porosity percentage of scaffolds were also measured by the compressive strength test and Archimedean method, respectively. In order to verify the cell compatibility, MG63 bone marrow cells were cultured on the surface of the specimens. The results showed that the addition of titanium dioxide to the scaffold of bredigite resulted in decrease of porosity and increase of compressive strength of scaffolds from 0.299 to 0.687 MPa. Furthermore, the coated scaffold with chitosan polymer reduced porosity from 83 to 63 percent and a remarkable improvement in compressive strength from 0.585 to 2.339 MPa. The results of the antibacterial test showed that in composite scaffolds, The diameter of the inhibition zone is 22 and 29 mm, in the culture media of Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive), respectively. On the other hand, the results of cell compatibility and cell adhesion tests showed that the scaffolds had no toxicity and the growth, proliferation, and adhesion of MG63 bone cells adjacent to the scaffolds was desirable. Therefore, the scaffold in this study can be used as an ideal scaffold for use in bone tissue engineering.

In-vitroassessment of ß-tricalcium phosphate/bredigite-ciprofloxacin (CPFX) scaffolds for bone treatment applications.

In the present study, ß-tricalcium phosphate (ß-TCP) scaffolds with various amounts of bredigite (Bre) were fabricated by the space holder method. The effect of bredigite content on the structure, mechanical properties,in vitrobioactivity, and cell viability was investigated. The structural assessment of the composite scaffolds presented interconnected pores with diameter of 300-500 µm with around 78%-82% porosity. The results indicated that the compressive strength of the scaffolds with 20% bredigite (1.91 MPa) was improved in comparison with scaffolds with 10% bredigite (0.52 MPa), due to the reduction of the average pore and grain sizes. Also, the results showed that the bioactivity and biodegradability of ß-TCP/20Bre were better than that of ß-TCP/10Bre. Besides, in this study, the release kinetics of ciprofloxacin (CPFX) loaded ß-TCP/Bre composites as well as the ability of scaffolds to function as a sustained release drug carrier was investigated. Drug release pattern of ß-TCP/bredigite-5CPFX scaffolds exhibited the rapid burst release of 43% for 3 h along with sustained release (82%) for 32 h which is favorable for bone infection treatment. Antibacterial tests revealed that the antibacterial properties of ß-TCP/bredigite scaffolds are strongly related to the CPFX concentration, wherein the scaffold containing 5% CPFX showed the most significant zone of inhibition (33 ± 0.5 mm) againstStaphylococcus aureus. The higher specific surface areas of nanostructure ß-TCP/bredigite scaffolds containing CPFX lead to an initial rapid release followed by constant drug delivery. MTT assay showed that the cell viability of ß-TCP/bredigite scaffold loading with up to 1%-3% CPFX (95 ± 2%), is greater than for scaffolds containing 5% CPFX (84 ± 2%). In Overall, it may suggested that ß-TCP/bredigite containing 1%-3% CPFX possesses great cell viability and antibacterial activity and be employed as bactericidal biomaterials and bone infection treatment.

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/fibrinogen/bredigite nanofibrous membranes and their integration with osteoblasts for guided bone regeneration.

Guided bone regeneration (GBR) has been established to be an effective method for the repair of defective tissues, which is based on isolating bone defects with a barrier membrane for faster tissue reconstruction. The aim of the present study is to develop poly (hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/fibrinogen (FG)/bredigite (BR) membranes with applicability in GBR. BR nanoparticles were synthesized through a sol-gel method and characterized using transmission electron microscopy and X-ray diffractometer. PHBV, PHBV/FG, and PHBV/FG/BR membranes were fabricated using electrospinning and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle, pore size, thermogravimetric analysis and tensile strength. The electrospun PHBV, PHBV/FG, and PHBV/FG/BR nanofibers were successfully obtained with the mean diameter ranging 240-410 nm. The results showed that Young's modulus and ultimate strength of the PHBV membrane reduced upon blending with FG and increased by further incorporation of BR nanoparticles, Moreover hydrophilicity of the PHBV membrane improved on addition of FG and BR. The in vitro degradation assay demonstrated that incorporation of FG and BR into PHBV matrix increased its hydrolytic degradation. Cell-membrane interactions were studied by culturing human fetal osteoblast cells on the fabricated membrane. According to the obtained results, osteoblasts seeded on PHBV/FG/BR displayed higher cell adhesion and proliferation compared to PHBV and PHBV/FG membrane. Furthermore, alkaline phosphatase activity and alizarin red-s staining indicated enhanced osteogenic differentiation and mineralization of cells on PHBV/FG/BR membranes. The results demonstrated that developed electrospun PHBV/FG/BR nanofibrous mats have desired potential as a barrier membrane for guided bone tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1154-1165, 2019.

The extracts of bredigite bioceramics enhanced the pluripotency of human dental pulp cells.

Biomaterials have a profound effect on tissue engineering and regenerative medicine, but few studies have reported the role of extracts from bioceramics in the regulation of stem cell pluripotency. The present study investigated the effects of bioceramics extracts, including silicate bredigite (Ca7 MgSi4 O16 ) and conventional ß-tricalcium phosphate (ß-TCP), on the pluripotency and the multilineage differentiation potential of human dental pulp cells (hDPCs). Basic fibroblast growth factor (bFGF), which is a known regulator of hDPCs pluripotency, was used as a reference. Bredigite extracts significantly promoted cell growth, proliferation, TERT expression and maintained hDPCs in a presenescent state. The extracts of bredigite significantly up-regulated the expression of pluripotency-related genes such as Stro1, Oct4 and Sox2, and further promoted the multilineage differentiation of hDPCs after odontogenic/adipogenic induction. The stimulation of bredigite extracts on hDPCs pluripotency was comparable to that of bFGF, whereas ß-TCP extracts lacked these properties. Our results suggested for the first time that bredigite extracts enhance the pluripotency of dental-derived stem cells, paving the way for extended applications in regenerative medicine. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3465-3474, 2017.

Mechanical and cytotoxicity evaluation of nanostructured hydroxyapatite-bredigite scaffolds for bone regeneration.

Despite the attractive characteristics of three-dimensional pure hydroxyapatite (HA) scaffolds, due to their weak mechanical properties, researches have focused on the development of composite scaffolds via introducing suitable secondary components. The aim of this study was to develop, for the first time, three-dimensional HA-bredigite (Ca7MgSi4O16) scaffolds containing various amounts of bredigite nanopowder (0, 5, 10 and 15wt.%) using space holder technique. Transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction spectroscopy were applied in order to study the morphology, fracture surface and phase compositions of nanopowders and scaffolds. Furthermore, the effects of scaffold composition on the mechanical properties, bioactivity, biodegradability, and cytotoxicity were also evaluated. Results showed that the composite scaffolds with average pore size in the range of 220-310µm, appearance porosity of 63.1-75.9% and appearance density of 1.1±0.04g/cm(3) were successfully developed, depending on bredigite content. Indeed, the micropore size of the scaffolds reduced with increasing bredigite content confirming that the sinterability of the scaffolds was improved. Furthermore, the compression strength and modulus of the scaffolds significantly enhanced via incorporation of bredigite content from 0 to 15wt.%. The composite scaffolds revealed superior bioactivity and biodegradability with increasing bredigite content. Moreover, MTT assay confirmed that HA-15wt.% bredigite scaffold significantly promoted cell proliferation compared to tissue culture plate (control) and HA scaffold. Based on these results, three-dimensional HA-bredigite scaffolds could be promising replacements for HA scaffolds in bone regeneration.

Biodegradable mesoporous calcium-magnesium silicate-polybutylene succinate scaffolds for osseous tissue engineering.

The structural features of bone engineering scaffolds are expected to exhibit osteoinductive behavior and promote cell adhesion, proliferation, and differentiation. In the present study, we employed synthesized ordered mesoporous calcium-magnesium silicate (om-CMS) and polybutylene succinate (PBSu) to develop a novel scaffold with potential applications in osseous tissue engineering. The characteristics, in vitro bioactivity of om-CMS/PBSu scaffold, as well as the cellular responses of MC3T3-E1 cells to the composite were investigated. Our results showed that the om-CMS/PBSu scaffold possesses a large surface area and highly ordered channel pores, resulting in improved degradation and biocompatibility compared to the PBSu scaffold. Moreover, the om-CMS/PBSu scaffold exhibited significantly higher bioactivity and induced apatite formation on its surface after immersion in the simulated body fluid. In addition, the om-CMS/PBSu scaffold provided a high surface area for cell attachment and released Ca, Mg, and Si ions to stimulate osteoblast proliferation. The unique surface characteristics and higher biological efficacy of the om-CMS/PBSu scaffold suggest that it has great potential for being developed into a system that can be employed in osseous tissue engineering.

Improvement of biodegradability, bioactivity, mechanical integrity and cytocompatibility behavior of biodegradable mg based orthopedic implants using nanostructured Bredigite (Ca7MgSi 4O 16) bioceramic coated via ASD/EPD technique.

This research explored the influence of surface modification of AZ91 Mg alloy on the biodegradation, bioactivity, mechanical integrity and cytocompatibility of the alloy. For this purpose, a nanostructured bredigite (Ca7MgSi4O16) ceramic coating was prepared on biodegradable AZ91 Mg alloy through anodic spark deposition and electrophoretic deposition method. The phase composition and surface morphology of the coated alloy were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. The properties of samples were investigated by electrochemical measurements, immersion test, compression examination and cell culturing. The results showed that the degradation resistance, bioactivity, mechanical integrity and cytocompatibility of biodegradable Mg alloy were improved by the anodic spark deposition and electrophorretic deposition of the nanostructured bredigite coating. Therefore, the nanostructured bredigite ceramic coating is identified as a good coating for AZ91 Mg alloy for the purpose of making biodegradable metallic orthopedic implants.

Fluoro-edenite fibres induce lung cell apoptosis: an in vivo study.

We previously showed that apoptosis in the lungs of sheep exposed to fluoro-edenite fibres is induced via the receptor pathway. The present study was performed to gain further insights into the mechanisms of activation of programmed cell death induced by the fibres. Fluoro-edenite fibres are similar in size and morphology to some amphibolic asbestos fibres. They have been found in benmoreitic lavas, in the local stone quarry, in building materials and in road paving at Biancavilla, a town in eastern Sicily (Italy), where epidemiological surveys revealed a cluster of mortality from pleural mesothelioma. Inhalation of asbestos fibres can cause chronic inflammation and carcinogenesis. Since fluoro-edenite has been shown to activate the apoptotic process, we set out to characterise the expression of apoptosis-regulating proteins in fluoro-edenite-exposed lung disease and sought to determine if apoptosis results from fluoro-edenite exposure. Lung tissue from apparently healthy sheep habitually grazing near Biancavilla was processed for immunohistochemical localisation of bcl-2 and bax. Results showed epithelial and interstitial bax overexpression, especially in cells directly in contact with the fibres, and negative bcl-2 immunoexpression. TUNEL-positive cells were detected in alveoli and connective tissue. The integrity of alveolar epithelium and alveolar apoptosis are critical determinants in the pathways that initiate fibrogenesis in the lung and fibroblastic foci are usually found close to abnormal or denuded alveolar epithelium. Our results are consistent with the hypothesis that apoptosis is an important mechanism for removing cells with irreparable fluoro-edenite-induced genetic changes that predispose them to a neoplastic evolution.