Mesoporous bioactive glasses for the treatment of bone pathologies

Tesis de la Universidad Complutense de Madrid, Facultad de Farmacia, leída el 17-09-2018La presente tesis doctoral tiene como objetivo la obtención de vidrios mesoporosos bioactivos (MBGs) para ser utilizados en el tratamiento de defectos óseos asociados a patologías del tejido óseo. La motivación de este trabajo surge de la demanda de terapias regenerativas para el tratamiento de defectos óseos derivados de enfermedades como la osteoporosis, la infección o el cáncer. Generalmente la mayoría de los implantes óseos poseen una vida útil limitada y se implantan con fines sustitutivos. En la actualidad, relacionado en gran medida con el envejecimiento de la población, ha surgido la necesidad de diseñar materiales que favorezcan la regeneración ósea frente a los diseñados para su sustitución. En este sentido las biocerámicas bioactivas de tercera generación, en las que se engloban los MBGs presentan propiedades que favorecen la regeneración de defectos en el hueso promoviendo la restauración y reparación de los mismos. En la presente tesis hemos hemos abordado este objetivo siguiendo tres estrategias: 1. Optimización de las propiedades químicas y de la estructura porosa para determinar las composiciones químicas y propiedades texturales más adecuadas para los fines propuestos.2. Obtención de MBGs con capacidad regenerativa para tratamiento o prevención secundaria de tumores óseos e infecciones en el hueso.3. Obtención de andamios macroporosos de MBGs para regeneración de hueso en pacientes osteoporóticos...The objective of this thesis has been to obtain mesoporous bioactive glasses (MBG) tobe used in the treatment of pathologies associated with bone tissue. The motivation for this work arises by the demand for regenerative therapies for the treatment of bone defects derived from diseases such as osteoporosis, infection or cancer. Most bone implants generally have a limited lifespan and are implanted for replacement purposes. Currently, due to the ageing of the population, the need has arisen to design materials that favour bone regeneration as opposed to bone replacement. In this sense, the third generation bioactive bioceramics including MBGs have properties that favor the regeneration of defects in the bone, promoting their restoration and repair. This objective has been addressed through three strategies: 1. Optimization of chemical properties and porous structure to determine the most suitable chemical compositions and textural properties for the proposed purposes. 2. Obtaining regenerative MBGs for secondary treatment or prevention of bone tumors and bone infections. 3. Obtaining macroporous scaffolding of MBG for bone regeneration in osteoporotic patients...Fac. de FarmaciaTRUEunpu

Targeting Agents in Biomaterial-Mediated Bone Regeneration

Bone diseases are a global public concern that affect millions of people. Even though current treatments present high efficacy, they also show several side effects. In this sense, the development of biocompatible nanoparticles and macroscopic scaffolds has been shown to improve bone regeneration while diminishing side effects. In this review, we present a new trend in these materials, reporting several examples of materials that specifically recognize several agents of the bone microenvironment. Briefly, we provide a subtle introduction to the bone microenvironment. Then, the different targeting agents are exposed. Afterward, several examples of nanoparticles and scaffolds modified with these agents are shown. Finally, we provide some future perspectives and conclusions. Overall, this topic presents high potential to create promising translational strategies for the treatment of bone-related diseases. We expect this review to provide a comprehensive description of the incipient state-of-the-art of bone-targeting agents in bone regeneration

Novel ion-doped mesoporous glasses for bone tissue engineering: Study of their structural characteristics influenced by the presence of phosphorous oxide

Ion-doped binary SiO2-CaO and ternary SiO2-CaO-P2O5 mesoporous bioactive glasses were synthesized and characterized to evaluate the influence of P2O5 in the glass network structure. Strontium, copper and cobalt oxides in a proportion of 0.8 mol% were selected as dopants because the osteogenic and angiogenic properties reported for these elements. Although the four glass compositions investigated presented analogous textural properties, TEM analysis revealed that the structure of those containing P2O5 exhibited an increased ordered mesoporosity. Furthermore, 29Si NMR revealed that the incorporation of P2O5 increased the network connectivity and that this compound captured the Sr2 +, Cu2 + and Co2 + ions preventing them to behave as modifiers of the silica network. In addition, 31P NMR results revealed that the nature of the cation directly influences the characteristics of the phosphate clusters. In this study, we have proven that phosphorous oxide entraps doping-metallic ions, granting these glasses with a greater mesopores order

Molecular gates in mesoporous bioactive glasses for the treatment of bone tumors and infection

[EN] Silica mesoporous nanomaterials have been proved to have meaningful application in biotechnology and biomedicine. Particularly, mesoporous bioactive glasses are recently gaining importance thanks to their bone regenerative properties. Moreover, the mesoporous nature of these materials makes them suitable for drug delivery applications, opening new lines in the field of bone therapies. In this work, we have developed innovative nanodevices based on the implementation of adenosine triphosphate (ATP) and e-poly-l-lysine molecular gates using a mesoporous bioglass as an inorganic support. The systems have been previously proved to work properly with a fluorescence probe and subsequently with an antibiotic(levofloxacin) and an antitumoral drug(doxorubicin). The bioactivity of the prepared materials has also been tested, giving promising results. Finally, in vitro cell culture studies have been carried out; demonstrating that this gated devices can provide useful approaches for bone cancer and bone infection treatments.Spanish Government for projects MAT2015-64139-C04-01-R, MAT-2013-43299-R, MAT2015-64831-R (MINECO/FEDER) and for project CS02010-11384-E (Agening-MICINN). Also, Generalitat Valenciana (project PROMETEOII/2014/047) and CIBER-BBN (project SPRING) are acknowledged for their support. MVR acknowledges funding from the European Research Council (Advanced Grant VERDI; ERC-2015-AdG Proposal No. 694160). LP thanks Universitat Politecnica de Valencia for her FPI grant. NGC is greatly indebted to Ministerio de Ciencia e Innovation for her predoctoral fellowship. The authors also wish to thank the staff of the ICTS Centro Nacional de Microscopia Electronica of the Universidad Complutense de Madrid (Spain) for the assistance in the scanning electron microscopy.Polo, L.; Gómez-Cerezo, N.; Aznar, E.; Vivancos, J.; Sancenón Galarza, F.; Arcos, D.; Vallet, M.... (2017). Molecular gates in mesoporous bioactive glasses for the treatment of bone tumors and infection. Acta Biomaterialia. 50:114-126. https://doi.org/10.1016/j.actbio.2016.12.025S1141265

The effect of biomimetic mineralization of 3D-printed mesoporous bioglass scaffolds on physical properties and in vitro osteogenicity

Three-dimensional Mesoporous bioactive glasses (MBGs) scaffolds has been widely considered for bone regeneration purposes and additive manufacturing enables the fabrication of highly bioactive patient-specific constructs for bone defects. Commonly, this process is performed with the addition of polymeric binders that facilitate the printability of scaffolds. However, these additives cover the MBG particles resulting in the reduction of their osteogenic potential. The present work investigates a simple yet effective phosphate-buffered saline immersion method for achieving polyvinyl alcohol binder removal while enables the maintenance of the mesoporous structure of MBG 3D-printed scaffolds. This resulted in significantly modifying the surface of the scaffold via the spontaneous formation of a biomimetic mineralized layer which positively affected the physical and biological properties of the scaffold. The extensive surface remodeling induced by the deposition of the apatite-like layer lead to a 3-fold increase in surface area, a 5-fold increase in the roughness, and 4-fold increase in the hardness of the PBS-immersed scaffolds when compared to the as-printed counterpart. The biomimetic mineralization also occurred throughout the bulk of the scaffold connecting the MBGs particles and was responsible for the maintenance of structural integrity. In vitro assays using MC3T3-E1 pre-osteoblast like cells demonstrated a significant upregulation of osteogenic-related genes for the scaffolds previously immersed in PBS when compared to the as-printed PVA-containing scaffolds. Although the pre-immersion scaffolds performed equally towards osteogenic cell differentiation, our data suggest that a short immersion in PBS of MBG scaffolds is beneficial for the osteogenic properties and might accelerate bone formation after implantation

Effects of a mesoporous bioactive glass on osteoblasts, osteoclasts and macrophages

A mesoporous bioactive glass (MBG) of molar composition 75SiO2-20CaO-5P2O5 (MBG-75S) has been synthetized as a potential bioceramic for bone regeneration purposes. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption studies and transmission electron microscopy (TEM) demonstrated that MBG-75S possess a highly ordered mesoporous structure with high surface area and porosity, which would explain the high ionic exchange rate (mainly calcium and silicon soluble species) with the surrounded media. MBG-75S showed high biocompatibility in contact with Saos-2 osteoblast-like cells. Concentrations up to 1 mg/ml did not lead to significant alterations on either morphology or cell cycle. Regarding the effects on osteoclasts, MBG-75S allowed the differentiation of RAW264.7 macrophages into osteoclast-like cells but exhibiting a decreased resorptive activity. These results point out that MBG-75S does not inhibit osteoclastogenesis but reduces the osteoclast bone-resorbing capability. Finally, in vitro studies focused on the innate immune response, evidenced that MBG-75S allows the proliferation of macrophages without inducing their polarization towards the M1 pro-inflammatory phenotype. This in vitro behavior is indicative that MBG-75S would just induce the required innate immune response without further inflammatory complications under in vivo conditions. The overall behavior respect to osteoblasts, osteoclasts and macrophages, makes this MBG a very interesting candidate for bone grafting applications in osteoporotic patients

The response of pre-osteoblasts and osteoclasts to gallium containing mesoporous bioactive glasses.

Mesoporous bioactive glasses (MBGs) in the system SiO2-CaO-P2O5-Ga2O3 have been synthesized by the evaporation induced self-assembly method and subsequent impregnation with Ga cations. Two different compositions have been prepared and the local environment of Ga(III) has been characterized using 29Si, 71Ga and 31P NMR analysis, demonstrating that Ga(III) is efficiently incorporated as both, network former (GaO4 units) and network modifier (GaO6 units). In vitro bioactivity tests evidenced that Ga-containing MBGs retain their capability for nucleation and growth of an apatite-like layer in contact with a simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Finally, in vitro cell culture tests evidenced that Ga incorporation results in a selective effect on osteoblasts and osteoclasts. Indeed, the presence of this element enhances the early differentiation towards osteoblast phenotype while disturbing osteoclastogenesis. Considering these results, Ga-doped MBGs might be proposed as bone substitutes, especially in osteoporosis scenarios

Incorporation and effects of mesoporous SiO2-CaO nanospheres loaded with ipriflavone on osteoblast/osteoclast cocultures

Mesoporous nanospheres in the system SiO2-CaO (NanoMBGs) with a hollow core surrounded by a radial arrangement of mesopores were characterized, labeled with FITC (FITC-NanoMBGs) and loaded with ipriflavone (NanoMBG-IPs) in order to evaluate their incorporation and their effects on both osteoblasts and osteoclasts simultaneously and maintaining the communication with each other in coculture. The influence of these nanospheres on macrophage polarization towards pro-inflammatory M1 or reparative M2 phenotypes was also evaluated in basal and stimulated conditions through the expression of CD80 (as M1 marker) and CD206 (as M2 marker) by flow cytometry and confocal microscopy. NanoMBGs did not induce the macrophage polarization towards the M1 pro-inflammatory phenotype, favoring the M2 reparative phenotype and increasing the macrophage response capability against stimuli as LPS and IL-4. NanoMBG-IPs induced a significant decrease of osteoclast proliferat ion and resorption activity after 7 days in coculture with osteoblasts, without affecting osteoblast proliferation and viability. Drug release test demonstrated that only a fraction of the payload is released by diffusion, whereas the rest of the drug remains within the hollow core after 7 days, thus ensuring the local long-term pharmacological treatment beyond the initial fast IP release. All these data ensure an appropriate immune response to these nanospheres and the potential application of NanoMBG-IPs as local drug delivery system in osteoporotic patients

Silicon substituted hydroxyapatite/VEGF scaffolds stimulate bone regeneration in osteoporotic sheep.

Silicon-substituted hydroxyapatite (SiHA) macroporous scaffolds have been prepared by robocasting. In order to optimize their bone regeneration properties, we have manufactured these scaffolds presenting different microstructures: nanocrystalline and crystalline. Moreover, their surfaces have been decorated with vascular endothelial growth factor (VEGF) to evaluate the potential coupling between vascularization and bone regeneration. In vitro cell culture tests evidence that nanocrystalline SiHA hinders pre-osteblast proliferation, whereas the presence of VEGF enhances the biological functions of both endothelial cells and pre-osteoblasts. The bone regeneration capability has been evaluated using an osteoporotic sheep model. In vivo observations strongly correlate with in vitro cell culture tests. Those scaffolds made of nanocrystalline SiHA were colonized by fibrous tissue, promoted inflammatory response and forested osteoclast recruitment. These observations discard nanocystalline SiHA as a suitable material for bone regeneration purposes. On the contrary, those scaffolds made of crystalline SiHA and decorated with VEGF exhibited bone regeneration properties, with high ossification degree, thicker trabeculae and higher presence of osteoblasts and blood vessels. Considering these results, macroporous scaffolds made of SiHA and decorated with VEGF are suitable bone grafts for regeneration purposes, even in adverse pathological scenarios such as osteoporosis