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Organic-inorganic hybrid materials are known for their outstanding chemical and physical properties. Although some studies have been published regarding the use of hybrids for biomedical applications, relationship between hydrophilic character and biodegradation, bioactivity and biocompatibility has not been studied yet. The sol–gel method has been chosen for the manufacturing of siloxane-polyurethane hybrids for the exceptional potential of the method to obtain nanostructured materials. The effect of the amount of the urethane oligomer (OPU) on the structure, hydrophilic character, degradability, bioactivity and citotoxicity was investigated. Gelling time of these hybrids increases linearly with the decrease on the Siloxane/OPU ratio up to an 80/20 value. Hydrophilic character of the hybrids can be modulated and affects dramatically the degradation rate of the specimens. A hybrid with a 50/50 Siloxane/OPU ratio displayed an appropriate degradation rate, bioactivity and lack of cell toxicity that makes this material a candidate for further studies for applications in bone regeneration.Los materiales híbridos Orgánico-Inorgánico son conocidos por sus excepcionales propiedades químicas y físicas. Aunque se han publicado algunos estudios respecto al uso de híbridos para aplicaciones biomédicas, aun faltan estudios que determinen la relación que existe entre el carácter hidrofílico de estos materiales y las propiedades que les permiten ser utilizados como biomateriales: degradación, bioactividad y biocompatibilidad. El método sol-gel se ha escogido para la fabricación de híbridos debido a la posibilidad de obtener materiales nanoestructurados que comprenden un componente orgánico y un inorgánico. Se investigó el efecto de la cantidad del olígomero de uretano (OPU) sobre la estructura, el carácter hidrofílico, la degradabilidad, la bioactividad y la citotoxicidad. El tiempo de gelificación de estos híbridos incrementa linealmente con la disminución en la relación Siloxano/OPU hasta un valor de 80/20. El carácter hidrofílico de los híbridos se puede modular y afectar considerablemente la velocidad de degradación de las muestras. Un híbrido con una relación 50/50 Siloxane/OPU muestra una velocidad de degradación, una bioactividad y falta de toxicidad que hacen a este material un candidato para futuros estudios para aplicaciones en regeneración ósea.

Nanospinel MgAlO powder was obtained by a sol-gel method at low-temperature processing. It was synthesized using aluminum tri-sec-butoxide and magnesium nitrate hexahydrate as precursors, in an acid medium at 80 °C. Heat treatments of the dried gel were performed from 200 to 1000 °C (∆ T = 100 °C) and the powders were characterized by SEM, XRD, TG/DTA, FT-IR, and HR-TEM. A mixture of semispherical nanoparticles (<50 nm) of boehmite and unreacted magnesium nitrate was found after the sol-gel reaction. According to HR-TEM and XRD results, a low-crystalline spinel MgAlO started forming at 300 °C, which is a lower temperature than the reported for the same phase in other works. A mechanism of reaction is proposed to explain the formation of spinel at low temperature. At 800 and 900 °C a spinel mono-phase totally crystalline was observed. At 1000 °C, the spinel MgAlO phase is well defined but a second phase, magnesium oxide, was found to be about 6% of the final composition. The crystal sizes were 2.272 ± 0.054, 5.222 ± 0.030, 11.610 ± 0.064, and 25.140 ± 0.20 nm for the material heat treated at 700, 800, 900, and 1000 °C, respectively. Graphical abstract: [ABSTRACT FROM AUTHOR]

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Hyaluronan (HA) is a natural biodegradable biopolymer; its biological functions include cell adhesion, cell proliferation, and differentiation as well as decreasing inflammation, angiogenesis, and regeneration of damaged tissue. This makes it a suitable candidate for fabricating nanomaterials with potential use in tissue engineering. However, HA nanofiber production is restricted due to the high viscosity, low evaporation rate, and high surface tension of HA solutions. Here, hybrids in the form of continuous and randomly aligned polyvinyl alcohol (PVA)-(HA)-siloxane nanofibers were obtained using an electrospinning process. PVA-HA fibers were crosslinked by a 3D siloxane organic-inorganic matrix via sol-gel that restricts natural hydrophilicity and stiffens the structure. The hybrid nanofiber mats were characterized by FT-IR, micro-Raman spectroscopy, SEM, and biological properties. The PVA/HA ratio influenced the morphology of the hybrid nanofibers. Nanofibers with high PVA content (10PVA-8 and 10PVA-10) form mats with few beaded nanofibers, while those with high HA content (5PVA-8 and 5PVA-10) exhibit mats with mound patterns formed by "ribbon-like" nanofibers. The hybrid nanofibers were used as mats to support osteoblast growth, and they showed outstanding biological properties supporting cell adhesion, cell proliferation, and cell differentiation. Importantly, the 5PVA-8 mats show 3D spherical osteoblast morphology; this suggests the formation of tissue growth. These novel HA-based nanomaterials represent a relevant advance in designing nanofibers with unique properties for potential tissue regeneration.

Hybrid materials have been studied because in these materials the properties of organic components, such as elasticity and biodegradability, could be combined with the properties of inorganic components, such as good biological response, thereby transforming them into a single material with improved properties. In this work, Class I hybrid materials based on polyester-urea-urethanes and titania were obtained using the modified sol-gel method. This was corroborated using the FT-IR and Raman techniques which highlighted the formation of hydrogen bonds and the presence of Ti-OH groups in the hybrid materials. In addition, the mechanical and thermal properties and degradability were measured using techniques, such as Vickers hardness, TGA, DSC, and hydrolytic degradation; these properties could be tailored according to hybridization between both organic and inorganic components. The results show that Vickers hardness increased by 20% in hybrid materials as compared to polymers; also, the surface hydrophilicity increases in the hybrid materials, improving their cell viability. Furthermore, cytotoxicity in vitro test was carried out using osteoblast cells for intended biomedical applications and they showed non-cytotoxic behavior.

Organic-inorganic hybrid materials overcome drawbacks associated with alginate hydrogels. In this work, covalently coupled silica-alginate hybrids were prepared by Schiff base formation and sol-gel reaction using alginate dialdehyde (ADA), (3-Aminopropyl) triethoxysilane (APTES), and APTES/tetraethylorthosilicate (TEOS) precursors. The influence of the polysaccharide/inorganic ratio, the nature of the inorganic precursor and the ionic crosslinking ability are studied. Prepared hybrids were characterized by FT-IR, 13 C and 29 Si NMR spectroscopies, SEM, and rheology. For ADA/APTES hybrids, at higher ADA content, Schiff base formation is predominant, but at lower ADA content, the sol-gel reaction is prevalent. However, the progress of the sol-gel reactions for ADA/(APTES+TEOS), is favored with higher ADA compositions. Introducing a posterior ionic crosslinking treatment was possible, increasing the moduli in ADA/(APTES+TEOS) hybrids from 86,207 Pa for 1.5 ADA/Si to 362,171 Pa for 1.5 ADA/Si-Ca. In-situ ADA-Silica hybrid hydrogels containing both ionic and covalent crosslinking can be successfully synthesized with the proposed method. CARBPOL-D-21-01042., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The preparation of silica-alginate hybrid hydrogels by a sol-gel route is proposed in this work. The in-situ synthesis of silica networks from tetraethoxysilane (TEOS) and aminopropyltriethoxysilane (APTES) precursors in an alginate matrix is assayed. The experimental parameters were analyzed in three consecutive stages to obtain hybrid materials with specific properties. Stage 1: effect of water and catalyst ratios. Stage 2: effect of the inorganic precursor's ratio. Stage 3: effect of concentration of the alginate solution. The hydrolysis-condensation reactions of the silica precursors were regulated by the alginate concentration, the silica precursor nature, and the HCl/inorganic/H 2 O ratio. Hybrids prepared with both silica precursors generate longer silica chains. High alginate amounts increase the storage modulus of synthesized hybrids, and high catalyst ratios reduce their stability. Compositions with alginate content of 5 and 8 (wt/v)%, TEOS/APTES weight ratio of 74/26, and without catalyst are suitable to evaluation for their application in tissue engineering., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In the present work, the synthesis of segmented polyurethanes functionalized with catechol moieties within the hard or the soft segment is presented. For this purpose, a synthetic route of a new catechol diol was designed. The direct insertion of this catechol-free derivative into the rigid phase led to segmented polyurethanes with low performance (σ max ≈ 4.5 MPa). Nevertheless, when the derivative was formally located within the soft segment, the mechanical properties of the corresponding functionalized polyurethane improved considerably (σ max ≈ 16.3 MPa), owing to a significant increase in the degree of polymerization. It is proposed that this difference in reactivity could probably be attributed to a hampering effect of this catecholic ring during the polyaddition reaction. To corroborate this hypothesis, a protection of the aromatic ring was carried out, blocking the hampering effect and avoiding secondary reactions. The polyurethane bearing the protected catechol showed the highest molecular weight and the highest stress at break described to date (σ max ≈ 66.1 MPa) for these kind of catechol-functionalized polyurethanes. Therefore, this new approach allows for the obtention of high-performance polyurethane films and can be applied in different sectors, benefiting from the molecular adhesion introduced by the catechol ring.

In this study, an in vitro evaluation of the human osteoblasts response to Organically Modified Silicate (ORMOSIL) biomaterials was conducted. These materials were synthetized by sol-gel process being modified with zirconia (ZrO 2 ) and/or Ca 2+ . The materials were immersed into phosphate buffer solution (PBS) in order to test precipitation of mimetic apatite-like on their surfaces. ORMOSILs were characterized by SEM, FT-IR and X-RD analysis. The response of osteoblast to ORMOSILs was analyzed as a measure of cell adhesion, proliferation and differentiation. The results showed that the addition of Ca 2+ ions modifies the surface morphology of ORMOSILs by forming precipitates of mimetic apatite-like with cauliflower and scales morphologies. On the other hand, biological results suggest that the incorporation of zirconia to ORMOSILs increases their ability to support cell adhesion and proliferation. However, the inclusion of both zirconia and Ca 2+ in the ORMOSILs decreases their biological compatibility by showing less cell proliferation and lower osteonectin expression, a protein related to osteoblasts. The unfavorable effect of Ca 2+ on cell proliferation and cell viability could be due to its ability to induce the formation of mimetic apatite-like with incompatible morphology. The analysis of other proteins related to bone formation on ORMOSIL-Zr and ORMOSIL-Zr-Ca surfaces demonstrated clear expression of osteopontin and osteocalcin in cells growth. In the case of ORMOSIL-Zr, the expression of osteonectin occurred at early stages while the expression of osteopontin and osteocalcin begun at later stages, indicating a switch from an early to a mature stage being stimulated by the biomaterial. Together, these results highlight the important role of zirconia and Ca 2+ ions in the composition of materials regulating their biocompatibility when used as scaffolds in bone regeneration., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This review focuses on recently developed alginate injectable hydrogels and alginate composites for applications in bone tissue regeneration, and it evaluates the alternatives to overcome the problems that avoid their utilization in the field. Section 2 covers the properties of alginates that have made them useful for medical applications, in particular their ionic gelling ability for preparing injectable compositions used as delivery drugs systems. The advantages and shortcomings of these preparations are revised together with the chemical modifications assayed. Section 3 describes how it has been taken advantage of alginates into the new field of biofabrication and the developments in bone engineering. The state of the art of this field is reviewed. Finally in Section 4, new developments and approaches that in opinion of the authors can lead to a breakthrough in bone tissue engineering using alginates are introduced., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Two series of segmented polyurethanes were obtained and their mechanical and thermal properties as well as their biodegradability and cytotoxicity were evaluated. The chemical nature of the polyurethanes was varied by using either 1,4 butanediol (poly-ester-urethanes, PEUs) or l-lysine ethyl ester dihydrochloride (poly-ester-urea-urethanes, PEUUs) as chain extenders. Results showed that varying the hard segment influenced the thermal and mechanical properties of the obtained polymers. PEUs showed strain and hardness values of about 10⁻20 MPa and 10⁻65 MPa, respectively. These values were higher than the obtained values for the PEUUs due to the phase segregation and the higher crystallinity observed for the polyester-urethanes (PEUs); phase segregation was also observed and analyzed by XRD and DSC. Moreover, both series of polymers showed hydrolytic degradation when they were submerged in PBS until 90 days with 20% of weight loss. In vitro tests using a Human Osteoblastic cell line (Hob) showed an average of 80% of cell viability and good adhesion for both series of polymers.

The aim of this work is to evaluate the effect of chitosan content (1, 3 and 5 wt %) dispersed in polylactic acid (PLA) on the structure and properties of composites. Also, the hydrolytic degradation, and the cell viability and adhesion of human MG-63 osteoblasts are analyzed to determine the composites' suitability for use in tissue engineering. For the manufacture of the materials, natural chitosan was extracted chemically from shrimp exoskeleton. The composites were fabricated by extrusion, because it is a low-cost process, it is reproducible, and it does not compromise the biocompatibility of the materials. FT-IR and XRD show that the chitosan does not change the polymer structure, and interactions between the composite components are discarded. In vitro degradation tests show that the composites do not induce significant pH changes in phosphate buffer solution due to their low susceptibility to hydrolytic degradation. The adhesion and morphological characteristics of the osteoblasts are evaluated using confocal microscopy and scanning electron microscopy. The cell viability is determined by the MTT assay. Osteoblasts adhesion is observed on the surface of PLA and composites. A higher amount of chitosan, higher number of cells with osteoblastic morphology, and mineralized nodules are observed on the composite surface. The highest metabolic activity is evidenced at 21 days. The results suggest that the Polylactic acid/chitosan composites are potentially suitable for use as a biomaterial.

The aims of this paper are: (1) to review the current state of the art in the field of cartilage substitution and regeneration; (2) to examine the patented biomaterials being used in preclinical and clinical stages; (3) to explore the potential of polymeric hydrogels for these applications and the reasons that hinder their clinical success. The studies about hydrogels used as potential biomaterials selected for this review are divided into the two major trends in tissue engineering: (1) the use of cell-free biomaterials; and (2) the use of cell seeded biomaterials. Preparation techniques and resulting hydrogel properties are also reviewed. More recent proposals, based on the combination of different polymers and the hybridization process to improve the properties of these materials, are also reviewed. The combination of elements such as scaffolds (cellular solids), matrices (hydrogel-based), growth factors and mechanical stimuli is needed to optimize properties of the required materials in order to facilitate tissue formation, cartilage regeneration and final clinical application. Polymer combinations and hybrids are the most promising materials for this application. Hybrid scaffolds may maximize cell growth and local tissue integration by forming cartilage-like tissue with biomimetic features., Competing Interests: The authors declare no conflicts of interest.