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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, 13C and 29Si -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 86207Pa for 1.5 ADA/Si to 362171Pa 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., Instituto Politécnico Nacional, México (IPN-SIP 20196660 and IPN-SIP 20201294), AEI/FEDER,UE (DPI2017-90147-R), CONACYT scholarship.

The search of suitable combinations of stem cells, biomaterials and scaffolds manufacturing methods have become a major focus of research for bone engineering. The aim of this study was to test the potential of dental pulp stem cells to attach, proliferate, mineralize and differentiate on 3D printed polycaprolactone (PCL) scaffolds. A 100% pure Mw: 84,500 +- 1000 PCL was selected. 5 x 10 x 5 mm3 parallelepiped scaffolds were designed as a wood-pilled structure composed of 20 layers of 250 microm in height, in a non-alternate order ([0,0,0,90,90,90º]). 3D printing was made at 170 ºC. Swine dental pulp stem cells (DPSCs) were extracted from lower lateral incisors of swine and cultivated until the cells reached 80% confluence. The third passage was used for seeding on the scaffolds. Phenotype of cells was determined by flow Cytometry. Live and dead, Alamar blue™, von Kossa and alizarin red staining assays were performed. Scaffolds with 290 + 30 micron strand diameter, 938 x 80 micron pores in the axial direction and 689 x 13 micron pores in the lateral direction were manufactured. Together, cell viability tests, von Kossa and Alizarin red staining indicate the ability of the printed scaffolds to support DPSCs attachment, proliferation and enable differentiation followed by mineralization. The selected material-processing technique-cell line (PCL-3D printing-DPSCs) triplet can be though to be used for further modelling and preclinical experiments in bone engineering studies., Grant PAPIIT IA207420, UNAM, México and AEI/FEDER, UE (DPI2017-90147-R) Spain.

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., Instituto Politécnico Nacional, Mexico (IPN-SIP 20196660), AEI/FEDER, UE (DPI2017-90147-R)., CONACYT scholarship

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&ndash, 20 MPa and 10&ndash, 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 potential of cryogels to be used as scaffolds in tissue engineering. Scaffolds based on the α-tricalcium phosphate reinforced PDMAEMA (Poly(dimethyl aminoethyl methacrylate))/PHEMA (poly(hydroxyethyl methacrylate)) system were prepared and human trabecular bone-derived cells (HTBs) and bone marrow derived-mesenchymal stem cells (BM-MSCs) cultured on them. Several features, such as porosity, pore shape, molecular weight between crosslinks and mesh size, are studied. The most suitable PDMAEMA/PHEMA ratio for cell proliferation has been assessed and the viability, adhesion, proliferation and expression of osteoblastic biochemical markers are evaluated. The PDMAEMA/PHEMA ratio influences the scaffolds porosity. Values between 53% ± 5.7% for a greater content in PHEMA and 75% ± 5.5% for a greater content in PDMAEMA have been obtained. The polymer ratio also modifies the pore shape. A greater content in PDMAEMA leads also to bigger network mesh size. Each of the compositions were non-cytotoxic, the seeded cells remained viable for both BM-MSCs and HTBs. Thus, and based on the structural analysis, specimens with a greater content in PDMAEMA seem to provide a better structural environment for their use as scaffolds for tissue engineering. The α-tricalcium phosphate incorporation into the composition seems to favor the expression of the osteogenic phenotype., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

The purpose of this work is to study the dissolution mechanism of SiO2-based bioactive hybrid materials containing both CaO and P2O5 in their structures and to determine the influence of apatite crystallization over the surface features of the hybrids during degradation. Hybrid materials were synthesized using sol–gel method. Tetraethoxysilane (TEOS), hydroxyl terminated polydimethylsiloxane (PDMS), Ca(NO3)2·4H2O, and triethyl phosphate (TEP) were used as reactants. The degradation and bioactivity of the hybrid materials were tested by soaking the specimens into simulated body fluid (SBF). Raman spectroscopy, tensiometry and N2 adsorption/desorption curves were used to measure the changes during the degradation experiments. Several mathematical approaches have been taken to analyze the results. The growth of an apatite layer on the surface of SiO2-modified PDMS-P2O5-CaO hybrid materials occurs together with degradation of the silica-based matrix. The dissolution kinetics depends upon the composition of the material. It varies from a surface-driven mechanism in the case of low-P2O5 samples to a degradation path which fits into a Weibull type kinetic model, typical of matrix dissolution processes in materials enriched in P2O5. During degradation, the surface parameters, fractal constant and anisotropy of the pores were determined. The slight increase of the fractal constant in low-containing P2O5 materials suggests the formation of a homogeneous silica-like layer in the first stage of degradation, which also works as anchoring nucleus for subsequent apatite formation. In all the cases, the degradation leads to ink-bottle shaped pores, increasing their volume as degradation occurs, but keeping their neck shape., This work was supported by SIP-IPN 20150064 Project (Mexico), DGICYT Project, MAT2014-51918-C2-1-R (Spain), Fundación General CSIC (Programa ComFuturo) (A. Tamayo). DA Sánchez – Téllez also acknowledges CONACYT for the scholarship given.

Two bisphosphonates (BPs), namely 1-hydroxy-2-[4-aminophenyl]ethane-1,1-diphosphonic acid (APBP) and 1-hydroxy-2-[3-indolyl]ethane-1,1-diphosphonic acid (IBP), have been synthesized and incorporated to acrylic injectable and self-curing formulations. Alendronic acid monosodium trihydrated salt (ALN) containing cement was formulated as control. These systems have potential applications in low density hard tissues affected by ailments characterized by a high osteoclastic resorption, i.e. osteoporosis and osteolysis. Values of curing parameters of APBP and IBP were acceptable to obtain pastes with enough fluency to be injected through a biopsy needle into the bone cavity. Working times ranged between 8 and 15 min and maximum temperature was around 508C. Cured systems stored for a month in synthetic body fluid had compressive strengths between 90 and 96 MPa and modulus between 1.2 and 1.3 GPa, which suggest mechanical stabilization after setting and in the short time. BPs were released in PBS at an initial rate depending on the corresponding chemical structure in the order ALN > APBP > IBP to give final concentrations in PBS of 2.21, 0.44, and 0.19 mol/mL for ALN, APBP, and IBP, respectively. Cytotoxicities of bisphosphonates were evaluated, IC50 values being in the order APBP > ALN > IBP. Absence of cytotoxicity coming from leachables of the cured systems was observed in all cases independently of the BP. An improved cell growth and proliferation for the systems loaded with APBP and IBP compared with that loaded with ALN was observed, as assessed by measuring cell adhesion and proliferation, and total DNA content