In situ sol-gel synthesis of hyaluronan derivatives bio-nanocomposite hydrogels.

The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid (HA) followed by the development of nanocomposite hydrogels directly in situ by biomineralization of photocrosslinkable HA polymers through sol-gel synthesis. In this way, it has been possible to overcome some limitations due to classical approaches based on the physical blending of inorganic fillers into polymer matrix. To this aim, methacrylated and maleated HA, synthesized with similar degree of substitution (DS) were compared in terms of mechanical and physico-chemical properties. The success of in situ biomineralization was highlighted by reflect Fourier transform infrared spectroscopy and thermogravimetric analysis. Furthermore, mechanical characterization demonstrated the reinforcing effect of inorganic fillers evidencing a strong correlation with DS. The swelling behavior resulted to be correlated with filler concentration. Finally, the cytotoxicity tests revealed the absence of toxic components and an increase of cell proliferation over culture time was observed, highlighting these bio-nanocomposite hyaluronan derivatives as biocompatible hydrogel with tunable properties.

Comparative facile methods for preparing graphene oxide-hydroxyapatite for bone tissue engineering.

Motivated by the success of using graphene oxide (GO) as a nanofiller of composites, there is a drive to search for this new kind of carbon material as a bioactive component in ceramic materials. In the present study, biomineralized GO was prepared by two different approaches, represented by in situ sol-gel synthesis and biomimetic treatment. It was found that in the biocomposites obtained by the sol-gel approach, the spindle-like hydroxyapatite nanoparticles, with a diameter of ca. 5 ± 0.37 nm and a length of ca. 70 ± 2.5 nm, were presented randomly and strongly on the surface. The oxygen-containing functional groups, such as hydroxyl and carbonyl, present on the basal plane and edges of the GO sheets, play an important role in anchoring calcium ions, as demonstrated by FT-IR and TEM investigations. A different result was obtained for biocomposites after biomimetic treatment: an amorphous calcium phosphate on GO sheet was observed after 5 days of treatment. These different approaches resulted in a diverse effect on the proliferation and differentiation of osteogenic mesenchymal stem cells. In fact, in biocomposites prepared by the sol-gel approach the expression of an early marker of osteogenic differentiation, ALP, increases with the amount of GO in the first days of cell culture. Meanwhile, biomimetic materials sustain cell viability and proliferation, even if the expression of alkaline phosphatase activity in a basal medium is delayed. These findings may provide new prospects for utilizing GO-based hydroxyapatite biocomposites in bone repair, bone augmentation and coating of biomedical implants and broaden the application of GO sheets in biological areas. Copyright © 2016 John Wiley & Sons, Ltd.

Properties of carbon nanotube-dispersed Sr-hydroxyapatite injectable material for bone defects.

This study concerns the synthesis of gel materials based on carbon nanotubes dispersed strontium-modified hydroxyapatite (Sr-HA) at different compositions obtained by sol-gel technology and their influence on human-bone-marrow-derived mesenchymal stem cells. Furthermore, an evaluation of the influence of nanotubes and Strontium on physico-chemical, morphological, rheological and biological properties of hydroxyapatite gel was also performed. Morphological analysis (scanning electron microscopy) shows a homogeneous distribution of modified nanotubes in the ceramic matrix improving the bioactive properties of materials. The biological investigations proved that Sr-HA/carbon nanotube gel containing 0-20 mol (%) of Sr showed no toxic effect and promote the expression of early and late markers of osteogenic differentiation in cell culture performed in basal medium without osteogenic factors. Finally, the SrHA/carbon nanotube gels could have a good potential application as filler in bone repair and regeneration and may be used in the osteoporotic disease treatment.

Effect of citric acid crosslinking cellulose-based hydrogels on osteogenic differentiation.

Understanding the relationships between material surface properties and cellular responses is essential to designing optimal material surfaces for implantation and tissue engineering. In this study, cellulose hydrogels were crosslinked using a non-toxic and natural component namely citric acid. The chemical treatment induces COOH functional groups that improve the hydrophilicity, roughness, and materials rheological properties. The physiochemical, morphological, and mechanical analyses were performed to analyze the material surface before and after crosslinking. This approach would help determine if the effect of chemical treatment on cellulose hydrogel improves the hydrophilicity, roughness, and rheological properties of the scaffold. In this study, it was demonstrated that the biological responses of human mesenchymal stem cell with regard to cell adhesion, proliferation, and differentiation were influenced in vitro by changing the surface chemistry and roughness.

Heat treatment of Na2O-CaO-P2O5-SiO2 bioactive glasses: densification processes and postsintering bioactivity.

Because of their excellent bioactivity, bioactive glasses are increasingly diffused to produce biomedical devices for bone prostheses, to face the dysfunctions that may be caused by traumatic events, diseases, or even natural aging. However, several processing routes, such as the production of scaffolds or the deposition of coatings, include a thermal treatment to apply or sinter the glass. The exposure to high temperature may induce a devetrification phenomenon, altering the properties and, in particular, the bioactivity of the glass. The present contribution offers an overview of the thermal behavior and properties of two glasses belonging to the Na2O-CaO-P2O5-SiO2 system, to be compared to the standard 45S5 Bioglass(®). The basic goal is to understand the effect of both the original composition and the thermal treatment on the performance of the sintered glasses. The new glasses, the one (BG_Na) with a high content of Na2O, the other (BG_Ca) with a high content of CaO, were fully characterized and sintering tests were performed to define the most interesting firing cycles. The sintered samples, treated at 880°C and 800°C respectively, were investigated from a microstructural point of view and their mechanical properties were compared to those of the bulk (not sintered) glass counterparts. The effect of sintering was especially striking on the BG_Ca material, whose Vickers hardness increased from 598.9 ± 46.7 HV to 1053.4 ± 35.0 HV. The in vitro tests confirmed the ability of the glasses, both in bulk and sintered form, of generating a hydroxyapatite surface layer when immersed in a simulated body fluid. More accurate biological tests performed on the sintered glasses proved the high bioactivity of the CaO-rich composition even after a heat treatment.

Biomineralized porous composite scaffolds prepared by chemical synthesis for bone tissue regeneration.

Scaffold design is a key factor in the clinical success of bone tissue engineering grafts. To date, no existing single biomaterial used in bone repair and regeneration fulfils all the requirements for an ideal bone graft. In this study hydroxyapatite/polycaprolactone (HA/PCL) composite scaffolds were prepared by a wet chemical method at room temperature. The physico-chemical properties of the composite materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, while scaffold morphology was investigated by scanning electron microscopy (SEM) with energy-dispersive spectroscopy to validate the process used for synthesis. Finally, the response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic phenotype was evaluated using the Alamar blue assay, SEM and alkaline phosphatase activity. Microstructural analysis indicated that the HA particles were distributed homogeneously within the PCL matrix. The biological results revealed that the HA/PCL composite scaffolds are suitable for the proliferation and differentiation of MSCs in vitro, supporting osteogenesis after 15 days. All the results indicate that these scaffolds meet the requirements of materials for bone tissue engineering and could be used for many clinical applications in orthopaedic and maxillofacial surgery.

Sol-gel synthesis, characterization and bioactivity of poly(ether-imide)/TiO2 hybrid materials.

Novel organic-inorganic hybrid materials were synthesized by the sol-gel method from a multicomponent solution containing titanium butoxide, 6 weight % (wt%) or 12 wt% poly(ether-imide) (PEI), water and chloroform. The structure of the interpenetrating network is realized by hydrogen bonds between the Ti-OH group (H-donator) in the sol-gel intermediate species and the carboxylic group (H-acceptor) in the repeating units of the polymer. By Fourier transform infrared (FTIR) analysis the presence of hydrogen bonds between organic-inorganic components of the hybrid materials were proved. The morphology of the hybrid materials was studied by scanning electron microscopy (SEM). The structure of a molecular level dispersion was disclosed by an atomic force microscope (AFM), pore size distribution and surface measurements. The AFM and SEM analyzes confirmed that the PEI/TiO2 samples can be considered homogenous organic/inorganic hybrid materials because in both the compositions studied the average domains were less than 400 nm in size. The bioactivity of the synthesized hybrid materials was demonstrated by the formation of a layer of hydroxyapatite on the surface of the PEI/TiO2 samples soaked in a fluid simulating the composition of human blood plasma (SBF), demonstrated by SEM and energy dispersive spectroscopy (EDS) microscopy.

Characterization, bioactivity and ampicillin release kinetics of TiO2 and TiO24SiO2 synthesized by sol-gel processing.

Local drug delivery of antimicrobics by sustained release delivery system can be used to treat periodontal disease. Advantages of these systems may include maintaining high levels of antibiotic in the gingival crevicular fluid for a sustained period of time and ease of use with high patient acceptance. The materials used are TiO(2) and TiO(2)4SiO(2), mixed with sodium ampicillin, a broad-spectrum antibiotic, have been synthesized by sol-gel method. The amorphous nature of the gels was ascertained by X-ray diffraction analysis. Release kinetics in a simulated body fluid (SBF) have been subsequently investigated. The amount of sodium ampicillin released has been detected by UV-VIS spectroscopy and SEM. The release kinetics seems to occur in more than one stage. HPLC analysis has also been taken to ensure the integrity of ampicillin after the synthetic treatment. Finally, SEM micrographs and EDS analysis showed the formation of a hydroxyapatite layer on the surface of the samples soaked in SBF. Both the materials showed good release and could be used as drug delivery bioactive systems. High antimicrobial effects of samples against Escherichia coli and Streptococcus mutants were found.

Release kinetics of ampicillin, characterization and bioactivity of TiO2/PCL hybrid materials synthesized by sol-gel processing.

Poly(epsilon-caprolactone) (PCL 6, 12, and 24 wt %) and titanium (TiO2) organic-inorganic hybrid materials have been synthesized by the sol-gel method from a multicomponent solution containing titanium butoxide, poly(epsilon-caprolactone) (PCL), water, and chloroform (CHCl3). Sodium ampicillin was incorporated in the hybrid material to verify the effect as local controlled drug delivery system. The structure of a hybrid materials interpenetrating network is realized by hydrogen bonds between Ti-OH group (H-donator) in the sol-gel intermediate species and carboxylic group (H-acceptor) in the repeating units of the polymer. The presence of hydrogen bonds between organic/inorganic components of the hybrid materials was proved by FTIR analysis. The morphology of the hybrid materials was studied by scanning electron microscope (SEM). The structure of a molecular level dispersion has been disclosed by atomic force microscope (AFM), pore size distribution and surface measurements. The bioactivity of the synthesized hybrid materials has been showed by the formation of a layer of hydroxyapatite on the surface of TiO2/PCL samples soaked in a fluid simulating the composition of the human blood plasma. The amount of sodium ampicillin released has been detected by UV-vis spectroscopy and SEM. The release kinetics seems to occur in more than one stage. HPLC analysis has also been taken to ensure the integrity of ampicillin after the synthetic treatment.

Sol-gel processing of drug delivery materials and release kinetics.

Silica, calcium (5 mol%) silicate and silica/polycaprolactone hybrid inorganic/organic amorphous materials, all mixed with sodium ampicillin, a broad-spectrum antibiotic, have been synthesized by sol-gel method. The amorphous nature of the gels was ascertained by X-ray diffraction analysis. Release kinetics in a simulate body fluid (SBF) have been subsequently investigated. The amount of sodium ampicillin released has been detected by UV-Vis spectroscopy and SEM. The release kinetics seems to occur in more than one stage. Finally FTIR measurements and SEM micrograph showed the formation of a hydroxyapatite layer on the surface of the samples soaked in SBF. All data showed that these materials could be used as drug delivery bioactive systems.

Sol-gel synthesis, structure and bioactivity of polycaprolactone/CaO . SiO2 hybrid material.

A method has been developed to cast novel organic/inorganic polymer hybrids from multicomponent solutions containing tetramethyl orthosilicate, calcium nitrate tetrahydrate, polycaprolactone, water, and methylethyketone via sol-gel process. The existence of the hydrogen bonds between organic and inorganic components of the hybrid and hydroxyapatite formation on the surface was proved by Fourier transform infrared analysis. The morphology of the hybrid material was studied by scanning electron microscopy. The structure of a molecular level dispersion was disclosed by atomic force microscopy, pore size distribution, and surface measurements. The infrared spectra of the hybrid relative to sample soaked in a fluid simulating the composition of human blood plasma suggests that polycaprolactone/CaO * SiO(2) hybrid material synthesised via sol-gel process is bioactive as well as the CaO * SiO(2) gel glass.

Antibacterial and bioactive silver-containing Na2O x CaO x 2SiO2 glass prepared by sol-gel method.

The antibacterial effect of addition of silver oxide to Na2O x CaO x 2SiO2 glass have been studied. Silver containing and silver free Na2O x CaO x 2SiO2 glasses have been prepared by sol-gel synthesis using tetramethil orthosilicate, sodium ethoxide, calcium nitrate tetrahydrate and silver nitrate as starting materials and methyl ethyl ketone as solvent. The gel was examined by differential thermal analysis, thermo gravimetric analysis, FTIR spectroscopy and X-ray diffraction analysis. Antibacterial and bioactive tests on gel glass powders, obtained after a heat treatment of 2 h at 600 degrees C of the dried gel, were carried out. High antimicrobial effects of samples against Escherichia coli and Streptococcus mutans were found. FTIR measurements and SEM micrographs have ascertained the formation of a hydroxyapatite layer on the surface of samples soaked in a simulated body fluid for different times.