Bone tissue scaffolds made from either natural or synthetic polymers are employed to promote bone healing. However, lack of sufficient or poor mechanical properties such as low integrity and ...stability reduces their medical applications. Crosslinking, defined as induction of chemical or physical links among polymer chains, is a simple method generally used to modify mechanical, biological and degradation properties of hydrogels. Although crosslinking through chemical reactions improves the mechanical properties of bone substitutes, most of the reagents used for this aim demonstrate undesirable effects and may exert toxic reactions. Glutaraldehyde is a widely-used chemical crosslinker with unique ability to crosslink a wide variety of biomaterials; however, many contradictory views have been recently raised on its cytotoxic effects. By keeping this limit in mind, green chemicals or natural crosslinking agents have been shown to provide desired improvements in mechanical properties of bone scaffolds. Therefore, developing more efficient crosslinking materials and methods are desirable to obtain crosslinked scaffolds with perfect properties in bone tissue engineering from different biopolymers such as collagen, gelatin, cellulose, chitosan, alginate, etc. In this review, we focused on developed or developing modalities used to improve mechanical properties of various bone scaffolds and matrices based on common crosslinking reagents.
► The alginate content was studied on properties of aqueous polyurethane dispersions. ► Excellent miscibility was shown on the compositions of polyurethane and alginate. ► The morphology of alginate ...in polyurethane matrix was shown as particulate with different sizes. ► The presence of alginate in microstructure was determined by sodium peak in EDX.
A series of aqueous polyurethane dispersions were synthesized by the reaction of polytetramethylene glycol and isophorone diisocyanate, extended with dimethylol propionic acid. Their chemical structures were characterized using FTIR, 1H NMR, and 13C NMR, and thermal properties were determined by DMTA. Then, a number of aqueous polyurethane dispersions–sodium alginate (PUD/SA) compositions were prepared by addition of sodium alginate solution with different concentrations into the aqueous polyurethane dispersion. Characterization of chemical structure and thermal properties of these blends were performed by FTIR, EDX and DMTA, respectively. The morphology of the alginate in polyurethane matrix was studied by SEM. The hydrophilicity of the prepared samples decreases by increasing the content of sodium alginate in blends. These observations were attributed to the increase of hydrophilicity of the blends as a consequence of addition of hydrophilic carboxylate, hydroxyl and ether functional groups of the alginate to them.
The aim of this study is to prepare nanocomposite hydrogel based on gelatin/oxidized alginate, and evaluate its reinforcement by incorporation of nanohydroxyapatite (nHA) for use in bone tissue ...engineering applications. We used Schiff-base reaction as a click chemistry to prepare nanocomposite hydrogels. Additionally, the nHA was modified using sodium alendronate as a bisphosphonate through formation of coordinate bonds (chelate formation) to prepare bisphosphonate-modified hydroxyapatite (nHABP). The presence of bisphosphonate in the network can improve the cytocompatibility of the scaffolds and suppress the nanoparticles aggregation by inducing steric repulsion. Improved mechanical and rheological properties in the samples containing nHABP is due to the enhanced dispersion of modified nanoparticles as a result of the additional interaction between amine groups in the nHABP and aldehyde groups in the polymeric matrix. We demonstrated how the presence of bisphosphonate ligand in the oxidized alginate-gelatin network can improve nanoparticles dispersion via Schiff-base reaction.
Osteoarthritis, which typically arises from aging, traumatic injury, or obesity, is the most common form of arthritis, which usually leads to malfunction of the joints and requires medical ...interventions due to the poor self-healing capacity of articular cartilage. However, currently used medical treatment modalities have reported, at least in part, disappointing and frustrating results for patients with osteoarthritis. Recent progress in the design and fabrication of tissue-engineered microscale/nanoscale platforms, which arises from the convergence of stem cell research and nanotechnology methods, has shown promising results in the administration of new and efficient options for treating osteochondral lesions. This paper presents an overview of the recent advances in osteochondral tissue engineering resulting from the application of micro- and nanotechnology approaches in the structure of biomaterials, including biological and microscale/nanoscale topographical cues, microspheres, nanoparticles, nanofibers, and nanotubes.
•Plasma treatment of polypropylene was performed using both O2 and Ar atmospheres.•Plasma treated polypropylenes were analyzed by both FTIR and AFM techniques.•Polyurethane-urea ionomer was found as ...an efficient coating for treated polypropylene.•This coating increases surprisingly adhesion strength of oxygen treated polypropylene.
In present research, polypropylene (PP) was selected as a model nonpolar substrate for chemical modification using plasma. In the first step, the PP samples were treated using oxygen and argon atmospheres, individually. The prepared samples were analyzed using both FTIR and AFM techniques. The output of these techniques revealed that the carbonyl, carboxylic acid and its derivatives have been formed on the surface of PP. Afterward, a series of aqueous polyurethane-urea dispersions were synthesized as the novel polar coating for modified nonpolar polymers and characterized by different techniques including FTIR, DSC, TGA, mechanical properties and contact angle. Finally, the plasma treated samples were coated by prepared polyurethane ionomer. The results of pull-off analysis confirmed the significant role of the polyurethane as an extremely polar coating to create hydrogen bonding with functional groups on the surface of treated PP. The adhesion strength of polypropylenes increased from 0.04MPa to 0.61MPa for neat and oxygen-based plasma treated samples, respectively.
Hypothesis: Due to the presence of intra- and inter molecular hydrogen bonding in alginate chemical structure, its electrospinning capability is weak. However, this weakness can be improved through ...substitution of hydroxyl groups by sulfate groups. This article focuses on the role of degree of substitution of sulfate groups on the physicochemical properties of electrospinning solutions, such as viscosity, electrical conductivity and electrospinning conditions. Methods: Sodium sulfated alginate (SSA) was synthesized through the reaction of sodium alginate and chlorosulfonic acid in formamide as the solvent. The amount of chlorosulfonic acid was varied in order to obtain the SSA samples with different degrees of substitution. The chemical structures of neat alginate and SSA were studied by FTIR and 1H NMR spectroscopy. Degree of sulfation of samples was measured using CHNS elemental analysis, and the electrical conductivity and viscosity of SSA solutions were measured. The SSA nanofibers were fabricated using electrospinning and further crosslinked by a solution of calcium chloride to improve its hydrolytic stability. Finally, the fiber diameter and mechanical properties of the nanofibrous mat were studied by SEM and a tensile mechanical machine. Findings: Both FTIR and 1H NMR analyses have confirmed the formation of sulfate groups in SSA structure. Based on elemental analysis, the degree of substitution (DS) of SSA samples has been measured as 0.9 and 0.5 for SSA1 and SSA0.5, respectively. The electrical conductivity and viscosity of the SSA solutions also increased and decreased by increasing DS, respectively. The SSA1 sample showed better electrospinning capability and higher SSA content in dry electrospun mat compared to those in SSA0.5 sample. Finally, the crosslinked SSA1 mat revealed a lower mechanical strength compared to SSA0.5 mat due to lower crosslink density and higher chain scission of polymeric chains resulted from sulfation reaction.
The biological factors secreted from cells and cell-based products stimulate growth, proliferation, and migration of the cells in their microenvironment, and play vital roles in promoting wound ...healing. The amniotic membrane extract (AME), which is rich in growth factors (GFs), can be loaded into a cell-laden hydrogel and released to a wound site to promote the healing of the wound. The present study was conducted to optimize the concentration of the loaded AME that induces secretion of GFs and structural collagen protein from cell-laden AME-loaded collagen-based hydrogels, to promote wound healing
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In this experimental study, fibroblast-laden collagen-based hydrogel loaded with different concentrations of AME (0.1, 0.5, 1, and 1.5 mg/mL, as test groups) and without AME (as control group), were incubated for 7 days. The total proteins secreted by the cells from the cell-laden hydrogel loaded with different concentrations of AME were collected and the levels of GFs and type I collagen were assessed using ELISA method. Cell proliferation and scratch assay were done to evaluate the function of the construct.
The results of ELISA showed that the concentrations of GFs in the conditioned medium (CM) secreted from the cell-laden AME-loaded hydrogel were significantly higher than those secreted by only the fibroblast group. Interestingly, the metabolic activity of fibroblasts and the ability of the cells to migrate in scratch assay significantly increased in the CM3-treated fibroblast culture compared to other groups. The concentrations of the cells and the AME for preparation of CM3 group were 106 cell/mL and 1 mg/mL, respectively.
We showed that 1 mg/ml of AME loaded in fibroblast-laden collagen hydrogel significantly enhanced the secretion of EGF, KGF, VEGF, HGF, and type I collagen. The CM3 secreted from the cell-laden AME-loaded hydrogel promoted proliferation and scratch area reduction
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•Sodium alginate coated Fe3O4 nanoparticles (Alg–Fe3O4) as a novel superparamagnetic adsorbent were prepared by in situ coprecipitation method.•The Alg–Fe3O4 nanoparticles were used for removal of ...malachite green (MG) from aqueous solutions using batch adsorption technique.•The results of FTIR and TGA confirmed that sodium alginate was successfully coated on the surface of Fe3O4 nanoparticles.•The maximum adsorption capacity obtained from Langmuir isotherm equation was 47.84mg/g.•The adsorption of MG onto Alg–Fe3O4 nanoparticles followed the pseudo-second-order kinetic model.
In this study, superparamagnetic sodium alginate-coated Fe3O4 nanoparticles (Alg–Fe3O4) as a novel magnetic adsorbent were prepared by in situ coprecipitation method, in which Fe3O4 nanoparticles were precipitated from FeCl3 and FeCl2 under alkaline medium in the presence of sodium alginate. The Alg–Fe3O4 nanoparticles were used for removal of malachite green (MG) from aqueous solutions using batch adsorption technique. The characterization of synthesized nanoparticles was performed using XRD, FTIR, TEM, TGA and vibrating sample magnetometer (VSM) techniques. FTIR analysis of synthesized nanoparticles provided the evidence that sodium alginate was successfully coated on the surface of Fe3O4 nanoparticles. The FT-IR and TGA characterization showed that the Alg–Fe3O4 nanoparticles contained about 14% (w/w) of sodium alginate. Moreover, TEM analysis indicated that the average diameter of the Alg–Fe3O4 nanoparticles was about 12nm. The effects of adsorbent dosage, pH and temperature were investigated on the adsorption properties of MG onto Alg–Fe3O4 nanoparticles. The equilibrium adsorption data were modeled using the Langmuir and Freundlich isotherms. The maximum adsorption capacity obtained from Langmuir isotherm equation was 47.84mg/g. The kinetics of adsorption of MG onto Alg–Fe3O4 nanoparticles were investigated using the pseudo-first-order and pseudo-second-order kinetic models. The results showed that the adsorption of MG onto nanoparticles followed pseudo-second-order kinetic model.
•Novel chemically-bonded alginates into the polyurethane structures were synthesized.•All alginate based polyurethanes were soluble in common aprotic organic solvents.•Alginate was used as a chain ...extender in polyurethane structure for the first time.•All alginate based polyurethanes were synthesized under catalyst-free conditions.•Properties of samples were extremely dependent on ionic nature of polyurethanes.
The novel soluble alginate-based polyurethanes in organic solvents were synthesized by the reaction of NCO-terminated prepolymers and tributylammonium alginate (TBA-Alg) for the first time. The chemical structures of synthesized polyurethanes were characterized using FTIR, 1H NMR and TGA. The reaction completion was confirmed by disappearing of NCO band in FTIR spectra. Furthermore, a peak at 4.71ppm and some small peaks at a range of 4.12–4.37ppm in the 1H NMR of alginate-based polyurethanes were assigned to the backbone of alginate. The results of both FTIR and 1H NMR were remarkably confirmed by TGA data. The ionic nature of polyurethane backbone not only affects on thermal properties of samples, but it also changes the chemically-bonded alginate morphology. Both polyether and polyester based non-ionic polyurethanes extended by TBA-Alg illustrated the distinct alginate, whereas those ionomers extended by alginate were appeared as the continuous systems at nanoscale.
•The challenges and solutions of alginate electrospinning were reviewed for the first time.•High density of intra- and intermolecular hydrogen bonding restricts alginate electrospinnability.•Alginate ...electrospinnability can be improved by blending with carrier polymers.•Electrospinning of alginate can be dramatically facilitated through chemical modifications.•Alginate nanofibers can be used in tissue engineering and drug delivery systems.
Alginate as a naturally-derived biomaterial with marine algae sources has gained much attention in both laboratorial and industrial applications due to its structural and chemical resemblance to extracellular matrix (ECM) as well as desirable properties like biocompatibility, biodegradability, processability and low cost. Electrospun alginate nanofibrous scaffolds have found wide applications in biomedical field such as tissue engineering, biomedicine and drug delivery systems. However, electrospinning of alginate is challenging due to the low solubility and high viscosity of high molecular weight alginate, high density of intra- and intermolecular hydrogen bonding, polyelectrolyte nature of aqueous solution and lack of appropriate organic solvent. The aim of this review is to summarize the challenges and obstacles in alginate electrospinning reported in the literature as well as the introduced solutions for them, in order to open new opportunities for more intended and successful investigations in the field.
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