Effects of formaldehyde solution and nanoparticles on mechanical properties and biodegradation of gelatin/nano β-TCP scaffolds

In this study, gelatin/beta tricalcium phosphate (β-TCP) nanocomposite scaffolds were prepared by solvent casting method. The cross-linking method was carried out by adding formaldehyde to gelatin. The microparticles of sodium chloride were used as porogen agent. Characterization of nano β-TCP was performed using XRD, FTIR, and SEM. Results showed that the size of the particles is about 100 nm with spherical morphology. In addition, the scaffold characterization was carried out using FTIR and SEM techniques. Observations showed a porous texture with pore size between 100 and 400 μm. The biodegradability and bioactivity evaluations of the scaffolds were done by immersing them in a simulated body fluid solution for different time periods. The biodegradability studies demonstrated a reduction in the degradation rate of gelatin/β-TCP nanocomposite scaffolds due to the presence of β-TCP nanoparticles. The obtained results of bioactivity tests confirmed the formation of apatite layer on the surface of the scaffolds. Furthermore, the effects of porosity, cross-linking agent, and β-TCP nanoparticles on the bending and compressive properties of the composite scaffolds were examined. According to the mechanical examinations of the scaffolds, the best bending and compressive properties occurred in the presence of 10 and 20 wt% of β-TCP nanoparticles, respectively. The appropriate mechanical properties and biodegradation rate for tissue engineering applications obtained at 1 g of the formaldehyde solution.     

How geometry,size, and surface properties of tailor-made particles control the efficiency of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite nanocomposites

Bioactive calcium phosphate nanoparticles as reinforcing filler have widely been used to produce polymer nanocomposite scaffolds suitable for application in bone tissue engineering; however, no study has investigated the effect of geometry, size, and surface properties of these nanoparticles on physical and mechanical behavior of scaffolds. This study was therefore devoted to determine how the critical features of the reinforcing nanoparticles could tailor the efficiency of polymeric nanocomposites. For this, we developed fibrous nanocomposite systems in which poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, was combined with hydroxyapatite (HA) nanoparticles having different sizes, geometries, surface chemical groups, and concentrations. The results showed that critical properties could be controlled by incorporating appropriate amounts of nanoparticles with a specific geometry and surface properties. It was also seen that the tensile modulus of fibrous nanocomposite increased from 77 MPa for neat PHBV to about 161 MPa for the nanocomposites containing 15 wt% surface-modified nanoparticles with elongated morphology.     

Three​-dimensional porous poly(ε-caprolactone)/beta-tricalcium phosphate microsphere-aggregated scaffold for bone tissue engineering

In this study, porous scaffolds made of polycaprolactone (PCL)/β-tricalcium phosphate (BTCP) biocomposite were fabricated for bone tissue engineering (BTE) applications. The microsphere-aggregated scaffolds were prepared with various BTCP concentrations (10wt%, 20wt%, 50wt%) by the freeze-drying method. The porosity of obtained microsphere-aggregated scaffolds with various pore sizes was 80–85%, where this value was about 70% for the PCL/BTCP (50) sample with no microsphere formation. The results indicated that adding BTCP has enhanced mechanical strength, and the mineralization of PCL/BTCP composite scaffolds has been increased compared to the pure PCL scaffolds in simulated body fluid (SBF). The adhesion and proliferation of mouse bone marrow mesenchymal stem cells (mMSCs) seeded onto PCL/BTCP scaffolds were enhanced compared to the PCL. In addition, in terms of differentiation, the incorporation of BTCP led to increasing the mineral deposition and alkaline phosphatase activity of mMSCs. The synergistic effect of using microsphere-aggregated scaffolds along with BTCP as a reinforcing agent in PCL biocomposite showed that these porous biocomposite scaffolds have the potential application in BTE.     

Synthesis and cytocompatibility of collagen/hydroxyapatite nanocomposite scaffold for bone tissue engineering

Collagen/hydroxyapatite nanocomposite scaffolds were prepared by in situ precipitation and freeze‐drying approach. The synthesized collagen/hydroxyapatite nanocomposites were characterized using various modalities. It was revealed that the inorganic phase in the nanocomposite was carbonate‐substituted hydroxyapatite with low crystallinity. Morphology studies showed the uniform distribution of hydroxyapatite particles in the collagen hydrogel. In addition, hydroxyapatite particles were gradually becoming irregular enough and the surface morphology had more wrinkles with the increase of inorganic component. Morphology, mechanical properties and cell biocompatibility of the prepared nanocomposite scaffolds were evaluated. The scaffolds presented a well‐developed macropore structure with a pore size ranging from 100 to 200 μm and the pore size of scaffold can also be regulated by changing the organic/inorganic weight ratio. Furthermore, the growth of MG63 cells on scaffolds showed they could significantly promote the proliferation of cells and could be potential candidate for bone engineering applications. POLYM. COMPOS., 81–90, 2016. © 2014 Society of Plastics Engineers     

Polyhydroxybutyrate/chitosan/bioglass nanocomposite as a novel electrospun scaffold: fabrication and characterization

Scaffolds and their features play a central role in tissue engineering; so this study is based on the production of a series of electrospun PHB/Chitosan/nBG nanocomposite scaffolds with 9 wt% polyhydroxybutyrate, 10, 15 and 20 wt% chitosan and 7.5, 10 and 15 wt% nanobioglass (nBG). Electrospinning process was performed with optimal conditions of spinning machine including voltage of 16 kV, syringe-collector spacing of 16 cm, and output rate of 1 µl per hour. The developed phases and the formation of chemical bonds between ceramic and polymer bands were studied through XRD and FTIR analyses. The FE-SEM and TEM analyses showed uniform morphology of nanofibers and dispersion of bioglass nanoparticles in the fiber structure. The presence of 10 wt% bioglass nanoparticles and 15 wt% chitosan increased the tensile strength of fibers to 3.42 MPa, which was about four times greater than strength of control sample (pure PHB). The developed fibers were kept 28 days in SBF solution and 60 days in PBS solution to assess their bioactivity and biodegradability. The results showed that the presence of bioglass nanoparticles leads to a dramatic increase in absorption of calcium and phosphorus ions and weight loss of scaffold. The developed scaffold can be used for bone and teeth tissue engineering applications.     

Mechanical modeling of silk fibroin/TiO2 and silk fibroin/fluoridated TiO2 nanocomposite scaffolds for bone tissue engineering

Biocompatible and biodegradable three-dimensional scaffolds are commonly porous which serve to provide suitable microenvironments for mechanical supporting and optimal cell growth. Silk fibroin (SF) is a natural and biomedical polymer with appropriate and improvable mechanical properties. Making a composite with a bioceramicas reinforcement is a general strategy to prepare a scaffold for hard tissue engineering applications. In the present study, SF was separately combined with titanium dioxide (TiO₂) and fluoridated titanium dioxide nanoparticles (TiO₂-F) as bioceramic reinforcements for bone tissue engineering purposes. At the first step, SF was extracted from Bombyx mori cocoons. Then, TiO₂ nanoparticles were fluoridated by hydrofluoric acid. Afterward, SF/TiO₂ and SF/TiO₂-F nanocomposite scaffolds were prepared by freeze-drying method to obtain a porous microstructure. Both SF/TiO₂ and SF/TiO₂-F scaffolds contained 0, 5, 10, 15 and 20 wt% nanoparticles. To evaluate the efficacy of nanoparticles addition on the mechanical properties of the prepared scaffolds, their compressive properties were assayed. Likewise, the pores morphology and microstructure of the scaffolds were investigated using scanning electron microscopy. In addition, the porosity and density of the scaffolds were measured according to the Archimedes’ principle. Afterward, compressive modulus and microstructure of the prepared scaffolds were evaluated and modeled by Gibson–Ashby’s mechanical models. The results revealed that the compressive modulus predicted by the mechanical model exactly corresponds to the experimental one. The modeling approved the honeycomb structure of the prepared scaffolds which possess interconnected pores.

     

High loading boron nitride chemically bonded with silicone rubber to enhance thermal neutron shielding and flexibility of polymer nanocomposites

Flexible materials with excellent radiation shielding and flexibility are essential to the personal protective equipments (PPEs) for protecting workers from nuclear radiations. However, it is an enormous challenge to obtain the desired materials since high loading filler in polymer nanocomposites usually promotes radiation shielding while restrains its flexibility. Here, a facile “thiol-ene click” means is applied to chemically bond high loading boron nitride (BN) nanoparticles with silicone rubber (SR) in SR/BN nanocomposites for thermal neutron shielding. Uniform dispersion of BN nanoparticles and good compatibility of interfaces in the nanocomposites with high loading filler lead to increased flexibility instead of decrease. In particular, the nanocomposite with 40 wt% BN displays 911% of elongation at break that is about 50% enhancement to that of neat SR. Furthermore, higher loading BN in the nanocomposites means better thermal neutron shielding. Namely, enhanced thermal neutron shielding and flexibility is achieved at SR/BN nanocomposite with 40 wt% BN. The present work provides a facile strategy towards superior integrated performance of flexible materials for radiation shielding, such as wearable devices.     

Synergistic enhancement of thermal conductivity by addition of graphene nanoplatelets to three-dimensional boron nitride scaffolds for polyamide 6 composites

Three-dimensional boron nitride/graphene nanoplatelets (3D-BN-GNP) scaffolds were fabricated using an ice-templating method and polyamide 6 (PA6)-based composites were prepared by vacuum impregnation of caprolactam monomers into the scaffolds, followed by polymerization. The BN sheets in the PA6/3D-BN and PA6/3D-BN-GNP composites display a predominant parallel alignment along the ice-crystal formation constructing thermally conductive paths. The addition of few GNPs assists the dispersion of BN sheets in the PA6/3D-BN-GNP composites and repair the broken thermal paths caused by local agglomeration of the BN sheets. Consequently, GNPs play a morphology-promoted synergistic role in the enhancement of the thermal conductivity of the PA6/3D-BN-GNP composites. The PA6/3D-BN-GNP composite prepared with 23.40 wt% BN sheets and 2.60 wt% GNPs exhibits the highest thermal conductivity of 2.80 W m⁻¹ K⁻¹, which is 833% and 33% higher than the values recorded for the pure PA6 and the PA6/3D-BN composite at BN loading of 26.18 wt%, respectively. Infrared imaging analysis revealed that the surface of the PA6/3D-BN-GNP composite has a fast response to heating and cooling, suggesting the potential of the composites in thermal management applications.     

Reinforcement and chemical cross-linking in collagen-based scaffolds in cartilage tissue engineering: a comparative study

Mechanical strength and biocompatibility are issues of most concern for scaffolds in cartilage tissue engineering. Collagen modification is always used to strengthen scaffolds. There are mainly two ways for collagen modification: inclusion of reinforcing phase to form composites and chemical cross-linking. To explore an alternative approach, the collagen hydrogel modified by a reinforcement phase was compared with cross-linking. Collagen-alginate hydrogel (CAH) and collagen hydrogel cross-linked by genipin (CGH), which were different in modification methods, were chosen candidates. A comprehensive study was carried out on mechanical, structural and biological properties including swelling ratio measurement, in vitro degradation, AFM, mechanical test, thermogravimetric analysis, and in vitro cartilage tissue engineering. The results showed that mechanical strength of collagen was more enhanced for CGH than CAH, as evidenced by analysis of swelling ratio, in vitro degradation, AFM, mechanical test and thermostability. MTT and histological results showed that CGH was superior to CAH with less cytotoxicity and more chondrocytes distributed as well as more aggrecan secreted. With the increase in culture time, the cytotoxicity of cross-linker may be alleviated. CGH may provide a more favorable biomimetic environment for cartilage growth. All these indicated that selecting a cross-linker with a minimal cytotoxicity could be more promising for collagen modification, with improvements observed in both physical and biological properties. For reinforcement, it was required that the incorporated component should be equipped with better or equivalent properties compared with collagen. This study provided important implications to engineering collagen-based hydrogels for cartilage graft applications.     

Enhanced mechanical and anisotropic thermal conductive properties of polyimide nanocomposite films reinforced with hexagonal boron nitride nanosheets

To attain thermally conductive but electrically insulating polymer films, in this study, polyimide (PI) nanocomposite films with 1–30 wt% functionalized hexagonal boron nitride nanosheets (BNNSs) were fabricated via solution casting and following imidization. The microstructures, mechanical and thermal conductive properties of PI/BNNS nanocomposite films were examined by taking account of the relative content, anisotropic orientation, and interfacial interaction of BNNS and PI matrix. The scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffractometry data revealed that BNNSs with hydroxy and amino functional groups have specific molecular interactions with PI matrix and they form stacked aggregates in the nanocomposite films with high BNNS loadings of 10–30 wt%. The tensile mechanical strength/modulus, thermal degradation temperatures, and thermal conductivity of the nanocomposite films were found to be significantly enhanced with increasing the BNNS loadings. For the nanocomposite films with 1–30 wt% BNNS loadings, the in-plane thermal conductivity was measured to be 1.82–2.38 W/mK, which were much higher than the out-of-plane values of 0.35–1.14 W/mK. The significant anisotropic thermal conductivity of the nanocomposite films was found to be owing to the synergistic anisotropic orientation effects of both BNNS and PI matrix. It is noticeable that the in-plane and out-of-plane thermal conductivity values of the nanocomposite film with 30 wt% BNNS were ~1.31 and ~3.35 times higher than those of neat PI film, respectively.     

Synthesis of ultralong hydroxyapatite micro/nanoribbons and their application as reinforcement in collagen scaffolds for bone regeneration

Ultralong hydroxyapatite (HAp) micro/nanoribbons were successfully synthesized by a simple hydrothermal method without using any organic solvents and templates. The ultralong HAp micro/nanoribbons were up to several hundred micrometers in length and 100–400?nm in width. The growth process and mechanism of this micro/nanoribbons were also analyzed in this study. Moreover, the ultralong HAp micro/nanoribbons were used as reinforcement in collagen scaffolds and the HAp/collagen composite scaffolds were fabricated by freeze-drying process without cross-linking. The morphological results demonstrated homogeneous interconnected porous structure in 20?wt% and 35?wt% HAp reinforced scaffolds. The compressive modulus of the 35?wt% HAp/collagen composite was about 6 times that of the pure collagen scaffold. The ultralong HAp reinforced collagen scaffold possesses a porous structure, good flexibility as well as elasticity, and thus it is promising for used as bone repair material.     

Preparation and characterization of collagen/silica composite scaffolds for peripheral nerve regeneration

To improve the regeneration of peripheral nerve system, the silica nanoparticles of various concentrations were synthesized in collagen solution and formed to silica incorporated porous collagen structures. We examined various properties such as morphology, chemical composition, wettability, porosity, swelling ratio and degradation behavior of the composite scaffolds. Schwann cells culture was used to evaluate the effect of the collagen/silica composite materials on nerve regeneration. And the content of DNA in Schwann cells was measured. We ascertained that the silica nanoparticles could be incorporated into collagen scaffolds successfully. The incorporation of silica nanoparticles could increase the hydrophobicity, decrease porosity, swelling ratio and degradation rate of the collagen scaffolds. Further, the attachment and proliferation of Schwann cells on the silica incorporated porous collagen patch was much better than that of the collagen patch as control. The number and DNA contents of the cells on the composite scaffolds increased firstly and then decreased with the increment of nanoparticles concentration. It was optimal to combine silica of 25 μg/mL for achieving best cell attachment and proliferation with the highest DNA contents compared with other samples. These results indicate that silica incorporated porous collagen patch may be potentially used as implanted scaffold materials for the peripheral nerve regeneration.     

Construction of hexagonal boron nitride@polystyrene nanocomposite with high thermal conductivity for thermal management application

Hexagonal boron nitride (BN) hold great promise as emerging building blocks for thermal interface materials owing to their outstanding heat transfer performance. Herein, we report a carboxylated polystyrene-coated hydroxylated BN (BN–OH@PS-COOH) nanocomposite with highly thermal conductivity (TC) and extraordinary mechanical properties for thermal management. The exfoliated BN-OH nanosheets were obtained via molten alkali hydroxide pretreatment and sonication. Subsequently, PS-COOH nanospheres were grew on the surface of BN-OH nanosheets by in situ polymerization. Noncovalent interactions between PS-COOH and BN-OH are favor to reduce interfacial thermal resistance, which contributes to accelerate heat transport. As a result, the TC of the resultant BN-OH@PS-COOH nanocomposite with 12 wt% BN-OH addition is 1.131 W/mK, which is much higher than that of neat PS (0.186 W/mK) and BN/PS blend nanocomposite (0.312 W/mK). Moreover, the BN-OH@PS-COOH nanocomposite exhibits outstanding mechanical properties. Our study may stimulate novel perspectives on the design of high-performance polymer-based thermal interface materials.     

Bacterial cellulose/collagen composite: Characterization and first evaluation of cytocompatibility

The novel bacterial cellulose (BC)/collagen composites were prepared by immersing wet BC pellicle excreted by Acetobacter xylinum in collagen solution followed by freeze‐drying process. The product looks like a foam structure. The morphology of BC/collagen composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images showed that collagen molecules was not only coated on the BC fibrils surface but also could penetrate inside BC and hydrogen bond interactions were formed between BC and collagen. The prepared BC/collagen composite was also characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and mechanical test. With the incorporation of collagen in the BC, no changes happened in the crystal structure but the thermal stability was improved. Tensile test results indicate that the Young's Modulus and tensile strength have a big increase while the elongation at break has a slight decrease. The cytocompatibility of composite was preliminarily evaluated by cell adhesion studies. The tests were carried out using 3T3 fibroblast cells. The cells incubated with BC/collagen scaffolds for 48 h were capable of forming cell adhesion and proliferation. It showed much better cytocompatibility than pure BC. So, the prepared BC/collagen scaffolds are bioactive and may be suitable for cell adhesion/attachment suggesting that these scaffolds can be used for wound dressing or tissue‐engineering scaffolds. Therefore, these results suggest that these novel BC/collagen scaffolds may have the potential to be sued for some biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Optimisation of two-step sintering parameters to produce bioactive and dense zirconia-hydroxyapatite composite ceramics

3Y-TZP along with Hydroxyapatite (HAp) are common bioceramics used in bone tissue engineering scaffolds to yield better patient outcomes and faster healing times. However, significant differences in thermal expansion of these ceramics result in challenges to co-sintering these materials without losing functionality and strength. In this work, a two-step sintering (TSS) process was utilised to co-sinter composites using (1-x)3Y-TZP and xHAp where x varies between 20 and 80 wt%. A peak temperature of 1300 °C, a plateau temperature of 1175 °C, a holding time of 600 min and heating rate of 10 °C/min were the optimum TSS conditions for all compositions. The TSS process produced specimens with grain sizes between 0.5 and 1.2 µm and a compression strength between 88 and 176 MPa. The similarity in compression strength of these zirconia-hydroxyapatite composites with natural bone and the retention of HAp make them suitable for bone tissue engineering applications in load bearing areas.     

Porous boron nitride nanofibers/PVA hydrogels with improved mechanical property and thermal stability

Polyvinyl alcohol (PVA) hydrogel is a promising material possessing good chemical stability, high water absorption, excellent biocompatibility and biological aging resistant. However, the poor mechanical performance of PVA hydrogel limits its applications. Here we report the utilization of one-dimensional (1D) BN nanofibers (BNNFs) as nanofillers into PVA matrix to prepare a novel kind of BNNFs/PVA composite hydrogel via a cyclic freezing and thawing method. For comparison, the composite hydrogels using spherical BN nanoparticles i.e. BN nanospheres (BNNSs) as fillers were also prepared. The mechanical properties, thermal stabilities and swelling behaviors of the composite hydrogels were investigated in detail. Our study indicates that the mechanical properties of the hydrogels can be improved by adding of BNNFs. After loading of BNNFs into PVA with content of 0.5?wt%, the compressive strength of the composite hydrogel increases by 252% compared with that of pure PVA hydrogel. The tensile performance of BNNFs/PVA composite hydrogels has also been improved. Impressive 87.8% increases in tensile strengths can be obtained with 1?wt% BNNFs added. In addition, with the increase of BNNFs content, the thermal stability and the swelling ratio of hydrogels are increased gradually. The swelling ratio of hydrogel increases by 56.3% with only 1?wt% BNNFs added. In comparison, the improvement effects of the BNNS fillers on the mechanical strengths and swelling ratios are much weaker. The enhanced effects of BNNFs can be ascribed to the strong hydrogen bond interaction between BNNFs and PVA. The high aspect ratios of the nanofibers should also be took into account.     

3D Printed Poly(𝜀-caprolactone)/Hydroxyapatite Scaffolds for Bone Tissue Engineering: A Comparative Study on a Composite Preparation by Melt Blending or Solvent Casting Techniques and the Influence of Bioceramic Content on Scaffold Properties

Bone tissue engineering has been developed in the past decades, with the engineering of bone substitutes on the vanguard of this regenerative approach. Polycaprolactone-based scaffolds are fairly applied for bone regeneration, and several composites have been incorporated so as to improve the scaffolds’ mechanical properties and tissue in-growth. In this study, hydroxyapatite is incorporated on polycaprolactone-based scaffolds at two different proportions, 80:20 and 60:40. Scaffolds are produced with two different blending methods, solvent casting and melt blending. The prepared composites are 3D printed through an extrusion-based technique and further investigated with regard to their chemical, thermal, morphological, and mechanical characteristics. In vitro cytocompatibility and osteogenic differentiation was also assessed with human dental pulp stem/stromal cells. The results show the melt-blending-derived scaffolds to present more promising mechanical properties, along with the incorporation of hydroxyapatite. The latter is also related to an increase in osteogenic activity and promotion. Overall, this study suggests polycaprolactone/hydroxyapatite scaffolds to be promising candidates for bone tissue engineering, particularly when produced by the MB method.     

Nano boron nitride laminated poly(ethyl methacrylate)/poly(vinyl alcohol) composite films imprinted with silver nanoparticles as gas barrier and bacteria resistant packaging materials

Herein, nano boron nitride (BN) laminated poly(ethyl methacrylate) (PEMA)/poly(vinyl alcohol) (PVA) nanocomposite films are fabricated by using a simple in situ polymerization technique with incorporation of silver nanoparticles (Ag NPs). Structural investigations of PEMA/PVA/Ag@BN nanocomposite thin films are carried out by Fourier-transform infrared spectroscopy, dynamic light scattering, X-ray diffraction analysis, ¹H nuclear magnetic resonance, ¹³C nuclear magnetic resonance, and mass spectrometry. The change in morphology of PEMA/PVA matrix due to the reinforcement of BN platelets are identified by electron microscopic studies. The unique tortuous paths are achieved by the dispersion of BN platelets by which gas penetration is restricted with enhancing the barrier properties of the material by 6.5 folds at 5 wt% BN content as compared with neat PEMA/PVA. Acid and alkali resistant along with biodegradability behavior of as-synthesized nanocomposites are studied. From limiting oxygen index (LOI) results, it is found that the prepared materials are fire retardant in nature owing to effective reinforcement of BN layers. Antibacterial activities of PEMA/PVA/Ag@BN nanocomposite are studied by Xanthomonas citri or axonopodis pv. Citri, Escherichia coli, and Xanthomonas oryzae pv. Oryzae because of Ag NPs reinforcement. The substantial improvements in gas barrier, fire retardant, and antibacterial properties enable the materials for packaging application.     

Facile fabrication of near-infrared light-responsive shape memory nanocomposite scaffolds with hierarchical porous structures

In this work, the near-infrared (NIR) light-responsive shape memory scaffolds with hierarchical porous structures are designed and facilely formed by freeze drying of 3D printed viscous gel-like pickering emulsions, which are stabilized by hydrophobically modified graphene oxide (g-GO) and silica nanoparticles, and contain thermo-responsive poly(d , l -lactic acid-co-trimethylene carbonate) (PLMC) in the oil phase. The prepared scaffolds display an interconnected filament structure with hierarchical pores and high porosity. The incorporation of g-GO nanoparticles into PLMC matrix prompts that the scaffold shape memory can be triggered by NIR light with fast shape recovery. Moreover, the in vitro mineralization experiment shows that the scaffolds have biological activity, and the drug release study demonstrates that the scaffolds can be used as drug carriers with efficient drug release capacity. Furthermore, cell culture assays based on mouse bone mesenchymal stem cells exhibit that the scaffolds own good cytocompatibility. Therefore, the facile preparation and remote activation of the shape memory nanocomposite scaffolds with hierarchical porous structure and multifunctionality represents a highly attractive candidate as minimally invasive implantation scaffolds for bone tissue engineering applications.     

The effect of filler content on mechanical properties and cell response of elastomeric PGS/apatite foam scaffolds

Poly(glycerol sebacate) (PGS) is a novel polymeric material intended for applications in tissue engineering (TE). This study involves synthesizing the PGS prepolymer (pPGS) and subsequent manufacturing of porous PGS-based scaffolds with an addition of hydroxyapatite (HAp) by means of thermally induced phase separation followed by thermal cross-linking and salt-leaching (TIPS-TCL-SL). The study aims to investigate the effect of the apatite filler content on properties and morphology of porous PGS/HAp scaffolds. The emphasis is put on the mechanical behavior of the material characterized by means of compression tests and dynamic thermal mechanical analysis (DMTA). In addition to the reference polymer scaffold, the composites with filler contents of 10, 20 and 30 wt% have been examined. Our research revealed that the HAp content does not affect the mechanical properties in a directly proportional manner. The 30 wt% addition of HAp resulted in frayed structure and decrease in the mechanical parameters in comparison to other tested specimens. On the other hand, an addition of 10% did not sufficiently boost the properties. Therefore, a 20% addition of HAp was concluded to have superior mechanical properties in comparison to other analyzed specimens. A similar relationship results from the DMTA studies. Moreover, the strain sweep and frequency sweep tests confirmed the stability of the mechanical parameters in various conditions, as well as the elastomeric nature of the materials. Finally, the material did not exhibit cytotoxicity against standard L929 fibroblasts and cells readily populated the scaffolds.