Potential Applications In Bone Tissue Engineering Research Articles

Osteoblast and osteoclast activity on collagen-based 3D printed scaffolds enriched with strontium-doped bioactive glasses and hydroxyapatite nanorods for bone tissue engineering

Bone tissue engineering (BTE) aims to promote bone regeneration by means of the synergistic effect of biomaterials, cells, and other factors, as potential alternative to conventional treatments for bone fractures. To this aim, a composite material was developed, based on collagen type I, strontium-enriched mesoporous bioactive glasses, and hydroxyapatite nanorods as bioactive and biomimetic components. Nanostructured scaffolds were 3D printed and subsequently chemically crosslinked with genipin to improve mechanical properties and stability. The developed nanostructured system was maintained in culture until 3 weeks with a co-culture of human bone cells to provide anex vivomodel of bone microenvironment and examine the cellular crosstalk and signaling pathways through paracrine cell activities. Human osteoblasts (OBs), derived from trabecular bone, and human osteoclast precursors (OCs), isolated from buffy coat samples were involved, with OBs seeded on the scaffold and OC precursors seeded in a transwell device. When compared to the material without inorganic components, the bioactive and biomimetic scaffold positively influenced cell proliferation and cell metabolic activity, boosting alkaline phosphatase activity of OBs, and reducing OC differentiation. Thus, the bioactive and biomimetic system promoted an enhanced cellular response, highlighting its potential application in BTE.

Design of gelatin cryogel scaffolds with the ability to release simvastatin for potential bone tissue engineering applications

Tissue engineering aims to improve or restore damaged tissues by using scaffolds, cells and bioactive agents. In tissue engineering, one of the most important concepts is the scaffold because it has a key role in keeping up and promoting the growth of the cells. It is also desirable to be able to load these scaffolds with drugs that induce tissue regeneration/formation. Based on this, in our study, gelatin cryogel scaffolds were developed for potential bone tissue engineering applications and simvastatin loading and release studies were performed. Simvastatin is lipoliphic in nature and this form is called inactive simvastatin (SV). It is modified to be in hydrophilic form and converted to the active form (SVA). For our study's drug loading and release process, simvastatin was used in both inactive and active forms. The blank cryogels and drug-loaded cryogels were prepared at different glutaraldehyde concentrations (1, 2, and 3%). The effect of the crosslinking agent and the amount of drug loaded were discussed with morphological and physicochemical analysis. As the glutaraldehyde concentration increased gradually, the pores size of the cryogels decreased and the swelling ratio decreased. For the release profile of simvastatin in both forms, we can say that it depended on the form (lipophilic and hydrophilic) of the loaded simvastatin.

Physical, mechanical characterization, and artificial neural network modeling of biodegradable composite scaffold for biomedical applications

The performance of substitute osteoconductive scaffolds in guiding new bone formation and creating vital biological conditions in living organisms is of crucial importance. In this study, bioresorbable scaffolds were synthesized by incorporating polyvinyl alcohol (PVA) with hydroxyapatite nanoparticles (n-HAP) and Iron oxide (Fe3O4) nanoparticles (NPs) (MNPs) using a freeze-drying technique. Subsequently, the magnetic nanocomposite scaffolds were immersed in a phosphate-buffered saline (PBS) solution for 24 days to assess their degradability percentage. The physicochemical and morphological properties of the magnetic nanocomposite scaffolds were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Furthermore, the mechanical behavior was examined, while the pore dimensions and porosity were determined using immersion-based techniques. Noteworthy attributes of the magnetic nanocomposite scaffolds were observed, including a maximum swelling capacity of 176 %, a substantial porosity of 72.7%, and impressive mechanical characteristics, such as a compressive strength of 4.61 MPa and an elastic modulus of 2.13 GPa. The degradation study conducted in a PBS solution revealed that the scaffold with the highest n-HAP content (20 wt%) exhibited a degradation rate of approximately 21% after a 24-day period. The influence of environmental conditions, including time, temperature, and salt-containing environments, on the swelling behavior and bio-resorption of the scaffolds was examined. Additionally, an artificial neural network (ANN) was developed to forecast the impact of weight percentages of n-HAP and MNPs on various scaffold properties. According to the ANN predictions, increasing the weight percentages of n-HAP and MNPs resulted in a reduction in pore size, an increase in porosity, and an improvement in the mechanical properties of the scaffolds. Moreover, the incorporation of a higher number of nanoparticles led to increased absorption and swelling, facilitating bone tissue formation. Satisfactory accuracy in predicting scaffold properties was demonstrated through error analysis and linear regression plots, aiding designers in selecting appropriate weight percentages of nanoparticles for future designs. The findings indicate that the synthesized magnetic nanocomposite scaffold closely resembles the physical and mechanical characteristics of natural bone tissue. The utilization of an ANN for performance assessment demonstrated favorable efficiency and effectiveness. Therefore, the significance of the current study lies in the comprehensive investigation of the synthesis and characterization of a biodegradable magnetic nanocomposite scaffold, as well as the utilization of an ANN-based approach to predict and optimize its properties for potential bone tissue engineering applications.

Additive manufacturing of 3D networks based on poly(lactic acid) and amine functionalized graphene oxide as a platform for scaffolds

AbstractIn the present study, 3D networks were printed using the fused deposition modeling (FDM) technique. The purpose was investigate the printability of graphene oxide (GO)‐based composites for potential bone tissue engineering applications. Poly(lactic acid) (PLA) filaments containing GO and amine functionalized GO (N‐GO) were produced by melt extrusion and employed to print 3D networks. The cytotoxicity, morphological, rheological, and thermal behavior of the samples were compared. The morphological, rheological, and wettability analyses indicated an improvement in dispersion of GO throughout the matrix of PLA when GO was amine functionalized. The viscoelastic and flow properties, as determined by rheology, indicated that printed PLA samples containing freeze‐dried GO had lower viscosity than other composites, with a viscosity of 59.4 (Pa s), a decrease of nine times when compared with pure PLA, while the PLA containing N‐GO presented an improved viscoelastic interaction. PLA contact angle (108°) decreased by 87° and 84° for N‐GO and GO, respectively. The thermal analyses depicted that the incorporation of freeze‐dried GO and N‐GO had no effect on the crystallinity or thermal transitions of PLA matrix, maintaining its thermal stability. Finally, the cytotoxicity analysis indicated that the composites were not toxic throughout the cell culture assay and were found to promote cell viability, especially for the PLA/N‐GO network. Thus, these results revealed a vast horizon toward the use of GO/biodegradable polymers as platforms to print 3D networks to be applied as scaffolds.

Site-specific periosteal cells with distinct osteogenic and angiogenic characteristics.

This study aimed to investigate the site-specific characteristics of rat mandible periosteal cells (MPCs) and tibia periosteal cells (TPCs) to assess the potential application of periosteal cells (PCs) in bone tissue engineering (BTE). MPCs and TPCs were isolated and characterized. The potential of proliferation, migration, osteogenesis and adipogenesis of MPCs and TPCs were evaluated by CCK-8, scratch assay, Transwell assay, alkaline phosphatase staining and activity, Alizarin Red S staining, RT‒qPCR, and Western blot (WB) assays, respectively. Then, these cells were cocultured with human umbilical vein endothelial cells (HUVECs) to investigate their angiogenic capacity, which was assessed by scratch assay, Transwell assay, Matrigel tube formation assay, RT‒qPCR, and WB assays. MPCs exhibited higher osteogenic potential, higher alkaline phosphatase activity, and more mineralized nodule formation, while TPCs showed a greater capability for proliferation, migration, and adipogenesis. MPCs showed higher expression of angiogenic factors, and the conditioned medium of MPCs accelerated the migration of HUVECs, while MPC- conditioned medium induced the formation of more tubular structure in HUVECs in vitro. These data suggest that compared to TPCs, MPCs exert more consequential proangiogenic effects on HUVECs. PCs possess skeletal site-specific differences in biological characteristics. MPCs exhibit more eminent osteogenic and angiogenic potentials, which highlights the potential application of MPCs for BTE. Autologous bone grafting as the main modality for maxillofacial bone defect repair has many limitations. Constituting an important cell type in bone repair and regeneration, MPCs show greater potential for application in BTE, which provides a promising treatment option for maxillofacial bone defect repair.

Enhanced bone tissue regeneration using a 3D-printed poly(lactic acid)/Ti6Al4V composite scaffold with plasma treatment modification

The mechanical and biological properties of polylactic acid (PLA) need to be further improved in order to be used for bone tissue engineering (BTE). Utilizing a material extrusion technique, three-dimensional (3D) PLA-Ti6Al4V (Ti64) scaffolds with open pores and interconnected channels were successfully fabricated. In spite of the fact that the glass transition temperature of PLA increased with the addition of Ti64, the melting and crystallization temperatures as well as the thermal stability of filaments decreased slightly. However, the addition of 3–6 wt% Ti64 enhanced the mechanical properties of PLA, increasing the ultimate compressive strength and compressive modulus of PLA-3Ti64 to 49.9 MPa and 1.9 GPa, respectively. Additionally, the flowability evaluations revealed that all composite filaments met the print requirements. During the plasma treatment of scaffolds, not only was the root-mean-square (Rq) of PLA (1.8 nm) increased to 60 nm, but also its contact angle (90.4°) significantly decreased to (46.9°). FTIR analysis confirmed the higher hydrophilicity as oxygen-containing groups became more intense. By virtue of the outstanding role of plasma treatment as well as Ti64 addition, a marked improvement was observed in Wharton's jelly mesenchymal stem cell attachment, proliferation (4′,6-diamidino-2-phenylindole staining), and differentiation (Alkaline phosphatase and Alizarin Red S staining). Based on these results, it appears that the fabricated scaffolds have potential applications in BTE.

Controlling the hierarchical microstructure of bioceramic scaffolds by 3D printing of emulsion inks

Mechanical and biological properties constitute the most fundamental requirements for bone tissue engineering (BTE) scaffolds. Nonetheless, existing fabrication strategies find it difficult to prepare highly porous BTE scaffolds for improved biological properties while also preserving sufficient mechanical properties that are compatible with the natural bone. Inspired by the hierarchical porous materials in Nature, hierarchical porous BTE scaffolds can achieve a combination of superior mechanical efficiency and biological functions. With this in mind, this study reports the fabrication of hierarchical porous hydroxyapatite (hpHA) scaffolds by 3D printing of emulsion inks. The scaffolds exhibit high porosity up to 73.7%, featuring 3D printed macropores of 300 – 400 µm and emulsion templated microporosity of < 20 µm. Via formulation of the emulsion inks, such as varying the oil volume and adding Pluronic® F-127, this process demonstrates effective control of the microporosity and pore morphology of the scaffolds. The scaffolds are mechanically compatible with the natural cancellous bone, with compressive strength in the range of 1.41 – 7.84 MPa and Young’s modulus of 57.3 – 304 MPa. Furthermore, the elastic admissible strain (EAS) and specific energy absorption (SEA) of the hpHA scaffolds can be increased up to 4.4% and 1.22 kJ/kg, respectively, indicating greatly enhanced mechanical performances owing to the hierarchical porous structure. Meanwhile, improved cell attachment, spreading and proliferation are observed in these scaffolds with their additional microporosity. Hence, the hpHA scaffolds in this study show great potential in BTE applications, and the reported process of 3D printing of emulsion inks is a promising fabrication strategy for further optimization of highly porous BTE scaffolds.

Macroporous silicon-wollastonite scaffold with Sr/Se/Zn/Mg-substituted hydroxyapatite/chitosan hydrogel

The scaffolds, which morphologically and physiologically mimic natural features of the bone, are of a high demand for regenerative medicine. To address this challenge, bioactive porous silicon/wollastonite (SC) scaffold has been developed for potential bone tissue engineering applications. Additive manufacturing through the selective laser melting approach has been exploited to fabricate computer-aided designed scaffolds with a pore size of 400 μm. To increase the biocompatibility and osteogenic properties of SC scaffolds, the hydrogel based on a mixture of four mono-substituted hydroxyapatites (sHAp) and biopolymer chitosan (CHT) has been incorporated into SC by impregnation and freeze-gelation method. The pore size of 400 μm of SC has provided enough space for the impregnation of polymer solution and composite (CHT/sHAp) suspension to form highly porous hydrogel within pores. By the combination of SC and CHT/sHAp, both cell attachment and homogeneous proliferation on SC scaffold as well as mechanical properties of CHT/sHAp hydrogel have been improved.

HPMC crosslinked chitosan/hydroxyapatite scaffolds containing Lemongrass oil for potential bone tissue engineering applications

The chitosan (CS), hydroxypropyl methyl cellulose (HPMC), hydroxyapatite (HAp and Lemon grass oil (LGO) based scaffolds was prepared by freeze gelation method. The composite formation was confirmed by FTIR (Fourier-transform infrared spectroscopy) analysis and surface morphology was evaluated by SEM (Scanning Electron Microscopy) analysis. The mechanical strength, biodegradation, swelling, porosity and antibacterial activity were evaluated on the basis of LGO contents. The scaffold structure was porous and the mechanical strength was enhanced as a function of LGO contents. The scaffold properties analysis revealed the biodegradation nature and swelling behavior of CS-HPMC-HAp-LGO was also affected significantly as a function of LGO contents. The cytotoxicity of CS-HPMC-HAp-LGO was studied against MC3T3-E1 cells and based on cell viability, no toxic sign was observed. The antimicrobial activity was evaluated against S. aureus and CS-HPMC-HAp-LGO scaffolds showed promising activity, which was varied as a function of LGO contents. The findings revealed that the CS-HPMC-HAp-LGO are biocompatible and have potential for bone tissue engineering.

Nano zinc oxide and nano bioactive glass reinforced chitosan/poly(vinyl alcohol) scaffolds for bone tissue engineering application

The present study was to develop a hybrid chitosan-based bionanocomposite for potential bone tissue engineering applications. Chitosan (C)/Poly(vinyl alcohol) (P)/nano bioactive glass (B)/nano Zinc Oxide (Z) were fabricated by sol-gel assisted solvent casting method. In this method, several CPBZ nanocomposites have been studied by varying the ratios of nano ZnO (0.05%, 0.1%, 0.2%) to yield CPBZ1, CPBZ2 and CPBZ3 hybrid scaffolds. TEM, FESEM- EDAX, XRD and FTIR analyses were performed to characterize the macrostructure of CPBZ bionanocomposites. Nano ZnO of size 20 nm and nano bioactive glass of size 6–10 nm was synthesized and characterized by TEM analysis. The in vitro bioactivity studies confirmed the formation of apatite minerals that results in direct bone bonding implant. SEM revealed the macroporous structure with a pore size of about 10 µm and hydrophilic rough surface. The phase composition of nano ZnO embedded in CPBZ scaffolds was examined by XRD. The characteristic functional groups and the chemical interactions associated with the organic-inorganic phase were analyzed by FTIR. The results of mechanical studies by a universal testing machine (UTM) demonstrated an increase in the tensile strength and apparent density after the addition of nano bioactive glass and nano ZnO. The integration of nano Zinc Oxide in the polymer matrix increased the swelling ratio up to 298% and maintained the delayed biodegradation behavior around 38%, while the pH remained neutral (7.4). The antibacterial activity evaluated by Salmonella typhi and Enterococcus faecalis pathogens showed a better zone of inhibition for gram positive E. faecalis. The hemocompatibility study proves that the CPBZ nanocomposites are blood compatible and showed a hemolytic ratio of less than 2%. The results demonstrated that the prepared bionanocomposites could act as an extracellular matrix in osteogenic tissue engineering.

A preliminary study on the synthesis of biogenic derived hydroxyapatite /medicinal plant extracts composite for potential bone tissue engineering applications

The bone minerals of Hydroxyapatite (Ca10(PO4)6OH2, HAP) are widely utilized in bone repair because of its close similarity to human hard tissues like bone and teeth. HAP has good biocompatible and osteoconductive properties. Naturally derived HAP materials have been widely used in various fields of biomedical applications like filling bones and coating in orthopedics and dental implantation. Hydroxyapatite has considerable mechanical properties, bioactivity, nontoxicity and does not cause any allergic reaction when placed inside the body. To develop an antimicrobial composite for the enhancement of the properties in the tissue engineering applications, HAP powders were prepared by refluxing the cuttlebone (Cb) with diammonium hydrogen phosphate. To the obtained Cb-HAP powders, Carica papaya (Cp) leaf extract was mixed under ultrasonic irradiation techniques to form the Cp induced Cb-HAP composite. Thus, the present work is a preliminary study on the synthesis of Cb-HAP powders and Cp induced Cb-HAP composite for tissue engineering applications. Furthermore, the phase structure and functional group analysis of the prepared composites were investigated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR). The morphology of the prepared composite was evaluated by using the Scanning electron microscope (SEM). In addition, the antibacterial activities of the composites were investigated against gram positive and gram-negative pathogens such as E. coli and S. aureus through disc diffusion method. From the obtained results, it can be clear that the Cp induced Cb-HAP exhibited enhanced bacterial inhibition. The observed physicochemical and antibacterial activity suggest that the Cp induced Cb-HAP composite can serve as potential biocomposite for bone tissue engineering applications.

Hydroxyapatite composite scaffold for bone regeneration via rapid prototyping technique: a review

PurposeRapid prototyping (RP) technology is widely used in many fields in recent years. Bone tissue engineering (TE) is an interdisciplinary field involving life sciences, engineering and materials science. Hydroxyapatite (HAp) are similar to natural bone and it has been extensively studied due to its excellent biocompatibility and osteoconductivity. This paper aims to review nanoscaled HAp-based scaffolds with high porosity fabricated by various RP methods for bone regeneration.Design/methodology/approachThe review focused on the fabrication methods of HAp composite scaffolds through RP techniques. The paper summarized the evaluation of these scaffolds on the basis of their biocompatibility and biodegradability through in vitro and in vivo tests. Finally, a summary and perspectives on this active area of research are provided.FindingsHAp composite scaffold fabricated by RP methods has been widely used in bone TE and it has been deeply studied by researchers during the past two decades. However, its brittleness and difficulty in processing have largely limited its wide application in TE. Therefore, the formability of HAp combined with biocompatible organic materials and fabrication techniques could be effectively enhanced, and it can be used in bone TE applications finally.Originality/valueThis review paper presented a comprehensive study of the various types of HAp composite scaffold fabricated by RP technologies and introduced their potential application in bone TE, as well as future roadmap and perspective.

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

AbstractIn 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.

Beneficial Influence of Water-Soluble PEG-Functionalized C60 Fullerene on Human Osteoblast Growth In Vitro.

The purpose of this study was to make an initial assessment of new PEG (polyethylene glycol)-functionalized C60 fullerene derivative for potential bone tissue engineering applications. Thus, Fourier Transform Infrared spectroscopy analysis, thermogravimetric analysis, and cyclic voltammetry measurement were performed. Moreover, cell culture experiments in vitro were carried out using normal human osteoblasts. Cell viability and proliferation were evaluated using colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test as well as by fluorescent staining. It was demonstrated that resultant derivative possessed good solubility in water, high temperature stability, and retained favorable electron accepting properties of C60 fullerene core. Most important, new fullerene derivatives at low concentrations did not exhibit cytotoxic effect and supported osteoblast proliferation compared to control. Thanks to all mentioned properties of new PEG-functionalized C60 fullerene derivative, it seems that it could be used as a component of polymer-based bone scaffolds in order to enhance their biological properties.

3D pore-interconnected calcium phosphate bone blocks for bone tissue engineering

Pore size and connectivity of artificial bone scaffolds play key role in regulating cell ingrowth and vascularization during healing. The objective of this study was to develop a novel process for preparing 3D pore-interconnected open-cell bone substitutes with varying pore sizes. This was achieved by thermal-induced expansion, drying, then sintering the mixture of biphasic calcium phosphate (BCP) and a thermal responsive porogen comprising chitosan (CS) and hydroxypropyl methyl cellulose (HPMC). The interpolymer complexes (IPCs) of CS/HPMC were prepared and investigated by FT-IR. The mixtures of IPCs/BCP were heated up to 100 °C for analyzing their thermal expansion properties. This resulted in ~13% and ~42% volume increment for IPC-1/BCP and IPC-2/BCP, respectively, while ~230% volume increased in the case of IPC-3/BCP (therefore chosen for sintering bone blocks). Heating rate-dependent (0.20–0.25 °C/min range) sintering profiles for IPC-3/BCP were utilized to produce BCP bone blocks. Gasification of IPC during sintering resulted in the formation of interconnected porous structures, and the morphology was investigated by SEM, revealing varying sizes ranging from 106 ± 13 μm to 1123 ± 75 μm. The pore size range of bone blocks from 235 ± 46 μm to 459 ± 76 μm portrayed significantly high MC3T3-E1 cell viability with prominent filopodial extensions, and elongated cells, depicting efficient biocompatibility. Therefore, the process for preparing porous interconnected 3D bone blocks were feasible, thereby serving as an alternative for potential bone tissue engineering applications.

Poly(d,l-Lactic acid) Composite Foams Containing Phosphate Glass Particles Produced via Solid-State Foaming Using CO2 for Bone Tissue Engineering Applications.

This study reports on the production and characterization of highly porous (up to 91%) composite foams for potential bone tissue engineering (BTE) applications. A calcium phosphate-based glass particulate (PGP) filler of the formulation 50P2O5-40CaO-10TiO2 mol.%, was incorporated into biodegradable poly(d,l-lactic acid) (PDLLA) at 5, 10, 20, and 30 vol.%. The composites were fabricated by melt compounding (extrusion) and compression molding, and converted into porous structures through solid-state foaming (SSF) using high-pressure gaseous carbon dioxide. The morphological and mechanical properties of neat PDLLA and composites in both nonporous and porous states were examined. Scanning electron microscopy micrographs showed that the PGPs were well dispersed throughout the matrices. The highly porous composite systems exhibited improved compressive strength and Young’s modulus (up to >2-fold) and well-interconnected macropores (up to ~78% open pores at 30 vol.% PGP) compared to those of the neat PDLLA foam. The pore size of the composite foams decreased with increasing PGPs content from an average of 920 µm for neat PDLLA foam to 190 µm for PDLLA-30PGP. Furthermore, the experimental data was in line with the Gibson and Ashby model, and effective microstructural changes were confirmed to occur upon 30 vol.% PGP incorporation. Interestingly, the SSF technique allowed for a high incorporation of bioactive particles (up to 30 vol.%—equivalent to ~46 wt.%) while maintaining the morphological and mechanical criteria required for BTE scaffolds. Based on the results, the SSF technique can offer more advantages and flexibility for designing composite foams with tunable characteristics compared to other methods used for the fabrication of BTE scaffolds.

Bioactive yet antimicrobial structurally stable collagen/chitosan/lysine functionalized hyaluronic acid – based injectable hydrogels for potential bone tissue engineering applications

Novel, biocompatible, multifunctional, injectable genipin crosslinked collagen/chitosan/lysine-modified hyaluronic acid based hydrogels (ColChHAmod) were prepared in a facile, one-step procedure. The novelty of the current approach lies in the functionalization of hyaluronic acid (HA) with primary amine groups by lysine attachment, and its further use as a component of the injectable sol. The obtained derivative, HAmod, could form, upon crosslinking with genipin, covalent bonds with other components of the hydrogel network, resulting in structurally stable, better-defined hydrogels. We have demonstrated that, by adjusting HAmod content and genipin concentration, hydrogels with tunable physicochemical characteristics (swelling, wettability, tendency for enzymatic degradation) and properties adequate for the potential bone tissue regeneration can be prepared. Storage modulus measurements indicated that HAmod has positive effect on mechanical characteristics of hydrogels prepared. It was also revealed that the ColChHAmod-based hydrogels are characterized by a high porosity (85–95%). The in situ rheological measurements confirmed the injectability of the obtained hydrogels. The in vitro cell culture studies showed that the surface of all materials prepared was biocompatible, as they supported proliferation and adhesion of osteoblast-like cells followed by ALP expression. The intrinsic antibacterial activity of the hydrogels against Escherichia coli was also demonstrated in in vitro experiment.

Composite Membranes of Poly(ε-caprolactone) with Bisphosphonate-Loaded Bioactive Glasses for Potential Bone Tissue Engineering Applications.

Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester with numerous biomedical applications. PCL membranes show great potential in guided tissue regeneration because they are biocompatible, occlusive and space maintaining, but lack osteoconductivity. Therefore, two different types of mesoporous bioactive glasses (SiO2-CaO-P2O5 and SiO2-SrO-P2O5) were synthesized and incorporated in PCL thin membranes by spin coating. To enhance the osteogenic effect of resulting membranes, the bioglasses were loaded with the bisphosphonate drug ibandronate prior to their incorporation in the polymeric matrix. The effect of the composition of the bioglasses as well as the presence of absorbed ibandronate on the physicochemical, cell attachment and differentiation properties of the PCL membranes was evaluated. Both fillers led to a decrease of the crystallinity of PCL, along with an increase in its hydrophilicity and a noticeable increase in its bioactivity. Bioactivity was further increased in the presence of a Sr substituted bioglass loaded with ibandronate. The membranes exhibited excellent biocompatibility upon estimation of their cytotoxicity on Wharton’s Jelly Mesenchymal Stromal Cells (WJ-SCs), while they presented higher osteogenic potential in comparison with neat PCL after WJ-SCs induced differentiation towards bone cells, which was enhanced by a possible synergistic effect of Sr and ibandronate.

Halloysite Nanotube Based Scaffold for Enhanced Bone Regeneration.

Bone regeneration remains a clinical challenge with limited bone substitutes, urging for effective alternative strategies. Nanotubes, especially carbon nanotubes and titanium dioxide nanotubes, have been widely utilized for bone regeneration; however, their further applications were limited by the composition and degradability. As naturally occurring aluminosilicate nanoclay, halloysite nanotubes (HNTs), with good biocompatibility, functionality, and nanotubular structures, may be a promising platform for promoting bone regeneration. Herein, we presented a HNTs incorporated hydrogel and explored the potential bone tissue engineering applications of HNTs. The HNTs encapsulated hydrogel was simply fabricated by using the photopolymerization method with gelatin methacrylate (GelMA) and HNTs. The incorporation of HNTs led to an enhanced mechanical performance while maintaining a good cytocompatibility in vitro. The osteogenic activities of the HNTs incorporated platform have also been studied in vitro and in vivo. Remarkably, the addition of HNTs obviously upregulated the expression of osteogenic differentiation-related genes and concomitant protein of human dental pulp stem cells (hDPSCs) and therefore facilitated subsequent bone regeneration in calvarial defects of rats. Overall, the results obtained in this study highlight the bone regeneration capacity of HNTs, which may enhance current understanding of HNTs, and present a promising alternative strategy for bone regeneration.

Heparin-dopamine functionalized graphene foam for sustained release of bone morphogenetic protein-2.

The recently developed three-dimensional (3D) graphene foam (GrF) is intriguing for potential bone tissue engineering applications because it provides stem cells with a 3D porous substrate for osteogenic differentiation. However, the nature of graphene's structure lacks functional groups, thus making it difficult for further modification such as immobilization or conjugation of growth factors, which are normally required to promote tissue regeneration. To explore the potential of GrF functionalization and sustained release of therapeutic proteins, we fabricated a modified 3D GrF scaffold with bio-inspired heparin-dopamine (Hepa-Dopa) molecules using a highly scalable chemical vapour deposition method. Our data indicated that Hepa-Dopa modification resulted in significantly higher bone morphogenetic protein-2 (BMP2) binding ability and longer release capacity compared with the untreated scaffolds. Importantly, the heparin-functionalized 3D GrF significantly improved the exogenous BMP2-induced osteogenic differentiation. Therefore, our study, for the first time, indicated that the 3D GrF can be biomimetically functionalized with Hepa-Dopa and be used for sustained release of BMP2, thereby inducing osteogenic differentiation and suggesting promising potential as a new multifunctional carrier for therapeutic proteins and stem cells in bone tissue engineering.