The calcium silicate/alginate composite: preparation and evaluation of its behavior as bioactive injectable hydrogels

Guar-Based Injectable Thermoresponsive Hydrogel as a Scaffold for Bone Cell Growth and Controlled Drug Delivery

In this study, an injectable thermoresponsive hydroxypropyl guar-graft-poly(N-vinylcaprolactam) (HPG-g-PNVCL) copolymer was synthesized by graft polymerization. The reaction parameters such as temperature, time, monomer, and initiator concentrations were varied. In addition, the HPG-g-PNVCL copolymer was modified with nano-hydroxyapatite (n-HA) by in situ covalent cross-linking using divinyl sulfone (DVS) cross-linker to obtain HPG-g-PNVCL/n-HA/DVS composite material. Grafted copolymer and composite materials were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, proton nuclear magnetic resonance spectroscopy (1H NMR), and differential scanning calorimetry. The morphology of the grafted copolymer (HPG-g-PNVCL) and the composite (HPG-g-PNVCL/n-HA/DVS) was examined using scanning electron microscopy (SEM), which showed interconnected porous honeycomb-like structures. Using Ultraviolet-visible spectroscopy, low critical solution temperature for HPG-g-PNVCL was observed at 34 °C, which is close to the rheology gel point at 33.5 °C. The thermoreversibility of HPG-g-PNVCL was proved by rheological analysis. The HPG-g-PNVCL hydrogel was employed for slow release of the drug molecule. Ciprofloxacin, a commonly known antibiotic, was used for sustainable release from the HPG-g-PNVCL hydrogel as a function of time at 37 °C because of viscous nature and thermogelation of the copolymer. In vitro cytotoxicity study reveals that the HPG-g-PNVCL thermogelling polymer works as a biocompatible scaffold for osteoblastic cell growth. Additionally, in vitro biomineralization study of HPG-g-PNVCL/n-HA/DVS was conducted using a simulated body fluid, and apatite-like structure formation was observed by SEM.

Fluorine-ion-releasing injectable alginate nanocomposite hydrogel for enhanced bioactivity and antibacterial property

The creation of a moist environment and promotion of cell proliferation and migration together with antibacterial property are critical to the wound-healing process. Alginate (Alg) is an excellent candidate for injectable wound dressing materials because it can form a gel in a mild environment. Taking advantage of its gelation property, an injectable nano composite hydrogel containing nano-sized (about 90 nm) calcium fluoride (CaF₂) particles was developed using in-situ precipitation process. The amount of released fluorine (F^-) ion from the nanocomposite hydrogel increased with increasing CaF₂ content inside the composite hydrogel and the ions stimulated both the proliferation and migration of fibroblast cells in vitro. The antibacterial property of the composite hydrogel against E. coli and S. aureus was confirmed through colony formation test where the number of bacterial colonies significantly decreased compared to Alg hydrogel. The in vivo results based on a full-thickness wound model showed that the nanocomposite hydrogel effectively enhanced the deposition of the extracellular matrix compared to that of the Alg hydrogel. This study demonstrates the potential of this nanocomposite hydrogel as a bioactive injectable wound-dressing material with the ability to inhibit bacterial growth and stimulate cell proliferation and migration for accelerated wound healing.

Bioactive Injectable Hydrogels Containing Desferrioxamine and Bioglass for Diabetic Wound Healing

Diabetic wound is hard to heal mainly because of the difficulty in vascularization in the wound area. Accumulating results have shown that desferrioxamine (DFO) can promote secretion of hypoxia inducible factor-1 (HIF-1α), thereby upregulating the expression of angiogenic growth factors and facilitating revascularization. Our preliminary study has demonstrated that Si ions in bioglass (BG) can upregulate vascular endothelial growth factor (VEGF) expression, thus promoting revascularization. It is hypothesized that the combined use of BG and DFO may have a synergistic effect in promoting VEGF expression and revascularization. To prove this, we first determined DFO concentration range that had no apparent cytotoxicity on human umbilical vein endothelial cells (HUVECs). Then, the optimal concentration of DFO promoting tube formation of HUVECs was determined by cell migration and tube formation assays. In addition, we demonstrated that combination use of BG and DFO improved the migration and tube formation of HUVECs as compared with the use of either BG or DFO alone as BG and DFO could synergistically upregulate VEGF expression. Furthermore, a sodium alginate hydrogel containing both BG and DFO was developed, and this hydrogel better facilitated diabetic skin wound healing than the use of either BG or DFO alone as BG and DFO in the hydrogels worked synergistically in promoting HIF-1α and VEGF expression and subsequently vascularization in the wound sites. Therefore, in this study, the synergistic effect in promoting revascularization between BG and DFO was first demonstrated and an injectable hydrogel simultaneously containing BG and DFO was developed for enhancing repair of diabetic chronic skin defects by taking advantages of the synergistic effects of BG and DFO in promoting revascularization. The study opens up a new prospect for the development of skin repair-promoting biomaterials.

3D bioactive composite scaffolds for bone tissue engineering

Bone is the second most commonly transplanted tissue worldwide, with over four million operations using bone grafts or bone substitute materials annually to treat bone defects. However, significant limitations affect current treatment options and clinical demand for bone grafts continues to rise due to conditions such as trauma, cancer, infection and arthritis. Developing bioactive three-dimensional (3D) scaffolds to support bone regeneration has therefore become a key area of focus within bone tissue engineering (BTE). A variety of materials and manufacturing methods including 3D printing have been used to create novel alternatives to traditional bone grafts. However, individual groups of materials including polymers, ceramics and hydrogels have been unable to fully replicate the properties of bone when used alone. Favourable material properties can be combined and bioactivity improved when groups of materials are used together in composite 3D scaffolds. This review will therefore consider the ideal properties of bioactive composite 3D scaffolds and examine recent use of polymers, hydrogels, metals, ceramics and bio-glasses in BTE. Scaffold fabrication methodology, mechanical performance, biocompatibility, bioactivity, and potential clinical translations will be discussed.

Bioglass Activated Albumin Hydrogels for Wound Healing

In this study, a novel Bioglass/albumin composite hydrogel with controllable injectability, good adhesiveness, and bioactivity, is developed by utilizing dual-functional bioactive ions released from Bioglass, which on one side controls the gelling time by creating an alkaline environment to regulate the cross-linking reaction between human serum albumin and succinimidyl succinate modified poly(ethylene glycol), and on the other side stimulates wound healing. The composite hydrogel exhibits adhesive property that is superior to clinically used fibrin and cyanoacrylate glues. The gelation time of the composite hydrogel could be regulated via changing the amounts of Bioglass which endows the hydrogel with good injectability. The in vivo experiment confirms that this composite hydrogel has good bioactivity to stimulate angiogenesis and enhance chronic wound healing. Moreover, for the first time, the concentrations of the bioactive ions released from the composite hydrogel in situ are quantified during wound healing using a microdialysis technique, and a correlation of the in vitro and in vivo concentration of ions released from the hydrogel is determined, which is extremely important for understanding the bioactivity mechanisms of Bioglass/bioceramic-based biomaterials and designing biomaterials for tissue regeneration.

Bone tissue engineering strategy based on the synergistic effects of silicon and strontium ions

Multipotent human bone marrow mesenchymal stem cells (hBMSCs) are commonly used as seed cells in bone tissue engineering, but their clinical application is limited due to two challenges. One is the expansion of hBMSCs without loss of the stemness, and the other is the stimulation of osteogenic differentiation of hBMSCs when combined with biomaterials. In this study we demonstrated an approach by firstly elucidating the functional effects and optimal concentrations of Si and Sr ions on the proliferation and osteogenic differentiation of hBMSCs, and then designing bioactive bioceramic/alginate hydrogels which could release Si and Sr bioactive ions in the same optimal concentrations range for activation of the cells in vivo. The results showed that Si and Sr ions could synergistically stimulate cell proliferation without losing the stemness. Furthermore, at higher concentrations, Si and Sr ions stimulated osteogenic differentiation instead of enhancing proliferation. The designed bioactive hydrogels revealed activity to stimulate not only the osteogenic differentiation of encapsulated hBMSCs, but also the blood vessel formation in vivo. These results suggested that the design of biomaterials based on the biological function of different material elements was an effective approach for bone tissue engineering applications.

STATEMENT OF SIGNIFICANCE

The clinical application of multipotent human bone marrow mesenchymal stem cells (hBMSCs) in bone tissue engineering is limited due to two challenges. One is the expansion of cells without loss of the stemness, and the other is the stimulation of osteogenic differentiation of hBMSCs within the biomaterial scaffolds. Herein, we demonstrated an approach by firstly elucidating the functional effects and optimal concentrations of Si and Sr ions on the proliferation without losing stemness and osteogenic differentiation of hBMSCs, and then designing a bioactive bioceramic/alginate hydrogel which could release Si and Sr ions for in vivo activation of cells. The bioactive hydrogels revealed activity to stimulate not only osteogenic differentiation of encapsulated hBMSCs, but also the blood vessel formation in vivo. Our work provided an effective approach to design effective biomaterials for tissue engineering.

Hydrogel scaffolds for differentiation of adipose-derived stem cells

Natural extracellular matrices (ECMs) have been widely used as a support for the adhesion, migration, differentiation, and proliferation of adipose-derived stem cells (ADSCs). However, poor mechanical behavior and unpredictable biodegradation properties of natural ECMs considerably limit their potential for bioapplications and raise the need for different, synthetic scaffolds. Hydrogels are regarded as the most promising alternative materials as a consequence of their excellent swelling properties and their resemblance to soft tissues. A variety of strategies have been applied to create synthetic biomimetic hydrogels, and their biophysical and biochemical properties have been modulated to be suitable for cell differentiation. In this review, we first give an overview of common methods for hydrogel preparation with a focus on those strategies that provide potential advantages for ADSC encapsulation, before summarizing the physical properties of hydrogel scaffolds that can act as biological cues. Finally, the challenges in the preparation and application of hydrogels with ADSCs are explored and the perspectives are proposed for the next generation of scaffolds.

Novel alginate/hydroxyethyl cellulose/hydroxyapatite composite scaffold for bone regeneration: In vitro cell viability and proliferation of human mesenchymal stem cells

Sodium alginate (SA)/hydroxyethylcellulose (HEC)/hydroxyapatite (HA) composite scaffolds were explored for enhanced in vitro bone regeneration. The SA/HEC/HA composites were synthesized using the lyophilization technique and further cross-linked in the presence of calcium ions to form composite hydrogel networks. The physicochemical, thermal behavior and morphology properties of the prepared scaffolds were characterized through XRD, DSC/TGA, FTIR and SEM. Furthermore, the mechanical behavior of the under investigated scaffolds was determined using texture analyzer. The in vitro bioactivity in SBF and adsorption of bovine serum albumin as well as cell viability for all the prepared scaffolds were also tested. The results indicated that the higher HA concentration (40wt%) enhanced the mechanical properties (23.9MPa), bioactivity and protein adsorption. Cell viability of the tested scaffolds confirmed the non-toxicity of the fabricated systems on the human mesenchymal stem cells (hMSCs). Proliferation capability was also confirmed for the tested scaffolds after 3 and 7days, but the higher HA-containing scaffold showed increased cell populations specially after 7days compared to HA-free scaffolds. This novel composite material could be used in bone tissue engineering as a scaffold material to deliver cells and biologically active molecules.

Alginate-aker injectable composite hydrogels promoted irregular bone regeneration through stem cell recruitment and osteogenic differentiation

With SAG usage, the hBMSC migration ability was stimulated through CXCR4 elevation while osteogenic differentiation was promotedviathe ERK signaling pathway.

Evaluation of MC3T3 Cells Proliferation and Drug Release Study from Sodium Hyaluronate-1,4-butanediol Diglycidyl Ether Patterned Gel

A pattern gel has been fabricated using sodium hyaluronate (HA) and 1,4-butanediol diglycidyl ether (BDDGE) through the micro-molding technique. The cellular behavior of osteoblast cells (MC3T3) in the presence and absence of dimethyloxalylglycine (DMOG) and sodium borate (NaB) in the pattern gel (HA-BDDGE) has been evaluated for its potential application in bone regeneration. The Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance spectroscopy (13C NMR), and thermogravimetric analysis (TGA) results implied the crosslinking reaction between HA and BDDGE. The scanning electron microscopy (SEM) analysis confirmed the formation of pattern on the surface of HA-BDDGE. The gel property of the crosslinked HA-BDDGE has been investigated by swelling study in distilled water at 37 °C. The HA-BDDGE gel releases DMOG in a controlled way for up to seven days in water at 37 °C. The synthesized gel is biocompatible and the bolus drug delivery results indicated that the DMOG containing patterned gel demonstrates a better cell migration ability on the surface than NaB. For local delivery, the pattern gel with 300 µM NaB or 300 µM DMOG induced cell clusters formation, and the gel with 150 µM NaB/DMOG showed high cell proliferation capability only. The vital role of NaB for bone regeneration has been endorsed from the formation of cell clusters in presence of NaB in the media. The in vitro results indicated that the pattern gel showed angiogenic and osteogenic responses with good ALP activity and enhanced HIF-1α, and Runx2 levels in the presence of DMOG and NaB in MC3T3 cells. Hence, the HA-BDDGE gel could be used in bone regeneration application.

3D printed scaffolds of calcium silicate-doped β-TCP synergize with co-cultured endothelial and stromal cells to promote vascularization and bone formation

Synthetic bone scaffolds have potential application in repairing large bone defects, however, inefficient vascularization after implantation remains the major issue of graft failure. Herein, porous β-tricalcium phosphate (β-TCP) scaffolds with calcium silicate (CS) were 3D printed, and pre-seeded with co-cultured human umbilical cord vein endothelial cells (HUVECs) and human bone marrow stromal cells (hBMSCs) to construct tissue engineering scaffolds with accelerated vascularization and better bone formation. Results showed that in vitro β-TCP scaffolds doped with 5% CS (5%CS/β-TCP) were biocompatible, and stimulated angiogenesis and osteogenesis. The results also showed that 5%CS/β-TCP scaffolds not only stimulated co-cultured cells angiogenesis on Matrigel, but also stimulated co-cultured cells to form microcapillary-like structures on scaffolds, and promoted migration of BMSCs by stimulating co-cultured cells to secrete PDGF-BB and CXCL12 into the surrounding environment. Moreover, 5%CS/β-TCP scaffolds enhanced vascularization and osteoinduction in comparison with β-TCP, and synergized with co-cultured cells to further increase early vessel formation, which was accompanied by earlier and better ectopic bone formation when implanted subcutaneously in nude mice. Thus, our findings suggest that porous 5%CS/β-TCP scaffolds seeded with co-cultured cells provide new strategy for accelerating tissue engineering scaffolds vascularization and osteogenesis, and show potential as treatment for large bone defects.

Cell-laden hydrogels for osteochondral and cartilage tissue engineering

Despite tremendous advances in the field of regenerative medicine, it still remains challenging to repair the osteochondral interface and full-thickness articular cartilage defects. This inefficiency largely originates from the lack of appropriate tissue-engineered artificial matrices that can replace the damaged regions and promote tissue regeneration. Hydrogels are emerging as a promising class of biomaterials for both soft and hard tissue regeneration. Many critical properties of hydrogels, such as mechanical stiffness, elasticity, water content, bioactivity, and degradation, can be rationally designed and conveniently tuned by proper selection of the material and chemistry. Particularly, advances in the development of cell-laden hydrogels have opened up new possibilities for cell therapy. In this article, we describe the problems encountered in this field and review recent progress in designing cell-hydrogel hybrid constructs for promoting the reestablishment of osteochondral/cartilage tissues. Our focus centers on the effects of hydrogel type, cell type, and growth factor delivery on achieving efficient chondrogenesis and osteogenesis. We give our perspective on developing next-generation matrices with improved physical and biological properties for osteochondral/cartilage tissue engineering. We also highlight recent advances in biomanufacturing technologies (e.g. molding, bioprinting, and assembly) for fabrication of hydrogel-based osteochondral and cartilage constructs with complex compositions and microarchitectures to mimic their native counterparts.

STATEMENT OF SIGNIFICANCE

Despite tremendous advances in the field of regenerative medicine, it still remains challenging to repair the osteochondral interface and full-thickness articular cartilage defects. This inefficiency largely originates from the lack of appropriate tissue-engineered biomaterials that replace the damaged regions and promote tissue regeneration. Cell-laden hydrogel systems have emerged as a promising tissue-engineering platform to address this issue. In this article, we describe the fundamental problems encountered in this field and review recent progress in designing cell-hydrogel constructs for promoting the reestablishment of osteochondral/cartilage tissues. Our focus centers on the effects of hydrogel composition, cell type, and growth factor delivery on achieving efficient chondrogenesis and osteogenesis. We give our perspective on developing next-generation hydrogel/inorganic particle/stem cell hybrid composites with improved physical and biological properties for osteochondral/cartilage tissue engineering. We also highlight recent advances in biomanufacturing and bioengineering technologies (e.g. 3D bioprinting) for fabrication of hydrogel-based osteochondral and cartilage constructs.

Injectable hydrogels for cartilage and bone tissue engineering

Tissue engineering has become a promising strategy for repairing damaged cartilage and bone tissue. Among the scaffolds for tissue-engineering applications, injectable hydrogels have demonstrated great potential for use as three-dimensional cell culture scaffolds in cartilage and bone tissue engineering, owing to their high water content, similarity to the natural extracellular matrix (ECM), porous framework for cell transplantation and proliferation, minimal invasive properties, and ability to match irregular defects. In this review, we describe the selection of appropriate biomaterials and fabrication methods to prepare novel injectable hydrogels for cartilage and bone tissue engineering. In addition, the biology of cartilage and the bony ECM is also summarized. Finally, future perspectives for injectable hydrogels in cartilage and bone tissue engineering are discussed.

Multifunctional Hydrogels Prepared by Dual Ion Cross-Linking for Chronic Wound Healing

The creation of a moist environment and promotion of blood vessel formation are critical for wound healing. Sodium alginate (SA) hydrogel, which has good biocompatibility and is able to provide a moist environment, has been widely used as a wound dressing. However, it lacks antibacterial ability and bioactivities, which would facilitate chronic wound healing. On the basis of the gelation characteristics of SA and the bioactive hardystonite (HS) bioceramic, we designed a unique, bioactive, injectable composite hydrogel through double ion cross-linking, in which divalent ions, such as Ca²⁺ and Zn²⁺ function as cross-linkers; Zn²⁺ also functions as an antibacterial component and as nutrition for wound healing, and Si ions play a key role in determining the bioactivity of the hydrogel. With the controlled release of divalent ions, such as Ca²⁺ and Zn²⁺ from HS, the gelation process of the composite hydrogel could be efficiently controlled. In addition, in vitro results reveal that the composite hydrogel stimulated proliferation and migration of both human dermal fibroblasts and human umbilical vein endothelial cells, and the in vivo results show that the wound-healing process is obviously enhanced, and the formation of epithelium and blood vessels are evidently advanced. This study indicates the potential of the SA/HS hydrogel as a multifunctional injectable wound dressing with the ability to inhibit bacterial growth and stimulate angiogenesis and wound healing.

S. S, Agarwal T, Pradhan S, Pal K, Giri S, Maiti TK, Banerjee I. Gum tragacanth–alginate beads as proangiogenic–osteogenic cell encapsulation systems for bone tissue engineering

The presence of gum tragacanth in calcium alginate beads makes them more osteo-conductive and proangiogenic.

Preparation of in situ forming and injectable alginate/mesoporous Sr-containing calcium silicate composite cement for bone repair

In situ formation of injectable alginate/mesoporous Sr-containing calcium silicate nanoparticle cements via internal crosslinking to obtain higher stability injectability and strength.

Injectable bioactive akermanite/alginate composite hydrogels for in situ skin tissue engineering

Injectable bioactive SA/Aker hydrogels formed by crosslinking of bioactive ions, which recruit stem cells and enhance skin regeneration.

Application of hydrogels in heart valve tissue engineering

With an increasing number of patients requiring valve replacements, there is heightened interest in advancing heart valve tissue engineering (HVTE) to provide solutions to the many limitations of current surgical treatments. A variety of materials have been developed as scaffolds for HVTE including natural polymers, synthetic polymers, and decellularized valvular matrices. Among them, biocompatible hydrogels are generating growing interest. Natural hydrogels, such as collagen and fibrin, generally show good bioactivity but poor mechanical durability. Synthetic hydrogels, on the other hand, have tunable mechanical properties; however, appropriate cell-matrix interactions are difficult to obtain. Moreover, hydrogels can be used as cell carriers when the cellular component is seeded into the polymer meshes or decellularized valve scaffolds. In this review, we discuss current research strategies for HVTE with an emphasis on hydrogel applications. The physicochemical properties and fabrication methods of these hydrogels, as well as their mechanical properties and bioactivities are described. Performance of some hydrogels including in vitro evaluation using bioreactors and in vivo tests in different animal models are also discussed. For future HVTE, it will be compelling to examine how hydrogels can be constructed from composite materials to replicate mechanical properties and mimic biological functions of the native heart valve.

Injectable and pH-Responsive Silk Nanofiber Hydrogels for Sustained Anticancer Drug Delivery

Silk is useful as a drug carrier due to its biocompatibility, tunable degradation, and outstanding capacity in maintaining the function of drugs. Injectable silk hydrogels could deliver doxorubicin (DOX) for localized chemotherapy for breast cancer. To improve hydrogel properties, thixotropic silk nanofiber hydrogels in an all-aqueous solution were prepared and used to locally deliver DOX. The silk hydrogels displayed thixotropic capacity, allowing for easy injectability followed by solidification in situ. The hydrogels were loaded with DOX and released the drug over eight weeks with pH- and concentration-dependent release kinetics. In vitro and in vivo studies demonstrated that DOX-loaded silk hydrogels had good antitumor response, outperforming the equivalent dose of free DOX administered intravenously. Thixotropic silk hydrogels provide improved injectability to support sustained release, suggesting promising applications for localized chemotherapy.

Thermosensitive injectable in-situ forming carboxymethyl chitin hydrogel for three-dimensional cell culture

Injectable hydrogels have gained great attentions for cell therapy and tissue regeneration as a result of the applications in minimally invasive surgical procedures with the ease of handling and complete filling of the defect area. Here, a novel biodegradable, thermosensitive and injectable carboxymethyl chitin (CMCH) hydrogel was developed for three-dimensional (3D) cell culture. The obtained CMCH solution remained transparent liquid flowing easily at low temperatures and gelled rapidly at 37°C. The gelation time of CMCH hydrogels could be easily tuned by varying temperature and the degree of carboxymethylation, which facilitates the cell encapsulation process at room temperature and in-situ forming hydrogel at body temperature. Moreover, the CMCH-14 hydrogels in PBS buffer remained stable and continuous porous structure and could be degraded in the presence of lysozyme or hyaluronidase. HeLa cells proliferated sustainably and self-assembled to form 3D multicellular spheroids with high cell activity on the surface of CMCH-14 hydrogel. Encapsulation of COS-7 cells within the in-situ forming CMCH hydrogel demonstrated that CMCH hydrogels promoted cell survival and proliferation. In vivo mouse study of the CMCH hydrogels showed good in-situ gel formation and tissue biocompatibility. Thus, the biodegradable thermosensitive injectable CMCH hydrogels hold potential for 3D cell culture and biomedical applications.

STATEMENT OF SIGNIFICANCE

Biodegradable hydrogels have been widely studied for cell therapy and tissue regeneration. Herein, we report a novel thermosensitive injectable carboxymethyl chitin (CMCH) hydrogel for 3D cell culture, which was synthesized homogeneously from the bioactive natural chitin through the "green" process avoiding using organic solvent. The CMCH solutions exhibited rapid thermoresponsive sol-to-gel phase transition behavior at 37°C with controllable gelation times, which facilitates the cell encapsulation process at room temperature and in-situ forming hydrogel at body temperature. Importantly, in vitro 3D cell culture and in vivo mouse study of the CMCH hydrogel showed promotion of cell survival and proliferation, good in-situ gel formation and biocompatibility. We believe that such thermosensitive injectable CMCH hydrogels would be very useful for biomedical applications, such as tumor model for cancer research, post-operative adhesion prevention, the regeneration of cartilage and central nervous system and so on.

The stimulation of osteogenic differentiation of embryoid bodies from human induced pluripotent stem cells by akermanite bioceramics

Induced pluripotent stem cells (iPSCs) have great potential as seed cells for tissue engineering applications. Previous studies have shown that iPSCs could be induced to differentiate into bone forming cells. However, in a tissue engineering approach, seeding cells in biomaterials is required, and the effect of biomaterials on cell growth and differentiation is critical for the success of the formation of engineered tissues. In this study, we investigated the effect of akermanite, a bioactive ceramic, on the osteogenic differentiation of embryoid body (EB) cells derived from human iPSCs. The results showed that, in the presence of osteogenic factors (ascorbic acid, dexamethasone, and β-glycerophosphate), ionic extracts of akermanite enhanced the osteogenic differentiation of EB cells as compared with normal osteogenic medium. Alkaline phosphatase (ALP) activity and the expression of osteogenic marker genes such as osteocalcin (OCN), collagen (COL-1), RUNX2, and BMP2 are significantly increased by the stimulation of akermanite ceramic extracts at certain concentration ranges. More interesting is that the medium containing extracts of akermanite but without osteogenic factors also showed stimulatory effects on the osteogenic differentiation of EB cells as compared to normal growth medium without osteogenic factors, such as ascorbic acid, dexamethasone, and β-glycerophosphate, not at the early stage of culture, but only at the later stage of the culture period (21 days). These results suggest that akermanite as a bioactive material together with human iPSCs might be used for bone tissue engineering applications.

Design of a thermosensitive bioglass/agarose-alginate composite hydrogel for chronic wound healing

Chronic wounds are a major health problem around the world, and there is a need to develop new types of dressing materials to enhance chronic wound healing. Humidity and angiogenic conditions are two important factors that may significantly affect the healing process. Therefore, a new wound dressing system based on bioglass (BG) and agarose-alginate (AA) has been designed, which can create a moist environment and improve the angiogenic condition of the wound area at the same time. The obtained BG/AA hydrogel has thermosensitivity allowing it to gel at physiological temperature through the interaction between the agarose and alginate polymer chains, and the chains can be further cross-linked by ions released from BG. The BG/AA hydrogel can promote migration of fibroblast and endothelial cells and it can also enhance the angiogenesis of endothelial cells in a fibroblast-endothelial cell co-culture model in vitro. The potential of the BG/AA hydrogel as a wound dressing has been further evaluated by using the rabbit ear ischemic wound model. The results demonstrate that the BG/AA hydrogel can enhance blood vessel and epithelium formation, which contribute to wound healing. The present study suggests that this new BG/AA hydrogel system may be used as a bioactive dressing for chronic wound healing.

Nanomaterials: the next step in injectable bone cements

Injectable bone cements (IBCs) are biocompatible materials that can be used as bone defect fillers in maxillofacial surgeries and in orthopedic fracture treatment in order to augment weakened bone due to osteoporosis. Current clinically available IBCs, such as polymethylmethacrylate and calcium phosphate cement, have certain advantages; however, they possess several drawbacks that prevent them from gaining universal acceptance. New gel-based injectable materials have also been developed, but these are too mechanically weak for load-bearing applications. Recent research has focused on improving various injectable materials using nanomaterials in order to render them suitable for bone tissue regeneration. This article outlines the requirements of IBCs, the advantages and limitations of currently available IBCs and the state-of-the-art developments that have demonstrated the effects of nanomaterials within injectable systems.

The gelation process and protein absorption property of injectable SA-CMBC hydrogel used for procoagulant material

CMBC showed obvious influence on properties of injectable SA-CMBC hydrogel, containing gelation time, mechanical property, protein absorption and procoagulant property.

In vitro characterization and mechanical properties of β-calcium silicate/POC composite as a bone fixation device

Calcium silicate (CS, CaSiO3 ) is a bioactive, degradable, and biocompatible ceramic and has been considered for its potential in the field of orthopedic surgery. The objective of this study is the fabrication and characterization of the β-CS/poly(1.8-octanediol citrate) (POC) biocomposite, with the goals of controlling its weight loss and improving its biological and mechanical properties. POC is one of the most biocompatible polymers, and it is widely used in biomedical engineering applications. The degradation and bioactivity of the composites were determined by soaking the composites in phosphate-buffered saline and simulated body fluid, respectively. Human osteoblast cells were cultured on the composites to determine their cell proliferation and adhesion. The results illustrated that the flexural and compressive strengths were significantly enhanced by a modification of 40% POC. It was also concluded that the degradation bioactivity and amelioration of cell proliferation increased significantly with an increasing β-CS content.