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

Misleading Pore Size Measurements in Gelatin and Alginate Hydrogels Revealed by Confocal Microscopy

It is a well-documented phenomenon that the porous structure of hydrogels observed with vacuum-based imaging techniques is generated during the freezing and drying process employed prior to observation. Nevertheless, vacuum-based techniques, such as scanning electron microscopy (SEM), are still being commonly used to measure pore sizes in hydrogels, which is often not representative of the actual pore size in hydrated conditions. The frequent underestimation of the impact of freezing and drying on hydrogel structures could stem from a lack of cross-fertilization between materials science and biomedical or food science communities, or from the simplicity and visually appealing nature of SEM imaging, which may lead to an overemphasis on its use. Our study provides a straightforward and impactful way of pinpointing this phenomenon exploiting two hydrogels ubiquitously applied in tissue engineering, including gelatin methacryloyl and alginate as proof-of-concept hydrogels. By comparing images of the samples in the native hydrated state, followed by freezing, freeze-drying, and rehydration using SEM and confocal microscopy, we highlight discrepancies between hydrogel pore sizes in the hydrated versus the dry state. To conclude, our study offers recommendations for researchers seeking insight in hydrogel properties and emphasizes key factors that require careful control when using SEM as a characterization tool.

Metal Ion-Containing Hydrogels: Synthesis, Properties, and Applications in Bone Tissue Engineering

Hydrogel, as a unique scaffold material, features a three-dimensional network system that provides conducive conditions for the growth of cells and tissues in bone tissue engineering (BTE). In recent years, it has been discovered that metal ion-containing hybridized hydrogels, synthesized with metal particles as the foundation, exhibit excellent physicochemical properties, osteoinductivity, and osteogenic potential. They offer a wide range of research prospects in the field of BTE. This review provides an overview of the current state and recent advancements in research concerning metal ion-containing hydrogels in the field of BTE. Within materials science, it covers topics such as the binding mechanisms of metal ions within hydrogel networks, the types and fabrication methods of various metal ion-containing hydrogels, and the influence of metal ions on the properties of hydrogels. In the context of BTE, the review delves into the osteogenic mechanisms of various metal ions, the applications of metal ion-containing hydrogels in BTE, and relevant experimental studies in vitro and in vivo. Furthermore, future improvements in bone repair can be anticipated through advancements in bone bionics, exploring interactions between metal ions and the development of a wider range of metal ions and hydrogel types.

Soft yet mechanically robust injectable alginate hydrogels with processing versatility based on alginate/hydroxyapatite hybridization

The salient gelling feature of alginate via forming the egg-box structure with calcium ions has received extensive interests for different applications. Owing to the interfacial incompatibility of rigid inorganic solids with soft polymers, the requirement of overall stereocomplexation with calcium released from uniformly distributed solids in alginate remains a challenge. In this study, a novel alginate-incorporated calcium source was proposed to tackle the intractable dispersion for the preparation of injectable alginate hydrogels. Calcium phosphate synthesis in alginate solution yielded CaP-alginate hybrids as a calcium source. The physicochemical characterization confirmed the CaP-alginate hybrid was a nano-scale alginate-hydroxyapatite complex. The colloidally stable CaP-alginate hybrids were uniformly dispersed in alginate solutions even under centrifugation. The calcium-induced gelling of the CaP-alginate hybrids-loaded alginate solutions formed soft yet tough hydrogels including transparent sheets and knittable threads, confirming the homogeneous gelation of the hydrogel. The gelation time, injectability and mechanical properties of the hydrogels could be adjusted by changing preparation parameters. The prepared hydrogels showed uniform porous structure, excellent swelling, wetting properties and cytocompatibility, showing a great potential for applications in different fields. The present strategy with organic/inorganic hybridization could be exemplarily followed in the future development of functional hydrogels especially associated with the interface integration.

Cuprorivaite/hardystonite/alginate composite hydrogel with thermionic effect for the treatment of peri-implant lesion

Peri-implant lesion is a grave condition afflicting numerous indi-viduals with dental implants. It results from persistent periodontal bacteria accumulation causing inflammation around the implant site, which can primarily lead to implant loosening and ultimately the implant loss. Early-stage peri-implant lesions exhibit symptoms akin to gum disease, including swelling, redness and bleeding of the gums surrounding the implant. These signs indicate infection and inflammation of the peri-implant tissues, which may result in bone loss and implant failure. To address this problem, a thermionic strategy was applied by designing a cuprorivaite-hardystonite bioceramic/alginate composite hydrogel with photothermal and Cu/Zn/Si multiple ions releasing property. This innovative approach creates a thermionic effect by the release of bioactive ions (Cu2+ and Zn2+ and SiO 3 2 - ) from the composite hydrogel and the mild heat environment though the photothermal effect of the composite hydrogel induced by near-infrared light irradiation. The most distinctive advantage of this thermionic effect is to substantially eliminate periodontal pathogenic bacteria and inhibit inflammation, while simultaneously enhance peri-implant osseointegration. This unique attribute renders the use of this composite hydrogel highly effective in significantly improving the survival rate of implants after intervention in peri-implant lesions, which is a clinical challenge in periodontics. This study reveals application potential of a new biomaterial-based approach for peri-implant lesion, as it not only eliminates the infection and inflammation, but also enhances the osteointegration of the dental implant, which provides theoretical insights and practical guidance to prevent and manage early-stage peri-implant lesion using bioactive functional materials.

Structure, rheological properties, and biocompatibility of Laponite® cross-linked starch/polyvinyl alcohol hydrogels

Hydrogels, owing to their unique porous structures, hydrophilic properties, and biocompatibility, are being developed as scaffolds for bone grafts. However, the use of toxic initiators or cross-linking agents is a drawback. To overcome this, we developed Laponite®/cross-linked starch/polyvinyl alcohol (PVA) hydrogels prepared by one-step solution mixing. The structure, rheological properties, and biocompatibility of the hydrogels were investigated. Zeta potential, Fourier transform infrared, and X-ray diffraction analyses showed that hydrogen bonding and electrostatic interactions jointly maintained the structure of the cross-linked hydrogel systems. At a Laponite® concentration of 10 %, the hydrogel with a starch/PVA ratio of 2:2 exhibited a uniform porous structure, the highest storage modulus (G'), and the lowest degradation rate. At a starch/PVA ratio of 2:2, the G' increased; however, the degradation rate decreased with the increase in Laponite® content from 5 % to 20 %. These results indicate that the mechanical strength and degradation rate of the hydrogels could be adjusted by altering the starch/PVA ratio and the amount of Laponite®. In vitro cytotoxicity experiments showed that the Laponite®/starch/PVA (LSP) hydrogels were non-toxic to MC3T3-E1 cells. The starch/PVA ratio had no obvious effect on the proliferation of MC3T3-E1 cells, but an increase in Laponite® content significantly promoted cell proliferation. In summary, the results suggest that these LSP hydrogels have great potential for applications in bone tissue engineering.

A biomaterial-based therapy for lower limb ischemia using Sr/Si bioactive hydrogel that inhibits skeletal muscle necrosis and enhances angiogenesis

Muscle necrosis and angiogenesis are two major challenges in the treatment of lower-limb ischemic diseases. In this study, a triple-functional Sr/Si-containing bioceramic/alginate composite hydrogel with simultaneous bioactivity in enhancing angiogenesis, regulating inflammation, and inhibiting muscle necrosis was designed to treat lower-limb ischemic diseases. In particular, sodium alginate, calcium silicate and strontium carbonate were used to prepare injectable hydrogels, which was gelled within 10 min. More importantly, this composite hydrogel sustainedly releases bioactive Sr²⁺ and SiO₃ ^2- ions within 28 days. The biological activity of the bioactive ions released from the hydrogels was verified on HUVECs, SMCs, C2C12 and Raw 264.7 cells in vitro, and the therapeutic effect of the hydrogel was confirmed using C57BL/6 mouse model of femoral artery ligation in vivo. The results showed that the composite hydrogel stimulated angiogenesis, developed new collateral capillaries, and re-established the blood supply. In addition, the bioactive hydrogel directly promoted the expression of muscle-regulating factors (MyoG and MyoD) to protect skeletal muscle from necrosis, inhibited M1 polarization, and promoted M2 polarization of macrophages to reduce inflammation, thereby protecting skeletal muscle cells and indirectly promoting vascularization. Our results indicate that these bioceramic/alginate composite bioactive hydrogels are effective biomaterials for treating hindlimb ischemia and suggest that biomaterial-based approaches may have remarkable potential in treating ischemic diseases.

A bifunctional bortezomib-loaded porous nano-hydroxyapatite/alginate scaffold for simultaneous tumor inhibition and bone regeneration

Treatments of osteolytic lesions due to malignant metastasis remain one of the major clinical challenges. The residual tumor cells after surgical resections and an acidic tumor microenvironment are unfavorable for osteogenic induction. Bortezomib (BTZ), a proteasome inhibitor used in chemotherapy, also has an osteogenic potential in concentration- and Ca²⁺-dependent manners. In this study, controlled delivery of BTZ in a novel bifunctional scaffold based on nano-hydroxyapatite (nHA) and sodium alginate (SA) nanocomposite, namely BTZ/nHA@SA, has been explored. By smartly adjusting microenvironments, a sustainable release of Ca²⁺ from nHA could be achieved, which was not only able to cross-link SA but also to regulate the switch between the dual functions of tumor inhibition and bone regeneration of BTZ to promote the osteogenic pathway. The freeze-dried BTZ/nHA@SA scaffold has excellent interconnectivity, is capable to promote the attachment and proliferation of mouse embryonic osteoblast precursor cells, as well as effectively induces breast cancer cell death in vitro. Furthermore, in vivo, studies using a mouse tumor model and a rabbit femoral defect model showed that the BTZ/nHA@SA scaffold could promote tumor ablation, and also enhance bone repair. Therefore, the BTZ/nHA@SA scaffold has unique dual functions of inhibiting tumor recurrence and promoting bone tissue regeneration simultaneously. This smart bi-functional scaffold offers a promising novel approach for oncological treatments by synchronously orchestrating tumor inhibition and tissue regeneration for the repair of neoplastic bone defects.

Multi-leveled Nanosilicate Implants Can Facilitate Near-Perfect Bone Healing

Several studies have shown that nanosilicate-reinforced scaffolds are suitable for bone regeneration. However, hydrogels are inherently too soft for load-bearing bone defects of critical sizes, and hard scaffolds typically do not provide a suitable three-dimensional (3D) microenvironment for cells to thrive, grow, and differentiate naturally. In this study, we bypass these long-standing challenges by fabricating a cell-free multi-level implant consisting of a porous and hard bone-like framework capable of providing load-bearing support and a softer native-like phase that has been reinforced with nanosilicates. The system was tested with rat bone marrow mesenchymal stem cells in vitro and as a cell-free system in a critical-sized rat bone defect. Overall, our combinatorial and multi-level implant design displayed remarkable osteoconductivity in vitro without differentiation factors, expressing significant levels of osteogenic markers compared to unmodified groups. Moreover, after 8 weeks of implantation, histological and immunohistochemical assays indicated that the cell-free scaffolds enhanced bone repair up to approximately 84% following a near-complete defect healing. Overall, our results suggest that the proposed nanosilicate bioceramic implant could herald a new age in the field of orthopedics.

Evaluation of innovative polyvinyl alcohol/ alginate/ green palladium nanoparticles composite scaffolds: Effect on differentiated human dental pulp stem cells into osteoblasts

Three-dimensional (3D) scaffolds are attracting great concern for bone tissue engineering applications. However, selecting an appropriate material with optimal physical, chemical, and mechanical properties is considered a great challenge. The green synthesis approach is essential to avoid the production of harmful by-products through textured construction, sustainable, and eco-friendly procedures. This work aimed at the implementation of natural green synthesized metallic nanoparticles for the development of composite scaffolds for dental applications. In this study, innovative hybrid scaffolds of polyvinyl alcohol/alginate (PVA/Alg) composite loaded with various concentrations of green palladium nanoparticles (Pd NPs) have been synthesized. Various characteristic analysis techniques were used to investigate the synthesized composite scaffold's properties. The SEM analysis revealed impressive microstructure of the synthesized scaffolds dependent on the Pd NPs concentration. The results confirmed the positive effect of Pd NPs doping on the sample stability over time. The synthesized scaffolds were characterized by the oriented lamellar porous structure. The results confirmed the shape stability, without pores breakdown during the drying process. The XRD analysis confirmed that doping with Pd NPs does not affect the crystallinity degree of the PVA/Alg hybrid scaffolds. The mechanical properties results (up to 50 MPa) confirmed the remarkable effect of Pd NPs doping and its concentration on the developed scaffolds. The MTT assay results showed that the incorporation of Pd NPs into the nanocomposite scaffolds is necessary for increasing cell viability. According to the SEM results, the scaffolds with Pd NPs provided the differentiated grown osteoblast cells with enough mechanical support and stability and the cells had a regular form and were highly dense. In conclusion, the synthesized composite scaffolds expressed suitable biodegradable, osteoconductive properties, and the ability to construct 3D structures for bone regeneration, making them a potential option for treating critical deficiencies of bone.

Therapeutic application of hydrogels for bone-related diseases

Bone-related diseases caused by trauma, infection, and aging affect people’s health and quality of life. The prevalence of bone-related diseases has been increasing yearly in recent years. Mild bone diseases can still be treated with conservative drugs and can be cured confidently. However, serious bone injuries caused by large-scale trauma, fractures, bone tumors, and other diseases are challenging to heal on their own. Open surgery must be used for intervention. The treatment method also faces the problems of a long cycle, high cost, and serious side effects. Studies have found that hydrogels have attracted much attention due to their good biocompatibility and biodegradability and show great potential in treating bone-related diseases. This paper mainly introduces the properties and preparation methods of hydrogels, reviews the application of hydrogels in bone-related diseases (including bone defects, bone fracture, cartilage injuries, and osteosarcoma) in recent years. We also put forward suggestions according to the current development status, pointing out a new direction for developing high-performance hydrogels more suitable for bone-related diseases.

Multi-functional wound dressings based on silicate bioactive materials

Most traditional wound dressings passively offer a protective barrier for the wounds, which lacks the initiative in stimulating tissue regeneration. In addition, cutaneous wound healing is usually accompanied by various complicated conditions, including bacterial infection, skin cancer, and damaged skin appendages, bringing further challenges for wound management in clinic. Therefore, an ideal wound dressing should not only actively stimulate wound healing but also hold multi-functions for solving problems associated with different specific wound conditions. Recent studies have demonstrated that silicate bioceramics and bioglasses are one type of promising materials for the development of wound dressings, as they can actively accelerate wound healing by regulating endothelial cells, dermal fibroblasts, macrophages, and epidermal cells. In particular, silicate-based biomaterials can be further functionalized by specific structural design or doping with functional components, which endow materials with enhanced bioactivities or expanded physicochemical properties such as photothermal, photodynamic, chemodynamic, or imaging properties. The functionalized materials can be used to address wound healing with different demands including but not limited to antibacterial, anticancer, skin appendages regeneration, and wound monitoring. In this review, we summarized the current research on the development of silicate-based multi-functional wound dressings and prospected the development of advanced wound dressings in the future.

Bone tumors effective therapy through functionalized hydrogels: current developments and future expectations

Primary bone tumors especially, sarcomas affect adolescents the most because it originates from osteoblasts cells responsible for bone growth. Chemotherapy, surgery, and radiation therapy are the most often used clinical treatments. Regrettably, surgical resection frequently fails to entirely eradicate the tumor, which is the primary cause of metastasis and postoperative recurrence, leading to a high death rate. Additionally, bone tumors frequently penetrate significant regions of bone, rendering them incapable of self-repair, and impairing patients' quality of life. As a result, treating bone tumors and regenerating bone in the clinic is difficult. In recent decades, numerous sorts of alternative therapy approaches have been investigated due to a lack of approved treatments. Among the novel therapeutic approaches, hydrogel-based anticancer therapy has cleared the way for the development of new targeted techniques for treating bone cancer and bone regeneration. They include strategies such as co-delivery of several drug payloads, enhancing their biodistribution and transport capabilities, normalizing accumulation, and optimizing drug release profiles to decrease the limitations of current therapy. This review discusses current advances in functionalized hydrogels to develop a new technique for treating bone tumors by reducing postoperative tumor recurrence and promoting tissue repair.

Anti-Inflammatory and Prochondrogenic In Situ-Formed Injectable Hydrogel Crosslinked by Strontium-Doped Bioglass for Cartilage Regeneration

Directed differentiation of bone marrow mesenchymal stem cells (BMSCs) toward chondrogenesis plays a predominant role in cartilage repair. However, the uncontrolled inflammatory response to implants is found to impair the stability of scaffolds and the cartilage regeneration outcome. Herein, we fabricated an injectable hydrogel crosslinked by strontium-doped bioglass (SrBG) to modulate both human BMSC (hBMSC) differentiation and the inflammatory response. The results revealed that the introduction of Sr ions could simultaneously enhance the proliferation of hBMSCs, upregulate cartilage-specific gene expression, and improve the secretion of glycosaminoglycan. Moreover, after cultured with SA/SrBG extracts in vitro, a majority of macrophages were polarized toward the M2 phenotype and subsequently facilitated the chondrogenic differentiation of hBMSCs. Furthermore, after the composite hydrogel was injected into a cartilage defect model, neonatal cartilage-like tissues with a smooth surface and tight integration with original tissues could be found. This study suggests that the synergistic strategy based on an enhanced differentiation ability and a regulated inflammatory response is promising and may lead the way to new anti-inflammatory biomaterials.

Injectable nanocomposite hydrogels as an emerging platform for biomedical applications: A review

Hydrogels have attracted much attention for biomedical and pharmaceutical applications due to the similarity of their biomimetic structure to the extracellular matrix of natural living tissues, tunable soft porous microarchitecture, superb biomechanical properties, proper biocompatibility, etc. Injectable hydrogels are an exciting type of hydrogels that can be easily injected into the target sites using needles or catheters in a minimally invasive manner. The more comfortable use, less pain, faster recovery period, lower costs, and fewer side effects make injectable hydrogels more attractive to both patients and clinicians in comparison to non-injectable hydrogels. However, it is difficult to achieve an ideal injectable hydrogel using just a single material (i.e., polymer). This challenge can be overcome by incorporating nanofillers into the polymeric matrix to engineer injectable nanocomposite hydrogels with combined or synergistic properties gained from the constituents. This work aims to critically review injectable nanocomposite hydrogels, their preparation methods, properties, functionalities, and versatile biomedical and pharmaceutical applications such as tissue engineering, drug delivery, and cancer labeling and therapy. The most common natural and synthetic polymers as matrices together with the most popular nanomaterials as reinforcements, including nanoceramics, carbon-based nanostructures, metallic nanomaterials, and various nanosized polymeric materials, are highlighted in this review.

Enhanced delivery efficiency and sustained release of biopharmaceuticals by complexation-based gel encapsulated coated microneedles: rhIFNα-1b example

Coated microneedles (MNs) are widely used for delivering biopharmaceuticals. In this study, a novel gel encapsulated coated MNs (GEC-MNs) was developed. The water-soluble drug coating was encapsulated with sodium alginate (SA) in situ complexation gel. The manufacturing process of GEC-MNs was optimized for mass production. Compared to the water-soluble coated MNs (72.02% ± 11.49%), the drug delivery efficiency of the optimized GEC-MNs (88.42% ± 6.72%) was steadily increased, and this improvement was investigated through in vitro drug release. The sustained-release of BSA was observed in vitro permeation through the skin. The rhIFNα-1b GEC-MNs was confirmed to achieve biosafety and 6-month storage stability. Pharmacokinetics of rhIFNα-1b in GEC-MNs showed a linearly dose-dependent relationship. The AUC of rhIFNα-1b in GEC-MNs (4.51 ng/ml·h) was bioequivalent to the intradermal (ID) injection (5.36 ng/ml·h) and significantly higher than water-soluble coated MNs (3.12 ng/ml·h). The rhIFNα-1b elimination half-life of GEC-MNs, soluble coated MNs, and ID injection was 18.16, 1.44, and 2.53 h, respectively. The complexation-based GEC-MNs have proved to be more efficient, stable, and achieve the sustained-release of water-soluble drug in coating MNs, constituting a high value to biopharmaceutical.

Calcium silicate enhances immunosuppressive function of MSCs to indirectly modulate the polarization of macrophages

Bioactive silicate ceramics (BSCs) have been widely reported to be able to induce bone tissue regeneration, but the underlying mechanisms have not been fully elucidated. Previous studies have reported that ionic products of BSCs can promote bone regeneration by directly simulating osteogenic differentiation of mesenchymal stem cells (MSCs) and modulating the polarization of macrophages to create a favorable inflammation microenvironment for initiating bone regeneration cascades. However, the immunomodulatory ability of MSCs also plays a critical role in bone regeneration but the effects of BSCs on the immunomodulatory ability of MSCs have been rarely investigated. This study aims to investigate the effects of ionic products of BSCs on the immunoregulatory ability of MSCs to further understand the mechanism of BSCs enhancing bone regeneration. Results showed that ionic products of calcium silicate (CS), one of the representative BSCs, could enhance the immunosuppressive function of human bone marrow mesenchymal stem cells (HBMSCs) by up-regulating the expression of immunosuppressive factors in HBMSCs via NF-κB pathway. In addition, CS-activated HBMSCs showed stronger stimulatory effects on M2 polarization of macrophages than CS ionic products. Furthermore, the macrophages educated by CS-activated HBMSCs showed stronger stimulatory effects on the early osteogenic differentiation of HBMSCs than the ones regulated by CS ionic products. These results not only provide further understanding on the mechanism of BSCs enhancing bone regeneration but also suggest that it is critical to consider the effects of biomaterials on the immunomodulatory function of the tissue forming cells when the immunomodulatory function of biomaterials is investigated.

Biomaterials in bone and mineralized tissue engineering using 3D printing and bioprinting technologies

This review focuses on recently developed printable biomaterials for bone and mineralized tissue engineering. 3D printing or bioprinting is an advanced technology to design and fabricate complex functional 3D scaffolds, mimicking native tissue forin vivoapplications. We categorized the biomaterials into two main classes: 3D printing and bioprinting. Various biomaterials, including natural, synthetic biopolymers and their composites, have been studied. Biomaterial inks or bioinks used for bone and mineralized tissue regeneration include hydrogels loaded with minerals or bioceramics, cells, and growth factors. In 3D printing, the scaffold is created by acellular biomaterials (biomaterial inks), while in 3D bioprinting, cell-laden hydrogels (bioinks) are used. Two main classes of bioceramics, including bioactive and bioinert ceramics, are reviewed. Bioceramics incorporation provides osteoconductive properties and induces bone formation. Each biopolymer and mineral have its advantages and limitations. Each component of these composite biomaterials provides specific properties, and their combination can ameliorate the mechanical properties, bioactivity, or biological integration of the 3D printed scaffold. Present challenges and future approaches to address them are also discussed.

Silicate bioceramics elicit proliferation and odonto-genic differentiation of human dental pulp cells

This study aimed to investigate the effects of silicates on the proliferation and odontogenic differentiation of human dental pulp cells (hDPCs) in vitro. HDPCs were cultured in the presence of calcium silicate (CS) extracts, while calcium hydroxide (CH) extracts and culture medium without CH or CS were used as the control groups. The calcium and phosphorus ion concentrations in the CS were similar to those in the control groups, but the concentration of silicon ions in the CS extracts was higher than that in the control groups. HDPCs cultured with CS and CH extracts at dilution of 1/128 proliferated significantly more than those cultured with the control treatments. CS extracts promoted cell migration, enhanced the expression of odontogenic marker genes and conspicuously increased odontogenesis-related protein production and the release of cytokines, suggesting that CS bioactive ceramics possess excellent biocompatibility and bioactivity and have the potential for application as pulp-capping agents.

Recent Development of Alginate-Based Materials and Their Versatile Functions in Biomedicine, Flexible Electronics, and Environmental Uses

Alginate is a natural polysaccharide that is easily chemically modified or compounded with other components for various types of functionalities. The alginate derivatives are appealing not only because they are biocompatible so that they can be used in biomedicine or tissue engineering but also because of the prospering bioelectronics that require various biomaterials to interface between human tissues and electronics or to serve as electronic components themselves. The study of alginate-based materials, especially hydrogels, have repeatedly found new frontiers over recent years. In this Review, we document the basic properties of alginate, their chemical modification strategies, and the recent development of alginate-based functional composite materials. The newly thrived functions such as ionically conductive hydrogel or 3D or 4D cell culturing matrix are emphasized among other appealing potential applications. We expect that the documentation of relevant information will stimulate scientific efforts to further develop biocompatible electronics or smart materials and to help the research domain better address the medicine, energy, and environmental challenges faced by human societies.

Cobalt doped nano-hydroxyapatite incorporated gum tragacanth-alginate beads as angiogenic-osteogenic cell encapsulation system for mesenchymal stem cell based bone tissue engineering

Angiogenic-osteogenic cell encapsulation system is a technical need for human mesenchymal stem cell (hMSC)-based bone tissue engineering (BTE). Here, we have developed a highly efficient hMSC encapsulation system by incorporating bivalent cobalt doped nano-hydroxyapatite (HAN) and gum tragacanth (GT) as angiogenic-osteogenic components into the calcium alginate (CA) beads. Physico-chemical characterizations revealed that the swelling and degradation of HAN incorporated CA-GT beads (GT-HAN) were 1.34 folds and 2 folds higher than calcium alginate (CA) beads. Furthermore, the diffusion coefficient of solute molecule was found 2.5-fold higher in GT-HAN with respect to CA bead. It is observed that GT-HAN supports the long-term viability of encapsulated hMSC and causes 50% less production of reactive oxygen species (ROS) in comparison to CA beads. The expression of osteogenic differentiation markers was found 1.5-2.5 folds higher in the case of GT-HAN in comparison to CA. A similar trend was observed for hypoxia inducible factor 1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF). The soluble secretome from hMSC encapsulated in the GT-HAN induced proliferation of endothelial cells and supported tube formation (2.5-fold higher than CA beads). These results corroborated that GT-HAN could be used as an angiogenic-osteogenic cell encapsulation matrix for hMSC encapsulation and BTE application.

Incorporation of Bioglass Improved the Mechanical Stability and Bioactivity of Alginate/Carboxymethyl Chitosan Hydrogel Wound Dressing

Recently, hydrogel wound dressings were popular in wound healing because of their advantages over traditional gauze dressings. The alginate/carboxymethyl chitosan (SA/CMCS) hydrogel wound dressing has been widely studied because of its biocompatibility and antibacterial ability. However, the poor mechanical stability and lack of bioactivity limit their applications. Bioglass (BG) has been well acknowledged as a bioactive material, and SA/BG hydrogels have been reported to be able to promote wound healing. Calcium ions released from BG can further cross-link SA, which may enhance the mechanical stability of the SA/CMCS hydrogels. Therefore, in this study, BG was incorporated into SA/CMCS hydrogel in order to obtain a bioactive alginate/CMCS/BG (SA/CMCS/BG) hydrogel wound dressing with improved mechanical stability. Results showed that the Young's modulus of SA/CMCS/BG hydrogel was three times higher than that of SA/CMCS hydrogel. In addition to better antibacterial and coagulation properties, SA/CMCS/BG hydrogels possess stronger bioactivity than SA/CMCS hydrogels as they could accelerate skin wound closure by regulating the host inflammation responses, stimulating angiogenesis, and enhancing collagen deposition in wound sites, which suggests that SA/CMCS/BG hydrogels are good candidates for clinic wound dressings.

Sustained Calcium(II)-Release to Impart Bioactivity in Hybrid Glass Scaffolds for Bone Tissue Engineering

In this study, we integrated different calcium sources into sol-gel hybrid glass scaffolds with the aim of producing implants with long-lasting calcium release while maintaining mechanical strength of the implant. Calcium(II)-release was used to introduce bioactivity to the material and eventually support implant integration into a bone tissue defect. Tetraethyl orthosilicate (TEOS) derived silica sols were cross-linked with an ethoxysilylated 4-armed macromer, pentaerythritol ethoxylate and processed into macroporous scaffolds with defined pore structure by indirect rapid prototyping. Triethyl phosphate (TEP) was shown to function as silica sol solvent. In a first approach, we investigated the integration of 1 to 10% CaCl2 in order to test the hypothesis that small CaCl2 amounts can be physically entrapped and slowly released from hybrid glass scaffolds. With 5 and 10% CaCl2 we observed an extensive burst release, whereas slightly improved release profiles were found for lower Calcium(II) contents. In contrast, introduction of melt-derived bioactive 45S5 glass microparticles (BG-MP) into the hybrid glass scaffolds as another Calcium(II) source led to an approximately linear release of Calcium(II) in Tris(hydroxymethyl)aminomethane (TRIS) buffer over 12 weeks. pH increase caused by BG-MP could be controlled by their amount integrated into the scaffolds. Compression strength remained unchanged compared to scaffolds without BG-MP. In cell culture medium as well as in simulated body fluid, we observed a rapid formation of a carbonated hydroxyapatite layer on BG-MP containing scaffolds. However, this mineral layer consumed the released Calcium(II) ions and prevented an additional increase in Calcium(II) concentration in the cell culture medium. Cell culture studies on the different scaffolds with osteoblast-like SaOS-2 cells as well as bone marrow derived mesenchymal stem cells (hMSC) did not show any advantages concerning osteogenic differentiation due to the integration of BG-MP into the scaffolds. Nonetheless, via the formation of a hydroxyapatite layer and the ability to control the pH increase, we speculate that implant integration in vivo and bone regeneration may benefit from this concept.

Polysaccharide-Based In Situ Self-Healing Hydrogels for Tissue Engineering Applications

In situ hydrogels have attracted increasing interest in recent years due to the need to develop effective and practical implantable platforms. Traditional hydrogels require surgical interventions to be implanted and are far from providing personalized medicine applications. However, in situ hydrogels offer a wide variety of advantages, such as a non-invasive nature due to their localized action or the ability to perfectly adapt to the place to be replaced regardless the size, shape or irregularities. In recent years, research has particularly focused on in situ hydrogels based on natural polysaccharides due to their promising properties such as biocompatibility, biodegradability and their ability to self-repair. This last property inspired in nature gives them the possibility of maintaining their integrity even after damage, owing to specific physical interactions or dynamic covalent bonds that provide reversible linkages. In this review, the different self-healing mechanisms, as well as the latest research on in situ self-healing hydrogels, is presented, together with the potential applications of these materials in tissue regeneration.

Hydrogel as a Biomaterial for Bone Tissue Engineering: A Review

Severe bone damage from diseases, including extensive trauma, fractures, and bone tumors, cannot self-heal, while traditional surgical treatment may bring side effects such as infection, inflammation, and pain. As a new biomaterial with controllable mechanical properties and biocompatibility, hydrogel is widely used in bone tissue engineering (BTE) as a scaffold for growth factor transport and cell adhesion. In order to make hydrogel more suitable for the local treatment of bone diseases, hydrogel preparation methods should be combined with synthetic materials with excellent properties and advanced technologies in different fields to better control drug release in time and orientation. It is necessary to establish a complete method to evaluate the hydrogel's properties and biocompatibility with the human body. Moreover, establishment of standard animal models of bone defects helps in studying the therapeutic effect of hydrogels on bone repair, as well as to evaluate the safety and suitability of hydrogels. Thus, this review aims to systematically summarize current studies of hydrogels in BTE, including the mechanisms for promoting bone synthesis, design, and preparation; characterization and evaluation methods; as well as to explore future applications of hydrogels in BTE.

PDA/Cu Bioactive Hydrogel with "Hot Ions Effect" for Inhibition of Drug-Resistant Bacteria and Enhancement of Infectious Skin Wound Healing

Quick and effective sterilization of drug-resistant bacteria inevitably became an ever-growing global challenge. In this study, a multifunctional composite (PDA/Cu-CS) hydrogel mainly composed of polydopamine (PDA) and copper-doped calcium silicate ceramic (Cu-CS) was prepared. It was confirmed that PDA/copper (PDA/Cu) complexing in the composite hydrogel played a key role in enhancing the photothermal performance and antibacterial activity. Through a unique "hot ions effect", created by the heating of Cu ions through the photothermal effect of the composite hydrogel, the hydrogel showed high-efficiency, quick, and long-term inhibition of methicillin-resistant Staphylococcus aureus and Escherichia coli. In addition, the hydrogel possessed remarkable bioactivity to stimulate angiogenesis. The in vivo results confirmed that the "hot ions effect" of the composite hydrogel removed existing infection in the wound area efficiently and significantly promoted angiogenesis and collagen deposition during infectious skin wound healing. Our results suggested that the design of multifunctional hydrogels with "hot ions effect" may be an effective therapeutic approach for the treatment of infectious wounds.

Local intramyocardial delivery of bioglass with alginate hydrogels for post-infarct myocardial regeneration

Heart failure (HF) is a common and serious manifestation after myocardial infarction (MI). Despite their clinical importance, current treatments for MI still have several limitations. Revascularization has been proven to have positive effects on MI-induced damage. Currently biomaterial-based angiogenesis strategies represent potential candidates for MI treatment. Bioglass (BG) is a commercially available family of bioactive glasses. BG has angiogenic properties and thus might be an attractive alternative for MI treatments. Here, we loaded BG in sodium alginate (BGSA), locally injected it into peri-infarct myocardial tissue and examined its suitability for inducing cardiac angiogenesis and eventually improving cardiac function following MI. Cardiac function was evaluated via echocardiography. Infarct morphometry, angiogenesis, apoptosis and angiogenic protein expression were all analysed 4 weeks after BGSA injection. Compared with the control treatment, BGSA was sufficient to prompt angiogenesis, suppress apoptosis, up-regulate the expression of angiogenic proteins, attenuate infarct size, preserve wall thickness and eventually improve cardiac function. Our results demonstrate the feasibility and effectiveness of BGSA in myocardial regeneration via angiogenesis, suggesting that BGSA is a potential therapeutic strategy for post-infarct myocardial regeneration.

Dual-enzymatically crosslinked hyaluronic acid hydrogel as a long-time 3D stem cell culture system

Stem cell-based tissue engineering shows enormous potential for regenerative medicine. Three-dimensional (3D) stem cell culture is the most basic aspect of tissue engineering. However, achievement of a perfect scaffold for highly efficient 3D cell culture is currently still limited. Herein, a new hyaluronic acid hydrogel dual-enzymatically crosslinked by horseradish peroxidase and choline oxidase is developed as a 3D stem cell culture system. This hydrogel possesses superior stability over two months, controllable biodegradability with hyaluronidases, a high swelling ratio exceeding 6000%, and excellent cytocompatibility in vitro and biocompatibility in vivo. More importantly, a long-time and highly cellular activity 3D culture of bone marrow-derived mesenchymal stem cells was achieved in vitro over 20 days. All these encouraging results highlight the great potential of this new hydrogel for 3D culture and tissue engineering.

Single-walled carbon nanotubes loaded hydroxyapatite-alginate beads with enhanced mechanical properties and sustained drug release ability

Single-walled carbon nanotubes (SWCNTs) containing biomaterial with enhanced mechanical properties for the potential orthopedic application were synthesized and investigated. X-ray diffraction and X-ray fluorescence analysis were indications of the formation of calcium-deficient (Ca/P = 1.65) hydroxyapatite (HA) with a small carbonate content under influence of microwave irradiation. The investigated mechanical properties (maximal relative deformation, compressive strength and Young's modulus) of SWCNT loaded HA-alginate composites confirm their dependence on SWCNTs content. The compressive strength of HA-alginate-SWCNT and the HA-alginate control (202 and 159 MPa, respectively) lies within the values characteristic for the cortical bone. The addition of 0.5% SWCNT, in relation to the content of HA, increases the Young's modulus of the HA-alginate-SWCNT (645 MPa) compared to the SWCNT-free HA-alginate sample (563 MPa), and enhances the material shape stability in simulated physiological conditions. Structural modeling of HA-alginate-SWCNT system showed, that physical adsorption of SWCNT into HA-alginate occurs by forming triple complexes stabilized by solvophobic/van der Waals interactions and H-bonds. The high-performance liquid chromatography demonstrated the influence of SWCNTs on the sustained anaesthesinum drug (used as a model drug) release (456 h against 408 h for SWCNT-free sample). Cell culture assay confirmed biocompatibility and stimulation of osteoblast proliferation of 0.05% and 0.5% SWCNT-containing composites during a 3-day cultivation. All these facts may suggest the potential possibility of using the SWCNT-containing materials, based on HA and alginate, for bone tissue engineering.

Bioactive, degradable and multi-functional three-dimensional membranous scaffolds of bioglass and alginate composites for tissue regenerative applications

Multifunctional bioactive hydrogel ECM like membrane for 3D dynamic tissue/disease modelling.

Silanized NaCa2HSi3O9 nanorods with a reduced pH increase on Ti for improving osteogenesis and angiogenesis in vitro

NaCa₂HSi₃O₉ nanorods with silane layers allow efficient Ca and Si release and controlled pH increase, and can enhance osteogenesis and angiogenesis on the Ti implant surface.

Microneedles combined with a sticky and heatable hydrogel for local painless anesthesia

In view of the inherent defects of traditional syringe anesthesia (pain, inaccurate anesthesia area, swelling after injection, slow recovery etc.), this article proposed a new anesthesia system based on microneedles and a hydrogel. After loading with AuNPs, a sticky PDA-PAM-AuNP hydrogel with near-infrared (NIR) light response properties was prepared here. After using microneedles (to open the skin of the target anesthesia area), a hydrogel patch embedded with a medical anesthetic soaked sponge was pasted to realize local painless anesthesia. The effects of anesthesia can also be modulated by external NIR. Compared to traditional syringe anesthesia, this hydrogel + microneedle method resulted in reduced pain, higher anesthetic accuracy and faster recovery, making it a promising local anesthesia alternative in clinical applications.

Inhibition of the negative effect of high glucose on osteogenic differentiation of bone marrow stromal cells by silicon ions from calcium silicate bioceramics

Human bone marrow stem cells (hBMSCs) are exploited for miscellaneous applications in bone tissue engineering where they are mainly used as seed cells. However, high glucose (HG) environment has negative impacts on the proliferation and osteogenic differentiation of hBMSCs, thus reducing the bone formation in diabetic patients. In our former research works, we discovered that silicon (Si) ions extracted from silicate-based bioceramics are able to stimulate the proliferation and osteogenic differentiation of hBMSCs under normal culture condition. This study aimed to investigate if Si ions could prevent HG-induced inhibition of proliferation and osteogenesis of hBMSCs. We found that 2.59 ppm concentration of Si ions promoted the proliferation of hBMSCs under HG condition. The results from alkaline phosphatase (ALP) activity assay, Alizarin red S staining and quantitative real-time PCR analysis of osteogenic genes (BMP2, RUNX2, ALP, COL1 and OCN) demonstrated that the 15.92 ppm concentration of Si ions prevented HG-induced inhibition of the osteogenic differentiation of hBMSCs. Moreover, application of Si ions reduced the level of reactive oxygen species in HG-treated hBMSCs. In HG-treated hBMSCs following 15.92 ppm Si ions treatment, activation of BMP2/SMAD signaling pathway was detected, as indicated by the increased expression of BMP2 receptors and its downstream genes such as SMAD1, SMAD4 and SMAD5. Taken together, we provide evidence that the specific concentration of Si ions compensated HG-induced inhibition of proliferation and osteogenic differentiation of hBMSCs through antioxidant effect and modulation of BMP2/SMAD pathway. The results suggest that silicate-based bioceramics might be good scaffold biomaterials for bone engineering applications in diabetes patients.

Harmonious Biomaterials for Development of In situ Approaches for Locoregional Delivery of Anti-cancer Drugs: Current Trends

Locoregional drug delivery is a novel approach for the effective delivery of anti-cancer agents as it exposes the tumors to high concentration of drugs. In situ gelling systems have fetched paramount attention in the field of localized cancer chemotherapy due to their targeted delivery, ease of preparation, prolonged or sustained drug release and improved patient compliance. Numerous polymers have been investigated for their properties like swelling along with biodegradation, drug release and physicochemical properties for successful targeting of the drugs at the site of implantation. The polymers such as chitosan, Hyaluronic Acid (HA), poloxamer, Poly Glycolic Lactic Acid (PGLA) and Poly Lactic Acid (PLA) tend to form in situ hydrogels and have been exploited to develop localized delivery vehicles. These formulations are administered in the solution form and on exposure to physiological environment such as temperature, pH or ionic composition they undergo phase conversion into a hydrogel drug depot. The use of in situ gelling approach has provided prospects to increase overall survival and life quality of cancer patient by enhancing the bioavailability of drug to the site of tumor by minimizing the exposure to normal cells and alleviating systemic side effects. Because of its favorable safety profile and clinical benefits, United States Food and Drug Administration (U.S. FDA) has approved polymer based in situ systems for prolonged locoregional activity. This article discusses the rationale for developing in situ systems for targeted delivery of anti-cancer agents with special emphasis on types of polymers used to formulate the in situ system. In situ formulations for locoregional anti-cancer drug delivery that are marketed and are under clinical trials have also been discussed in detail in this article.

Grape Seed-Inspired Smart Hydrogel Scaffolds for Melanoma Therapy and Wound Healing

Grape-seed extracts contain rich flavonoids with oligomeric proanthocyanidins (OPC). In this study, OPC containing hydrogel scaffolds can function as a natural photothermal agent for melanoma therapy and bioactive biomaterial for wound healing. Inspired by grape-seed extracts, OPC were explored as a photothermal agent and endowed the hydrogel scaffolds with excellent and controlled photothermal ability. The rheological property of the hydrogel scaffolds responded to irradiation time of near infrared (NIR) laser, and OPC contents. The compressive mechanical property of the hydrogel scaffolds was well modulated by NIR laser irradiation with different impact durations. The controlled high temperature induced by OPC-containing hydrogel scaffolds under NIR laser irradiation could effectively kill melanoma cells and suppress tumor growth. In addition, OPC-containing hydrogel scaffolds supported the proliferation and migration of human dermal fibroblasts and human umbilical vein endothelial cells, as well as obviously promoted angiogenesis and skin regeneration in both tumor-caused and chronic wounds. Therefore, OPC-containing hydrogel scaffolds possessed controlled photothermal, rheological, and compressive mechanical properties under NIR laser stimuli, as well as excellent biocompatibility and bioactivity for melanoma therapy and wound healing.

In vivo systemic toxicity assessment of an oxidized dextrin-based hydrogel and its effectiveness as a carrier and stabilizer of granular synthetic bone substitutes

The worldwide incidence of bone disorders is raising, mainly due to aging population. The lack of effective treatments is pushing the development of synthetic bone substitutes (SBSs). Most ceramic-based SBSs commercially available display limited handling properties. Attempting to solve these issues and achieve wider acceptance by the clinicians, granular ceramics have been associated with hydrogels (HGs) to produce injectable/moldable SBSs. Dextrin, a low-molecular-weight carbohydrate, was used to develop a fully resorbable and injectable HG. It was first oxidized with sodium periodate and then cross-linked with adipic acid dihydrazide. The in vivo biocompatibility and safety of the dextrin-based HG was assessed by subacute systemic toxicity and skin sensitization tests, using rodent models. The results showed that the HG did not induce any systemic toxic effect, skin reaction, or genotoxicity, neither impaired the bone repair/regeneration process. Then, the HG was successfully combined with granular bone substitute, registered as Bonelike (250-500 μm) to obtain a moldable/injectable SBS, which was implanted in tibial fractures in goats for 3 and 6 weeks. The obtained results showed that HG allowed the stabilization of the granules into the defect, ensuring effective handling, and molding properties of the formulation, as well as an efficient cohesion of the granules. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1678-1689, 2019.

Preparation and properties of dopamine-modified alginate/chitosan-hydroxyapatite scaffolds with gradient structure for bone tissue engineering

Three-dimensional (3D) homogenous scaffolds composed of natural biopolymers have been reported as superior candidates for bone tissue engineering. There are still remaining challenges in fabricating the functional scaffolds with gradient structures to similar with natural bone tissues, as well as high mechanical properties and excellent affinity to surround tissues. Herein, inspired by the natural bone structure, a gradient-structural scaffold composed of functional biopolymers was designed to provide an optimized 3D environment for promoting cell growth. To increase the interactions among the scaffolds, dopamine (DA) was employed to modify alginate (Alg) and needle-like nano-hydroxyapatite (HA) was prepared with quaternized chitosan as template. The obtained dopamine-modified alginate (Alg-DA) and quaternized chitosan-templated hydroxyapatite (QCHA) were then used to fabricate the porous gradient scaffold by "iterative layering" freeze-drying technique with further crosslinking by calcium ions (Ca²⁺ ). The as-prepared Alg-DA/QCHA gradient scaffolds were possessed seamlessly integrated layer structures and high levels of porosity at around 77.5%. Moreover, the scaffolds showed higher compression modules (1.7 MPa) than many other biopolyermic scaffolds. The gradient scaffolds showed appropriate degradation rate to satisfy with the time of the bone regeneration. Both human chondrocytes and fibroblasts could adhesive and growth well on the scaffolds in vitro. Furthermore, an excellent osteogenetic activity of the gradient scaffold can effectively promote the regeneration of the bone tissue and accelerate the repair of the bone defects in vivo, compared with that of the scaffold with the homogenous structure. The novel multilayered scaffold with gradient structure provided an interesting option for bone tissue engineering. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1615-1627, 2019.

A Cocktail-Inspired Male Birth Control Strategy with Physical/Chemical Dual Contraceptive Effects and Remote Self-Cleared Properties

Inspired by cocktails, we designed a medium term (2-20 weeks) male contraceptive strategy. Through a sequential injection process of four reagents (calcium alginate hydrogel, PEG-Au nanoparticles (PEG-AuNps), EDTA, and PEG-AuNps), physical clogging of the vas deferens and chemical inhibition of the sperm motility were realized simultaneously. The contraceptive period could be directly preset by adjusting the injection ratio of each reagent. More interesting, the embolism area could be readily dredged through a short-time noninvasive near-infrared irradiation. The present study offered an effective and reversible manner to fill the gap of current medium-term contraceptive strategy. In addition, the proposed in vivo pipeline plugging technology, with a flexible noninvasive self-cleared characteristic, might also provide a convenient and reliable strategy for some other biomedical engineering researches.

Chitosan/Calcium Silicate Cardiac Patch Stimulates Cardiomyocyte Activity and Myocardial Performance after Infarction by Synergistic Effect of Bioactive Ions and Aligned Nanostructure

Cardiac tissue engineering (CTE) remains a great challenge to construct a cell-inductive scaffold that has positive effects on cardiac cell behaviors and cardiac tissue repair. In this study, we for the first time demonstrated that Si ions evidently stimulated the expression of cardiac-specific genes and proliferation of neonatal rat cardiomyocytes (NRCMs) at concentration ranges of 0.13-10.78 ppm. Accordingly, the optimized concentrations of calcium silicate (CS) were incorporated into the controllable aligned chitosan electrospun nanofibers, constructing the composite cardiac patch scaffolds. These scaffolds showed synergistic effect of bioactive chemical and structural signals on both cardiomyocytes and endothelial cells with aligned cell morphology and enhanced viability and function characterized by upregulated expressions of cardiac and angiogenic specific markers, improved myofilament structure, and better Ca²⁺ transients of NRCMs as compared to the scaffolds free of CS component or with disordered structures. The in vivo studies further demonstrated that the NRCM-seeded aligned CS/chitosan cardiac patch evidently improved cardiac function via limiting the scar area and promoting angiogenesis in postmyocardial infarction rats. Conclusively, our study highlights the potential application of bioactive ions and nanostructured biomaterials in CTE, and the CS/chitosan composite cardiac patch may be a promising scaffold for repair of infarcted myocardium.

Nanocement Produced from Borosilicate Bioactive Glass Nanoparticles Composited with Alginate

A novel injectable bone cement was prepared using sol–gel derived borosilicate bioactive glass nanoparticles as a solid phase and sodium alginate solution as a liquid phase. The gelation reaction of the alginate was modulated by Ca2+ ions released from the borosilicate glass phase, which in turn greatly depended on the boron content of the borosilicate glass phase. Such a gelation reaction not only significantly enhanced the anti-washout property of the bone cements, but also allowed control of the setting, handling properties, and compressive strength of the composite bone cements. Consequently, bone cements with controllable performances can be developed by simply adjusting the B2O3/SiO2 ratio of the borosilicate glass phase. Borosilicate bioactive glass with 20–30 mol-% borate contents exhibit a short setting time, good compressive strength, injectability, and anti-washout properties. With controllable performances and excellent bioactivity, the borosilicate bioactive glass/sodium alginate (BSBG/SA) composite bone cements are highly attractive for bone filling and regeneration applications.

Bioceramic akermanite enhanced vascularization and osteogenic differentiation of human induced pluripotent stem cells in 3D scaffolds in vitro and vivo

A growing number of studies suggest that the modulation of cell differentiation by biomaterials is critical for tissue engineering. In previous work, we demonstrated that human induced pluripotent stem cells (iPSCs) are remarkably promising seed cells for bone tissue engineering. In addition, we found that the ionic products of akermanite (Aker) are potential inducers of osteogenic differentiation of iPSCs. Furthermore, composite scaffolds containing polymer and bioceramics have more interesting properties compared to pure bioceramic scaffolds for bone tissue engineering. The characteristic of model biomaterials in bone tissue engineering is their ability to control the osteogenic differentiation of stem cells and simultaneously induce the angiogenesis of endothelia cells. Thus, this study aimed at investigating the effects of poly(lactic-co-glycolic acid)/Aker (PLGA-Aker) composite scaffolds on angiogenic and osteogenic differentiation of human iPSCs in order to optimize the scaffold compositions. The results from Alizarin Red S staining, qRT-PCR analysis of osteogenic genes (BMP2, RUNX2, ALP, COL1 and OCN) and angiogenic genes (VEGF and CD31) demonstrated that PLGA/Aker composite scaffolds containing 10% Aker exhibited the highest stimulatory effects on the osteogenic and angiogenic differentiation of human iPSCs among all scaffolds. After the scaffolds were implanted in nu/nu mice subcutaneous pockets and calvarial defects, H&E staining, BSP immunostaining, qRT-PCR analysis and micro-CT analysis (BMD, BV/TV) indicated that PLGA + 10% Aker scaffolds enhanced the vascularization and osteogenic differentiation of human iPSCs and stimulated the repair of bone defects. Taken together, our work indicated that combining scaffolds containing silicate bioceramic Aker and human iPSCs is a promising approach for the enhancement of bone regeneration.

Bioceramics akermanite enhanced vascularization and osteogenic differentiation of human iPSCs in 3D scaffolds in vitro and vivo.