A highly interweaved HA-SS-nHAp/collagen hybrid fibering hydrogel enhances osteoinductivity and mineralization

Hyaluronated nanohydroxyapatite responsively released from injectable hydrogels for targeted therapy of melanoma

Nanohydroxyapatite (nHAp) has attracted significant attention for its tumor suppression and tumor microenvironment modulation capabilities. However, a strong tendency to aggregate greatly affects its anti-tumor efficiency. To address this issue, a hydrogel platform consisting of thiolated hyaluronic acid (HA-SH) modified nanohydroxyapatite (nHAp-HA) and HA-SH was developed for sustained delivery of nHAp for melanoma therapy. The hydrophilic and negatively charged HA-SH significantly improved the size dispersion and stability of nHAp in aqueous media while conferring nHAp targeting effects. Covalent sulfhydryl self-cross-linking between HA-SH and nHAp-HA groups ensured homogeneous dispersion of nHAp in the matrix material. Meanwhile, the modification of HA-SH conferred the targeting properties of nHAp and enhanced cellular uptake through the HA/CD44 receptor. The hydrogel platform could effectively reduce the aggregation of nHAp and release nHAp in a sustained and orderly manner. Antitumor experiments showed that the modified nHAp-HA retained the tumor cytotoxicity of nHAp in vitro and inhibited the growth of highly malignant melanomas up to 78.6% while being able to induce the differentiation of macrophages to the M1 pro-inflammatory and antitumor phenotype. This study will broaden the application of nanohydroxyapatite in tumor therapy.

Potential actions of capsaicin for preventing vascular calcification of vascular smooth muscle cells in vitro and in vivo

Vascular calcification (VC) is an accurate risk factor and predictor of adverse cardiovascular events; however, there is currently no effective therapy to specifically prevent VC progression. Capsaicin (Cap) is a bioactive alkaloid isolated from Capsicum annuum L., a traditional medicinal and edible plant that is beneficial for preventing cardiovascular diseases. However, the effect of Cap on VC remains unclear. This study aimed to explore the effects and related mechanisms of Cap on aortic calcification in a mouse and on Pi-induced calcification in vascular smooth muscle cells (VSMCs). First, we established a calcification mouse model with vitamin D3 and evaluated the effects of Cap on calcification mice using von Kossa staining, calcium content, and alkaline phosphatase activity tests. The results showed that Cap significantly improved calcification in mice. VSMCs were then cultured in 2.6 mM Na2HPO4 and 50 μg/mL ascorbic acid for 7 days to obtain a calcification model, and we investigated the effects and mechanisms of Cap on VSMCs calcification by assessing the changes of calcium deposition, calcium content, and subsequent VC biomarkers. These results showed that Cap alleviated VSMCs calcification by upregulating the expressions of TRPV1. Moreover, Cap reduced the expression of Wnt3a and β-catenin, whereas DKK1 antagonised the inhibitory effect of Cap on VSMC calcification. This study is the first to offer direct evidence that Cap inhibits the Wnt/β-catenin signaling pathway by upregulating the expression of the TRPV1 receptor, resulting in the decreased expression of Runx2 and BMP-2, thereby reducing VSMC calcification. Our study may provide novel strategies for preventing the progression of VC. This could serve as a theoretical basis for clinically treating VC with spicy foods.

The combination of paeonol, diosmetin-7-O-β-D-glucopyranoside, and 5-hydroxymethylfurfural from Trichosanthis pericarpium alleviates arachidonic acid-induced thrombosis in a zebrafish model

Trichosanthis fruit (TF) is a classic medicinal material obtained from Shandong, China. The peel of this fruit (Trichosanthis pericarpium, TP) is known to exert anti-thrombotic effects. However, the anti-thrombotic active components and mechanisms of TP have yet to be fully elucidated. Combined with zebrafish models and high-performance liquid chromatography (HPLC), this study evaluated the endogenous anti-thrombotic effects with the combination of three compounds from TP. First, we used HPLC to investigate the components in the water extract of TP. Next, we used the zebrafish model to investigate the anti-thrombotic activity of the three compound combinations by evaluating a range of indicators. Finally, the expression of related genes was detected by real-time quantitative polymerase chain reaction (qPCR). HPLC detected a total of eight components in TP water extract, with high levels of paeonol (Pae), diosmetin-7-O-β-D-glucopyranoside (diosmetin-7-O-glucoside), and 5-hydroxymethylfurfural (5-HMF). The most significant anti-thrombotic activity was detected when the Pae: diosmetin-7-O-glucoside:5-HMF ratio was 4:3:3. qPCR analysis revealed that the abnormal expression levels of f2, fga, fgb, vwf, ptgs1, and tbxas1 induced by arachidonic acid (AA) were improved. The combination of Pae, diosmetin-7-O-glucoside, and 5-HMF may alleviate AA-induced thrombosis by inhibiting the inflammatory reaction, coagulation cascade reaction, and arachidonic acid metabolism pathways.

Nanostructured 3D-Printed Hybrid Scaffold Accelerates Bone Regeneration by Photointegrating Nanohydroxyapatite

Nanostructured biomaterials that replicate natural bone architecture are expected to facilitate bone regeneration. Here, nanohydroxyapatite (nHAp) with vinyl surface modification is acquired by silicon-based coupling agent and photointegrated with methacrylic anhydride-modified gelatin to manufacture a chemically integrated 3D-printed hybrid bone scaffold (75.6 wt% solid content). This nanostructured procedure significantly increases its storage modulus by 19.43-fold (79.2 kPa) to construct a more stable mechanical structure. Furthermore, biofunctional hydrogel with biomimetic extracellular matrix is anchored onto the filament of 3D-printed hybrid scaffold (HGel-g-nHAp) by polyphenol-mediated multiple chemical reactions, which contributes to initiate early osteogenesis and angiogenesis by recruiting endogenous stem cells in situ. Significant ectopic mineral deposition is also observed in subcutaneously implanted nude mice with storage modulus enhancement of 25.3-fold after 30 days. Meanwhile, HGel-g-nHAp realizes substantial bone reconstruction in the rabbit cranial defect model, achieving 61.3% breaking load strength and 73.1% bone volume fractions in comparison to natural cranium 15 weeks after implantation. This optical integration strategy of vinyl modified nHAp provides a prospective structural design for regenerative 3D-printed bone scaffold.

Hydroxyapatite-Tethered Peptide Hydrogel Promotes Osteogenesis

Hydroxyapatite (HAp) as natural bone composition is highly osteoinductive. To harvest its osteoinductivity in bone regenerative engineering, the HAp-supporting hydrogel is urgently needed to minimize inhomogeneous aggregation of HAp. Here, we developed a HAp-stabilizing hydrogel based on peptide self-assembly. FmocFFRR was efficient for HAp-capping due to arginine-phosphate interaction. Tethering FmocFFRR on the HAp surface facilitated self-assembly to form FmocFFRR/HAp hybrid hydrogel, enabling stable dispersion of HAp in it. The molecular interactions between FmocFFRR and HAp particles were studied using microscopic and spectral characterizations. FmocFFRR/HAp hydrogel exhibited more enhanced mechanical properties than FmocFFRR. The biocompatibility of FmocFFRR/HAp hydrogel was verified using an ATP assay and live-dead staining assay. More importantly, FmocFFRR/HAp hydrogel not only enabled cell attachment on its surface, but also supported 3D cell culturing inside the hydrogel. Further, 3D culturing of MC3T3-E1 preosteoblasts inside FmocFFRR/HAp hydrogel significantly enhanced the expressions of osteogenesis markers, including alkaline phosphate (ALP), type-I collagen (COL1), and osteocalcin (OCN), demonstrating the promoting effect of osteoblast differentiation. These findings inspire its potential application in bone regenerative engineering.

Advanced application of collagen-based biomaterials in tissue repair and restoration

In tissue engineering, bioactive materials play an important role, providing structural support, cell regulation and establishing a suitable microenvironment to promote tissue regeneration. As the main component of extracellular matrix, collagen is an important natural bioactive material and it has been widely used in scientific research and clinical applications. Collagen is available from a wide range of animal origin, it can be produced by synthesis or through recombinant protein production systems. The use of pure collagen has inherent disadvantages in terms of physico-chemical properties. For this reason, a processed collagen in different ways can better match the specific requirements as biomaterial for tissue repair. Here, collagen may be used in bone/cartilage regeneration, skin regeneration, cardiovascular repair and other fields, by following different processing methods, including cross-linked collagen, complex, structured collagen, mineralized collagen, carrier and other forms, promoting the development of tissue engineering. This review summarizes a wide range of applications of collagen-based biomaterials and their recent progress in several tissue regeneration fields. Furthermore, the application prospect of bioactive materials based on collagen was outlooked, aiming at inspiring more new progress and advancements in tissue engineering research.

Graphical Abstract

Stem Cell-Laden Hydrogel-Based 3D Bioprinting for Bone and Cartilage Tissue Engineering

Tremendous advances in tissue engineering and regenerative medicine have revealed the potential of fabricating biomaterials to solve the dilemma of bone and articular defects by promoting osteochondral and cartilage regeneration. Three-dimensional (3D) bioprinting is an innovative fabrication technology to precisely distribute the cell-laden bioink for the construction of artificial tissues, demonstrating great prospect in bone and joint construction areas. With well controllable printability, biocompatibility, biodegradability, and mechanical properties, hydrogels have been emerging as an attractive 3D bioprinting material, which provides a favorable biomimetic microenvironment for cell adhesion, orientation, migration, proliferation, and differentiation. Stem cell-based therapy has been known as a promising approach in regenerative medicine; however, limitations arise from the uncontrollable proliferation, migration, and differentiation of the stem cells and fortunately could be improved after stem cells were encapsulated in the hydrogel. In this review, our focus was centered on the characterization and application of stem cell-laden hydrogel-based 3D bioprinting for bone and cartilage tissue engineering. We not only highlighted the effect of various kinds of hydrogels, stem cells, inorganic particles, and growth factors on chondrogenesis and osteogenesis but also outlined the relationship between biophysical properties like biocompatibility, biodegradability, osteoinductivity, and the regeneration of bone and cartilage. This study was invented to discuss the challenge we have been encountering, the recent progress we have achieved, and the future perspective we have proposed for in this field.

Bioinspired Hydrogel Anchoring 3DP GelMA/HAp Scaffolds Accelerates Bone Reconstruction

Seeking high biological activity and osteoinductive ability has always been an urgent problem for three-dimensional-printed (3DP) bony implants. Here, a 3DP methacrylic anhydride-modified gelatin (GelMA)/hydroxyapatite (HAp) scaffold with a high solid content of 82.5% was prepared and anchored by a functionalized polyphenol hydrogel. The scaffold and hydrogel were organically integrated into a bioinspired bony implant (HGH) by phenolic hydroxyl of hyaluronan derivatives conjugating amino groups of collagen I and GelMA and further chelating calcium ions of HAp. Compared with a simplex 3DP scaffold, this freeze-dried HGH presented better water retention, delayed degradation, and mechanical stability. It could promote migration, proliferation, and osteogenic differentiation of bone marrow stem cells in vitro. One week of implantation showed that it promoted directional migration of endogenous stem cells and early osteogenesis and angiogenesis. After 15 week surgery of rabbit skull defects, the BV/TV value of HGH returned to 73% of the normal group level. This strategy provided a new research idea for bone regeneration.

The Relationship between Osteoinduction and Vascularization: Comparing the Ectopic Bone Formation of Five Different Calcium Phosphate Biomaterials

Objective: The objective of this study is to compare the bone induction of five kinds of calcium phosphate (Ca-P) biomaterials implanted in mice and explore the vascularization and particle-size-related osteoinductive mechanism. Methods: The following five kinds of Ca-P biomaterials including hydroxyapatite (HA) and/or tricalcium phosphate (TCP) were implanted in the muscle of 30 BALB/c mice (n = 6): 20 nm HA (20HA), 60 nm HA (60HA), 12 µm HA (12HA), 100 nm TCP (100TCP) and 12 µm HA + 100 nm TCP (HATCP). Then, all animals were put on a treadmill to run 30 min at a 6 m/h speed each day. Five and ten weeks later, three mice of each group were killed, and the samples were harvested to assess the osteoinductive effects by hematoxylin eosin (HE), Masson’s trichrome and safranine−fast green stainings, and the immunohistochemistry of the angiogenesis and osteogenesis markers CD31 and type I collagen (ColI). Results: The numbers of blood vessels were 139 ± 29, 118 ± 25, 78 ± 15, 65 ± 14 in groups HATCP, 100TCP, 60HA and 20HA, respectively, which were significantly higher than that of group 12HA (12 ± 5) in week 5 (p < 0.05). The area percentages of new bone tissue were (7.33 ± 1.26)% and (8.49 ± 1.38)% in groups 100TCP and HATCP, respectively, which were significantly higher than those in groups 20HA (3.27 ± 0.38)% and 60HA (3.43 ± 0.27)% (p < 0.05); however, no bone tissue was found in group 12HA 10 weeks after transplantation. The expression of CD31 was positive in new blood vessels, and the expression of ColI was positive in new bone tissue. Conclusions: Nanoscale Ca-P biomaterials could induce osteogenesis in mice muscle, and the osteoinductive effects of TCP were about 124% higher than those of 20HA and 114% higher than those of 60HA. The particle size of the biomaterials affected angiogenesis and osteogenesis. There was a positive correlation between the number of blood vessels and the area percentage of new bone tissue; therefore, osteoinduction is closely related to vascularization. Our results provide an experimental basis for the synthesis of calcium−phosphorus matrix composites and for further exploration of the osteoinductive mechanism.

An injectable gellan gum-based hydrogel that inhibits Staphylococcus aureus for infected bone defect repair

The treatment of infected bone defects in complex anatomical structures, such as oral and maxillofacial structures, remains an intractable clinical challenge. Therefore, advanced biomaterials that have excellent anti-infection activity and allow convenient delivery are needed. We fabricated an innovative injectable gellan gum (GG)-based hydrogel loaded with nanohydroxyapatite particles and chlorhexidine (nHA/CHX). The hydrogel has a porous morphology, suitable swelling ratio, and good biocompatibility. It exerts strong antibacterial activity against Staphylococcus aureus growth and biofilm formation in vitro. We successfully established an infected calvarial defect rat model. Bacterial colony numbers were significantly lower in tissues surrounding the bone in rats of the GG/nHA/CHX group after debride surgery and hydrogel implantation in the defect regions than in rats of the blank group. Rats in the GG/nHA/CHX group exhibited significantly increased new bone formation compared to those in the blank group at 4 and 8 weeks. These findings indicate that gellan gum-based hydrogel with nHA/CHX can accelerate the repair of infected bone defects.

Boron Nano-hydroxyapatite Composite Increases the Bone Regeneration of Ovariectomized Rabbit Femurs

Osteoporosis is a systemic metabolic disease defined by a decreased bone mineral density, microarchitectural deterioration, and an increased incidence of fragility fractures that may lead to morbidity and mortality. Boron may stimulate new bone formation and regeneration, when combined with nano-hydroxyapatite. We questioned whether injecting boron-containing nano-hydroxyapatite composites with hyaluronan increased the bone mineral density and new bone formation in osteoporotic rabbit femurs. The regenerative effects of injectable boron-containing nano-hydroxyapatite composites from 6 to 12 weeks, which may prevent osteoporotic femoral fractures, were assessed. Boron-containing (10 μg/ml) nano-hydroxyapatite composites were injected into the intramedullary femoral cavity with hyaluronan. These significantly increased the histomorphometric new bone surface to the total bone surface ratio at 6 and 9 weeks. The micro-tomographic bone volume to the total volume ratio and bone mineral density in osteoporotic rabbit femurs increased when compared to the hyaluronan (p = 0.004, p = 0.004, p = 0.004, p = 0.01, respectively) and the sham-control (p = 0.01, p = 0.004, p = 0.01, p = 0.037, respectively) groups. The boron-containing group had a higher bone mineralization and new bone formation compared to the nano-hydroxyapatite group, although the difference was not statistically significant. These findings reveal that intramedullary injection of boron-containing nano-hydroxyapatite with hyaluronan increases new bone formation and mineralization in ovariectomized rabbit femurs. Boron-containing nano-hydroxyapatite composites are promising tissue engineering biomaterials that may have regenerative potential in preventing primary and/or secondary femoral fractures in osteoporosis patients.

Collagen-based biocomposites inspired by bone hierarchical structures for advanced bone regeneration: ongoing research and perspectives

Bone is a hard-connective tissue composed of matrix, cells and bioactive factors with a hierarchical structure, where the matrix is mainly composed of type I collagen and hydroxyapatite. Collagen fibers assembled by collagen are the template for mineralization and make an important contribution to bone formation and the bone remodeling process. Therefore, collagen has been widely clinically used for bone/cartilage defect regeneration. However, pure collagen implants, such as collagen scaffolds or sponges, have limitations in the bone/cartilage regeneration process due to their poor mechanical properties and osteoinductivity. Different forms of collagen-based composites prepared by incorporating natural/artificial polymers or bioactive inorganic substances are characterized by their interconnected porous structure and promoting cell adhesion, while they improve the mechanical strength, structural stability and osteogenic activities of the collagen matrix. In this review, various forms of collagen-based biocomposites, such as scaffolds, sponges, microspheres/nanoparticles, films and microfibers/nanofibers prepared by natural/synthetic polymers, bioactive ceramics and carbon-based materials compounded with collagen are reviewed. In addition, the application of collagen-based biocomposites as cytokine, cell or drug (genes, proteins, peptides and chemosynthetic) delivery platforms for proangiogenesis and bone/cartilage tissue regeneration is also discussed. Finally, the potential application, research and development direction of collagen-based biocomposites in future bone/cartilage tissue regeneration are discussed.

Preparation and Degradation Characteristics of MAO/APS Composite Bio-Coating in Simulated Body Fluid

In this work, ZK60 magnesium alloy was employed as a substrate material to produce ceramic coatings, containing Ca and P, by micro-arc oxidation (MAO). Atmospheric plasma spraying (APS) was used to prepare the hydroxyapatite layer (HA) on the MAO coating to obtain a composite coating for better biological activity. The coatings were examined by various means including an X-ray diffractometer, a scanning electron microscope and an energy spectrometer. Meanwhile, an electrochemical examination, immersion test and tensile test were used to evaluate the in vitro performance of the composite coatings. The results showed that the composite coating has a better corrosion resistance. In addition, this work proposed a degradation model of the composite coating in the simulated body fluid immersion test. This model explains the degradation process of the MAO/APS coating in SBF.

Constructing a biomimetic nanocomposite with the in situ deposition of spherical hydroxyapatite nanoparticles to induce bone regeneration

Inspired by the nanostructure of bone, biomimetic nanocomposites comprising natural polymers and inorganic nanoparticles have gained much attention for bone regenerative applications. However, the mechanical and biological performances of nanocomposites are largely limited by the inhomogeneous distribution, uncontrolled size and irregular morphology of inorganic nanoparticles at present. In this work, an innovative in situ precipitation method has been developed to construct a biomimetic nanocomposite which consists of spherical hydroxyapatite (HA) nanoparticles and gelatin (Gel). The homogeneous dispersion of HA nanoparticles in nHA-Gel endowed it with a low swelling ratio, enhanced mechanical properties and slow degradation. Moreover, strontium (Sr) was incorporated into HA nanoparticles to further enhance the bioactivity of nanocomposites. In vitro experiments suggested that nHA-Gel and Sr-nHA-Gel facilitated cell spreading and promoted osteogenic differentiation of bone-marrow-derived mesenchymal stem cells (BMSCs) as compared to pure Gel and mHA-Gel conventional composites developed by mechanical mixing. In vivo rat critical-sized calvarial defect repair further confirmed that nHA-Gel and Sr-nHA-Gel possessed relatively effective bone regenerative abilities among the four groups. Collectively, the biomimetic nanocomposites of nHA-Gel and Sr-nHA-Gel have good efficacy in inducing bone regeneration and would be a promising alternative to bone grafts for clinical applications.

Preparation and characterisation of a gellan gum-based hydrogel enabling osteogenesis and inhibiting Enterococcus faecalis

Infections are the leading cause of failure of osteogenic material implantation. Antibiotic treatment, treatment with bone cement, or collagen sponge placement can result in drug resistance and difficulties in operation. To address this, gellan gum (GG) was selected in this study and prepared as an injectable hydrogel containing chlorhexidine (CHX) and nanohydroxyapatite (nHA) that overcomes these intractable problems. Scanning electron microscopy and micro-computed tomography revealed a three-dimensional polymeric network of the hydrogel. The hydrogel had excellent biocompatibility, as detected by cell counting kit-8 and Live/Dead assay. Bone marrow mesenchymal stem cells could be encapsulated into the network, showing that the structure was suitable for cell growth. Additionally, loading the hydrogel with nHA improved its mechanical, biodegradable, and osteogenic properties. Quantitative alkaline phosphatase and Alizarin Red S staining validated its osteogenic ability. Furthermore, antibacterial activity assessment showed that the hydrogel loaded with 50 μg/mL CHX inhibited Enterococcus faecalis in a concentration-dependent manner. Thus, we report an injectable GG-based hydrogel with superior antibacterial effect against E. faecalis and osteogenesis, which holds promise for treating infectious bone defects caused by refractory periradicular periodontitis.