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Polymer-based scaffolds with different degradability have been investigated to screen the matrix whose degradation rate is more closely matched with the bone regeneration rate. However, these comparisons are inclined to be compromised by the animal individual differences. In this study, we constructed an integrated scaffold model comprising four parts with different degradability and bioactivity to achieve an in situ comparison of bone regeneration ability of different scaffolds. Slow-degradable polycaprolactone (PCL), fast-degradable poly (lactic-co-glycolic acid) (PLGA), and silica-coated PCL and PLGA scaffolds were assembled into a round sheet to form a hydroxyapatite (HA)-free integrated scaffold. HA-doped PCL, PLGA, and silica-coated PCL and PLGA scaffolds were assembled to create an HA-incorporated integrated scaffold. The in vivo experimental results demonstrated that the local acid microenvironment caused by the rapid degradation of PLGA interfered with the osteogenic process promoted by PCL-based scaffolds in defect areas implanted with HA-free integrated scaffolds. Since the incorporation of HA alleviated the acidic microenvironment to some extent, each scaffold in HA-incorporated scaffolds exhibited its expected bone regeneration capacity. Consequently, it is feasible to construct an integrated structure for comparing the osteogenic effects of various scaffolds in situ, when there is no mutual interference between the materials. The strategy presented in this study inspired the structure design of biomaterials to enable in situ comparison of bone regeneration capacity of scaffolds., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The combined design of scaffold structure and multi-biological factors is a prominent strategy to promote bone regeneration. Herein, a composite scaffold of mesoporous hydroxyapatite (HA) microspheres loaded with the bone morphogenetic protein-2 (BMP-2) and a poly(DL-lactic-co-glycolic acid) (PLGA) matrix is constructed by 3D printing. Furthermore, the chemokine stromal cell-derived factor-1α (SDF-1α) is adsorbed on a scaffold surface to achieve the sequential release of the dual-biofactors. The results indicate that the rapid release of SDF-1α chemokine on the scaffold surface effectively recruits bone marrow-derived mesenchymal stem cells (BMSCs) to the target defect area, whereas the long-term sustained release of BMP-2 from the HA microspheres in the degradable PLGA matrix successfully triggers the osteogenic differentiation in the recruited BMSCs, significantly promoting bone regeneration and reconstruction. In addition, these structures/biofactors specially combining scaffold exhibit significantly better biological performance than that of other combined scaffolds, including the bare HA/PLGA scaffold, the scaffold loaded with SDF-1α or BMP-2 biofactor alone, and the scaffold with surface SDF-1α and BMP-2 dual-biofactors. The utilization of mesoporous HA, the assembly method, and sequential release of the two biofactors in the 3D printed composite scaffold present a new method for future design of high-performance bone repairing scaffolds., (© 2023 Wiley-VCH GmbH.)

Magnesium (Mg) and its alloys exhibit an excellent prospect for orthopedic clinical application due to their outstanding biodegradability and mechanical adaptability. However, the rapid corrosion rate/latent device-associated infections may lead to a failed internal fixation of Mg-based implants. Herein, a novel composite coating consisted of outer copper-doped zeolitic imidazolate frameworks-8 and inner hydroxyapatite (Cu@ZIF-8/HA) was in situ constructed on AZ31B Mg alloy via a two-step approach of hydrothermal treatment and seeded solvothermal method. The results verified that the electrochemical impedance of the obtained Cu 45 @ZIF-8/HA composite coating increased by two orders of magnitude to 6.6013 × 10 4 Ω·cm 2 compared to that of bare Mg alloy. This was attributed to the reduced particle size of ZIF-8 nanoparticles due to the doped copper ions, which could be effectively grown in situ on the micro-nano flower-like structure of the HA-coated Mg alloy. Meanwhile, the Cu@ZIF-8/HA coating exhibited excellent antibacterial properties due to the release of copper ions and zinc ions from Cu@ZIF-8 dissolved in bacterial culture solution. The ICP results unraveled that the released concentration of copper and zinc ions could enhance the activity of alkaline phosphatase in the appropriate range during MC3T3-E1 cell culture in vitro for 7 days. This research revealed that the preparation of multifunctional metal-organic frameworks coating doped with antimicrobial metal ions via the seed layer solvothermal method was significant for studying the antimicrobial properties, osteogenic performance and corrosion resistance of Mg-based bioactive coatings., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Bone tissue engineering scaffolds with similar composition, structure, and mechanical properties to natural bone are conducive to bone regeneration. The objective of this study was to prepare hydroxyapatite/poly (lactic-co-glycolic acid) (HA/PLGA) three-dimensional porous scaffolds with HA content close to natural bone and strong mechanical strength to promote osteogenesis. To achieve this, we modified HA microspheres with polyvinyl alcohol to create an inorganic filler to endow the HA/PLGA printing ink with higher HA content and excellent printing fluidity for 3D printing. We successfully printed a series of HA/PLGA scaffolds with different HA contents. The highest HA content reached 60 wt%, which is close to the mineral percentage in natural bone. The composition, structure, mechanical properties, and in vitro degradability of the fabricated scaffolds were systematically characterized. The cytocompatibility and osteogenic activity of the fabricated HA/PLGA scaffolds were evaluated by in vitro cell culture and rabbit femoral defect repair experiments in vivo. The results indicated that the HA/PLGA composite scaffold with 45 wt% HA had the highest compressive strength of more than 40 MPa, which was six times higher than that of the pure PLGA scaffold. The incorporation of HA microspheres into the PLGA matrix significantly improved the cell adhesion, proliferation, and osteogenic differentiation of bone marrow stem cells (BMSCs) cultured on the surface of the scaffolds. Animal experiments showed that the HA/PLGA composite with 45 wt% HA exhibited the best structure maintenance and osteogenic performance in vivo. The prepared HA/PLGA composite 3D scaffold with HA microsphere reinforcement has considerable application potential in the field of large bone defect repair., Competing Interests: Declaration of competing interest No conflict of interest exits in the submission of this manuscript, and manuscript is approved by all authors for publication., (Copyright © 2021. Published by Elsevier B.V.)

The ideal scaffold for bone repair should have a hierarchical pore structure and gradient degradation performance to satisfy the uniform adhesion and proliferation of cells in the scaffold at the early stage of implantation, as well as providing space for the subsequent regeneration of bone tissue. To this end, we developed a hierarchical polylactic acid glycolic acid copolymer (PLGA)/nano-hydroxyapatite (n-HA)/gelatin (Gel) (PHG) scaffold with a printed PLGA/n-HA (PH) framework and a Gel network filler for bone regeneration by the combination of 3D printing and freeze-drying technologies. The fabricated PHG scaffold features large front hole size (>1100 μm × 1100 μm) and side hole size (>500 μm) to provide sufficient open space and reliable integrated support for cell and tissue ingrowth. The gelatin network filled in the PH framework played the role of a cell holder just like an extracellular matrix (ECM) in the early stage. In vitro degradation experiments revealed that the gelatin network completely degraded within 5 weeks while the structural integrity of the framework still remained at the 32nd week. The results of cell culture confirmed that the PHG scaffold was more conducive to cell attachment. In vivo assessments in a rat femoral defect model showed that PHG scaffolds were more favored for new bone formation and achieving a tighter bond between the scaffold and the original tissues. The hierarchical PHG scaffold has great application potential in bone tissue engineering and will provide a reference for the model design of bone scaffolds.

The purpose of this study was to fabricate a low-immunogenicity fish collagen (FC) and bioactive nanohydroxyapatite (n-HA) enhanced poly(lactide- co-glycolide) (PLGA) nanofibrous membrane for guided bone regeneration (GBR) via electrospinning. The physicochemical properties and morphology study revealed that FC and n-HA particles were homogeneously dispersed in the PLGA fibrous matrix. Notably, the formation of enhanced polymeric chain network due to the interaction between FC and PLGA significantly improved the tensile strength of the PLGA membrane. The incorporation of FC altered the degradation behavior of fibers and accelerated the degradation rate of the PLGA-based membranes. Moreover, the membranes exhibited favorable cytocompatibility with bone mesenchymal stem cells (BMSCs) and human gingiva fibroblasts (HGF) cells. More importantly, the optimized membrane satisfied the requirements of the 'Biological evaluation of medical devices' during the incipient biosafety evaluation. All the results indicate that this composite fibrous membrane exhibits significant potential for guided bone or tissue regeneration.

A newly designed hydroxyapatite-polyurethane (HA-PU) composite scaffold was prepared by polymerizing glyceride of castor oil (GCO) with isophorone diisocyanate (IPDI) and HA as fillers. The aim of this study was to determine the effect of HA fillers on the mechanical properties and osteogenesis capacity of the composite scaffolds. The physical and biological properties of the scaffold were evaluated by SEM observation, mechanical testing, cell culture and animal experiments. The results showed that HA fillers enhanced the mechanical properties of PU composite scaffolds such as compressive strength and elastic modulus. The mechanical properties of the scaffolds were seen to increase with increase in HA loading. The compressive strength of composite scaffold with 0 wt%, 20 wt%, 40 wt% of HA was 0.6 ± 0.1 MPa, 2.1 ± 0.1 MPa, and 4.6 ± 0.3 MPa, respectively. In vitro biodegradation studies of scaffolds were carried out. The results showed that all of the scaffolds were susceptible to cholesterol esterase (CE) -catalyzed degradation. HA-PU composite scaffolds exhibited a high affinity to osteoblastic cells and were good template for cell growth and proliferation. When implanted in bone defects of rats, PU scaffolds incorporated HA were biocompatible with the tissue host and had no immune rejection. Moreover, the higher the loading of HA in the composite scaffold, the better chances of osteogenesis. It confirmed that the prepared HA-PU composite scaffolds can be promising candidate for bone repair and bone tissue engineering., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The dipping-drying procedure and cross-linking method were used to make drug-loaded chitosan (CS) coating on nano-hydroxyapatite/polyamide66 (nHA/PA66) composite porous scaffold, endowing the scaffold controlled drug release functionality. The prefabricated scaffold was immersed into an aqueous drug/CS solution in a vacuum condition and then crosslinked by vanillin. The structure, porosity, composition, compressive strength, swelling ratio, drug release and cytocompatibility of the pristine and coating scaffolds were investigated. After coating, the scaffold porosity and pore interconnection were slightly decreased. Cytocompatibility performance was observed through an in vitro experiment based on cell attachment and the MTT assay by MG63 cells which revealed positive cell viability and increasing proliferation over the 11-day period in vitro. The drug could effectively release from the coated scaffold in a controlled fashion and the release rate was sustained for a long period and highly dependent on coating swelling, suggesting the possibility of a controlled drug release. Our results demonstrate that the scaffold with drug-loaded crosslinked CS coating can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to be a promising high performance biomaterial in bone tissue engineering.

Solving the issue of infection associated with implanted bone substitutes is one of the modern challenges of the biomedical engineering field. The purpose of this study was to develop a novel porous scaffold with sufficient antibacterial activity for bone repair or regeneration. Porous nanohydroxyapatite/polyurethane (n-HA/PU) composite scaffolds containing different amounts of silver phosphate particles were prepared through the in situ foaming method. Subsequently, their physicochemical properties, antibacterial abilities, and preliminary cytocompatibilities were evaluated. The results indicated that the porosity and mechanical properties of the n-HA/PU scaffolds incorporated with Ag3PO4 did not change significantly compared to n-HA/PU scaffold without Ag3PO4. The release of Ag(+) was time and concentration dependent, increasing with the immersion time and Ag3PO4 percentage in the scaffolds. A continuous Ag(+) release can last more than 3 weeks. The antibacterial tests and cytocompatibility evaluation revealed that n-HA/PU scaffolds with 3 wt% Ag3PO4 (n-HA/PU3) exhibit stronger antimicrobial effects as well as satisfactory cytocompatibility. The n-HA/PU3 scaffolds may hold great potential for application in the field of bone regeneration, especially for infection-associated bone defect repair.

To improve the mechanical properties of bone tissue and achieve the desired bone tissue regeneration for orthopedic surgery, newly designed hydroxyapatite/polyurethane (HA/PU) porous scaffolds were developed via in situ polymerization. The results showed that the molecular modification of PU soft segments by glyceride of castor oil (GCO) can increase the scaffold compressive strength by 48% and the elastic modulus by 96%. When nano-HA (n-HA) particles were incorporated into the GCO-PU matrix, the compressive strength and elastic modulus further increased by 49 and 74%, from 2.91 to 4.34 MPa and from 95 to 165.36 MPa, respectively. The n-HA particles with fine dispersity not only improved the interface bonding with the GCO-PU matrix but also provided effective bioactivity for bonding with bone tissue. The hierarchical structure and mechanical quality of the n-HA/GCO-PU composite scaffold were determined to be appropriate for the growth of cells and the regeneration of bony tissues, demonstrating promising prospects for bone repair and regeneration.

Biomaterial scaffolds meant to function as supporting structures to osteogenic cells play a pivotal role in bone tissue engineering. Recently, we synthesized an aliphatic polyurethane (PU) scaffold via a foaming method using non-toxic components. Through this procedure a uniform interconnected porous structure was created. Furthermore, hydroxyapatite (HA) particles were introduced into this process to increase the bioactivity of the PU matrix. To evaluate the biological performances of these PU-based scaffolds, their influence on in vitro cellular behavior and in vivo bone forming capacity of the engineered cell-scaffold constructs was investigated in this study. A simulated body fluid test demonstrated that the incorporation of 40 wt % HA particles significantly promoted the biomineralization ability of the PU scaffolds. Enhanced in vitro proliferation and osteogenic differentiation of the seeded mesenchymal stem cells were also observed on the PU/HA composite. Next, the cell-scaffold constructs were implanted subcutaneously in a nude mice model. After 8 weeks, a considerable amount of vascularized bone tissue with initial marrow stroma development was generated in both PU and PU/HA40 scaffold. In conclusion, the PU/HA composite is a potential scaffold for bone regeneration applications., (© 2014 Wiley Periodicals, Inc.)

Modular tissue engineering holds great potential in regenerating natural complex tissues by engineering three-dimensional modular scaffolds with predefined geometry and biological characters. In modular tissue-like construction, a scaffold with an appropriate mechanical rigidity for assembling fabrication and high biocompatibility for cell survival is the key to the successful bioconstruction. In this work, a series of composite hydrogels (GH0, GH1, GH2, and GH3) based on a combination of methacrylated gelatin (GelMA) and hydroxyapatite (HA) was exploited to enhance hydrogel mechanical rigidity and promote cell functional expression for osteon biofabrication. These composite hydrogels presented a lower swelling ratio, higher mechanical moduli, and better biocompatibility when compared to the pure GelMA hydrogel. Furthermore, on the basis of the composite hydrogel and photolithograph technology, we successfully constructed an osteon-like concentric double-ring structure in which the inner ring encapsulating human umbilical vascular endothelial cells (HUVECs) was designed to imitate blood vessel tubule while the outer ring encapsulating human osteoblast-like cells (MG63s) acts as part of bone. During the coculture period, MG63s and HUVECs exhibited not only satisfying growth status but also the enhanced genic expression of osteogenesis-related and angiogenesis-related differentiations. These results demonstrate this GelMA-HA composite hydrogel system is promising for modular tissue engineering.

Fabrication of bioactive and mechanical matched bone substitutes is crucial for clinical application in bone defects repair. In this study, nano-hydroxyapatite/polyamide (nHA/PA) composite was coated on injection-moulded PA by a chemical corrosion and phase-inversion technique. The shear strength, gradient composition and pore structure of the bioactive coating were characterized. Osteoblast-like MG63 cells were cultured on pure PA and composite-coated PA samples. The cells' adhesion, spread and proliferation were determined using MTT assay and microscopy. The results confirm that the samples with the nHA/PA composite coating have better cytocompatibility and have no negative effects on cells. To investigate the in vivo biocompatibility, both pure PA and composite-coated PA cylinders were implanted in the trochlea of rabbit femurs and studied histologically, and the bonding ability with bone were determined using push-out tests. The results show that composite-coated implants exhibit better biocompatibility and the shear strength of the composite-coated implants with host bone at 12 weeks can reach 3.49±0.42 MPa, which is significantly higher than that of pure PA implants. These results indicate that composite-coated PA implants have excellent biocompatibility and bonding abilities with host bone and they have the potential to be applied in repair of bone defects., (© 2014 The Author(s) Published by the Royal Society. All rights reserved.)

Porous scaffolds for bone repair were prepared from newly designed segmented aliphatic polyurethane based on glyceride of castor oil and isophorone diisocyanate. To promote the scaffolds' biological and mechanical properties, hydroxyapatite powder was incorporated into the polymer matrix. The scaffold (named as HA/GCPU) with 40 wt% HA had an average pore size of 500 μm and a compressive strength of 4.6 MPa. The in vitro cell culture studies demonstrated that the HA/GCPU scaffold owned good cytocompatibility. The scaffold and cell-seeded scaffold were implanted in defects (Ф3 mm × 3 mm) of femoral condyle of Sprague-Dawley rats, respectively. New bone could extensively form in both the scaffold and cell-seeded scaffold. It indicates that the HA/GCPU composite scaffold has good prospect for bone repair and regeneration., (Copyright © 2014 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.)

The aim of this study is to investigate the influence of sterilization process using γ -ray radiation on the melting behavior, crystallization behavior, thermal stability, and mechanical properties of nanohydroxyapatite/polyamide66 (nHA/PA66) scaffolds for bone tissue engineering. The results show that the melting temperature, degree of crystallization, thermal stability, and mechanical properties of the composite scaffolds increased with the enhancement of radiation doses from 25 kGy to 50 kGy, especially the irradiation dose of 50 kGy which imposed a remarkable effect on these properties. However, a reverse trend was found when the 100 kGy irradiation dose was applied. In general, a conclusion can be drawn that sterilization using γ -ray radiation with proper dose has no adverse effect on the properties of nHA/PA66 composite scaffolds.

Natural bone is a complex material with well-designed architecture. To achieve successful bone integration and regeneration, the constituent and structure of bone-repairing scaffolds need to be functionalized synergistically based on biomimetics. In this study, a hybrid membrane composed of chitosan (CS), sodium carboxymethyl cellulose (CMC), and nano-hydroxyapatite (n-HA) was curled in a concentric manner to generate an anisotropic spiral-cylindrical scaffold, with compositional and structural properties mimicking natural bone. After optimization in terms of morphology, hydrophilicity, swelling and degradation pattern, the osteoblast cells seeded on the membrane of 60 wt% n-HA exhibited the highest cell viability and osteocalcin expression. In vivo osteogenesis assessment revealed that the spiral-cylindrical architecture played a dominant role in bone regeneration and osseointegration. Newly formed bone tissue grew through the longitudinal direction of the cylinder-shaped scaffold bridging both ends of the defect, bone marrow penetrated the entire scaffold and formed a medullary cavity in the center of the spiral cylinder. This study for the first time demonstrates that the spiral-cylindrical scaffold can promote complete infiltration of bone tissues in vivo, leading to successful osteointegration and functional reconstruction of bone defects. It suggests that the biomimetic spiral-cylindrical scaffold could be a promising candidate for bone regeneration applications.

Tightly bonding of bioactive coating is the first crucial need for orthopaedic implants. This study describes a novel and convenient technique to prepare bioactive coating with high adhesion on orthopaedic substitutes made of polymeric matrix. Here, a chemical corrosion method has been adopted to fabricate a coating on the surface of injection-moulded polyamide66 (PA66) substrates by corrosive nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite slurry. Scanning electron microscopy observation shows that a porous chemical corrosion region presents between the coating and dense PA66 substrate. Energy-dispersive X-ray spectroscopy analysis indicates that the chemical corrosion region is mainly composed of PA66 matrix, and the coating layer is an n-HA-rich layer. Both the pore size and n-HA composition increase gradually from the polymeric substrate towards the coating surface. Mechanical testing shows the bonding strength can reach 13.7 ± 0.2 MPa, which is much higher than that fabricated on polymeric matrix by other coating methods. The gradual transition in coating structure and composition benefits for the interface bonding and for the surface bone-bonding bioactivity. Subsequent cell experiments corroborate n-HA-rich coating and a porous structure is benefitting for cell attachment and proliferation. The convenient coating method could be popularized and applied on similar polymer implants to produce a tightly and porous bioactive coating for bone tissue regeneration.

High porosity of scaffold is always accompanied by poor mechanical property; the aim of this study was to enhance the strength and modulus of the highly porous scaffold of nanohydroxyapatite/polyamide66 (n-HA/PA66) by coating chitosan (CS) and to investigate the effect of CS content on the scaffold physical properties and cytological properties. The results show that CS coating can reinforce the scaffold effectively. The compress modulus and strength of the CS coated n-HA/PA66 scaffolds are improved to 32.71 and 2.38 MPa, respectively, being about six times and five times of those of the uncoated scaffolds. Meanwhile, the scaffolds still exhibit a highly interconnected porous structure and the porosity is approximate about 78%, slightly lower than the value (84%) of uncoated scaffold. The cytological properties of scaffolds were also studied in vitro by cocultured with osteoblast-like MG63 cells. The cytological experiments demonstrate that the reinforced scaffolds display favorable cytocompatibility and have no significant difference with the uncoated n-HA/PA66 scaffolds. The CS reinforced n-HA/PA66 scaffolds can meet the basic mechanical requirement of bone tissue engineering scaffold, presenting a potential for biomedical application in bone reconstruction and repair., (Copyright © 2011 Wiley Periodicals, Inc.)

Nano-hydroxyapatite/polyamide 6 (n-HA/PA6) composite scaffolds were prepared by a combined method of phase separation and particle leaching processing technique. The porous matrices were seeded with allogenic bone marrow-derived stem cells (BMSCs) and implanted in the critical-size calvarial defect (8-mm diameter) in rats. The adhesion, proliferation, and differentiation of BMSCs were demonstrated by (3-{4,5-dimethylthiazol-2yl}-2,5-diphenyl-2H-tetrazoliumbromide) assay, immunohistochemical staining, and scanning electron microscopy in vitro. Cell survival was tracked via fluorescent labeling in vivo. The regeneration process was evaluated by several techniques at 4, 8, and 16 weeks after implantation. According to the results, the porous n-HA/PA6 scaffolds are biocompatible and have no negative effects on the BMSCs in vitro. Nano-hydroxyapatite/polyamide 6 composite combined with BMSCs exhibited good biocompatibility and osteoconductivity and enhanced osteogenesis at the initial stage after implantation. The results demonstrated that porous n-HA/PA6 scaffold is a potential matrix for bone tissue engineering, and using BMSCs as seed cells on porous n-HA/PA6 might be an alternative procedure in repair of large defect due to enhanced osteogenesis and osteointegration.

A homogenous membrane composed of chitosan (CS), sodium carboxymethyl cellulose (NaCMC) and nano hydroxyapatite (n-HA) was prepared by a gradual electrostatic assembling (GEA) method. The physical and chemical properties of the membranes with different n-HA contents and CS/NaCMC ratios were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and mechanical test. The schematic formation mechanism of the membrane was discussed. The results show that GEA is an effective method to prepare the polyelectrolyte complex (PEC) membrane, in which oppositely charged CS-NaCMC polysaccharides can assemble mildly and gradually through electrostatic interaction to form the membrane framework, while the filled n-HA crystals can regulate the structure stability of the composite membrane. The optimum preparation condition for the PEC membrane can be fixed to a content of 60 wt% n-HA, an equivalent amount of CS to NaCMC and a drying temperature of 60°C. The PEC membrane may have good prospect for guided bone regeneration.

A nano-hydroxyapatite/polyamide 66 (nHA/PA66) composite with good bioactivity and osteoconductivity is employed to develop a novel porous membrane with an asymmetric structure. In order to investigate the biocompatibility and the effect on guided bone regeneration (GBR) of nHA/PA66 porous membrane, the proliferation, viability, morphology and alkaline phosphatase activity (ALP) of the osteoblast-like cell line (MG63) cultured on the membrane were studied in vitro. In vivo biocompatibility and osteogenesis of the fabricated membrane were assessed by comparing guiding rats calvarial bone defects regeneration with "gold standard" GBR material, expanded polytetrafluoroethylene (e-PTFE) membrane. In vitro experiments showed that the nHA/PA66 composite membrane had good cell affinity and cytocompatibility, in favor of cell proliferation. The in vivo study showed that the nHA/PA66 asymmetric porous membrane had a good GBR effect. All the results indicate that the asymmetric porous nHA/PA66 composite GBR membrane with good biocompatibility, high bioactivity and osteoconductivity exhibits good GBR effect and has a potential to be applied in GBR fields, especially in dental tissue regeneration.

This study describes a new drug-loaded coating scaffold applied in infection therapy during bone regeneration. Chitosan (CS) containing antibacterial berberine was coated on a nano-hydroxyapatite/polyamide66 (n-HA/PA66) scaffold to realize bone regeneration together with antimicrobial properties. The porous scaffold was fabricated using the phase-inversion method with a porosity of about 84% and macropore size of 400-600 μm. The morphology, mechanical properties and drug-release behavior were investigated at different ratios of chitosan to berberine. The results show that the elastic modulus and compressive strength of the coated scaffolds were improved to 35.4 MPa and 1.7 MPa, respectively, about 7 times and 3 times higher than the uncoated scaffolds. After a burst release of berberine within the first 3 h in PBS solution, a continuous berberine release can last 150 h, which is highly dependent on the coating concentration and suitable for antibacterial requirement of orthopaedic surgery. The bactericidal test confirms a strong antibiotic effect of the delivery system and the minimum inhibitory concentration of the drug is 0.02 mg/ml. Moreover, in vitro biological evaluation demonstrates that the coating scaffolds act as a good matrix for MG63 adhesion, crawl, growth and proliferation, suggesting that the antibacterial delivery system has no cytotoxicity. We expect the drug-delivery system to have a potential application in bone regeneration or defect repair.

This study was to evaluate enhanced bone formation by bone morphogenetic protein-7 (BMP-7) transduced MSCs on nano-hydroxyapatite/polyamide (n-HA/PA) composite scaffolds for bone tissue engineering in repair of mandibular defect. n-HA/PA scaffolds were prepared and rabbit MSCs were separated and expanded; and then infected with adenoviral-mediated BMP-7 in vitro. The MSCs-BMP-7 and MSCs were seeded on the porous scaffolds. Scaffold/MSCs-BMP-7 constructs and scaffold/MSCs constructs were implanted in the defects of rabbits' mandible as the experimental groups A (n = 18) and groups B (n = 18), respectively, the pure scaffolds were implanted as controls (group C, n = 18). Six animals were sacrificed at 4-, 8-, and 16-week postimplantation, respectively. Their mandibles were removed and processed for radiographic, biomechanical tests, histological, and histomorphometric analysis. Group A animals showed greater bone formation and earlier mineralization than group B at 4- and 8-week postimplantation and similarly group B more than group C. However, no difference was found among three groups at 16-week postimplantation. The results of this study suggest that BMP-7 transduced MSCs-n-HA/PA composite could significantly accelerate bone formation in the implant at early stage. BMP-7 mediated ex vivo gene transfer based on MSCs as seed cells, combined with porous n-HA/PA as scaffolds for bone tissue engineering might be an alternative or supplemental approach to repair the mandibular defects., (Copyright © 2010 Wiley Periodicals, Inc.)

The purpose of this study is to explore and develop biodegradable scaffold for bone regeneration or tissue engineering with the capacity of controlled drug delivery. Ceftazidime as a model drug was encapsulated in ethyl cellulose (EC) microspheres, which were subsequently incorporated in a hydroxyapatite/polyurethane (HA/PU) composite scaffold to generate an antibiotic drug delivery system. HA/PU scaffolds had an interconnected pore network with an average porosity of about 83%. The presence of microspheres in the composite scaffolds was confirmed by scanning electron microscopy. The drug-loaded EC microspheres were uniformly distributed in the HA/PU scaffold matrix and showed no significant effect on the pore structure of the scaffold. Incorporation of microspheres into scaffolds significantly reduced the initial burst release, and the system exhibited a sustained release of the model drug for up to 60 days. Moreover, the scaffold with drug-loaded microspheres was proved to be an effective drug delivery system with good cytocompatibility and antibacterial properties. The novel drug-loaded microsphere/scaffold composites developed in this study are promising to serve as vehicles for controlled drug delivery in bone regeneration or bone tissue engineering.

Nano-hydroxyapatite/polyamide 66 (nHA/PA66) composite with good bioactivity and osteoconductivity was employed to develop a novel porous membrane with asymmetric structure for guided bone regeneration (GBR). In order to test material cytotoxicity and to investigate surface-dependent responses of bone-forming cells, the morphology, proliferation, and cell cycle of bone marrow stromal cells (BMSCs) of rats cultured on the prepared membrane were determined. The polygonal and fusiform shape of BMSCs was observed by scanning electronic microscopy (SEM). The proliferation of BMSCs cultured on nHA/PA66 membrane tested by the MTT method (MTT: [3-{4,5-dimethylthiazol-2yl}-2,5-diphenyl-2H-tetrazoliumbromide]) was higher than that of negative control groups for 1 and 4 days' incubation and had no significant difference for 7 and 11 days' culture. The results of cell cycle also suggested that the membrane has no negative influence on cell division. The nHA/PA66 membranes were then implanted into subcutaneous sites of nine Sprague Dawley rats. The wounds and implant sites were free from suppuration and necrosis in all periods. All nHA/PA66 membranes were surrounded by a fibrous capsule with decreasing thickness 1 to 8 weeks postoperatively. In conclusion, the results of the in vitro and in vivo studies reveal that nHA/PA66 membrane has excellent biocompatibility and indicate its use in guided tissue regeneration (GTR) or GBR.

Implant-associated bacterial infection can jeopardize the clinical success of implants and result in loss of supporting bone. The purpose of this study was to develop a novel porous scaffold with long-term antibacterial activity for bone repair or regeneration. Porous nano-hydroxyapatite/titania/polyamide66 scaffolds containing different amounts of silver ions (Ag-nHA/TiO(2)/PA66) were prepared by a phase inversion technique. The release of silver ions from the porous scaffolds in simulated body fluid (SBF) and in the F12 cell culture medium was evaluated via atomic absorption spectrometry. The results showed that the release of Ag(+) was time and concentration dependent, increasing with the immersion time and the silver content in the scaffolds. On the other hand, the release property of Ag(+) was also influenced by the immersion medium. The cumulative Ag(+) release in the F12 medium with time increase parabolically, different from the linear increase or the zero-order release kinetics in the SBF medium. Compared to the slight fluctuation of the Ag(+) release rate in SBF during the whole immersion period, the initial fast release rate and the later sustained release rate of Ag(+) in the F12 medium could be more helpful for preventing implant-associated infection. Since the Ag-nHA/TiO(2) particles were embedded in the PA66 matrix, the long-term-sustained release should be related both to the relaxation of PA macromolecular chains due to the penetration of water and to the slow release of the substituted Ag(+) ions in the HA lattice. The sustained Ag(+) release with time indicates that the composite scaffold is suitable for a long-term antimicrobial application during the scaffold-assisted bone repair or regeneration.

In this article gentamicin (GM) impregnated microspheres were used to extend the drug release time for the treatment of chronic osteomyelitis. The granules were prepared in solution and consisted of nanohydroxyapatite (nHA), chitosan (CS) and GM loaded ethyl cellulose (EC) microspheres. A rabbit model with chronic osteomyelitis was made by using staphylococcus aureus and morrhuate sodium and special inspection methods were used to test the curative effects of the granules, such as microbiological investigations, tissue, and X-ray observations. The granules were provided with excellent drug release properties, 49 days in vitro and 45 days in vivo, moreover, they showed almost no cytotoxic for fibroblast and osteoblast. The findings indicated that the GM-impregnated CS/nHA/EC microspheres granules showed outstanding curative effect. Generally, it can be concluded that the granules containing GM impregnated microspheres may be used effectively in the treatment of the chronic osteomyelitis.

Objective: To evaluate the effects of the nano-hydroxyapatite/polyamide 6 (n-HA/PA6) on the proliferation and osteoblastic differentiation of rat bone marrow mesenchymal stem cells (BMSCs), and the feasibility of using both for constructing tissue engineered bone in the calvarias of rats with critical sized defects., Methods: The third passage of BMSCs were cultured in osteoblastic medium and seeded on the scaffolds of n-HA/PA6, the proliferation of the BMSCs was tested by MTT (3-{4,5-dimethylthiazol-2yl}-2,5-diphenyl-2H-tetrazolium-bromide) on scheduled dates, and the osteoblastic differentiation of the BMSCs were measured by alkaline phosphatase (ALP) staining. Furthermore, the scaffolds with or without BMSCs in rat calvarial defects, after 4 weeks, 8 weeks, and 16 weeks have been implanted. Histology and scanning electron microscope were used to test the bone healing in the different groups., Results: The BMSCs seeded on the n-HA/PA6 grew well, the proliferation of cells was not affected by the scaffold, and the staining of ALP was also positive. At 4 week and 8 week after implantation, the n-HA/PA6 with BMSCs showed more new bone formation on the surface of scaffolds, with a better osseointegration of implant and host bone when compared with the group of n-HA/PA6 without BMSCs. However, there was no significant difference between these two groups at 16 week., Conclusion: The porous n-HA/PA6 has no negative effects on the proliferation and osteoblastic differentiation of rat BMSCs, and using BMSCs as seed cells and n-HA/PA6 as scaffolds is a good choice for constructing tissue engineered bone due to the enhanced new bone formation and osseointegration.

Polymer nano-composite membranes, based on aliphatic biodegradable polyurethane (PU) elastomers and nano-hydroxyapatite (n-HA), were prepared by solvent casting and freeze-drying. The PU matrix was synthesized from 4,4'-dicyclohexylmethane diisocyanate (H(12) MDI), poly(ethylene glycol) (PEG), castor oil (CO) and 1,4-butandiol (BDO). The n-HA/PU membranes were characterized by SEM, XRD, IR, TG, mechanical test and in vitro biocompatibility. The results revealed that incorporation of 30 wt% n-HA into the PU matrix increased the tensile strength nearly by 186% and the elongation-at-break by 107% compared to pure PU. The addition of n-HA had the slight positive effect on the thermal stability of PU. Cell culture and MTT assays showed that the incorporation of n-HA into the PU matrix provided a favourable environment for initial cell adhesion, maintained cell viability and cell proliferation. These results suggested that the n-HA/PU composite membrane might be a prospective biodegradable guided bone regeneration (GBR) membrane for future applications.

Nano hydroxyapatite (n-HA) crystals carrying incorporated Fe ions were designed and synthesized by a co-precipitation method. The microstructure and morphology as well as magnetic property of the Fe-incorporated n-HA crystals (denoted as n-Fe-HA) were characterized by TEM, XRD and VSM. The results showed that lattice substitution or incorporation had occurred between Fe ions and n-HA, which was quite different from the mechanical mixture of Fe3O4 nanoparticles and n-HA crystals. The n-Fe-HA with a synthetic molar ratio of 1:2 (calculated by Fe3O4:HA) exhibited a needle like crystal shape and relatively good crystallinity. However, when the molar ratio was up to 1:1, some Fe3O4 nanoparticles were separated from n-Fe-HA crystals. The magnetization measurements showed that n-Fe-HA crystals were in superparamagnetic state, proving that the existence of Fe ions in n-HA crystals contributed to the magnetic properties of n-Fe-HA crystals. As one component of biomedical composite, n-Fe-HA has a potential to promote bone regeneration.

In the present study, a calcium carbonate and calcium oxide loaded nano-hydroxyapatite/chitosan bone cement was developed and its in vitro cell responses were investigated. The physico-chemical properties were represented in terms of setting time, compressive strength, and wettability. The results show that the setting time is about 15 min, the compressive strength is up to 17.80 +/- 0.45 MPa throughout the immersion period, and the static contact angle of the cement against water is 33.5 degrees +/- 2.7 degrees, indicating that the cement has good setting time, compressive strength, and wettability. Cytocompatibility test using human MG63 cells reveals a favorable cell viability and increased proliferation over a period of 11 days in culture. The composition and hydrophilic nature of the cement provide a friendly environment for the attachment and growth of cells. The novel composite bone cement could be useful in moderate stress-bearing applications of bone repair., ((c) 2008 Wiley Periodicals, Inc.)

Different concentrations of berberine were mixed with nano-hydroxyapatite/chitosan (n-HA/CS) bone cement to generate an antibiotic drug delivery system for treatment of bone defects. Properties of the system such as setting time, compressive strength, surface morphology, phase compositions, drug release profiles and antimicrobial activity were also characterized. It was shown that the setting time of the cement ranged from 17.03 +/- 0.50 min to 28.47 +/- 0.96 min and the compressive strength changed from 184.00 +/- 7.94 MPa to 120.33 +/- 9.02 MPa with the increase of berberine. The XRD, IR, and SEM analyses suggested that berberine powders were stable in the bone cement in simulated body fluid (SBF). In vitro release of berberine from the bioactive bone cement pellets in SBF could last more than 4 weeks. The release profiles of 1.0 wt % berberine loaded bone cement followed the Higuchi equation at the infusion stage. The drug loaded pellets can inhibit bacterial growth (Staphylococcus aureus) at the standardized berberine minimum inhibitory concentration of 0.02 mg/mL during berberine release from 1 to 28 days. The n-HA/CS bone cement only with 1.0 wt % berberine proved to be an efficient antibiotic drug delivery system., (Copyright 2008 Wiley Periodicals, Inc.)

In this study, a nano-hydroxyapatite/polyamide 66 (nHA/PA66) composite with good biocompatibility and high bioactivity is employed to develop novel asymmetric structure porous membranes for guided bone regeneration (GBR). FT-IR and XRD analyses suggest that chemical bonds are formed between nHA and PA66 both in composite powders and membranes. The fabricated membranes show gradient porous structure. SEM analysis reveal that pores less than 10 microm and pores with a size ranging from 30 microm to 200 microm distribute in the micropore layer and the spongy structure layer, respectively. The surface energy determination also reveals that the fabricated membranes have asymmetric surface properties on the two sides of the membrane. The incorporation of nHA in PA66 matrix improves the properties of the membrane. The elongation at break and the tensile strength of nHA/PA66-40 suggest that the composite membrane has good strength and toughness. The rough porous structure surface with high surface energy of nHA/PA66 composite membrane may be beneficial to promote cells immobility and differentiation into a mature phenotype producing mineralized matrix. The biocompatibility, bioactivity, osteoconductivity, asymmetric porous structure, mechanical properties and hydrophilicity of the composite membrane can meet the requirement of GBR technique.

Nanohydroxyapatite (n-HA)/zinc oxide (ZnO) complex was synthesized by a direct precipitation method, and the antibacterial capability and antibacterial mechanism of this complex were investigated in this article. Transmission electron microscope (TEM), Fourier transform infrared, X-ray photoelectronic spectroscopy (XPS), and X-ray diffraction (XRD) were used to analyze the materials. In addition, the antibacterial capacity of n-HA/ZnO complex was examined by bacteriolytic plate, inhibition effect, and antibacterial rate assays under light or without light. Furthermore, agarose gel electrophoresis of plasmid DNA (pUC18) was used to study biocidal action of this complex. The results of TEM observation revealed that the complex's rods had a single crystalline obelisk-like hexagonal wurtzite structure and the crystal retained the nanometer size. XRD analysis indicated that the phase of ZnO appeared and the lattice parameters of n-HA and ZnO changed. XPS spectra showed that the bonding energy of Ca, P, and O atoms changed in the complex. The analyses also showed that the two phases of ZnO and n-HA combined closely. Further, the results of the antibacterial test revealed that this complex possessed strong antibacterial capability; the antibacterial rate was 99.45% to S. aureus and 95.65% to E. coli under light, respectively. The antibacterial activity of this complex under light was better than without light, which was attributed to the generation of .OH under light. From the agarose gel electrophoresis, the dissolving solution of this complex could catalyze the cleavage of pUC18.

A novel porous composite material composed of hydroxyapatite, poly(vinyl alcohol) (PVA), and gelatin (Gel) was fabricated by emulsification. Scanning electron microscopy showed that the material had a well-interconnected porous structure including many macropores (100-500 microm) and micropores (less than 20 microm) on their walls. The composite had a porosity of 78% and showed high water absorption up to 312.7% indicating a good water-swellable behavior that is a characteristic of hydrogel materials. When immersed in water, the scaffold's weight continuously decreased. After immersion in simulated body fluid, the weight continuously increased because Ca(2+) and PO(3-) (4) ions deposited on the surface and the internal surfaces of the material pores. The deposit was proved to be carbonated hydroxyapatite by thin-film X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray analysis. The composite was detected to be non-cytotoxicity by MTT assay. The HA/PVA/Gel material was also implanted subcutaneously in the dorsal region of adult female rats. After 12 weeks of implantation, the porous material adhered tightly with the surrounding tissue, and the ingrowth of fibrous tissue as well as the material's partial degradation was observed, which partly indicated that the composite was biocompatible in vivo. In conclusion, the porous HA/PVA/Gel composite is a promising scaffold for cartilage tissue engineering with more studies., (Copyright 2007 Wiley Periodicals, Inc.)

Nano-hydroxyapatite (n-HA)/chitosan (CS)/konjac glucomannan (KGM) composite was prepared by coprecipitation method and investigated by thermal gravitivity/differentiate thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, inductively coupled plasma emission spectroscopy, scanning electron microscopy, and energy dispersive X-ray analyzer. The analyses showed that the three phases of n-HA, CS, and KGM combined closely to each other. Further, in vitro tests were conducted to investigate the degradation and bioactivity of the composite. During immersion in simulated body fluid (SBF), pores appeared and a new substance containing Ca and P formed on the surface of the composite. Also, the concentration of Ca and P in SBF changed and weight loss of the composite was observed during time. The composite revealed a high degradation in SBF. Evidently, the new composite has a potential to be used as a carrier of implantable drug delivery system. The biodegradation rate and route could be different from CS and KGM, which will provide an opportunity to control the degradation rate or drug releasing rate by simply adjusting the ratio of CS and KGM., ((c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.)

In this study, we prepared nano-hydroxyapatite/polyamide (n-HA/PA) composite scaffolds utilizing thermally induced phase inversion processing technique. The macrostructure and morphology as well as mechanical strength of the scaffolds were characterized. Mesenchymal stem cells (MSCs) derived from bone marrow of neonatal rabbits were cultured, expanded and seeded on n-HA/PA scaffolds. The MSC/scaffold constructs were cultured for up to 7 days and the adhesion, proliferation and differentiation of MSCs into osteoblastic phenotype were determined using MTT assay, alkaline phosphatase (ALP) activity and collagen type I (COL I) immunohistochemical staining and scanning electronic microscopy (SEM). The results confirm that n-HA/PA scaffolds are biocompatible and have no negative effects on the MSCs in vitro. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both pure n-HA/PA scaffolds and MSC/scaffold constructs were implanted in rabbit mandibles and studied histologically and microradiographically. The results show that n-HA/PA composite scaffolds exhibit good biocompatibility and extensive osteoconductivity with host bone. Moreover, the introduction of MSCs to the scaffolds dramatically enhanced the efficiency of new bone formation, especially at the initial stage after implantation. In long term (more than 12 weeks implantation), however, the pure scaffolds show as good biocompatibility and osteogenesis as the hybrid ones. All these results indicate that the scaffolds fulfill the basic requirements of bone tissue engineering scaffold, and have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery.

In order to improve the bonding strength of the hydroxyapatite (HA) coatings on the metal substrate, we prepared the HA-Ti/HA composite coatings by two-step electrodeposited method, and then we studied the component, microstructure, surface morphologies and the bonding strength of the HA-Ti/HA composite coatings. SBF test and cell culture in vitro were carried out to evaluate the biological properties of the composite coatings. The results showed that the bonding strength of the HA-Ti/HA composite coating (Ti, 51.2wt%) was as high as 21.2 MPa which was 3 times that of pure HA coatings. The coatings' surface was covered by carbonate-apatite layer after being immersed in SBF, and the bone marrow cells attached firmly and proliferated well on the surface of composite coatings. These findings indicate that the composite coatings possess good bioactivity and excellent biocompatibility.

The aim of this study was to evaluate the injectability, histocompatibility, function and other properties of the injectable bioactive bone repairing material of nano-hydroxyapatite and polyamide-66 (n-HA/PA66) composite. The XRD pattern, the relationship between the injectability and liquid-powder ratio, setting time and liquid-powder ratio, compressive strength and liquid-powder ratio were assessed. The size of the composite was determined to be 70 nm in length and 30 to 50 nm in width, and the molecular weight of polyamides-66 was 18000. The diameter of pores of the composite was about 200 to 400 micrometer. To evaluate the histocompatibility and function, 8 male dogs were studied with the injectable n-HA/PA66 composite implanted in the artificial defected alveolus of mandible on only one side to be compared with the intact alveolus on the other side. The specimens were taken at 4, 8, 12, 16 months after the implantation and the results were evaluated. The XRD pattern of the solidificated n-HA/PA66 composite was the same as the powdered n-HA/PA66 composite. The injectable n-HA/PA66 composite had a good injectability, 25 to 30 minutes setting time and about 37 MPa compressive strength when the liquid-powder ratio was 0.50. The healing of the gingiva was well at the implanted areas in all animals. The height of the repaired alveolar bone was obvious higher than that of the blank control. The earlier sign of ossification was histologically observed at 16 weeks after implantation. The injectable n-HA/PA66 composite has good biocompatibility and osteoconductive property. As an injectable material, with good maneuverability, it is useful for repairing irregular bone defects, especially in oral and maxillofacial surgery.