Natural origin hydroxyapatite scaffold as potential bone tissue engineering substitute

Fish scales derived natural hydroxyapatite (FS-HAp) scaffolds were prepared through solvent casting technique, which could mimic the structure of cortical and cancellous bone tissues of body system. The hydroxyapatite (HAp) biomaterial was synthesized by thermal decomposition of chemically treated fish scales. Fabricated scaffolds were characterized through morphological analysis, volumetric shrinkage, mechanical tests, and in vitro, in vivo biological studies. The projected scaffolds successfully mimic the cancellous/cortical bone system in terms of structure, porosity, mechanical strength, and exhibit excellent bioactive behavior. The FS-HAp scaffolds manifest good mechanical behaviors with Vickers Hardness (HV) of ~0.78 GPa, 0.52 GPa compressive stress, 190 MPa tensile stress and ~35% porosity on sintering at 1200 °C. In vitro and in vivo studies suggest these nontoxic HAp scaffolds graft with osteoconductive support, facilitating new cell growth on the developed scaffold surface. The graded grafts have a great potential for application as traumatized tissue augmentation substitute, and ideal for load-bearing bone applications.     

Fabrication and characterization of 3-dimensional PLGA nanofiber/microfiber composite scaffolds

Novel three-dimensional (3-D) nano-/microfibrous poly(lactic-co-glycolic acid) (PLGA) scaffolds were fabricated by hybrid electrospinning, involving a combination of solution electrospinning and melt electrospinning. The scaffolds consisted of a randomly oriented structure of PLGA microfibers (average fiber diameter = 28 μm) and PLGA nanofibers (average fiber diameter = 530 nm). From mercury porosimetry, the PLGA nano-/microfiber (10/90) scaffolds were found to have similar pore parameters to the PLGA microfiber scaffolds. PLGA nano-/microfibrous scaffolds were examined and compared with the PLGA microfiber scaffolds in terms of the attachment, spreading and infiltration of normal human epidermal keratinocytes (NHEK) and fibroblasts (NHEF). The cell attachment and spreading of both cell types were several times higher in the nano-/microfiber composite scaffolds than in the microfibrous scaffolds without nanofibers. This shows that the presence of nanofibers enhanced the attachment and spreading of the cells on the nano-/microfiber composite scaffolds. Moreover, the nanofibers helped the cells infiltrate easily into the scaffolds. Overall, this novel nano-/microfiber structures has great potential for the 3-D organization and guidance of cells provided for tissue engineering.     

Influence of carrier particle size, carrier ratio and addition of fine ternary particles on the dry powder inhalation performance of insulin-loaded PLGA microcapsules

The effects of carrier particle size, carrier ratio and addition of fine ternary agents on dry powder inhalation performance of insulin-loaded PLGA microcapsules were investigated. The use of mannitol with larger particle size in the lower carrier/microcapsules ratio led to higher deposition profiles of the drug. The fine spray dried mannitol and spray dried leucine as the ternary agents both decreased the deposition and dispersibility of microcapsules. It was concluded that addition of ternary component does not always improve aerosolization properties of DPI formulations. Carrier particle size, its flowability and carrier-drug ratio were shown to play an important role in DPI formulations.     

A porous hydroxyapatite scaffold for bone tissue engineering: Physico-mechanical and biological evaluations

Polymer sponge replication method was used in this study to prepare the macroporous hydroxyapatite scaffolds with interconnected oval shaped pores of 100-300 μm with pore wall thickness of ∼50 μm. The compression strength of 60 wt.% HA loaded scaffold was 1.3 MPa. The biological response of the scaffold was investigated using human osteoblast like SaOS2 cells. The results showed that SaOS2 cells were able to adhere, proliferate and migrate into pores of scaffold. Furthermore, the cell viability was found to increase on porous scaffold compared to dense HA. The expression of alkaline phosphate, a differentiation marker for SaOS2 cells was enhanced as compared to nonporous HA disc with respect to number of days of culture. The enhanced cellular functionality and the ability to support osteoblast differentiation for porous scaffolds in comparison to dense HA has been explained in terms of higher protein absorption on porous scaffold.     

Development and in vivo response of hydroxyapatite/whitlockite from chicken bones as bone substitute using a chitosan membrane for guided bone regeneration

Biomaterials that meet the requirements to stimulate bone tissue formation play a vital role in orthopedics and dentistry. In this work, chitosan and a biphasic, non-cytotoxic material hydroxyapatite/whitlockite were obtained from natural sources, which are available as organic waste. The osteogenic activity was assessed using a rabbit model animal with a chitosan barrier membrane in combination with a bone-filling graft substitute composed of hydroxyapatite/whitlockite. FT-IR results showed the typical absorption bands of the chitosan and hydroxyapatite. Moreover, the X-ray diffraction pattern revealed a typical hexagonal phase of hydroxyapatite and rhombohedral structures related to whitlockite. Masson's trichrome stain showed an early formation of extracellular matrix mineralized, in accord with the surface morphology of a cortical mature bond observed by Scanning Electron Microscopy. The immunocytochemistry results showed a significant increase of positive immunoreactive cells to osteonectin in the treated defects in comparison with the control defects 6 and 8 weeks postoperatively. Overall, the results confirm that the use of this low-cost and versatile biomaterial as a barrier membrane and a bone substitute graft are useful for bone tissue engineering.     

Preparation of a hemiporous hydroxyapatite scaffold and evaluation as a cell-mediated bone substitute

A hemiporous hydroxyapatite (HAp) scaffold was prepared to support the tissue engineered approach to the restoration of damaged bone. The scaffold comprised a porous cell-seeded part and a non-porous load bearing part. A wet processing technique of HAp suspensions was used to shape the hemiporous body. The structure of the porous part was tailored using a stack of heat treated porogen placed on the plaster. The prepared specimen had approximately 30 layers of connected pores, which could accommodate sufficient human bone marrow stromal cells (hBMSCs). The result of an in vitro test showed that hBMSCs successfully proliferated and produced extracellular matrices even at the pore in the deep portion of the scaffolds. The in vivo test in the distal femur of a rabbit showed the formation of new fibrous tissue and tubular vessels with red blood cells in the hBMSCs-seeded scaffold from the pores at the deepest portion as well as from the pore at the periphery of the scaffold. The result was in distinct contrast with the scaffold without cell loading. The preloading of cell was thus very effective in the migration of cells in spite of the unconfirmed connectivity among pores. The present casting approach had the merits of simplicity and versatility in tailoring the scaffold structure without an elaborate device.     

Mechanochemical synthesis and cold sintering of mussel shell-derived hydroxyapatite nano-powders for bone tissue regeneration

According to the circular economy principles, processing routes aiming at reducing the natural resources consumption and the energy demand can be addressed as ‘green’. In this framework, mussel shells, a natural feedstock of calcium carbonate, were successfully transformed into nano-crystalline hydroxyapatite by mechanochemical synthesis at room temperature after mixing with a phosphoric acid solution. The as-synthesized powder was then consolidated up to 82 % relative density by cold sintering (600 MPa, 200 °C). The materials were fully investigated by physical, chemical and thermal characterization techniques. Cold-sintered samples were also subjected to biaxial flexural strength test, showing a flexural resistance of 23 MPa. Cell viability assessment revealed that cold sintered hydroxyapatite derived from mussel shells promotes faster adhesion and spreading of human bone marrow-derived mesenchymal stem cells, in comparison to a commercial hydroxyapatite sintered at 1050 °C. Therefore, cold-sintered mussel shells-derived hydroxyapatite can be a promising future candidate scaffold for bone tissue regeneration.     

Synthesis of ultralong hydroxyapatite micro/nanoribbons and their application as reinforcement in collagen scaffolds for bone regeneration

Ultralong hydroxyapatite (HAp) micro/nanoribbons were successfully synthesized by a simple hydrothermal method without using any organic solvents and templates. The ultralong HAp micro/nanoribbons were up to several hundred micrometers in length and 100–400?nm in width. The growth process and mechanism of this micro/nanoribbons were also analyzed in this study. Moreover, the ultralong HAp micro/nanoribbons were used as reinforcement in collagen scaffolds and the HAp/collagen composite scaffolds were fabricated by freeze-drying process without cross-linking. The morphological results demonstrated homogeneous interconnected porous structure in 20?wt% and 35?wt% HAp reinforced scaffolds. The compressive modulus of the 35?wt% HAp/collagen composite was about 6 times that of the pure collagen scaffold. The ultralong HAp reinforced collagen scaffold possesses a porous structure, good flexibility as well as elasticity, and thus it is promising for used as bone repair material.     

Infection‐resistant hyperbranched epoxy nanocomposite as a scaffold for skin tissue regeneration

Implantable devices and scaffolds are recently the focal points of biomedical research to address various human ailments. Infections associated with such appliances face severe consequences. In this report, hyperbranched epoxy/clay ? silver nanocomposites are shown to be an infection‐resistant tough implantable scaffold material. ‘Green’ silver nanoparticle embedded nanocomposites with varying percentages of nanoparticles were prepared by an ex situ technique. The thermosetting nanocomposites demonstrated an improvement of mechanical properties (tensile strength from 38 to 60 MPa) and adhesive strength from 768 to 2819 MPa compared with the pristine polymeric system. The nanocomposite surface inhibited the growth of antibiotic‐resistant microbes such as Staphylococcus aureus, Escherichia coli and Candida albicans which are mostly responsible for surgical infections. The material is highly compatible with primary liver and cardiac cell lines of wistar rat. In vivo implantation of the material fostered wound healing in wistar rat. Hematological and histopathological parameters of the tested animals confirmed the compatibility of the scaffold with the in vivo system. Thus, the study forwards the nanocomposite as a potential infection‐resistant implantable scaffold for skin tissue regeneration. © 2014 Society of Chemical Industry     

Bi-/multi-modal pore formation of PLGA/hydroxyapatite composite scaffolds by heterogeneous nucleation in supercritical CO2 foaming

Scaffolds with multimodal pore structure are essential to cells differentiation and proliferation in bone tissue engineering.Bi-/multi-modal porous PLGA/hydroxyapatite composite scaffolds were prepared by supercritical CO_2 foaming in which hydroxyapatite acted as heterogeneous nucleation agent.Bimodal porous scaffolds were prepared under certain conditions,i.e.hydroxyapatite addition of 5%,depressurization rate of 0.3 MPa·min~(-1),soaking temperature of 55℃,and pressure of 9 MPa.And scaffolds presented specific structure of small pores(122 μm±66 μm)in the cellular walls of large pores(552μm±127μm).Furthermore,multimodal porous PLGA scaffolds with micro-pores(37 μm±11 μm)were obtained at low soaking pressure of 7.5 MPa.The interconnected porosity of scaffolds ranged from(52.53±2.69)% to(83.08±2.42)%by adjusting depressurization rate,while compression modulus satisfied the requirement of bone tissue engineering.Solvent-free CO_2 foaming method is promising to fabricate bi-/multi-modal porous scaffolds in one step,and bioactive particles for osteogenesis could serve as nucleation agents.     

Fabrication and characterization of aligned nanofibrous PLGA/Collagen blends as bone tissue scaffolds

Aligned nanofibrous blends of poly (d, l-lactide-co-glycolide) (PLGA) and collagen with various PLGA/collagen compositions (80/20, 65/35 and 50/50) were fabricated by electrospinning and characterized for bone tissue engineering. Morphological characterization showed that the addition of collagen to PLGA resulted in narrowing of the diameter distribution and a reduction in average diameter. Differential scanning calorimetric (DSC) studies showed that the triple helix structure of the native collagen was not destroyed during the fabrication process. However, the blending had a marked effect on the overall enthalpy of the blends, whereby the total enthalpy decreased as the collagen content decreased. Thermogravimetric analysis showed the addition of collagen increased the hydrophilicity of the scaffolds. The crosslinking of collagen to increase the biostability was done using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in ethanol and an overall ∼25% degree of crosslinking was achieved. The EDC crosslinking had little effect on the nanofibrous morphology of the 80/20 blend system; however, the nanofibrous features were compromised to some extent at higher collagen concentrations. The mechanical characterization under dry and wet conditions showed that increasing collagen content resulted in a tremendous decrease in the mechanical properties. However, crosslinking resulted in the increase in elastic modulus from 47 MPa to 83 MPa for the wet PLGA/Collagen 80/20 blend system, with little effect on the tensile strength. In conclusion, the aligned nanofibrous scaffold used in this study constitutes a promising material for bone tissue engineering.     

Biomimetic porous collagen/hydroxyapatite scaffold for bone tissue engineering

Bone defect and osteochondral injury frequently occur due to diseases or traumatism and bring a crucial challenge in orthopedics. The hybrid scaffold has shown promise as a potential strategy for the treatment of such defects. In this study, a novel biomimetic porous collagen (Col)/hydroxyapatite (HA) scaffold was fabricated through assembling layers of Col containing gradual amount of HA under the assistance of “iterative layering” freeze‐drying process. The scaffold presents a double gradient of highly interconnected porosity and HA content from top to bottom, mimicking the inherent physiological structure of bone. Owing to the biomimetic structure and component, significant increase of cell proliferation, alkaline phosphatase activity, and osteogenic differentiation in vitro was observed, illustrating potential application of the excellent Col/HA scaffold as a promising strategy for bone tissue engineering. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45271.     

Application of natural rubber latex as scaffold for osteoblast to guided bone regeneration

Natural rubber latex (NRL) from Hevea brasiliensis is a colloidal system composed of cis ‐1,4‐polyisoprene. Its applications have grown due its angiogenic and wound healing activity. NRL has been used in guided bone regeneration as barrier, enhancing bone formation. However, there has been no study reported so far which shows its in vitro biocompatibility with osteoblasts. Thus, the aim of this work was to apply thermally induced phase separation under several temperatures to induce porosity in NRL; and test its mechanical properties, cytotoxicity, cell adhesion, and mineralization with MC3T3‐E1. Only biomembranes submitted at ?20 and ?10 °C presented porosity. Fourier transform infrared spectroscopy showed no change in cis ‐1,4‐isoprene spectra. Biomembranes were elastic (Young's modulus < 1 MPa). According to ISO10993–5, NRL showed no cytotoxicity. Cells adhered on the NRL and produced mineral matrix as analyzed by scanning electron microscopy–energy‐dispersive spectrometry, von kossa, and Fourier transform infrared spectroscopy. Cells on NRL presented higher alkaline phosphatase activity, however, mineralization showed no difference by alizarin red S dye extraction. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45321.     

PLGA based drug delivery systems (DDS) for the sustained release of insulin: insight into the protein/polyester interactions and the insulin release behavior

BACKGROUND: Drug delivery systems (DDS) were designed using insulin as model drug and poly (lactic–co‐glycolic) copolymers (PLGA) as polymeric matrix. The carriers were synthesized by direct self‐assembly of the insulin and the polyester under mild conditions. RESULTS: The kind and level of association between the protein and the polymer were studied using computational methods (combined MM2/PM3) and spectroscopic tools (Fourier transform infrared (FTIR), energy dispersive X‐ray (EDX) and X‐ray fluorescence spectroscopy (XFS)). The effect of the number average molecular weight (M_n) of the copolymer on the association efficiency (AE) drug–polymer as well as on the release profile has been explored. Mathematical models were used to predict the insulin release kinetic and mechanism. CONCLUSIONS: Satisfactory protein/PLGA association efficiencies (between 77 and 99%) were registered depending on the M_n of the PLGA. Hydrophobic and hydrophilic interactions were detected between the protein and the polymeric network by computational analysis. In vitro release studies demonstrated that copolyesters of about 8600 and 1500 Da were suitable for the gradual release of insulin while PLGA oligomers of average molecular weight between 700 and 800 Da were unsuitable as DDS. The insulin release kinetics fits well with the Korsmeyer model, following the anomalous transport mechanism. Copyright © 2010 Society of Chemical Industry     

Inorganic calcium filled bacterial cellulose based hydrogel scaffold: novel biomaterial for bone tissue regeneration

Abstract

This work emphasizes the structural, physio-chemical characterization and cell biological efficiency analysis of novel inorganic calcium (only calcium phosphate and in combination of calcium phosphate & CaCO₃) filled bacterial cellulose (BC) based hydrogel scaffolds. FTIR and TG analysis indicates the presence of BC and inorganic calcium within the hydrogel scaffolds. SEM establishes the porous structures (50–200 µm). Swelling study indicates significant swelling ability in both calcium phosphate filled and calcium phosphate & CaCO₃ filled hydrogel scaffolds. Compressive strength (0.24–0.60?MPa) of the calcium filled hydrogel scaffolds are similar like trabecular bone. Significant cell viability (Lep-3) was further noticed until 72,120 and 168?h.     

阳离子PLGA纳米颗粒作为核酸疫苗递送载体的能力及其特性评价

目的对阳离子聚乳酸-羟基乙酸共聚物[poly(D,L-lactide-co-glycolide),PLGA]纳米颗粒作为核酸疫苗载体的能力及其特性进行评价。方法采用双重乳化法制备阳离子PLGA纳米颗粒,检测其粒径分布和表面电势,获得合成的最适方案。通过考察其形貌、吸附效率、抵抗核酸酶降解能力、细胞毒性、细胞摄取及转染真核表达质粒的能力,分析其作为核酸疫苗载体的适用性及可行性。结果由两种试剂修饰PLGA制备的纳米颗粒粒径分布、表面电势及分散性最佳;透射电镜及扫描电镜下观察粒径均一且呈规则球形;对质粒DNA的吸附效率可达65%;能够有效保护吸附于纳米颗粒的质粒DNA免受核酸酶降解;两种细胞系中的细胞毒性试验均显示细胞存活率高于80%;共聚焦显微镜下可观察到其能被细胞内化;间接免疫荧光试验结果表明,其能有效转染真核表达质粒并使其正确表达。结论成功制备了具有递送核酸疫苗能力的阳离子PLGA纳米颗粒,为核酸疫苗载体的发展奠定了理论基础。     

Glutaraldehyde‐crosslinked chitosan/hydroxyapatite bone repair scaffold and its application as drug carrier for icariin

Chitosan/hydroxyapatite (CS/HA) bone repair scaffolds crosslinked by glutaraldehyde (GA) were prepared. Characterization of morphology, structure, mechanical property, and porosity of scaffolds were evaluated. The influences of CS viscosity, HA content, and crosslinking degree on properties of scaffolds were discussed. SEM images showed that CS/HA scaffolds were porous with short rod‐like HA particles dispersing evenly in CS substrate. When [η]_CS = 5.75 × 10^?4, HA content = 65%, and crosslinking degree = 10%, the resulting CS/HA scaffolds had a flexural strength of 20 MPa and porosity of 60%, which could meet the requirements of bone repair materials. The scaffolds were used as drug carriers for icariin, and the impacts of loading time and crosslinking degree of scaffolds on drug‐loading dose were discussed. The suitable loading time was 24 h and it would be better to keep crosslinking degree no more than 10%. The drug release behavior demonstrated that the icariin‐loading CS/HA scaffolds could achieve basic drug sustained release effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1539–1547, 2013     

Peptide‐functionalized reduced graphene oxide as a bioactive mechanically robust tissue regeneration scaffold

Bioactive, synthetic materials represent next‐generation composites for tissue regeneration. Design of contemporary materials attempts to recapitulate the complexities of native tissue; however, few successfully mimic the order in nature. Recently, graphene oxide (GO ) has emerged as a scaffold due to its potential for bioactive functionalization and long‐range order instilled by the self‐assembly of graphene sheets. Chemical reduction of GO results in a more compatible material with enhanced properties but compromises the ability to functionalize the graphenic backbone. However, using Johnson–Claisen rearrangement chemistry, functionalization is achieved that is not liable to reduction. From reduced Claisen graphene, we polymerized short homopeptides from α ‐amino acid N ‐carboxyanhydride monomers of glutamate and lysine to result in functionalized graphenes (pGlu‐rCG and pLys‐rCG ) that are cytocompatible, degradable, and bioactive. Exposure to NIH‐3T3 fibroblasts and RAW 264.7 macrophages revealed that the materials are cytocompatible and do not alter important sub‐cellular compartments. Powders were hot pressed to form mechanically stiff (E ′: 41 and 49 MPa ), strong (UCS : 480 and 140 MPa ), and tough (U _T: 2898 and 584 J m^?3 × 10⁴) three‐dimensional constructs (pGlu‐rCG and pLys‐rCG, respectively). Overall, we report a robust chemistry and processing strategy for facile bioactive functionalization of compatible, reduced Claisen graphene for three‐dimensional biomedical applications. © 2017 Society of Chemical Industry     

A simple pathway in preparation of controlled porosity of biphasic calcium phosphate scaffold for dentin regeneration

A simple pathway in preparation of biphasic calcium phosphate scaffold of hydroxyapatite/beta-tricalcium phosphate with controlled pore size, shape and porosity using phosphoric acid and calcium carbonate was successfully developed. Microporosity was controlled by adjusting temperature and soaking time of the sintering process while macroporosity was obtained through addition of polyethylene spherical particles. The advantage of this method is that a highly pure biphasic calcium phosphate scaffold consisting of hydroxyapatite/beta-tricalcium phosphate in a controlled ratio of 20/80 with a mean pore size of 300 μm and 65% porosity can be produced. These properties of scaffold are of high potential for use in dentin regeneration.     

Nano-hydroxyapatite and nano-hydroxyapatite/zinc oxide scaffold for bone tissue engineering application

This research aims to evaluate the mechanical properties, biocompatibility, and degradation behavior of scaffolds made of pure hydroxyapatite (HA) and HA-modified by ZnO for bone tissue engineering applications. HA and ZnO were developed using sol-gel and precipitation methods respectively. The scaffolds properties were characterized using X-ray diffraction (XRD), Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), atomic absorption (AA), and atomic force microscopy (AFM). The interaction of scaffold with cells was assessed using in vitro cell proliferation and alkaline phosphatase (ALP) assays. The obtained results indicate that the HA/ZnO scaffolds possess higher compressive strength, fracture toughness, and density—but lower hardness—when compared to the pure HA scaffolds. After immersing the scaffold in the SBF solution, more deposited apatite appeared on the HA/ZnO, which results in the rougher surface on this scaffold compared to the pure HA scaffold. Finally, the in vitro biological analysis using human osteoblast cells reveals that scaffolds are biocompatible with adequate ALP activity.