Mechanism of in vitro reaction of a new scaffold ceramic similar to porous bone

A new way of obtaining bioactive and biodegradable 3D scaffold ceramics is presented with possible bone tissue engineering requests. This implies achieving eutectoid structures from certain systems by considering the different conduct of phases. In this study, the silicocarnotite-tricalcium phosphate subsystem was selected because silicocarnotite is bioactive and tricalcium phosphate is biodegradable. A biphasic porous calcium silicophosphate scaffold with high porosity and an interconnected macro- and micropores structure is presented. The scaffold’s morphology shows a eutectoid lamellae-type microstructure formed of alternating silicocarnotite and α-tricalcium phosphate layers. The eutectoid scaffold material, when placed in simulated body fluid, responds firstly by dissolving the silicocarnotite phase and then developing a hydroxyapatite microporous structure by pseudomorphic transformation of α-tricalcium phosphate lamellae. The achieved microstructure is like that of porous bone. Afterwards, Si-hydroxyapatite precipitation formed a layer on the scaffold surface by plugging the microporous structure and maintaining the scaffold’s 3D structure intact.     

Fabrication of Bioactive Scaffold of Poly(ɛ-Caprolactone) and Nanofiber Wollastonite Composite

A scaffold of nanofiber wollastonite (nf-WS) and poly(ɛ-caprolactone) (PCL) composite was fabricated, and the morphology, degradation, and cellular response to the scaffold were investigated. The results indicate that the composite scaffold contained open and interconnected pores ranging in size from 400 to 500 μm and exhibited a porosity of around 80%, as well as degradation of the scaffold in phosphate-buffered saline. MTT tests demonstrated that MG₆₃ cell proliferation was greater on the composite scaffold than on PCL alone at 4 and 7 days of culture. Moreover, the level of alkaline phosphatase activity of the cells cultured on the composite scaffold was higher than that in cells grown on PCL alone at 7 days, and scanning electron microscopy revealed significant osteoblast-like adhesion and ingrowth into the composite scaffold. Elevated levels of calcium (Ca) and silicon (Si) were detected in the culture medium during cell culture, and the continuous dissolution of nf-WS produced a Ca- and Si-rich environment that might stimulate cellular proliferation and differentiation. The composite scaffold was bioactive, as indicated by the formation of an apatite layer on the scaffold surface after immersion in cell medium.     

Ultrasonication‐Induced Modification of Hydroxyapatite Nanoparticles onto a 3D Porous Poly(lactic acid) Scaffold with Improved Mechanical Properties and Biocompatibility

A 3D porous poly(lactic acid) (PLA) scaffold with high porosity and well‐connected pores is fabricated using a vacuum‐assisted solvent casting technique. Its surface is modified with hydroxyapatite (HA) nanoparticles using ultrasonication to prepare an HA‐modified PLA/HA scaffold. For reference, an HA‐blended (b‐PLA‐HA) scaffold is fabricated via the solution blending method. The morphology, porosity, hydrophilicity, swelling ratio, mechanical properties, and cell viability of the PLA, b‐PLA‐HA, and PLA/HA scaffolds are systematically studied. The results show that HA nanoparticles are successfully introduced onto the surface of the PLA/HA scaffold, and strong interactions occur between the HA nanoparticles and the PLA matrix. The PLA/HA scaffold still has a high porosity of more than 85% after ultrasonication. The hydrophilicity and mechanical properties of the PLA/HA scaffold are significantly higher than those of the PLA and b‐PLA‐HA scaffolds. Compared with the PLA and b‐PLA‐HA scaffolds, the attachment and growth of mouse embryonic osteoblasts cells (MC3T3‐E1) cultured on the PLA/HA scaffold significantly improve, due to most HA nanoparticles on the surface, resulting in a good and direct interaction between the cells and the scaffold. Therefore, the PLA/HA scaffold possesses great potential to be used as a tissue engineering scaffold.     

Surface Modification of Electrospun TPU Nanofiber Scaffold with CNF Particles by Ultrasound‐Assisted Technique for Tissue Engineering

A straightforward, fast, and versatile technique is developed to fabricate nanofibrous scaffold with excellent hydrophilicity, mechanical properties, and biocompatibility for tissue engineering. The thermoplastic polyurethane (TPU) nanofiber is fabricated by utilizing electrospinning, and then its surface is modified through simply immersing it into cellulose nanofibrils (CNF) dispersion and subjecting to ultrasonication. The results show that the CNF particles are successfully absorbed on the surface of TPU nanofiber. By introducing CNF particles on the surface of TPU nanofiber, the hydrophilicity, mechanical properties of fabricated CNF‐absorbed TPU scaffold are significantly increased. Additionally, the adhesion and proliferation of human umbilical vein endothelial cells cultured on CNF‐absorbed TPU scaffold are prominently enhanced in comparison with those of cultured on TPU scaffold. These findings suggest that the ultrasound‐assisted technique opens up a new way to simply and effectively modify the surface of various scaffolds and the modified scaffold could be shown a great potential in 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.     

组织工程支架材料的研究进展

组织工程支架材料在组织工程研究中起中心作用，它不仅为特定的细胞提供结构支撑怍用，而且还起到模板作用，引导组织再生和控制组织结构。因此，寻找一种既有良好生物相容性和生物降解性又具有特定形状和连通三维多孔结构的支架材料是组织工程的一个重要方面。本文主要对组织工程中常用支架材料的研究进展进行了综述．并对组织工程支架材料目前存在的问题作了分析以及对其发展趋势进行了展望。     

Fabrication and characterization of natural origin chitosan‐ gelatin‐alginate composite scaffold by foaming method without using surfactant

A natural origin tripolymer scaffold from chitosan, gelatin, and alginate was fabricated by applying foaming method without adding any foam stabilizing surfactant. Previously, in foaming method of scaffold fabrication, toxic surfactants were used to stabilize the foam, but in this work, the use of surfactant has been avoided strictly, which can provide better environment for cellular response and viability. In foaming method, stable foam is produced simply by agitating the polymer (alginate‐gelatin) solution, and the foam is crosslinked with CaCl₂, glutaraldehyde, and chitosan to produce tripolymer alginate‐gelatin‐chitosan composite scaffold. Microscopic images of the composite scaffold revealed the presence of interconnected pores, mostly spread over the entire surface of the scaffold. The scaffold has a porosity of 90% with a mean pore size of 57 μm. Swelling and degradation studies of the scaffold showed that the scaffold possesses excellent properties of hydrophilicity and biodegradability. In vitro cell culture studies by seeding L929 mouse fibroblast cells on scaffold revealed excellent cell viability, proliferation rate and adhesion as indicated by MTT assay, DNA quantification, and phase contrast microscopy of cell‐scaffold construct. The natural origin composite scaffold fabricated by the simplest method i.e., foaming method, but without adding any surfactant, is cheap, biocompatible, and it might find potential applications in the field of tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Silk fibroin/chitosan/heparin scaffold: preparation,antithrombogenicity and culture with hepatocytes

Antithrombogenicity is very important for tissue engineering scaffolds used in situations involving contact with blood. A silk fibroin/chitosan (SFCS) scaffold has been developed for liver tissue engineering with porous structure, suitable mechanical properties and biocompatibility. Because the interaction between silk fibroin and blood coagulation factors can lead to blood coagulation, the anticoagulant property of the SFCS scaffold should be improved. Heparin was added into SFCS scaffold under mild conditions. The effects of heparin on the morphology, swelling properties, structure, porosity, mechanical properties, antithrombogenicity and cytocompatibility of the SFCS scaffold were studied. SFCS scaffold containing heparin maintains the porous structure and good mechanical properties of the fibroin‐based scaffold; moreover, it is not cytotoxic. Addition of heparin leads to the SFCS scaffold being blood‐compatible and an effective heparin‐delivering system. The anticoagulant property of the SFCS scaffold can be improved by the addition of heparin, which may be helpful for scaffolds used in situations involving contact with blood. Copyright © 2009 Society of Chemical Industry     

Preparation and characterization of nanohydroxyapatite strengthening nanofibrous poly(L‐lactide) scaffold for bone tissue engineering

A biomimetic nanofibrous poly(L ‐lactide) scaffold strengthened by nanohydroxyapatite particles was fabricated via a thermally induced phase separation technique. Scanning electron microscopy results showed that nanohydroxyapatite particles uniformly dispersed in the nanofibrous poly(L ‐lactide) scaffold (50–500 nm in fiber diameter) with slight aggregation at a high nHA content, but showed no influence on the interconnected macroporous and nanofibrous structure of the scaffold. The nanofibrous poly(L ‐lactide) scaffold presented a specific surface area of 34.06 m² g^?1, which was much higher than that of 2.79 m² g^?1 for the poly(L ‐lactide) scaffold with platelet structure. Moreover, the specific surface area of the nanofibrous scaffold was further enhanced by incorporating nanohydroxyapatite particles. With increasing the nanohydroxyapatite content, the compressive modulus and amount of bovine serum albumin adsorbed on the surface of the nanofibrous composite scaffold were markedly improved, as opposed to the decreased crystallinity. In comparison to poly(L ‐lactide) scaffold, both the nanofibrous poly(L ‐lactide) and poly(L ‐lactide)/nanohydroxyapatite scaffolds exhibited a faster degradation rate for their much larger specific surface area. The culture of bone mesenchymal stem cell indicated that the composite nanofibrous poly(L ‐lactide) scaffold with 50 wt % nanohydroxyapatite showed the highest cells viability among various poly(L ‐lactide)‐based scaffolds. The strengthened biomimetic nanofibrous poly(L ‐lactide)/nanohydroxyapatite composite scaffold will be a potential candidate for bone tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Pharmacokinetic Studies around the Mono‐ and Difunctionalization of a Bioavailable Cyclic Decapeptide Scaffold

We previously reported the design of several cyclic decapeptides based on a generic scaffold that achieved favorable oral bioavailability and exposure. With the goal to further investigate the potential of this approach, we describe herein the effect of mono‐ and difunctionalization of this scaffold. A series of cyclic decapeptides were therefore subjected to a range of in vitro assays and pharmacokinetic (PK) studies to investigate whether the introduction of polar or charged groups could be tolerated by the “engineered” scaffold while maintaining good PK profiles. Whereas the introduction of charged amino acids proved—besides maintaining low clearance—to conceal the inherent PK properties of the scaffold, the introduction of polar amino acids (i.e., threonine and pyridyl alanine) led to several cyclic decapeptides exhibiting excellent PK profiles together with a solubility that was significantly improved relative to that of previously reported cyclic decapeptides.     

Self-assembly of protein monolayers engineered for improved monoclonal immunoglobulin g binding

Bacterial outer membrane proteins, along with a filling lipid molecule can be modified to form stable self-assembled monolayers on gold. The transmembrane domain of Escherichia coli outer membrane protein A has been engineered to create a scaffold protein to which functional motifs can be fused. In earlier work we described the assembly and structure of an antibody-binding array where the Z domain of Staphylococcus aureus protein A was fused to the scaffold protein. Whilst the binding of rabbit polyclonal immunoglobulin G (IgG) to the array is very strong, mouse monoclonal IgG dissociates from the array easily. This is a problem since many immunodiagnostic tests rely upon the use of mouse monoclonal antibodies. Here we describe a strategy to develop an antibody-binding array that will bind mouse monoclonal IgG with lowered dissociation from the array. A novel protein consisting of the scaffold protein fused to two pairs of Z domains separated by a long flexible linker was manufactured. Using surface plasmon resonance the self-assembly of the new protein on gold and the improved binding of mouse monoclonal IgG were demonstrated.     

Fabrication and Characterization of Dual-Channeled Zirconia Ceramic Scaffold

A novel porous ceramic with a structure containing two three-dimensional (3D) pore channels in a tetragonal zirconia polycrystals (TZP) ceramic was fabricated using a combination of a CNC-machining method and slurry coating process. A graphite scaffold with a single interconnected 3D channel as a template was prepared using CNC machining and lamination. The surfaces of the graphite scaffold were then coated uniformly with the TZP slurry, followed by heat treatment at 900°C for 3 h in air to remove the graphite material completely via thermal oxidation and at 1400°C for 3 h in air to sinter the TZP walls. This process produced a dual-channeled TZP scaffold with an additional 3D channel, which replicated the 3D graphite structure with the pre-existing channel. The fabricated scaffold showed ultra-high porosity (91%), high surface area, and high compressive strength (2.04 MPa), as well as a tightly controlled pore structure.     

Structure-function studies of an engineered scaffold protein derived from Stefin A. II: Development and applications of the SQT variant

Constrained binding peptides (peptide aptamers) may serve as tools to explore protein conformations and disrupt protein-protein interactions. The quality of the protein scaffold, by which the binding peptide is constrained and presented, is of crucial importance. SQT (Stefin A Quadruple Mutant-Tracy) is our most recent development in the Stefin A-derived scaffold series. Stefin A naturally uses three surfaces to interact with its targets. SQT tolerates peptide insertions at all three positions. Peptide aptamers in the SQT scaffold can be expressed in bacterial, yeast and human cells, and displayed as a fusion to truncated pIII on phage. Peptides that bind to CDK2 can show improved binding in protein microarrays when presented by the SQT scaffold. Yeast two-hybrid libraries have been screened for binders to the POZ domain of BCL-6 and to a peptide derived from PBP2', specific to methicillin-resistant Staphylococcus aureus. Presentation of the Noxa BH3 helix by SQT allows specific interaction with Mcl-1 in human cells. Together, our results show that Stefin A-derived scaffolds, including SQT, can be used for a variety of applications in cellular and molecular biology. We will henceforth refer to Stefin A-derived engineered proteins as Scannins.     

Electrospun polylactide/silk fibroin–gelatin composite tubular scaffolds for small‐diameter tissue engineering blood vessels

Many synthetic scaffolds have been used as vascular substitutes for clinical use. However, many of these scaffolds may not show suitable properties when they are exposed to physiologic vascular environments, and they may fail eventually because of some unexpected conditions. Electrospinning technology offers the potential for controlling the composition, structure, and mechanical properties of scaffolds. In this study, a tubular scaffold (inner diameter = 4.5 mm) composed of a polylactide (PLA) fiber outside layer and a silk fibroin (SF)–gelatin fiber inner layer (PLA/SF–gelatin) was fabricated by electrospinning. The morphological, biomechanical, and biological properties of the composite scaffold were examined. The PLA/SF–gelatin composite tubular scaffold possessed a porous structure; the porosity of the scaffold reached 82 ± 2%. The composite scaffold achieved the appropriate breaking strength (1.28 ± 0.21 MPa) and adequate pliability (elasticity up to 41.11 ± 2.17% strain) and possessed a fine suture retention strength (1.07 ± 0.07 N). The burst pressure of the composite scaffold was 111.4 ± 2.6 kPa, which was much higher than the native vessels. A mitochondrial metabolic assay and scanning electron microscopy observations indicated that both 3T3 mouse fibroblasts and human umbilical vein endothelial cells grew and proliferated well on the composite scaffold in vitro after they were cultured for some days. The PLA/SF–gelatin composite tubular scaffolds presented appropriate characteristics to be considered as candidate scaffolds for blood vessel tissue engineering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Development of ciprofloxacin hydrochloride loaded poly(ethylene glycol)/chitosan scaffold as wound dressing

A novel ciprofloxacin hydrochloride loaded chitosan/poly(ethylene glycol) (PEG) composite scaffold was developed for wound dressing application. PEG incorporation in chitosan scaffold showed enhanced loading up to 5.4 % and increased cumulative release of the drug up to 35 % as compared to pure chitosan scaffold (20 %). The drug loading and control release of the drug has been explained by the morphological features and drug–polymer/polymer–polymer interactions revealed by SEM, FTIR and DSC. Bacterial growth inhibition evaluation using Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus confirmed the efficacy of released drug from the scaffolds (pure and PEG mixed chitosan). Swelling study, bacterial penetration, moisture vapour transmission rate, haematocompatibility and biodegradation profile supported the suitability of scaffold used as wound dressing materials. In-vivo study on mice finally validated the controlled rate of drug release showing the effectiveness of PEG incorporation into the scaffold for quicker and regulated wound healing.     

Three-Dimensional Culture of Cartilage Tissue on Nanogel-Cross-Linked Porous Freeze-Dried Gel Scaffold for Regenerative Cartilage Therapy: A Vibrational Spectroscopy Evaluation

This study presents a set of vibrational characterizations on a nanogel-cross-linked porous freeze-dried gel (NanoCliP-FD gel) scaffold for tissue engineering and regenerative therapy. This scaffold is designed for the in vitro culture of high-quality cartilage tissue to be then transplanted in vivo to enable recovery from congenital malformations in the maxillofacial area or crippling jaw disease. The three-dimensional scaffold for in-plate culture is designed with interface chemistry capable of stimulating cartilage formation and maintaining its structure through counteracting the dedifferentiation of mesenchymal stem cells (MSCs) during the formation of cartilage tissue. The developed interface chemistry enabled high efficiency in both growth rate and tissue quality, thus satisfying the requirements of large volumes, high matrix quality, and superior mechanical properties needed in cartilage transplants. We characterized the cartilage tissue in vitro grown on a NanoCliP-FD gel scaffold by human periodontal ligament-derived stem cells (a type of MSC) with cartilage grown by the same cells and under the same conditions on a conventional (porous) atelocollagen scaffold. The cartilage tissues produced by the MSCs on different scaffolds were comparatively evaluated by immunohistochemical and spectroscopic analyses. Cartilage differentiation occurred at a higher rate when MSCs were cultured on the NanoCliP-FD gel scaffold compared to the atelocollagen scaffold, and produced a tissue richer in cartilage matrix. In situ spectroscopic analyses revealed the cell/scaffold interactive mechanisms by which the NanoCliP-FD gel scaffold stimulated such increased efficiency in cartilage matrix formation. In addition to demonstrating the high potential of human periodontal ligament-derived stem cell cultures on NanoCliP-FD gel scaffolds in regenerative cartilage therapy, the present study also highlights the novelty of Raman spectroscopy as a non-destructive method for the concurrent evaluation of matrix quality and cell metabolic response. In situ Raman analyses on living cells unveiled for the first time the underlying physiological mechanisms behind such improved chondrocyte performance.     

Development of biodegradable scaffold using polylactic acid and polycaprolactone for cardiovascular application

The limitations of newly synthesized biodegradable stents are low mechanical strength, fracture stiffness, and fast degradability of the polymers. A cylindrical polymeric scaffold was proposed in combination of polylactic acid and polycaprolactone. The tensile strength of the blend was increased twice, though elongation has reduced threefold. The blend illustrated no chemical interaction between polymers. The scaffold was coated with docetaxel, and sustained release profile was observed for 56 days. The degradation of the scaffold was evaluated through change in mechanical properties, weight variation, and morphological studies. The developed hemocompatible polymeric scaffold may be used as for the cardiovascular application.     

N-乙烯基吡咯烷酮接枝改性聚乳酸组织工程支架的制备与性能

利用热致相分离技术制备了N-乙烯基吡咯烷酮接枝改性聚乳酸(M-PLA)组织工程支架。在接枝率36%条件下,讨论了聚合物浓度、水/二氧六环比例和粗化温度对支架孔隙度和微孔结构的影响;并进一步探讨了在相同制备工艺条件下,不同接枝率对支架结构的影响,并对M-PLA支架的亲水性和蛋白粘附性能进行测试。结果显示,在一定接枝率下,支架孔隙度随聚合物浓度增大而降低;水的添加有利于规则孔径的形成;粗化温度降低,支架孔径和孔隙度提高。与PLA支架相比,随着接枝率提高,共聚物支架孔隙度变化不大,孔径略减小,但孔隙规整性和连通性较好,亲水性和蛋白粘附率明显增大,生物相容性提高。     

Preparation of porous PLGA/HA/collagen scaffolds with supercritical CO2 and application in osteoblast cell culture

Biocompatible three-dimensional scaffolds for cell culturing may facilitate methods for the repair of damaged human tissues. A novel hybrid porous scaffold of poly(lactic-co-glycolic acid), hydroxyapatite and collagen was prepared using a supercritical CO₂ saturation technique. Expansion factors of scaffolds with different compositions were studied after supercritical CO₂ treatment to choose the optimal composition for three-dimensional culture. The supercritical CO₂ process conditions, such as saturation temperature, saturation time and saturation pressure were varied to evaluate their influence on pore structure. The results showed that the pore size and porosity of the scaffold could be controlled by manipulating these process conditions. The porous samples were characterized by environmental scanning electron microscopy, energy-dispersive X-ray spectroscope, Fourier transform infrared spectroscopy and X-ray diffractometry. Finally, MG-63 cells were successfully cultured on the porous scaffold as assessed by electron and confocal microscopy, confirming the biocompatibility of this new hybrid porous scaffold.     

Fabrication of a zirconia/calcium silicate composite scaffold based on digital light processing

Zirconia (ZrO₂) and calcium silicate (CS) are widely used in bone repair. Zirconia has excellent mechanical properties, while calcium silicate has exceptional biological activity. A porous ZrO₂/CS composite ceramic scaffold was formed by digital light processing (DLP) technology in this study. The microstructure analysis demonstrated that CS was embedded between ZrO₂ particles. Mechanical tests showed that interconnected CS particles could improve mechanical properties, while discrete CS particles led to a decrease in that. Cell experiments showed that adding CS to ZrO₂ had a positive effect on cell proliferation and differentiation. In vitro degradation test showed that the weight loss of scaffolds in four weeks increased form ?0.63%–1.42% with the increase of CS content. Moreover, the degradation of scaffold promoted the deposition of apatite, which was beneficial to the integration of the scaffold with living bone. In conclusion, the ZrO₂/CS composite scaffold had better biocompatibility compared with the ZrO₂ scaffold, which showed a potential solution for 3D printing bone repair scaffolds.