Compressive Strength Of Scaffolds Research Articles

Antibacterial activity and biocompatibility of zein scaffolds containing silver-doped bioactive glass

Composite 3D scaffolds combining natural polymers and bioceramics are promising candidates for bone tissue engineering (BTE). Zein, as a natural plant protein, offers several advantages, including biocompatibility, adequate strength properties, and low/no immunogenicity; however, it lacks bioactivity. Thus, composite zein: bioactive glass (BG) scaffolds are proposed as promising candidate for BTE applications, with silver-doping of bioactive glass providing an antibacterial effect against possible post-implantation infection. Therefore, the aim of this study was to investigate the in vitro antibacterial properties, biocompatibility, bioactivity and compressive strength of zein scaffolds containing silver-doped bioactive glass. BG nanoparticles, undoped and Ag-doped, were fabricated using the sol-gel method. 3D composite zein:BG scaffolds, containing 20 wt% BG, were prepared and their antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was assessed using the disc diffusion assay. Human osteoblast-like MG-63 cells were used to evaluate the in vitro biocompatibility of the prepared scaffold groups. In addition, the compressive strength of the scaffolds was determined using uniaxial compression strength testing and the scaffold interconnected porosity was measured using helium pycnometer. Disc diffusion assay showed that only zein scaffolds containing Ag-doped sol-gel BG are antibacterially positive against E. coli and S. aureus. Pure zein scaffolds and zein scaffolds containing sol-gel-derived BG showed no negative influence on the growth of MG-63 cells, as evident by the cells’ ability to survive, proliferate, and function on these scaffolds. Moreover, incorporating sol-gel-derived BG into zein scaffolds at zein:BG of 80:20 ratio showed bioactive properties with adequate porosity without affecting the scaffolds’ compressive strengths, which was similar to that of trabecular bone, suggesting that the new composites have potential for BTE applications in non-loaded bearing areas.

Improvement of cellular responses of genipin cross-linked chitosan/nano β-TCP composite scaffolds by surface modification with fibrin

In this study, genipin cross-linked freeze-gelled chitosan/nano β-Tricalcium Phosphate (β-TCP) composite scaffolds were successfully modified by using fibrin and characterized to make them more effective towards bone tissue regeneration. The modified scaffolds possess adequate pore size (56–179 μm) and desired porosity (72.0 ± 3.8%) for bone tissue engineering applications. There is no significant change in compressive strength of scaffolds was observed before (2.78 ± 0.14 MPa) and after (2.80 ± 0.13 MPa) fibrin coating. Notably, in-vitro cell culture study revealed the enhanced cellular responses such as cell attachment (Field emission-scanning electron microscopy), proliferation (DNA quantification assay) and differentiation (Alkaline phosphatase activity, estimation of total calcium content and expression of osteogenic specific genes) of seeded human mesenchymal stem cells (hMSCs). Further, the fibrin coating has added advantage of having fibrillar network facilitating transport of nutrients and metabolic waste to the seeded cells. Altogether, results indicate the potentiality of developed fibrin conjugated composite scaffolds for bone tissue engineering applications.

Supercritical CO2 deposition and foaming process for fabrication of biopolyester–ZnO bone scaffolds

ABSTRACTSubsequent supercritical CO2‐assisted deposition and foaming process followed by in situ synthesis was used to fabricate functional polylactide (PLA) and polylactide–poly(ɛ‐caprolactone) (PLA–PCL) bone scaffolds. Deposition of zinc bis(2‐thenoyltrifluoroacetonate) as a ZnO precursor onto biopolyester substrates (30 MPa; 110 °C) was followed by fast depressurization to create cellular structure. Contact time was optimized regarding the deposition yield (2 h), while PCL content in PLA was varied (1–10 wt %). Scaffolds impregnated with the precursor were treated with hydrazine alcoholic solution to obtain biopolyester–ZnO composites. Precursor synthesis and deposition onto the scaffolds was confirmed by Fourier‐transform infrared. Processed scaffolds had micron‐sized pores (d50 ∼ 20 μm). High open porosity (69–77%) and compressive strength values (2.8–8.3 MPa) corresponded to those reported for trabecular bone. PLA blending with PCL positively affected precursor deposition, crystallization rate, and compressive strength of the scaffolds. It also improved PLA surface roughness and wettability which are relevant for cell adhesion. ZnO improved compressive strength of the PLA scaffolds without significant effect on thermal stability. Analysis of structural, thermal, and mechanical properties of biopolyester–ZnO scaffolds testified a great potential of the obtained platforms as bone scaffolds. Proposed processing route is straightforward and ecofriendly, fast, easy to control, and suitable for processing of thermosensitive polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45824.

High strength yttria-reinforced HA scaffolds fabricated via honeycomb ceramic extrusion.

The present study investigated the effects of hydroxyapatite (HA) reinforced with yttria on porous scaffolds fabricated via honeycomb ceramic extrusion. Yttria was selected as it has been demonstrated to toughen other ceramics. Moreover, yttria has been surmised to suppress dehydroxylation in HA, a characteristic that prefigures decomposition thereof during sintering into mechanically weaker phases. However, the compressive strength of yttria-reinforced hydroxyapatite (Y-HA) porous scaffolds has hitherto not been reported. Y-HA was synthesised by calcining a commercially available HA with 10wt% yttria at 1000°C. Y-HA was then fabricated into porous scaffolds using an in-house honeycomb extruder, and subsequently sintered at 1200 and 1250°C. The results were compared to the uncalcined as-received commercial powder (AR-HA) and calcined pure HA powder at 1000°C (C-HA). It was discovered that calcination alone caused marked improvements to the stoichiometry, thermal stability, porosity and compressive strength of scaffolds. The improvements were ascribed to the calcined powders with less susceptibility to both agglomeration and enhanced densification. Still, differences were observed between C-HA and Y-HA at 1250°C. The compressive strength increased from 105.9 to 127.3MPa, a larger microporosity was descried and the HA matrix in Y-HA was more stoichiometric. The latter was confirmed by XRD and EDS analyses. Therefore, it was concluded that the reinforcing of hydroxyapatite with yttria improved the compressive strength and suppressed dehydroxylation of porous HA scaffolds. In addition, the compressive strength achieved demonstrated great potential for load-bearing application.

Preparation and Properties of Novel Maleated Poly (D, L-lactide-co-glycolide) Porous Scaffolds for Tissue Engineering

ABSTRACTThree-dimensional biodegradable porous scaffolds play an important role in tissue engineering. A new polymer based on maleated poly(lactic-co-glycolic acid) (MPLGA) was synthesized using direct melt copolymerization from maleic anhydride (MAH), D, L-lactide, and glycolide monomers. MPLGA porous biodegradable scaffolds were prepared by a solution-casting/salt-leaching method. The effects of content and size of the NaHCO3 porogen on the compressive strength of the MPLGA scaffolds were investigated, and the effect of content of the porogen on the porosity of the MPLGA scaffolds was also studied. The results indicated that MAH was grafted onto PLGA successfully and MPLGA scaffolds with interconnective and open pore structure were obtained. Increasing content of NaHCO3 porogen resulted in an increase of porosity and decrease of the compressive strength of the MPLGA scaffolds with the compressive strength of the scaffolds also decreasing with increasing porogen size.

Control of the structure and mechanical property of porous WS2 scaffold during freeze casting

Porous WS2 scaffolds with aligned lamellar pore were fabricated by freeze casting, and the pore morphology and size can be well controlled by adjusting the processing parameters during freeze casting process. The results indicated that the porosity and the compressive strength of porous WS2 were greatly affected by the concentration of gelatin. As the gelatin addition increased from 1 to 5 wt%, the porosity of porous WS2 scaffolds with initial solid content of 3 vol% decreased from 95.12 to 90.23%, and their compressive strength increased from 0.22 to 1.16 MPa. Moreover, the lamellar spacing and wall thickness could be tailored from 90 to 320 and 5 to 30 μm respectively by changing the cooling temperature. And the compressive strength of scaffolds has a slight increase with the decreases of cooling temperature. The porous WS2 scaffold with fine aligned lamellar structure and proper compressive strength are expected to be used for scaffold materials.

Biphasic calcium phosphate scaffolds fabricated by direct write assembly: Mechanical, anti-microbial and osteoblastic properties

The present work reports on the fabrication of 3-D porous calcium phosphate scaffolds by robocasting from biphasic (HA/β-TCP≈1.5) powders, undoped and co-doped with Sr and Ag. Scaffolds with different pore sizes and rod diameter of 410μm were fabricated and sintered at 1100°C. The size and morphology of the powder particles, and the concentrations of the processing additives, were shown to play major roles in the robocasting process. For all pore sizes tested, the compressive strength of scaffolds was comparable to or even higher than that of cancellous bone, and mechanical data could be systematically correlated with the porosity fraction. Co-doping the starting powders with Sr and Ag enhanced the mechanical strength of scaffolds, conferred good antimicrobial activity against Staphylococcus aureus and Escherichia coli, and did not induce any cytotoxic effects on human MG-63 cells. Furthermore, the co-doped powder was more effective in inducing pre-osteoblastic proliferation.

Biomimetic n-HA/GCO-PU composite scaffold with hierarchical structure for bone regeneration

Event Abstract Back to Event Biomimetic n-HA/GCO-PU composite scaffold with hierarchical structure for bone regeneration Yubao Li1, Limei Li1*, Yi Zuo1*, Qin Zou1 and Jidong Li1* 1 Analytical & Testing Center, Research Center for Nano Biomaterials, China Introduction: Matching structure to function is a challenge to synthetic biomaterials[1],[2]. The skeletal hierarchical structure from microscale to nanoscale formed by the cooperation of organic molecules and inorganic crystals, has not been fully investigated and utilized. Combination of nano-hydroxyapatite (n-HA) crystals and polyurethane (PU) block copolymer will give us a chance to establish a biomimetic hierarchical structure and realize biological function. This study has explored the effect of nano- to micro- structure on the mechanical and biological properties of the composite scaffold. Materials and Methods: The n-HA/PU composite scaffolds with 40 wt% n-HA crystals were made by in situ polymerization and simultaneous foaming[3]. Both pristine castor oil (CO) and glyceride of castor oil (GCO) were separately used to prepare PU scaffolds (named n-HA/CO-PU, n-HA/GCO-PU). The physico-chemical properties were analyzed by FTIR, XRD, XPS, NMR, DMA, SEM, TEM, mechanical test and micro-CT analysis. The cell behavior and bone regeneration capacity were also evaluated via in vitro culture and in vivo implantation. Results and Discussion: The composite scaffolds have been structured in three levels: the PU hard/soft block structure in molecular level, the n-HA crystals dispersed in PU matrix in nano-level (Fig. 1), and the porous scaffold structure in micro-level [Fig. 2]. The three level hierarchical structures may be similar to the segmented collagen, the mineral in organic matrix and the cancellous structure of natural bone, making up the material basis of high performance scaffold for bone regeneration[4]. The results showed that the modification of PU soft segment by GCO could largely increase the scaffold compressive strength by 48% and elastic modulus by 96%. The n-HA crystals with fine dispersity not only improved the interface bonding with PU matrix, but also provided good bioactivityfor bonding with bone tissue. The hierarchical structure and good mechanical quality of the n-HA/GCO-PU composite scaffold were found to be appropriate for growth of cells and regeneration of bony tissue [Fig. 2], presenting good prospect for bone repair and regeneration. Conclusion: We found that the use of glyceride of castor oil for soft segment, and the incorporation of n-HA crystals are crucial for the mechanical improvement of PU-based composite scaffolds; the scaffold composition, porous structure and mechanical quality are favorable for cell proliferation and new boneregeneration. Combination of the two factors afford better mechanical improvement, suggesting the important role of the tightly bonding interface between n-HA crystals and PU matrix. The nano- to micro- hierarchical structure, improved mechanical properties of the nano composite scaffold can be a biomimetic approach to natural bone tissue, presenting strong vitality in bone regeneration and reconstruction. The authors appreciate financial support from China NSFC fund (No. 31370971), Sichuan and Chengdu project (No. 2012FZ0125, 12DXYB145JH-005).

Hierarchical Structure and Mechanical Improvement of an n-HA/GCO–PU Composite Scaffold for Bone Regeneration

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.

Fabrication and in vitro biological activity of βTCP-Chitosan-Fucoidan composite for bone tissue engineering

We developed tricalcium phosphate-chitosan-fucoidan biocomposite scaffold (TCP-Ch-Fu) by using the freeze-drying technique. The fabricated biocomposite scaffolds were analyzed by spectroscopy and porosity measurement. The biomechanical properties of scaffolds were assessed by compression test and the results suggested that the incorporation of Fucoidan into the biocomposite improves the compression strength of scaffolds. Biomineralization of scaffolds was evaluated by soaking them in simulated body fluid and the results revealed that the addition of Fucoidan into the scaffolds enhanced the formation of apatite layer on the surface of biocomposite after 7 days of immersion. Alamar Blue assay confirmed that the cell viability of human-derived bone marrow stromal cell was superior in the TCP-Ch-Fuscaffold. The addition of Fucoidan to TCP-Ch increased the release of osteocalcin, confirming that it can support osteogenic differentiation of human mesenchymal stromal cells in in vitro culture. Thus, TCP-Ch-Fu could be a potential candidate for bone-tissue engineering applications.

Nano SiO2 and MgO improve the properties of porous β-TCP scaffolds via advanced manufacturing technology.

Nano SiO2 and MgO particles were incorporated into β-tricalcium phosphate (β-TCP) scaffolds to improve the mechanical and biological properties. The porous cylindrical β-TCP scaffolds doped with 0.5 wt % SiO2, 1.0 wt % MgO, 0.5 wt % SiO2 + 1.0 wt % MgO were fabricated via selective laser sintering respectively and undoped β-TCP scaffold was also prepared as control. The phase composition and mechanical strength of the scaffolds were evaluated. X-ray diffraction analysis indicated that the phase transformation from β-TCP to α-TCP was inhibited after the addition of MgO. The compressive strength of scaffold was improved from 3.12 ± 0.36 MPa (β-TCP) to 5.74 ± 0.62 MPa (β-TCP/SiO2), 9.02 ± 0.55 MPa (β-TCP/MgO) and 10.43 ± 0.28 MPa (β-TCP/SiO2/MgO), respectively. The weight loss and apatite-forming ability of the scaffolds were evaluated by soaking them in simulated body fluid. The results demonstrated that both SiO2 and MgO dopings slowed down the degradation rate and improved the bioactivity of β-TCP scaffolds. In vitro cell culture studies indicated that SiO2 and MgO dopings facilitated cell attachment and proliferation. Combined addition of SiO2 and MgO were found optimal in enhancing both the mechanical and biological properties of β-TCP scaffold.

Development of fibrin conjugated chitosan/nano β‐TCP composite scaffolds with improved cell supportive property for bone tissue regeneration

ABSTRACTIn the present study, an attempt has been made to improve cell supportive property of chitosan/nano beta tri‐calcium phosphate (β‐TCP) composite scaffolds by modification of scaffold surface with fibrin using ethyl‐3‐(3‐dimethylaminopropyl) carbodimide (EDC) as crosslinking agent. The developed fibrin conjugated chitosan/nano β‐TCP composite scaffolds possess desired pore size and porosity in the range of 45–151 µm and 81.4 ± 4.1%, respectively. No significant change in compressive strength of scaffolds was observed before and after fibrin conjugation. The calculated compressive strength of fibrin conjugated and non‐conjugated chitosan/nano β‐TCP scaffolds are 2.71 ± 0.14 MPa and 2.67 ± 0.11 MPa, respectively. Results of cell culture study have further shown an enhanced cell attachment, cell number, proliferation, differentiation, and mineralization on fibrin conjugated chitosan/nano β‐TCP scaffold. The uniform cell distribution over the scaffold surface and cell infiltration into the scaffold pores were assessed by confocal laser scanning microscopy. Furthermore, higher expression of osteogenic specific genes such as bone sialo protein, osteonectin, alkaline phosphatase, and osteocalcin (OC) on fibrin conjugated scaffolds was observed when compared to scaffolds without fibrin. Altogether, results indicate the potentiality of developed fibrin conjugated composite scaffolds for bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41534.

Preparation and characterization of porous Ag doped hydroxyapatite bioceramic scaffolds

Silver doped hydroxyapatite (HAp–Ag) containing different amounts of Ag (0.5wt% and 0.8wt%) was prepared using wet chemical precipitation method. In the synthesis process CaO, H3PO4 and AgNO3 were used as raw materials. Porous HAp and HAp–Ag scaffolds via viscous mass foaming technique were prepared from as-synthesized powders and obtained samples were sintered at different temperatures. According to the XRD data and SEM microstructure analysis, silver ions from HAp–Ag structure were excluded and additional silver phase during the sintering process was formed. Impact of sintering temperature (1000°C and 1200°C) on the porosity, density, specific surface area and mechanical properties of porous HAp and HAp–Ag scaffolds was evaluated. Total porosity of 71% (at 1000°C) and 54% (at 1200°C) was achieved. Incorporation of Ag into the HAp structure resulted in the decrease of porous scaffold compressive strength by 30–50% compared to pure HAp porous scaffolds. Increasing the sintering temperature of porous scaffolds up to 1200°C, it was possible to obtain samples with 2–4 times higher compressive strength, compared to samples sintered at 1000°C.

Evaluation Nanostructure Properties of Bioactive Glass Scaffolds for Bone Tissue Engineering

The use of biomaterials in bone tissue engineering newly has been developed. They are biocompatible material which are reabsorbed in body and replaced with newly formed tissue. Bioactive glass scaffolds will be appropriate candidates if pore morphology, size and structures are controlled. Scaffolds with nanostructure will provide these goals. In this research bioglass powder was synthesized with sol-gel method to achieve nanostructure powder. The glass powder was characterized with transmission electron microscope (TEM). Scaffolds were prepared with combination of bioglass powder and sugar as porogen followed by pressing at 80 MPa then sintering at 1050 oC. The morphology of sintered scaffolds was characterized with scanning electron microscope (SEM) and porosity was measured with density method. Mechanical properties were assessed with compressive strength. The TEM results show that synthesized powder has particle size about 25 nm. The SEM results show that nanopores and macropores are connectively distributed in whole part of scaffolds. The compressive strength of scaffolds was 0.8 MPa. Overall, the scaffold is suggested that is appropriate alternative for bone tissue engineering.

Biphasic calcium phosphate (BCP) macroporous scaffold with different ratios of HA/β-TCP by combination of gel casting and polymer sponge methods

Open and interconnected porous scaffolds were prepared with various ratios of hydroxyapatite (HA)/β-tricalcium phosphate by a combination of gel casting and polymer sponge methods to improve the mechanical properties and structure. The scaffolds were prepared using slurries containing 50 vol.-% of ceramic powders and sintered at 1100°C for 2 h. Thermogravimetric analysis result shows that the proper temperature to burn out organic materials and polyurethane foams is 600°C. The compressive strength was between 5·3 and 8·4 MPa. Field emission scanning electron microscope shows an open, relatively uniform and large interconnected porous structure with pore size ranging between 150 and 400 μm. X-ray diffraction and Brunauer–Emmett–Teller methods were employed to determine the microstructural crystallite and surface area respectively. The results show that the compressive strength of scaffolds increased with the increase in HA concentration. The reason can be explained by the increasing pore wall thickness and density in scaffolds.

Effect of crosslinking temperature on compression strength of gelatin scaffold for articular cartilage tissue engineering

A crosslinking method with directly crosslinking the gelatin gel by genipin was performed at 10–25 °C. The microstructure of the gelatin scaffold can be modulated by the crosslinking temperature. During repeated compression–swelling test, a plateau stress occurred. This plateau stress was relatively constant during the cyclic test. The cartilage tissue developed in the scaffold can largely enhance the compression strength of the scaffold and the scaffold with largest pore (350–500 μm, 25 °C-crosslinked) developed largest amount of the cartilage tissue after cell culture. With or without cell culture, the scaffold with smallest pore (50–150 μm, 10 °C-crosslinked) showed the highest compression strength. The pure gelatin scaffold can undergo reversible deformation for the motion of the articular cartilage.

Degradation and biocompatibility of porous nano-hydroxyapatite/polyurethane composite scaffold for bone tissue engineering

Porous scaffold containing 30 wt% nano-hydroxyapatite (n-HA) and 70 wt% polyurethane (PU) from castor oil was prepared by a foaming method and investigated by X-ray diffraction (XRD), Fourier transform infrared absorption (FTIR), scanning electron microscopy (SEM) techniques. The results show that n-HA particles disperse homogeneously in the PU matrix. The porous scaffold has not only macropores of 100–800 μm in size but also a lot of micropores on the walls of macropores. The porosity and compressive strength of scaffold are 80% and 271 kPa, respectively. After soaking in simulated body fluid (SBF), hydrolysis and deposition partly occur on the scaffold. The biological evaluation in vitro and in vivo shows that the n-HA/PU scaffold is non-cytotoxic and degradable. The porous structure provides a good microenvironment for cell adherence, growth and proliferation. The n-HA/PU composite scaffold can be satisfied with the basic requirement for tissue engineering, and has the potential to be applied in repair and substitute of human menisci of the knee-joint and articular cartilage.

Preparation of Porous Scaffolds of Borosilicate Bioglass

A borosilicate bioglass in Na_20-CaO-SiO_2-P_2O_5-B_2O_3 system is a bioactive and biodegrad- able material for tissue engineering.In this study,the bioactive porous scaffolds with three-dimensional interconnection were fabricated by replication technique,using borosilicate bioglass powder to form slurry with ethanol as solvent and ethyl-cellulose as additive.The compressive strength of scaffolds increases from 0.03MPa to 0.36MPa by adjusting the slurry load,the solid concentration and the ethyl- cellulose concentration in the slurry,while the pore size of scaffolds remains in the rangeot 300-500μm and the porosity maintains over 80%.According the analysis on Cellular Structure Model,it is sug- gested that employing high strength glass and optimizing slurry composition are effective approaches to improve cellular structure and increase scaffold strength.The compressive strength of another borosili- cate glass scaffolds made from Na_2O-K_2O-MgO-CaO-SiO_2-P_2O_5-B_2O_3 system can reach 5-8MPa based on the theory.These experiments show that the replication technique is a promising way to prepare bioglass scaffolds.

Effects of degradation and porosity on the load bearing properties of model hydroxyapatite bone scaffolds

Degradation of three types of model hydroxyapatite (HA) scaffolds was studied after in vitro degradation in a sodium acetate buffer (pH 4). Degradation was evaluated using compression testing, scanning electron microscopy (SEM), inductively coupled plasma (ICP) analysis, and weight measurements. Scaffolds were fabricated with a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. Scaffolds had a macrostructure resembling a lattice of rods. Scaffolds contained either macropores (270 or 680 microm in the x-y direction and 280 microm in the z-direction) and micropores (1-30-microm pores and pores <1 microm) or only macropores pores (270 microm in the x-y direction and 280 microm in the z-direction). A computer-aided design (CAD) program controlled the size and distribution of macropores; micropores were created by polymethylmethacrylate (PMMA) microsphere porogens (1-30-microm pore diameter) and controlled sintering (pores <1 microm). Percent weight loss of the scaffolds and calcium and phosphorus ion concentrations in solution increased as the degradation period increased for all scaffold types. After degradation, compressive strength and compressive modulus decreased significantly for those scaffolds with microporosity. For scaffolds without microporosity, the changes in strength and modulus after degradation were not statistically significant. The compressive strength of scaffolds without microporosity was significantly greater than the scaffolds with microporosity.