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Animals, Humans, Biocompatible Materials chemistry, Biocompatible Materials therapeutic use, Printing, Three-Dimensional, Prosthesis Design methods, and Tissue Scaffolds chemistry

Over the past decades, solid freeform fabrication (SFF) has emerged as the main technology for the production of scaffolds for tissue engineering applications as a result of the architectural versatility. However, certain limitations have also arisen, primarily associated with the available, rather limited range of materials suitable for processing. To overcome these limitations, several research groups have been exploring novel methodologies through which a construct, generated via SFF, is applied as a sacrificial mould for production of the final construct. The technique combines the benefits of SFF techniques in terms of controlled, patient-specific design with a large freedom in material selection associated with conventional scaffold production techniques. Consequently, well-defined 3D scaffolds can be generated in a straightforward manner from previously difficult to print and even "unprintable" materials due to thermomechanical properties that do not match the often strict temperature and pressure requirements for direct rapid prototyping. These include several biomaterials, thermally degradable materials, ceramics and composites. Since it can be combined with conventional pore forming techniques, indirect rapid prototyping (iRP) enables the creation of a hierarchical porosity in the final scaffold with micropores inside the struts. Consequently, scaffolds and implants for applications in both soft and hard tissue regeneration have been reported. In this review, an overview of different iRP strategies and materials are presented from the first reports of the approach at the turn of the century until now.

Animals, Bone and Bones physiology, Cartilage physiology, Humans, Temperature, Tissue Engineering methods, and Tissue Scaffolds chemistry

Developed in recent years, low-temperature deposition manufacturing (LDM) represents one of the most promising rapid prototyping technologies. It is not only based on rapid deposition manufacturing process but also combined with phase separation process. Besides the controlled macropore size, tissue-engineered scaffold fabricated by LDM has inter-connected micropores in the deposited lines. More importantly, it is a green manufacturing process that involves non-heating liquefying of materials. It has been employed to fabricate tissue-engineered scaffolds for bone, cartilage, blood vessel and nerve tissue regenerations. It is a promising technology in the fabrication of tissue-engineered scaffold similar to ideal scaffold and the design of complex organs. In the current paper, this novel LDM technology is introduced, and its control parameters, biomedical applications and challenges are included and discussed as well.
(Copyright © 2016 Elsevier B.V. All rights reserved.)

Compressive Strength, Elasticity, Ethylene Glycols chemistry, Microscopy, Electron, Scanning, Polyesters chemistry, Porosity, Surface Properties, Tissue Engineering, Viscosity, and Tissue Scaffolds chemistry

This study investigates the scaffolds' structural anisotropy (i.e. the effect of loading direction), viscoelasticity (i.e. the effect of cross head speed or strain rate), and the influence of simulated physiological environment (PBS solution at 37°C) on the mechanical properties. Besides, the in vitro degradation study has also been performed that evaluates the effect of variation in material and lay-down pattern on the scaffolds' degradation kinetics in terms of mass loss, and change in morphological and mechanical properties. Porous three dimensional (3D) scaffolds of polycarprolactone (PCL) and polycarprolactone-polyethylene glycol (PCL-PEG) were developed by laying down the microfilaments directionally layer-by-layer using an in-house built computer-controlled extrusion and deposition process, called desktop robot based rapid prototyping (DRBRP) system. The loading direction, strain rate and physiological environment directly influenced the mechanical properties of the scaffolds. In vitro degradation study demonstrated that both PCL and PCL-PEG scaffolds realized homogeneous hydrolytic degradation via surface erosion resulting in a consistent and predictable mass loss. The linear mass loss caused uniform and linear increase in porosity that accordingly led to the decrease in mechanical properties. The synthetic polymer had the potential to modulate hydrophilicity and/or degradability and consequently, the biomechanical properties of the scaffolds by varying the polymer constituents.
(Copyright © 2016 Elsevier B.V. All rights reserved.)

Animals, Humans, Porosity, Rats, Rats, Sprague-Dawley, Biomimetic Materials chemistry, Biomimetic Materials pharmacology, Bone Regeneration drug effects, Ceramics chemistry, Ceramics pharmacology, and Tissue Scaffolds chemistry

There is a clinical need for synthetic bioactive materials that can reliably repair intercalary skeletal tissue loss in load-bearing bones. Bioactive glasses have been investigated as one such material but their mechanical response has been a concern. Previously, we created bioactive silicate glass (13-93) scaffolds with a uniform grid-like microstructure which showed a compressive strength comparable to human cortical bone but a much lower flexural strength. In the present study, finite element modeling (FEM) was used to re-design the scaffold microstructure to improve its flexural strength without significantly lowering its compressive strength and ability to support bone infiltration in vivo. Then scaffolds with the requisite microstructures were created by a robotic deposition method and tested in four-point bending and compression to validate the FEM simulations. In general, the data validated the predictions of the FEM simulations. Scaffolds with a porosity gradient, composed of a less porous outer region and a more porous inner region, showed a flexural strength (34±5MPa) that was more than twice the value for the uniform grid-like microstructure (15±5MPa) and a higher compressive strength (88±20MPa) than the grid-like microstructure (72±10MPa). Upon implantation of the scaffolds for 12weeks in rat calvarial defects in vivo, the amount of new bone that infiltrated the pore space of the scaffolds with the porosity gradient (37±16%) was similar to that for the grid-like scaffolds (35±6%). These scaffolds with a porosity gradient that better mimics the microstructure of human long bone could provide more reliable implants for structural bone repair.
(Copyright © 2016 Elsevier B.V. All rights reserved.)

Cell Line, Tumor, Compressive Strength drug effects, Cryoultramicrotomy, Elastic Modulus drug effects, Humans, Molecular Weight, Polyesters pharmacology, Proton Magnetic Resonance Spectroscopy, Silicon Dioxide chemistry, Bone Regeneration drug effects, Cross-Linking Reagents pharmacology, Glass chemistry, Materials Testing methods, Phase Transition drug effects, and Tissue Scaffolds chemistry

We present a series of organic/inorganic hybrid sol-gel derived glasses, made from a tetraethoxysilane-derived silica sol (100% SiO2) and oligovalent organic crosslinkers functionalized with 3-isocyanatopropyltriethoxysilane. The material was susceptible to heat sterilization. The hybrids were processed into pore-interconnected scaffolds by an indirect rapid prototyping method, described here for the first time for sol-gel glass materials. A large panel of polyethylene oxide-derived 2- to 4-armed crosslinkers of molecular weights ranging between 170 and 8000Da were incorporated and their effect on scaffold mechanical properties was investigated. By multiple linear regression, 'organic content' and the 'content of ethylene oxide units in the hybrid' were identified as the main factors that determined compressive strength and modulus, respectively. In general, 3- and 4-armed crosslinkers performed better than linear molecules. Compression tests and cell culture experiments with osteoblast-like SaOS-2 cells showed that macroporous scaffolds can be produced with compressive strengths of up to 33±2MPa and with a pore structure that allows cells to grow deep into the scaffolds and form mineral deposits. Compressive moduli between 27±7MPa and 568±98MPa were obtained depending on the hybrid composition and problems associated with the inherent brittleness of sol-gel glass materials could be overcome. SaOS-2 cells showed cytocompatibility on hybrid glass scaffolds and mineral accumulation started as early as day 7. On day 14, we also found mineral accumulation on control hybrid glass scaffolds without cells, indicating a positive effect of the hybrid glass on mineral accumulation.
Statement of Significance: We produced a hybrid sol-gel glass material with significantly improved mechanical properties towards an application in bone regeneration and processed the material into macroporous scaffolds of controlled architecture by indirect rapid prototyping. We were able to produce macroporous materials of relevant porosity and pore size with compressive moduli, covering the range reported for cancellous bone while an even higher compressive strength was maintained. By multiple linear regression, we identified crosslinker parameters, namely organic content and the content of ethylene oxide units in the hybrids that predominantly determined the mechanics of the hybrid materials. The scaffolds proved to be cytocompatible and induced mineralization in SaOS-2 cells. This provides new insight on the critical parameters for the design of the organic components of covalent hybrid sol-gel glasses.
(Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Biocompatible Materials pharmacology, Calcium metabolism, Cell Line, Humans, Microscopy, Electron, Scanning, Phosphorus metabolism, Spectroscopy, Fourier Transform Infrared, Surface Properties, Bone Regeneration physiology, Osteoblasts physiology, and Tissue Scaffolds

The incidence of bone disorders, whether due to trauma or pathology, has been trending upward with the aging of the worldwide population. The currently available treatments for bone injuries are rather limited, involving mainly bone grafts and implants. A particularly promising approach for bone regeneration uses rapid prototyping (RP) technologies to produce 3D scaffolds with highly controlled structure and orientation, based on computer-aided design models or medical data. Herein, tricalcium phosphate (TCP)/alginate scaffolds were produced using RP and subsequently their physicochemical, mechanical and biological properties were characterized. The results showed that 60/40 of TCP and alginate formulation was able to match the compression and present a similar Young modulus to that of trabecular bone while presenting an adequate biocompatibility. Moreover, the biomineralization ability, roughness and macro and microporosity of scaffolds allowed cell anchoring and proliferation at their surface, as well as cell migration to its interior, processes that are fundamental for osteointegration and bone regeneration.

Animals, Cell Differentiation drug effects, Cell Proliferation drug effects, Cell Survival drug effects, Compressive Strength drug effects, Computer-Aided Design, Mesenchymal Stem Cells cytology, Mesenchymal Stem Cells drug effects, Mice, Molecular Weight, NIH 3T3 Cells, Osteogenesis drug effects, Rats, Durapatite pharmacology, Polyesters pharmacology, Polyethylene Glycols pharmacology, Surface-Active Agents pharmacology, Tissue Scaffolds chemistry, and Water chemistry

Two major factors hampering the broad use of rapid prototyped biomaterials for tissue engineering applications are the requirement for custom-designed or expensive research-grade three-dimensional (3D) printers and the limited selection of suitable thermoplastic biomaterials exhibiting physical characteristics desired for facile surgical handling and biological properties encouraging tissue integration. Properly designed thermoplastic biodegradable amphiphilic polymers can exhibit hydration-dependent hydrophilicity changes and stiffening behavior, which may be exploited to facilitate the surgical delivery/self-fixation of the scaffold within a physiological tissue environment. Compared to conventional hydrophobic polyesters, they also present significant advantages in blending with hydrophilic osteoconductive minerals with improved interfacial adhesion for bone tissue engineering applications. Here, we demonstrated the excellent blending of biodegradable, amphiphilic poly(D,L-lactic acid)-poly(ethylene glycol)-poly(D,L-lactic acid) (PLA-PEG-PLA) (PELA) triblock co-polymer with hydroxyapatite (HA) and the fabrication of high-quality rapid prototyped 3D macroporous composite scaffolds using an unmodified consumer-grade 3D printer. The rapid prototyped HA-PELA composite scaffolds and the PELA control (without HA) swelled (66% and 44% volume increases, respectively) and stiffened (1.38-fold and 4-fold increases in compressive modulus, respectively) in water. To test the hypothesis that the hydration-induced physical changes can translate into self-fixation properties of the scaffolds within a confined defect, a straightforward in vitro pull-out test was designed to quantify the peak force required to dislodge these scaffolds from a simulated cylindrical defect at dry versus wet states. Consistent with our hypothesis, the peak fixation force measured for the PELA and HA-PELA scaffolds increased 6-fold and 15-fold upon hydration, respectively. Furthermore, we showed that the low-fouling 3D PELA inhibited the attachment of NIH3T3 fibroblasts or bone marrow stromal cells while the HA-PELA readily supported cellular attachment and osteogenic differentiation. Finally, we demonstrated the feasibility of rapid prototyping biphasic PELA/HA-PELA scaffolds for potential guided bone regeneration where an osteoconductive scaffold interior encouraging osteointegration and a nonadhesive surface discouraging fibrous tissue encapsulation is desired. This work demonstrated that by combining facile and readily translatable rapid prototyping approaches with unique biomaterial designs, biodegradable composite scaffolds with well-controlled macroporosities, spatially defined biological microenvironment, and useful handling characteristics can be developed.

Animals, Anti-Bacterial Agents pharmacology, Cell Line, Cell Proliferation drug effects, Hydrophobic and Hydrophilic Interactions, Materials Testing, Mice, Microbial Sensitivity Tests, Particle Size, Porosity, Spectroscopy, Fourier Transform Infrared, Stress, Mechanical, Sus scrofa, Vancomycin pharmacology, X-Ray Diffraction, Bone Regeneration drug effects, Drug Delivery Systems methods, Durapatite chemistry, Gelatin chemistry, Silicon chemistry, and Tissue Scaffolds chemistry

Porous 3-D scaffolds consisting of gelatine and Si-doped hydroxyapatite were fabricated at room temperature by rapid prototyping. Microscopic characterization revealed a highly homogeneous structure, showing the pre-designed porosity (macroporosity) and a lesser in-rod porosity (microporosity). The mechanical properties of such scaffolds are close to those of trabecular bone of the same density. The biological behavior of these hybrid scaffolds is greater than that of pure ceramic scaffolds without gelatine, increasing pre-osteoblastic MC3T3-E1 cell differentiation (matrix mineralization and gene expression). Since the fabrication process of these structures was carried out at mild conditions, an antibiotic (vancomycin) was incorporated in the slurry before the extrusion of the structures. The release profile of this antibiotic was measured in phosphate-buffered saline solution by high-performance liquid chromatography and was adjusted to a first-order release kinetics. Vancomycin released from the material was also shown to inhibit bacterial growth in vitro. The implications of these results for bone tissue engineering applications are discussed.
(Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Alkaline Phosphatase metabolism, Bone Cements chemistry, Calcium Phosphates chemistry, Humans, Imaging, Three-Dimensional methods, Biocompatible Materials chemistry, Computer-Aided Design, Printing methods, Tissue Engineering methods, and Tissue Scaffolds chemistry

Objective: To review recent literature on three-dimensional (3-D) plotting as a rapid prototyping method for the manufacturing of patient specific biomaterial scaffolds and tissue engineering constructs.
Methods: Literature review and description of own recent work.
Results: In contrast to many other rapid prototyping technologies which can be used only for the processing of distinct materials, 3-D plotting can be utilized for all pasty biomaterials and therefore opens up many new options for the manufacturing of bi- or multiphasic scaffolds or even tissue engineering constructs, containing e. g. living cells.
Conclusion: 3-D plotting is a rapid prototyping technology of growing importance which provides flexibility concerning choice of material and allows integration of sensitive biological components.

Animals, Equipment Design, Porosity, Time Factors, Tissue Scaffolds adverse effects, Microarray Analysis instrumentation, Microspheres, Tissue Engineering instrumentation, and Tissue Scaffolds chemistry

Advanced scaffold fabrication techniques such as Rapid Prototyping (RP) are generally recognized to be advantageous over conventional fabrication methods in terms architectural control and reproducibility. Yet, most RP techniques tend to suffer from resolution limitations which result in scaffolds with uncontrollable, random-size pores and low porosity, albeit having interconnected channels which is characteristically present in most RP scaffolds. With the increasing number of studies demonstrating the profound influences of scaffold pore architecture on cell behavior and overall tissue growth, a scaffold fabrication method with sufficient architectural control becomes imperative. The present study demonstrates the use of RP fabrication techniques to create scaffolds having interconnected channels as well as controllable micro-size pores. Adopted from the concepts of porogen leaching and indirect RP techniques, the proposed fabrication method uses monodisperse microspheres to create an ordered, hexagonal closed packed (HCP) array of micro-pores that surrounds the existing channels of the RP scaffold. The pore structure of the scaffold is shaped using a single sacrificial construct which comprises the microspheres and a dissolvable RP mold that were sintered together. As such, the size of pores as well as the channel configuration of the scaffold can be tailored based on the design of the RP mold and the size of microspheres used. The fabrication method developed in this work can be a promising alternative way of preparing scaffolds with customized pore structures that may be required for specific studies concerning cell-scaffold interactions.

3T3 Cells, Animals, Biomechanical Phenomena, Cell Movement drug effects, Cell Proliferation drug effects, Ink, Mice, Microscopy, Electron, Scanning, Porosity, Printing, Fibroins pharmacology, Tissue Scaffolds, and Tomography, Optical Coherence

To date, naturally derived biomaterials are rarely used in advanced tissue engineering (TE) methods despite their superior biocompatibility. This is because these native materials, which consist mainly of proteins and polysaccharides, do not possess the ability to withstand harsh processing conditions. Unlike synthetic polymers, natural materials degrade and decompose rapidly in the presence of chemical solvents and high temperature, respectively. Thus, the fabrication of tissue scaffolds using natural biomaterials is often carried out using conventional techniques, where the efficiency in mass transport of nutrients and removal of waste products within the construct is compromised. The present study identified silk fibroin (SF) protein as a suitable material for the application of rapid prototyping (RP) or additive manufacturing (AM) technology. Using the indirect RP method, via the use of a mould, SF tissue scaffolds with both macro- and micro-morphological features can be produced and qualitatively examined by spectral-domain optical coherence tomography (SD-OCT). The advanced imaging technique showed the ability to differentiate the cells and SF material by producing high contrasting images, therefore suggesting the method as a feasible alternative to the histological analysis of cell growth within tissue scaffolds.
(Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.)

Biocompatible Materials, Biopolymers therapeutic use, Bone and Bones chemistry, Bone and Bones drug effects, Humans, Inorganic Chemicals therapeutic use, Osteocytes drug effects, Osteogenesis drug effects, Porosity, Biopolymers chemistry, Inorganic Chemicals chemistry, Tissue Engineering, and Tissue Scaffolds

In recent years, considerable progress has been achieved towards the development of customized scaffold materials, in particular for bone tissue engineering and repair, by the introduction of rapid prototyping or solid freeform fabrication techniques. These new fabrication techniques allow to overcome many problems associated with conventional bone implants, such as inadequate external morphology and internal architecture, porosity and interconnectivity, and low reproducibility. However, the applicability of these new techniques is still hampered by the fact that high processing temperature or a postsintering is often required to increase the mechanical stability of the generated scaffold, as well as a post-processing, i.e., surface modification/functionalization to enhance the biocompatibility of the scaffold or to bind some bioactive component. A solution might be provided by the introduction of novel inorganic biopolymers, biosilica and polyphosphate, which resist harsh conditions applied in the RP chain and are morphogenetically active and do not need supplementation by growth factors/cytokines to stimulate the growth and the differentiation of bone-forming cells.

Cartilage cytology, Cartilage physiology, Cartilage radiation effects, Humans, Photochemical Processes, Regenerative Medicine, Bioprinting methods, Prostheses and Implants, Tissue Engineering methods, and Tissue Scaffolds

New manufacturing technologies under the banner of rapid prototyping enable the fabrication of structures close in architecture to biological tissue. In their simplest form, these technologies allow the manufacture of scaffolds upon which cells can grow for later implantation into the body. A more exciting prospect is the printing and patterning in three dimensions of all the components that make up a tissue (cells and matrix materials) to generate structures analogous to tissues; this has been termed bioprinting. Such techniques have opened new areas of research in tissue engineering and regenerative medicine.

Animals, Biocompatible Materials, Microscopy, Electron, Scanning, Polylactic Acid-Polyglycolic Acid Copolymer, Rabbits, Tomography, X-Ray Computed, Bone and Bones chemistry, Lactic Acid chemistry, Polyesters chemistry, Polyglycolic Acid chemistry, Tissue Engineering, and Tissue Scaffolds

Three dimensional tissue engineered scaffolds for the treatment of critical defect have been usually fabricated by salt leaching or gas forming technique. However, it is not easy for cells to penetrate the scaffolds due to the poor interconnectivity of pores. To overcome these current limitations we utilized a rapid prototyping (RP) technique for fabricating tissue engineered scaffolds to treat critical defects. The RP technique resulted in the uniform distribution and systematic connection of pores, which enabled cells to penetrate the scaffold. Two kinds of materials were used. They were poly(ε-caprolactone) (PCL) and poly(D, L-lactic-glycolic acid) (PLGA), where PCL is known to have longer degradation time than PLGA. In vitro tests supported the biocompatibility of the scaffolds. A 12-week animal study involving various examinations of rabbit tibias such as micro-CT and staining showed that both PCL and PLGA resulted in successful bone regeneration. As expected, PLGA degraded faster than PCL, and consequently the tissues generated in the PLGA group were less dense than those in the PCL group. We concluded that slower degradation is preferable in bone tissue engineering, especially when treating critical defects, as mechanical support is needed until full regeneration has occurred.

Animals, Biomechanical Phenomena drug effects, Dogs, Fractures, Comminuted diagnostic imaging, Fractures, Comminuted therapy, Male, Radiography, Radius diagnostic imaging, Radius drug effects, Radius pathology, Time Factors, Calcium Phosphates pharmacology, Ceramics pharmacology, Chitosan pharmacology, Fracture Healing drug effects, Fractures, Comminuted pathology, Materials Testing methods, and Tissue Scaffolds chemistry

Background: Stabilization and bone healing of fractures in weight-bearing long bones are challenging. This study was conducted to evaluate the effect of a scaffold composed of chitosan fiber and calcium phosphate ceramics (CF/CPC scaffold) on stability and fracture repair in weight-bearing long bones.
Material/methods: Comminuted fractures of paired radiuses were created in 36 healthy, mature dogs. The left radius of each dog was classified in the experimental group and treated with CF/CPC scaffold, and the right one was not filled, and was used as a blank control. Of the 12 animals in each group that were killed at week 4, 8, and 12 after the operation, 6 were used for histological analysis, and the other 6 used were for biomechanical studies. Both radiuses from each animal were dissected free and stored for these analyses. All the animals underwent X-ray radiograph pre- and post-operatively. Computer-aided rapid-prototyping technologies were adopted for the fabrication of three-dimensional scaffolds with precise geometric control.
Results: X-ray showed that the bone fracture area in the experimental group was filled with callus at week 12 after surgery. Histological examination detected slow resorption of the cement and new bone formation since week 4. At week 12, the scaffold material partially degraded and was still present in all specimens. Mechanical testing revealed that the failure strength of the radiuses treated with CF/CPC scaffolds was about 3 times that of the radiuses without implanted scaffolds.
Conclusions: The effect of using CF/CPC scaffold in treating comminuted weight-bearing long bone fractures is satisfactory.

Animals, Biocompatible Materials chemistry, Cells, Cultured, Extracellular Matrix ultrastructure, Humans, Models, Anatomic, Polymers chemistry, Robotics, Tissue Engineering trends, Tissue Scaffolds trends, Tissue Engineering methods, and Tissue Scaffolds chemistry

Advances in scaffold design and fabrication technology have brought the tissue engineering field stepping into a new era. Conventional techniques used to develop scaffolds inherit limitations, such as lack of control over the pore morphology and architecture as well as reproducibility. Rapid prototyping (RP) technology, a layer-by-layer additive approach offers a unique opportunity to build complex 3D architectures overcoming those limitations that could ultimately be tailored to cater for patient-specific applications. Using RP methods, researchers have been able to customize scaffolds to mimic the biomechanical properties (in terms of structural integrity, strength, and microenvironment) of the organ or tissue to be repaired/replaced quite closely. This article provides intensive description on various extrusion based scaffold fabrication techniques and review their potential utility for TE applications. The extrusion-based technique extrudes the molten polymer as a thin filament through a nozzle onto a platform layer-by-layer and thus building 3D scaffold. The technique allows full control over pore architecture and dimension in the x- and y- planes. However, the pore height in z-direction is predetermined by the extruding nozzle diameter rather than the technique itself. This review attempts to assess the current state and future prospects of this technology.
(Copyright © 2011 Wiley Periodicals, Inc.)

Equipment Design, Humans, Time Factors, Tissue Engineering economics, Biocompatible Materials chemistry, Microtechnology instrumentation, Tissue Engineering instrumentation, and Tissue Scaffolds chemistry

To create composite synthetic scaffolds with the same degree of complexity and multilevel organization as biological tissue, we need to integrate multilevel biomaterial processing in rapid prototyping systems. The scaffolds then encompass the entire range of properties, which characterize biological tissue. A multilevel microfabrication system, PAM(2), has been developed to address this gap in material processing. It is equipped with different modules, each covering a range of material properties and spatial resolutions. Together, the modules in PAM(2) can be used to realize complex and composite scaffolds for tissue engineering, bringing us a step closer to real clinical applications. This chapter describes the PAM(2) system and discusses some of the practical issues associated with scaffold microfabrication and biomaterial processing.

Animals, Cattle, Freezing, Porosity, Serum Albumin, Bovine metabolism, Spectroscopy, Fourier Transform Infrared, Chitosan chemistry, Polyesters chemistry, Tissue Engineering, and Tissue Scaffolds

Engineered scaffolds have been shown to be critical to various tissue engineering applications. This paper presents the development of a novel three-dimensional scaffold made from a mixture of chitosan microspheres (CMs) and poly(L-lactide) by means of the rapid freeze prototyping (RFP) technique. The CMs were used to encapsulate bovine serum albumin (BSA) and improve the scaffold mechanical properties. Experiments to examine the BSA release were carried out; the BSA release could be controlled by adjusting the crosslink degree of the CMs and prolonged after the CMs were embedded into the PLLA scaffolds, while the examination of the mechanical properties of the scaffolds illustrates that they depend on the ratio of CMs to PLLA in the scaffolds as well as the cryogenic temperature used in the RFP fabrication process. The chemical characteristics of the PLLA/chitosan scaffolds were evaluated by Fourier transform infrared (FTIR) spectroscopy. The morphological and pore structure of the scaffolds were also examined by scanning electron microscopy and micro-tomography. The results obtained show that the scaffolds have higher porosity and enhanced pore size distribution compared to those fabricated by the dispensing-based rapid prototyping technique. This study demonstrates that the novel scaffolds have not only enhanced porous structure and mechanical properties but also showed the potential to preserve the bioactivities of the biomolecules and to control the biomolecule distribution and release rate.

Bacteria drug effects, Bacteria ultrastructure, Cell Line, Tumor, Cell Proliferation drug effects, Colony Count, Microbial, Fungi drug effects, Fungi ultrastructure, Humans, Microscopy, Electron, Scanning, Polymers pharmacology, Saliva drug effects, Bacterial Adhesion drug effects, Tissue Engineering methods, and Tissue Scaffolds chemistry

Scaffolds used in the field of tissue engineering should facilitate the adherence, spreading, and ingrowth of cells as well as prevent microbial adherence. For the first time, this study simultaneously deals with microbial and tissue cell adhesion to rapid prototyping-produced 3D-scaffolds. The cell growth of human osteosarcoma cells (CAL-72) over a time period of 3-11 days were examined on three scaffolds (PLGA, PLLA, PLLA-TCP) and compared to the adhesion of salivary microorganisms and representative germs of the oral flora (Porphyromonas gingivalis, Prevotella nigrescens, Candida albicans, Enterococcus faecalis, Streptococcus mutans, and Streptococcus sanguinis). Scanning electron microscopy (SEM), cell proliferation measurements, and determination of the colony forming units (CFU) were performed. The cell proliferation rates on PLLA and PLLA-TCP after 3, 7, and 11 days of cultivation were higher than on PLGA. On day 3 the proliferation rates on PLLA and PLLA-TCP, and on day 5 on PLLA-TCP, proved to be significantly higher compared to that of the control (culture plate). The strain which showed the most CFUs on all of the investigated scaffolds was P. gingivalis, followed by E. faecalis. No significant CFU differences were determined examining P. gingivalis among the biomaterials. In contrast, E. faecalis was significantly more adherent to PLGA and PLLA compared to PLLA-TCP. The lowest CFU values were seen with C. albicans and P. nigrescens. Salivary born aerobic and anaerobic microorganisms adhered significantly more to PLGA compared to PLLA-TCP. These results supported by SEM point out the high potential of PLLA-TCP in the field of tissue engineering.
(Copyright © 2011 Wiley Periodicals, Inc.)

Animals, Bone Substitutes, Dogs, Femur anatomy histology, Microtechnology, Porosity, Tissue Engineering methods, Tomography, X-Ray Computed, X-Ray Diffraction, Calcium Phosphates chemistry, Computer-Aided Design, and Tissue Scaffolds chemistry

The tissue engineering scaffolds with three-dimensional porous structure are regarded to be beneficial to facilitate a sufficient supply of nutrients and enable cell ingrowth in bone reconstruction. However, the pores in scaffolds tend to be blocked by the cell ingrowth and result in a restraint of nutrient supply in the further side of the scaffold. An indirect approach of combining the rapid prototyping and gel-casting technique is introduced in this study to fabricate beta-tricalcium phosphate (beta-TCP) scaffolds which not only have interconnected porous structure, but also have a microchannel network inside. The scaffold was designed with customized geometry that matches the defect area, and a double-scale (micropores-microchannel) porous structure inside that is beneficial for cell ingrowth. The scaffolds fabricated have an open, uniform, and interconnected porous architecture with a pore size of 200-400 microm, and posses an internal channel network with a diameter of 600 microm. The porosity was controllable. The compressive yield strength was 4.5 MPa with a porosity of 70 per cent. X-ray diffraction analysis shows that these fabrication processes do not change the crystal structure and chemical composition of beta-TCP. With this technique, it was also possible to fabricate porous scaffolds with desired pore size, porosity, and microchannel, as well as customized geometries by other bioceramics.