Journal Of Zhejiang University. Science. B [J Zhejiang Univ Sci B] 2017 Apr.; Vol. 18 (4), pp. 303-315.
Animals, Bone Regeneration, Bone Substitutes, Bone Transplantation, Humans, Printing, Three-Dimensional, Tissue Engineering instrumentation, Tissue Scaffolds, Bone and Bones physiology, Bone and Bones surgery, and Tissue Engineering methods
Bone defects arising from a variety of reasons cannot be treated effectively without bone tissue reconstruction. Autografts and allografts have been used in clinical application for some time, but they have disadvantages. With the inherent drawback in the precision and reproducibility of conventional scaffold fabrication techniques, the results of bone surgery may not be ideal. This is despite the introduction of bone tissue engineering which provides a powerful approach for bone repair. Rapid prototyping technologies have emerged as an alternative and have been widely used in bone tissue engineering, enhancing bone tissue regeneration in terms of mechanical strength, pore geometry, and bioactive factors, and overcoming some of the disadvantages of conventional technologies. This review focuses on the basic principles and characteristics of various fabrication technologies, such as stereolithography, selective laser sintering, and fused deposition modeling, and reviews the application of rapid prototyping techniques to scaffolds for bone tissue engineering. In the near future, the use of scaffolds for bone tissue engineering prepared by rapid prototyping technology might be an effective therapeutic strategy for bone defects.
Bottom-up tissue engineering requires methodological progress of biofabrication to capture key design facets of anatomical arrangements across micro, meso and macro-scales. The diffusive mass transfer properties necessary to elicit stability and functionality require hetero-typic contact, cell-to-cell signaling and uniform nutrient diffusion. Bioprinting techniques successfully build mathematically defined porous architecture to diminish resistance to mass transfer. Current limitations of bioprinted cell assemblies include poor micro-scale formability of cell-laden soft gels and asymmetrical macro-scale diffusion through 3D volumes. The objective of this work is to engineer a synchronized multi-material bioprinter (SMMB) system which improves the resolution and expands the capability of existing bioprinting systems by packaging multiple cell types in heterotypic arrays prior to deposition. This unit cell approach to arranging multiple cell-laden solutions is integrated with a motion system to print heterogeneous filaments as tissue engineered scaffolds and nanoliter droplets. The set of SMMB process parameters control the geometric arrangement of the combined flow's internal features and constituent material's volume fractions. SMMB printed hepatocyte-endothelial laden 200 nl droplets are cultured in a rotary cell culture system (RCCS) to study the effect of microgravity on an in vitro model of the human hepatic lobule. RCCS conditioning for 48 h increased hepatocyte cytoplasm diameter 2 μm, increased metabolic rate, and decreased drug half-life. SMMB hetero-cellular models present a 10-fold increase in metabolic rate, compared to SMMB mono-culture models. Improved bioprinting resolution due to process control of cell-laden matrix packaging as well as nanoliter droplet printing capability identify SMMB as a viable technique to improve in vitro model efficacy.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi = Zhongguo Xiufu Chongjian Waike Zazhi = Chinese Journal Of Reparative And Reconstructive Surgery [Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi] 2014 Mar; Vol. 28 (3), pp. 279-85.
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.
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.
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.