ABSTRACT
Whereas the two-dimensional (2D) visualisation of biological samples is routine, three-dimensional (3D) imaging remains a time-consuming and relatively specialised pursuit. Current commonly adopted techniques for characterising the 3D structure of non-calcified tissues and biomaterials include optical and electron microscopy of serial sections and sectioned block faces, and the visualisation of intact samples by confocal microscopy or electron tomography. As an alternative to these approaches, X-ray computed micro-tomography (microCT) can both rapidly image the internal 3D structure of macroscopic volumes at sub-micron resolutions and visualise dynamic changes in living tissues at a microsecond scale. In this Commentary, we discuss the history and current capabilities of microCT. To that end, we present four case studies to illustrate the ability of microCT to visualise and quantify: (1) pressure-induced changes in the internal structure of unstained rat arteries, (2) the differential morphology of stained collagen fascicles in tendon and ligament, (3) the development of Vanessa cardui chrysalises, and (4) the distribution of cells within a tissue-engineering construct. Future developments in detector design and the use of synchrotron X-ray sources might enable real-time 3D imaging of dynamically remodelling biological samples.
Subject(s)
Imaging, Three-Dimensional , Synchrotrons , Tomography, X-Ray Computed , Arteries/diagnostic imaging , Arteries/ultrastructure , Collagen/isolation & purification , Collagen/ultrastructure , Humans , Ligaments/diagnostic imaging , Ligaments/ultrastructure , Microscopy, Confocal , Tendons/diagnostic imaging , Tendons/ultrastructureABSTRACT
Perfusion bioreactors have been used in different tissue engineering applications because of their consistent distribution of nutrients and flow-induced shear stress within the tissue-engineering scaffold. A widely used configuration uses a scaffold with a circular cross-section enclosed within a cylindrical chamber and inlet and outlet pipes which are connected to the chamber on either side through which media is continuously circulated. However, fluid-flow experiments and simulations have shown that the majority of the flow perfuses through the center. This pattern creates stagnant zones in the peripheral regions as well as in those of high flow rate near the inlet and outlet. This non-uniformity of flow and shear stress, owing to a circular design, results in limited cell proliferation and differentiation in these areas. The focus of this communication is to design an optimized perfusion system using computational fluid dynamics as a mathematical tool to overcome the time-consuming trial and error experimental method. We compared the flow within a circular and a rectangular bioreactor system. Flow simulations within the rectangular bioreactor are shown to overcome the limitations in the circular design. This communication challenges the circular cross-section bioreactor configuration paradigm and provides proof of the advantages of the new design over the existing one.
Subject(s)
Bioreactors , Computer Simulation , Models, Theoretical , Tissue Engineering/instrumentation , Cell Division , Cells, Cultured/cytology , Cells, Cultured/metabolism , Culture Media , Equipment Design , Hydrodynamics , Perfusion , Permeability , Porosity , Tissue Scaffolds , ViscosityABSTRACT
There are several types of bioreactors currently available for the culture of orthopaedic tissue engineered constructs. These vary from the simple to the complex in design and culture. Preparation of samples for bioreactors varies depending on the system being used. This chapter presents data and describes tried and tested methodologies for the preparation of 3D samples for a Rotatory Synthecon Bioreactor (Cellon), a plate shaker, a perfusion system, and a Bose Electroforce Systems Biodynamic Instrument for the in vitro culture of bone and ligament tissue.
