Bioreactor Technology
Cellular and tissue bioengineering research aims to investigate and produce biological tissues with organ specific biochemical and biomechanical properties. This can be accomplished, in part, through the use of bioreactors. Bioreactor technology focuses on providing and maintaining optimal in vitro conditions, mimetic of the in vivo environment, to ultimately investigate mechanotransduction and cellular pathology, and to fabricate and optimise autologous tissue.
Cone and Plate Apparatus
The cone and plate apparatus can be used to investigate cellular pathology and mechanotransduction and to test viable tissue engineered constructs and/or isolated organs in vitro. It is capable of reproducing physiological time-dependent shear stress profiles and applying them to vascular cells or tissue constructs within the bioreactor. The device consists of a cone rotating on a stationary flat plate, on which cells are grown. The cone and plate device is an ideal fluid shear stress in vitro test system as it is capable of achieving a wide range of shear stresses and the design of the device is suitable for the temporal modulation of shear stress. Further development of this cone and plate system, to facilitate the study of naturally derived and synthetic scaffold materials and potential co-culturing capabilities, is currently under investigation.
Cone and Plate Device
The cone and plate apparatus utilised for this study is a standalone bioreactor. To ensure endothelial cell viability, cultures require a specific humid environment which constitutes of 95% Air and 5% CO2 at a temperature of 37ºC. The gas enters the bioreactor via a water bath heated to 37ºC ensuring a humidified culture environment. To ensure that the culture medium is maintained at 37ºC throughout the experiment, a heating element is incorporated into the design, which is maintained at a constant temperature. The temperature of the medium can be monitored throughout the experiment with a temperature sensor located within the bioreactor. A schematic of the biological environment and the controls are illustrated in figure 2.
Schematic of Biological Environment of Bioreactor and methods of controlling environment
- CO2 Supply
- Humidifier
- Biological Environment
- Motor
- Motor- Pulley System
- Spindles and Cones
- Six Well Plate
- Heat Sensor
- Heating Element
- Temperature Controller
Pressure System Bioreactor
A Pressure System Bioreactor was developed in the CABER cell culture laboratory and is designed to generate a defined cyclical inflow pressure, and expose tissue engineered constructs or isolated organs/cells to such pressure. The pressure pump takes humidified clean air from the incubator and generates pressure within the bioreactor, controlled by a titration valve. The major components of this bioreactor pressure system include a piston pump, air filters, semi-complaint tubes, a one way valve, pressure flow monitors, silicon sealants and a transparent autoclavable biochamber, Figure 3. Figure 4 shows the various parts of biochamber and the titration valve to control the pressure inside the bioreactor. This check valve allows for pressure control inside the system and can modify this pressure according to the physiological needs of the tissue or cells. The biochamber itself consists of three parts; the upper section which contains three inlet holes for pressure, the valve and the media instillation. The tissue engineered constructs are placed between the middle and lower sections. To facilitate drainage of media, an outlet valve is placed in the lower basement of the biochamber.
Bioreactor Pressure Function
As the pressure pump cycles, positively pressurised air is mobilized and introduced into the tubing system. The air exits the piston and enters the bioreator system through the air filter. The clean filtered pressurised air exerts a perpendicular direct pressure on the media on top of the cells or scaffold co-construct. The exit valve on top of the biochamber controls the amount of pressure applied to the system. Thus pulsatile, unidirectional air-fluid pressure is directed over the cells or developing vascular constructs, mimicking the pressures in mammalian vascular physiology. Moreover the pressure piston pump can vary the cycle rate, allowing for a wide range of physiological processes to be examined