Published: April 25th, 2013
We designed a novel mechanical loading bioreactor that can apply uniaxial or biaxial mechanical strain to a cartilage biocomposite prior to transplantation into an articular cartilage defect.
We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0.15% to 0.25% full scale.
We have designed a loading bioreactor that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. This device is primarily designed as a bioreactor for engineered replacements for articular cartilage; it could also be used for other load-bearing tissues in the human body. Our motivation in this bioreactor design stems from Drachman and Sokoloff 1, who made the seminal observation of abnormal formation of articular cartilage in paralyzed chick embryos due to absence of motion. Similarly, physical exercise is essential for development of normal muscle and bone. In keeping with....
1. Biaxial Loading Bioreactor Design
The device was tested by using agarose gels seeded with 20 million cells/ml chondrocytes and cultivated in the presence of uniaxial (compression) or biaxial (compression and shear) mechanical loading. Primary porcine chondrocytes were isolated from the articular cartilage of 2-4 month old pigs. 5 mm diameter and 1.5 mm thick samples were cultured in 2 ml of defined chondrogenic culture medium (High glucose DMEM, 1% ITS+ Premix, 100 U/ml penicillin, 100 μg/ml streptomycin, 2 mM L-glutamine, 2.5 μg/ml amphotericin B,.......
We have designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to tissue engineered constructs fabricated for transplantation. The device can be used as a bioreactor for in vitro cultivation of engineered biocomposites or as a testing device to describe the mechanical characteristics of the native tissue or after other treatments prior to. The device subjects engineered tissue constructs to biaxial mechanical loading with great precision of loading dose (amplitude and .......
This work was supported by the Office of Research and Development, RR&D Service, U.S. Department of Veterans Affairs, NIH COBRE 1P20RR024484, NIH K24 AR02128 and Department of Defense W81XWH-10-1-0643.....
|DMEM, High glucose, pyruvate
|Agarose Type II
|Penicillin Streptomycin Glutamine 100X
|Pen Strep Glutamine
|Nonessential Amino Acid Solution 100x
|Recombinant Human Transforming Growth Factor β1
|Model 31 Load Cell (1000 g)
|Single Channel Display
|50 mm Linear Encoded Travelmax Stage with Stepper Actuator
|Two Channel Stepper Motor Controller
|50 mm Trapezoidal Stepper Motor Drive (2)
|Adjustable Kinematic Locator (4)
|Precision Right Angle Plate
|Vertical Mounting Bracket
|Solid Aluminum Breadboard
|Gel Casting System with 1.5 mm and 0.75 mm spacer plates
|#1653312 and #1653310
|Disposable Biopsy Punch, 5 mm
|16 mm hollow punch
|Non-Tissue Culture Treated Plates, 24 Well, Flat Bottom
|Ultra-Moisture-Resistant Polysulfone sheet for loading platens
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