Development of a mechanically versatile bioreactor system for cellular microgravity and articular joint modeling
Keywords: Mechanical Engineering.

Cell and tissue health are influenced both by biochemical signaling factors and by the mechanical environment. Biochemical factors produced by cells can induce changes in a tissue's mechanical composition and properties; and, externally applied mechanical loading on a tissue can trigger various biochemical signaling responses. Likewise, severe underloading of tissues, as occurs in microgravity, can lead to tissue degeneration. Currently, no culture technology exists that can simultaneously capture biochemical crosstalk between co-cultures of different cell types as well as apply tissue-appropriate mechanical stimulation to them. Such a system would not only allow more for robust modeling of tissue degeneration and disease seen on Earth, but it would also provide a platform for better understanding cell health in reduced gravity conditions and for developing eventual therapeutic intervention for long-term human spaceflight travel. The primary objective of the research described this dissertation was to design, fabricate, and validate a novel bioreactor system capable of supporting both Earth- and space-based cell culture applications. The key features of the system include: small size, 2D and 3D culture capability, co-culture capability, mechanical stimulation via a contactless loading mechanism, and an adaptable and easily customizable architecture. The knee joint was used as a case study for demonstrating a prototype of the bioreactor given the well-documented interplay of mechanics and biochemical crosstalk on joint health. The work of this dissertation was divided into three parts. In the first part, a contactless loading mechanism for use with 3D cell culture was developed. Alginate hydrogels with a layer of iron-oxide nanoparticles were demonstrated to be compressible by both permanent magnets and electromagnets, and the biocompatibility of the gels was verified with a seven-day culture study. In the second part of this dissertation, two bioreactor modules with relevance to the knee joint were developed: a 3D culture module based on cartilage tissue and a 2D culture module based on synovial tissue. The contactless loading mechanism developed in the first part of the dissertation was integrated into the cartilage module in order to provide physiologically-relevant mechanical loading. For the synovium module, synoviocytes were cultured in monolayer on a permeable membrane with flow loops on either side of the membrane, representing the knee external vasculature and internal joint fluid. Fluid exchange between the two flow loops was confirmed, and synoviocyte viability was verified with a seven-day culture study. In the third and final part of this dissertation, the cartilage and synovium modules were integrated to form a baseline "joint-on-a-chip" bioreactor system. No negative biological effects were observed in either the chondrocytes or synoviocytes cultured in the bioreactor after seven days. However, the structural integrity of the magnetic alginate hydrogels in the cartilage module was unstable after multiple days in culture. Thus, further optimization of the 3D culture module is required. The cumulative work of this dissertation demonstrates a promising bioreactor technology that with further development can provide a platform for multiple Earth and space-based cell culture applications, including disease modeling and regenerative medicine therapeutics