ABSTRACT
The objective of this work was to engineer an automated system for the production of cultured epidermal autografts and sub-confluent cultured epidermal autografts. Human epidermal cells were grown directly on a transparent FEP film, which was held in place and surrounded by a polycarbonate growth chamber. The growth chambers were stacked to accommodate various surface area requirements. To monitor the development of the grafts, the upper-most growth chamber in the stack was periodically placed on a standard phase contrast microscope. The growth chambers were connected to a multi-channel peristaltic pump, which was controlled automatically to manage fluid-handling operations. Sub-confluent graft production involved removing the epidermal-film composite from the growth chambers and cutting desired graft geometries. Producing cultured epidermal autografts involved (1) removing the confluent epidermal-film composite from the growth chambers, (2) treating the composites with dispase, and (3) clipping the detached cultured epidermis to a synthetic support. Twelve to fifteen days were required to produce sub-confluent grafts (total surface area 3500-4500 cm2 50% confluent) and 18 to 24 d were required to produce standard cultured epidermal autografts (total surface area 3500-4500 cm2). The system reduces the tedious manual labor associated with producing cultured epidermal autografts.
Subject(s)
Bioreactors , Culture Techniques/methods , Epidermis/metabolism , Software , Transplantation, Autologous/methods , Carbon Dioxide/metabolism , Cell Division , Culture Techniques/instrumentation , Humans , Hydrogen-Ion Concentration , Keratinocytes/cytology , Keratinocytes/metabolism , Kinetics , Temperature , Time Factors , Transplantation, Autologous/instrumentationABSTRACT
The gas exchange portion of a phase-separated loop bioreactor was tested with respect to oxygen mass transfer and micromixing in accelerations of 0.01g, 1g, and 2g. A plot of the overall mass transfer coefficient versus gravity indicates the rate of oxygen transfer does not change as a function of acceleration. Also, it was determined that the micromixing did not exhibit significant changes in the various gravitational fields. These observations indicate the loop bioreactor should function independent of acceleration.
Subject(s)
Bioreactors , Ecological Systems, Closed , Hypergravity , Oxygen/chemistry , Space Flight/instrumentation , Weightlessness , Diazonium Compounds/chemistry , Equipment Design , Evaluation Studies as Topic , Life Support Systems/instrumentation , Naphthols/chemistry , Sulfanilic Acids/chemistryABSTRACT
The evolution of a phase-separated gravity-independent bioreactor is described. The initial prototype, a zero head-space manifold silicone membrane based reactor, maintained large diffusional resistances. Obtaining oxygen transfer rates needed to support carbon-recycling aerobic microbes is impossible if large resistances are maintained. Next generation designs (Mark I and II) mimic heat exchanger design to promote turbulence at the tubing-liquid interface, thereby reducing liquid and gas side diffusional resistances. While oxygen transfer rates increased by a factor of ten, liquid channeling prevented further increases. To overcome these problems, a Mark III reactor was developed which maintains inverted phases, i.e., media flows inside the silicone tubing, oxygen gas is applied external to the tubing. This enhances design through changes in gas side driving force concentration and liquid side turbulence levels. Combining an applied external pressure of four atmospheres with increased Reynolds numbers resulted in oxygen transfer intensities of 232 mmol O2/l/h (1000 times greater than first prototype and comparable to a conventional fermenter). A 1.0 liter Mark III reactor can potentially deliver oxygen supplies necessary to support cell cultures needed to recycle a 10 astronaut carbon load continuously.
