Latin American applied research
versión On-line ISSN 1851-8796
ITURRIA, M. et al. Basic design of lyophilization protocols for human bone tissues. Lat. Am. appl. res. [online]. 2010, vol.40, n.2, pp. 147-151. ISSN 1851-8796.
For lyophilization protocols, the shelf temperature, chamber total pressure, and process time must be selected to maximize equipment throughput while maintaining highly reliable product characteristics. A general method to estimate these operation parameters was devised and applied to the production protocols of human cancellous chips, cortical struts, and morselized bone to be used as osteoconductive allografts. The sample freezing point was estimated utilizing thermodynamic principles and the shelf temperature was set just below this value. The total chamber pressure was adjusted according to the water vapor pressure above ice, and the process time during main and final drying were estimated considering both the amount of water to be removed from each sample and the rate of heat transferred by contact and radiation from the surroundings. The initial pressure-shelf temperature-time surfaces projected for all the drying stages were tuned experimentally to yield optimized freeze-drying protocols for each type of sample.
Palabras llave : Freeze Drying; Bone Allograft; Heat Transfer.