| Summary: | In this study, a non destructive monitoring system for osteoblastic calcification in tissue-engineered bone in vitro was proposed and developed utilizing near-infrared light. The system consists of LEDs and a photo detector (PD) underneath a culture dish. The LED irradiates near-infrared light (I0) at 850 nm increasing its intensity to a tissue-engineered bone placed in the culture dish. The diffuse reflectance light (I) from the engineered bone is detected by the PD and the degree of calcification is evaluated by the slope of I0-I curve. A steeper slope represents higher degree of calcification. This system was calibrated with type I collagen sponge scaffolds deposited artificially with hydroxyapatite and the degree of calcification was expressed in bulk density (mg/cm3). Using this system, osteoblastic calcification in tissue-engineered bones composed of the collagen sponge scaffold and rat-primary cultured osteoblasts or MC3T3-E1 cells was monitored for 42 days. The system succeeded not only in monitoring an increase in the bulk density of the engineered bones with the culture period, but also in distinguishing the difference of calcification ability between the cells, i.e., the higher ability of rat-primary cells and the lower ability of MC3T3-E1 cells, which could not be confirmed by the observation under visible light. The results suggested the efficacy of our system using near infrared light in long-term monitoring of oeteogenesis in vitro, by which this optical monitoring system could contribute to bone tissue engineering and to basic bone biology as well.
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