Some delivery carriers with injectable characteristics were built using the thermosensitive chitosan/dextran-polylactide/glycerophosphate hydrogel and selected alginate microspheres for the controllable release of bone morphogenetic protein-2 (BMP-2). BMP-2 was first loaded into the microspheres with an average size of around 20 μm and the resulting microspheres were then embedded into the gel in order to achieve well-controlled BMP-2 release. The microsphere-embedded gels show their incipient gelation temperature at around 32 °C and pH at about 7.1. Some gels had their elastic modulus close to 1400 Pa and the ratio of elastic modulus to viscous modulus at around 34, revealing that they behaved like mechanically strong gels. Optimized microsphere-embedded gels were found to be able to administer the BMP-2 release without significant initial burst release in an approximately linear manner over a period of time longer than four weeks. The release rate and the released amount of BMP-2 from these gels could be regulated individually or cooperatively by the initial BMP-2 load and the dextran-polylactide content in the gels. Measurements of the BMP-2 induced alkaline phosphatase activity in C2C12 cells confirmed that C2C12 cells responded to BMP-2 in a dose-dependent way and the released BMP-2 from the microsphere-embedded gels well retained their bioactivity. In vivo assessment of some gels revealed that the released BMP-2 maintained its osteogenesis functions.
To find a simple and convenient method for age identification upon age-related pulp cavity narrowing, the mesiodistal diameters of the cervical pulp chamber, the middle and terminal parts of the root canal of the pulp cavity of 620 incisors were measured on radiographs taken in situ in 80 Chinese aged from 15 to 80. It was shown that the three mesiodistal diameters significantly decreased in a negative linear relationship with age (-0.4233 ≤ r ≥ -0.8465) in all incisors, but the narrowing velocity of the cervical pulp chamber and the middle part of the root canal in the maxillary incisors (b = -0.02 mm) was faster than that in the mandibular incisors (b = -0.01 mm). Accordingly, a mathematical model describing the ages as a function of any one of the three mesiodistal diameters of the pulp cavity was deduced, which would be useful for age identification in forensic medicine or archaeology.
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