RESUMO
BACKGROUND: Our previous findings have shown that poly(lactic acid)/hydroxyapatite (PLA/HA) composite biomaterials prepared by the supercritical carbon dioxide method have good physiochemical properties and biocompatibility. However, the composite materials only have osteoconductivity but no osteoinductivity. OBJECTIVE: To prepare icariin-PLA/HA (IC-PLA/HA) composite biomaterials with good osteoconduction and osteoinduction. METHODS: The supercritical carbon dioxide method was used to prepare IC-PLA/HA composite biomaterials containing 10-4, 10-5, 10-6mmol/g IC, named as IC-PLA/HA(1 000), IC-PLA/HA(100) and IC-PLA/HA(10). PLA/HA composite material served as controls. Biomechanical properties, porosity, sustained release characteristics were detected, and scanning electron microscope observation was performed, in order to screen out the optimal IC content in the composite materials. RESULTS AND CONCLUSION: (1) Compressive strength and elastic modulus of IC-PLA/HA(1 000), IC-PLA/HA(100) and IC-PLA/HA(10) showed no difference from those of PLA/HA. (2) The porosity of all the composite materials was over 75%, and there was still no difference among groups. (3) The IC release from IC-PLA/HA was faster within the first 3 days, and then reduced gradually. However, after 7 days, the IC release plateaued, and the IC release amount from the IC-PLA/HA(100) was close to 10-7mol/L that had been confirmed to be an effective and safe concentration in the previous experiments. (4) Under the scanning electron microscope, HA and PLA were mixed homogeneously and IC was difficult to be identified. The pore size of the IC-PLA/HA(100) ranged from 50 μm to 150 μm. Overall, the IC-PLA/HA composite biomaterials have good mechanical and sustained-release properties.
RESUMO
Rice leaf color mutants play a great role in research about the formation and development of chloroplasts and the genetic mechanism of the chlorophyll (Chl) metabolism pathway. pgl3 is a rice leaf color mutant derived from Xiushui11 (Oryza sativa L. spp. japonica), treated with ethyl methane sulfonate (EMS). The mutant exhibited a pale-green leaf (pgl) phenotype throughout the whole development as well as reduced grain quality. Map-based cloning of PGL3 revealed that it encodes the chloroplast signal recognition particle 43 kDa protein (cpSRP43). PGL3 affected the Chl synthesis by regulating the expression levels of the Chl synthesis-associated genes. Considerable reactive oxygen species were accumulated in the leaves of pgl3, and the transcription levels of its scavenging genes were down-regulated, indicating that pgl3 can accelerate senescence. In addition, high temperatures could inhibit the plant's growth and facilitate the process of senescence in pgl3.