Hydroxyapatite scaffolds have been being produced by a wide range of processes. The optimun material to be used as bone graft has to be partially resorbable, with resorption rates similar to new bone formation ones. The samples must have porosity compatible with tissue ingrowth. Hydroxyapatite and tricalcium phosphate ceramics are good choices for designing such materials. In the present study, polymeric sponges were coated with hydroxyapatite and sintered. The method consists of coating polyurethane sponges substrates in an aqueous solution rich in phosphate (PO4)3-and calcium (Ca)2+ions. The solution is composed by 0.5M Ca(OH)2, 0.3M H3PO4and 1M CH3CHCO2HOH (lactic acid) at pH of 3.7. The sponges were immersed in a beaker with the solution and heated up to 80°C to precipitate monetite on the sponge. Continuous and adherent coatings were formed on the surface of sponges interconections. These coatings were characterised by X-ray diffractometry and the only identified phase was monetite. The substrates were converted to hydroxyapatite in an alkali solution.The total conversion from monetite to hydroxyapatite was confirmed by XRD analyses. The struts were heat treated in order to eliminate the organic sponge and sinter the scaffolds. After sintering, hydroxyapatite and tricalcium phosphate were identified on the struts. Optical microscopy revealed the morphology of the struts, while scanning electron microscopy (SEM) showed the precipitates morphology. The method showed to be efficient in the production of porous scaffolds.
This investigation examined the effects of pharmacologically induced precocious puberty on cranial growth in Wistar rats. Forty-eight female newborn Wistar rats were divided into two groups: a control group (C) and an experimental group (E), with four subgroups of six animals each. The time interval from birth until sacrifice differed between the subgroups, and was set at 30, 60, 90, and 120 days. An intramuscular single dose (300 μg) of steroid hormone danazol was administered on day 5 after birth, as a means of inducing precocious puberty. Alizarin (2 mg/100 g) was administered to three animals in each subgroup three days prior to sacrifice. Body mass and dates corresponding to the beginning of the oestrous cycle were recorded. Craniometric measurements were undertaken. Histological analysis using light and fluorescence microscopy was then carried out to qualitatively and quantitatively evaluate the spheno-occipital synchondrosis and to visualize bone deposition patterns. The results were analysed with a Student's t-test and analysis of variance. Precocious puberty was effectively induced and differences between groups denoted an earlier maturation in the experimental rats. In qualitative analysis, a significant increase of total synchondrosis width was noted only in group E60, in comparison with C60, and an increase in the E90 subgroup cortical bone width compared with the C90 subgroup. Histomorphometrically, a statistical difference between total width values of subgroups E60 (434.3 μm) and C60 (323.5 μm) was detected. However, body mass and macroscopic measurements did not show statistically significant differences. An appropriate model for studying bone growth associated with precocious puberty in Wistar female rats was not achieved using steroid hormone danazol, when evaluated at 30 day intervals.
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