Application of nano-hydroxyapatite/chitosan scaffolds on rat calvarial critical-sized defects: A pilot study.

BACKGROUND: The purpose of this pilot study was to evaluate for the first time the effect of 75/25 w/w nano-Hydroxyapatite/Chitosan (nHAp/CS) scaffolds on Guided Bone Regeneration (GBR) in rat calvarial critical-sized defects (CSDs). MATERIAL AND METHODS: Six adult Sprague Dawley rats, 3 males and 3 females, were used. Two CSDs, full thickness and 5mm in diameter, were trephined in both sides of the parietal bone. The right CSD was filled with nHAp/CS scaffold, while the left CSD remained empty, as the control group. The wound was sutured in layers. Rats were euthanized with diethyl ether inhalation at 2, 4 and 8 weeks after surgical procedure. Histological and histomorphometric analysis was performed within distinct regions of interest (ROI): the lateral area inward of the middle sagittal seam; the lateral area outward of the middle sagittal seam and the central area. RESULTS: The mean surface of newly formed bone (in µm2) in the lateral area inward of the middle sagittal seam of all rats was significantly higher (P=0.039) in the experimental group (91733.00±38855.60) than the control group (46762.17±25507.97). The NOex-c, defined as total number of osteocytes (OST) in newly formed bone surface in experimental group [experimental OST] minus the total number of osteocytes in newly formed bone surface in control group [control OST], was significantly greater (P=0.029) at 4th week post-surgery. Within the experimental group, a statistically significant increase (P=0.042) in the surface of newly formed bone was noticed in rats euthanized in 4th week compared with rats euthanized in 2nd week after surgery in the lateral area inward of the middle sagittal seam. CONCLUSIONS: The results of this study suggest that 75/25 w/w nHAp/CS scaffolds should be considered as a suitable biomaterial for GBR.

Covalent attachment of a bioactive hyperbranched polymeric layer to titanium surface for the biomimetic growth of calcium phosphates.

This work is investigating the chemical grafting on Ti surface of a polymer/calcium phosphate coating of improved adhesion for enhanced bioactivity. For this purpose, a whole new methodology was developed based on covalently attaching a hyperbranched poly(ethylene imine) layer on Ti surface able to promote calcium phosphate formation in a next deposition stage. This was achieved through an intermediate surface silanization step. The research included optimization both of the reaction conditions for covalently grafting the intermediate organosilicon and the subsequent hyperbranched poly(ethylene imine) layers, as well as of the conditions for the mechanical and chemical pretreatment of Ti surface before coating. The reaction steps were monitored employing FTIR and XPS analyses, whereas the surface morphology and structure of the successive coating layers were studied by SEM combined with EDS. The analysis confirmed the successful grafting of the hybrid layer which demonstrated very good ability for hydroxyapatite growth in simulated body fluid.

Imaging of Dihexadecylphosphate Vesicles by AFM and Counterion Effect on Their Size and Stability

The effect of counterions on vesicles prepared from dihexadecylphosphate is investigated. Alkali metal ions as well as an organic guanidinium counterion have been employed and it has been found that the size of the vesicles is dependent on the size of the counterions. Specifically, the bigger the counterion the smaller are the vesicles that are formed. The vesicles exhibited very good stability which was not significantly affected by the nature of the counterion. It is interesting to note that a subtle chemical modification, viz., in the nature of the counterion, can have a significant bearing on the size and morphology of the vesicles. The implications in self-assembly occurring in biological systems are therefore easy to appreciate.