ABSTRACT
Collagen type I is a material widely used for 3D cell culture and tissue engineering. Different architectures, such as gels, sponges, membranes, and nanofibers, can be fabricated with it. In collagen hydrogels, the formation of fibrils and fibers depends on various parameters, such as the source of collagen, pH, temperature, concentration, age, etc. In this work, we study the fibrillogenesis process in collagen type I hydrogels with different types of microbeads embedded, using optical techniques such as turbidity assay and confocal reflectance microscopy. We observe that microbeads embedded in the collagen matrix hydrogels modify the fibrillogenesis. Our results show that carboxylated fluorescent microbeads accelerate 3.6 times the gelation, while silica microbeads slow down the formation of collagen fibrils by a factor of 1.9, both compared to pure collagen hydrogels. Our observations suggest that carboxylate microbeads act as nucleation sites and the early collagen fibrils bind to the microbeads.
Subject(s)
Collagen Type I , Hydrogels , Microspheres , Hydrogels/chemistry , Collagen Type I/chemistry , Animals , Collagen/chemistry , Tissue Engineering/methods , Hydrogen-Ion Concentration , Biocompatible Materials/chemistry , Silicon Dioxide/chemistry , Microscopy, Confocal , Temperature , Carboxylic Acids/chemistry , Materials TestingABSTRACT
The physicochemical properties and biological behavior of sintered-bovine-derived hydroxyapatite (BHAp) are here reported and compared to commercial synthetic-HAp (CHAp). Dense ceramics were sintered for 2 h and 4 h at 1200 °C to investigate their microstructure-structure-in-vitro behavior relationship for both HAp ceramics. Densification was directly proportional to sintering time, showing a grain coarsening behavior with a greater effect on BHAp. Lattice parameters, crystallite size, cell volume and Ca/P ratio were determined by Rietveld refinement of X-ray diffraction (XRD) patterns using GSAS®. Ionic substitutions (Naâº, Mg2+, CO32-) related to BHAp structure were associated with their position changes in the vibrational modes and correlated with the structural parameters obtained from the XRD analysis. Variations in the structural parameters and surface morphology were also evaluated after different soaking periods in simulated body fluid, which is associated with the formation of bone-like apatite layer and thus bioactivity. Mitochondrial activity (MTS) and lactate dehydrogenase (LDH) assays showed that the material released by the ceramics does not induce toxicity after exposure in human fetal osteoblastic (hFOB) cells. Furthermore, no statistically significant differences were found between the HAp obtained from different sources. These results show that BHAp can be used with no restrictions for the same biomedical applications as CHAp.
