The higher Si, Ca and P concentrations in the pellet matrix might be able to expedite the crystallization of the Ca-P layer on the pellet surface and hence lead to higher bioactivity in aqueous solutions.
Labelling for 2B6 was present throughout the pellet matrix (Fig. 4L).
Alizarin red and von Kossa staining were used to determine the extent of mineralisation and picro-sirius red staining was performed to demonstrate collagen fibril synthesis within the pellet matrix.
The presence of collagen fibrils within the cartilage progenitor pellet matrix was indicated by picro-sirius red staining (Fig. 4D) and on further analysis, detection of collagen type I (Fig. 4I) and collagen type II (Fig. 4J), by immunohistochemical methods, was revealed and indicated a differentiation process similar to that found during early development [44].
In addition, toluidine blue stained chondrogenic pellets indicated the presence of GAGs within the pellet matrix although this was seen at different intensities for each cell preparation.
These results indicate that during the period of 180 days, there was not sufficient physical and chemical degradation in the pellet matrix to modify the drug dissolution profile.
By varying the concentration of the test chemicals, it is possible to study dose-response relationships, and by changing the pellet matrix, the effects of release rate (dose rate) can be analyzed.
After washing, pelleted matrix was resuspended in 30 μL of 2× reducing NuPAGE® LDS Sample Buffer (Invitrogen) and boiled for 5 min. Samples were subjected to electrophoresis using precast NuPAGE® Novex 4 12% Bis-Tris gels (Invitrogen) and transferred to nitrocellulose membranes (Invitrogen).
The matrix was centrifuged at 16,000 g for 30 sec, and the pellet matrix-immune complex precipitate was washed with 500 µL of PBS buffer (5 times).
Despite the great benefits and flexibility in printing a wide range of bioinks, including tissue spheroids, tissue strands, cell pellets, decellularized matrix components, micro-carriers and cell-laden hydrogels, the technology currently faces several limitations and challenges.
