Spatial control of protein within biomimetically nucleated mineral

An ideal approach for bone tissue engineering allows for osteoconductivity, osteoinductivity, and cell transplantation. In this study, we examined coprecipitation and surface adsorption schemes with respect to their abilities to control the spatial quantity and localization of a model protein, bovine serum albumin (BSA), that is incorporated into a biomimetic apatite layer nucleated onto polylactic-co-glycolic acid (PLGA) films. Protein incorporation was characterized by determining protein: presence, quantity loaded, retention, effects on mineral morphology, and localization. FT-IR confirmed the presence of protein in all coprecipitation samples with stronger peaks in the coprecipitated samples compared to the surface adsorbed samples. Coprecipitation resulted in higher loading capacities and higher protein retention versus adsorption. Protein incorporation via coprecipitation changed the mineral morphology from sharp plate-like structures to more rounded structures, whereas, surface adsorption did not change mineral structure. By using confocal microscopy to examine the incorporation of fluorescently labeled proteins, spatial control over protein localization was exhibited. By controlling the loading quantity and localization of the model protein through the mineral thickness, a desired release profile can be achieved. A desired and effective delivery system of biological agents utilizing coprecipitation for bone regeneration can therefore be designed.