Biomimetic Morphogenesis of Strontium Chitosan-Gelatin Composite Aggregates via EPD and Biomineralization in vitro and in vivo.

Introduction: Biomineralization has been increasingly adopted for the synthesis of advanced materials with superior properties. Hierarchical architecture growth mimicking biomineralization has been studied using various organic molecules to template inorganic materials with controlled morphology. In our previous study, self-assembled Sr/CS/G(SrCO₃-chitosan-gelatin) aggregates were fabricated using electrophoretic deposition (EPD). This study is a further step toward understanding the morphogenesis of Sr/CS/G aggregates and its biomineralization.

Methods: Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to investigate the biomimetic morphogenesis of Sr/CS/G composite under various EPD parameters, such as polymer concentration, time, and voltage. The Sr/CS/G aggregates were immersed in H₂O, phosphate-buffered saline (PBS), and simulated body fluid (SBF) to study the bioactive apatite formation ability. In addition, biocompatibility of the composites were evaluated by Fluorescence staining, SEM in vitro. The osteogenic ability of the coatings induced by PBS were tested in vivo.

Results: The CS/G weight ratio, EPD time, and voltage were found to influence the morphogenesis of Sr/CS/G aggregates. SEM and TEM results showed that the Sr/CS/G aggregates exhibited fractal growth characteristics and morphological self-similarity. XRD results confirmed the formation of SrCO₃ crystals within the framework of chitosan and gelatin organic templates. Chitosan played a vital role in branching growth of the crystals, whereas gelatin guided the formation of composite spheres. The microstructural and compositional results reveal that the Sr/CS/G-induced apatite coating yielded a large quantity of apatite. These apatite coatings promote the cytocompatibility and osteogenesis of rat bone marrow mesenchymal stem cells (rBMSCs) in vitro. The coatings induced by PBS enhanced proliferation and mineralization in vitro, and enhanced angiogenesis and osteogenesis in vivo.

Conclusion: Sr/CS/G composites prepared via EPD are promising organic-inorganic templates for biomineralization. These findings provide important insights into understanding the mineralization process and optimizing the design of advanced biological materials.