Systematic study of stability, loading efficiency and release mechanisms, and cellular interaction of vaterite with various sizes

Porous vaterite particles are regarded as promising candidates for drug-carrying system due to their good biocompatibility, degradability, physicochemical properties. However, different particle sizes can significantly affect their drug loading efficiency (LE) and release mechanism through adsorption-desorption mechanism. Herein, we successfully synthesized CaCO3 with high content of nanoscale vaterite at subzero temperatures. The results of six different sizes of vaterite in water, PBS, SBF and NaCl revealed that particle size and medium composition had important effects on its stability. The dissolution and recrystallization kinetics of the particles were explored through the time-dependent curves of pH and Ca2+ concentration induced by the particles in PBS and SBF solutions, which provided support for the drugs release mechanism. The LE of these vaterites for Rhodamine-6G and the release mechanism in PBS and SBF media were systematically studied, indicating that smaller vaterites had higher LE and faster drug release rate, which were attributed to their higher overall surface area and free energy, and the release model supported that the drug release not only depended on diffusion mechanism but was affected by self-dissolution and recrystallization. Furthermore, vaterite exhibited good cytocompatibility through the co-culture of particles and cells, and the cells showed stronger interaction behavior to small vaterites compare to larger vaterites.