Construction of pH-responsive drug delivery platform with calcium carbonate microspheres induced by chitosan gels

Construction of simple and convenient platforms for controlled delivery of anti-cancer drugs is of great importance for medical science and pharmaceutics. Here, chitosan (CS) gels were used to induce the growth of calcium carbonate (CaCO3) microspheres, and the resulting CaCO3 microspheres were well dispersed within the three-dimensional (3D) network framework of the CS gels. The synthesized CaCO3/CS composites were then examined by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR) and X-ray diffractometry (XRD). Finally, the designed CaCO3/CS composites were used for loading and controlled delivery of methotrexate (MTX), an anti-cancer drug. The encapsulation ratio of MTX calculated by UV-vis spectroscopy was approximately 78.8%. In addition, pH-responsive delivery of MTX from the CaCO3/CS composites was successfully achieved due to the pH-sensitive property of CS, and the cumulative release of MTX could reach 93.3%, 86.6% and 77.6% at pH 8.5, 7.4 and 5.8, respectively.