In vitro release of theophylline and cytotoxicity of two new metal–drug complexes

Two new metal–drug complexes ([Mg(TPL) 2 (H 2 O) 4 ]) ( 1 ) and ([Ca(TPL) 2 (H 2 O) 4 ]·(TPL) 2 ( 2 ) (TPL = theophylline) were synthesized under hydrothermal conditions. Their structures were characterized by single crystal X-ray diffraction analysis, infrared spectrophotometry (IR) analysis, elemental analysis, X-ray powder diffraction (XPRD) analysis and thermogravimetric analysis (TGA). The TPL’s release rates of two complexes tablets were both obviously slower than the free TPL tablets under pure water or phosphate-buffered solution due to the coordination bonds and hydrogen bonds existence in the complexes. Compared with the cytotoxicity of TPL, two complexes showed better cytocompatibility toward NIH-3 T3 cells using an MTT assay, attributing to magnesium and calcium ions that they may have important functions for promoting the growth of NIH-3 T3 cells.