The hydrothermal reaction between bioactive metals ions Ca(II), Zn(II), and Mg(II), and clinically utilized bisphosphonate (BP) alendronic acid (ALEN) promotes the formation of several materials denominated as phosphonate-based biocompatible coordination polymers (pBioCPs). This work describes the systematic exploration of the effect of three variables M2+/BP molar ratio, temperature and pH, which yielded an unprecedented number of materials of enough crystal quality for structural elucidation (ALEN-Ca forms I and II, ALEN-Zn forms I and II). Crystal structure of these materials was unveiled by single crystal X-ray diffraction at 100 K and their solid-state properties revealed in tandem with other characterization techniques, namely, thermogravimetry, vibrational spectroscopy, and elemental analysis. The morphological and elemental along with the Raman spectra analysis initially evidenced that the formation of pBioCPs through a hydrothermal reaction had occurred. Moreover, the comparison of the thermograms between the BP ligand and the pBioCPs demonstrates the higher thermal stability of these materials. The unique crystalline arrangement of each structure is described including the apparent porosity displayed by ALEN-Ca form II. Lastly, the dissolution profile of the pBioCPs was tested and contrasted to that of the commercially employed ALEN-Na in generic (ALEN-Na USP) and brand name tablets (Fosamax®) using phosphate buffer solution (PBS) at pH = 7.40. Quantification of ALEN content, was performed by derivatization with Cu(II), which produced a complex suitable for quantification through UV-Vis spectroscopy at 240 nm. These results provide evidence of the enhanced thermal and dissolution properties of these materials and paves the way for better formulation strategies for this drug through the design of pBioCPs for the treatment of bone-related diseases.

Synthesis and elucidation of novel phosphonate-based biocompatible coordination polymers with enhanced dissolution properties

255th National Meeting (2018)

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