Metal complexes based on the carboxylic acid analog, benzene dicarboxylic acid (BDC), of benzene 1,4-bis(bisphosphonic acid), (BBPA) were previously reported. BDC was employed to obtain UiO-66 and MIL-53, which present surface areas of 1230 and 1000 m2/g, respectively. Of these, MIL-53 yielded significant drug loading (30 % wt.) and release (6 h) of caffeine. With these in mind, we designed BBPA-based complexes able to encapsulate drugs and provide high affinity to the bone. BBPA was synthesized using the Lecouvey reaction and employed as a ligand to construct BBPA-based complexes using three bioactive metals (Zn2+, Mg2+, and Ca2+). The ligand was characterized by nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), powder and single X-ray diffraction (PXRD, SCXRD), and differential scanning calorimetric (DSC) to confirm its molecular structure and physicochemical properties. Hydrothermal synthesis of BBPA with these metals yielded four crystals phases, namely, BBPA-Ca form I, BBPA-Ca form II, BBPA-Zn and BBPA-Mg. TGA, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), PXRD and SCXRD were utilized to characterize the BBPA-based complexes. Cytotoxicity assays of the ligand were performed using the human breast cancer MDA-MB-231 cell line. This cell line represents a very aggressive type of breast cancer that metastasized to the bone. The BBPA ligand presented IC50 &gt;100 µM at 24, 48 and 72 h of treatment. Future assays will be performed with normal osteoblast-like cell lines (hFOB 1.19) and include the metal-complexes. Binding assays are ongoing to determine the affinity of BBPA and BBPA-based complexes to hydroxyapatite (main mineral of bone). Moreover, to investigate the apparent solubility and aqueous stability of BBPA and BBPA-based complexes, dissolution experiments are being conducted in phosphate-buffered saline (PBS, pH = 7.4). This investigation will lead to design principles for bisphosphonate-based drug delivery systems with high affinity to the bone, potentiating these materials to treat multiple bone-related diseases.

Extended bisphosphonates metal complexes as potential drug delivery systems

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.