Fullerene (C60) derivatives have been extensively studied for a variety of medical applications, which include neuroprotective agents, HIV-1 protease inhibitors, photodynamic cancer therapeutics, medical contrast agents and radiotracers, slow release systems for aerosol liposome delivery, immunotherapy agents, and transfection vectors. The first part of this work is dedicated to the study of the in-vivo safety and efficacy of an orally-dosed bone-vectored C60-bisphosphonated compound as a therapeutic agent to prevent and treat osteoporosis.
Hydrophilic bisphosphonate groups are known to possess high affinity for the main bone mineral hydroxyapatite. Thus, functionalization of C 60 with bisphosphonate groups should lead to bone-vectored, water-soluble C60 derivatives. Previously developed C60[C(PO 3H2)2]2 was administered orally in a rat model of osteoporosis for eight weeks in two separate Experiments at doses of 1 mg/kg and 2.5 mg/kg, respectively. These studies demonstrated that C60[C(PO3H2)2]2 is safe in the rat model: no significant behavior changes occurred, weight gains were normal, and no significant pathology was noted in either the kidney, the liver or the esophagus of the animals. Micro-CT and DXA studies showed significant and positive changes in the bone architecture of the treated ovariectomized animals which proved, for the first time, that Cho-derivatives can be absorbed by the digestive tract and therefore that C60-based scaffolds can be used for oral drug delivery. Just as significantly, the studies also showed that C60[C(PO3H2)2]2 effectively targets bone, making the compound the first example of an in-vivo tissue- targeted C60-based drug.
The second part of this work is dedicated to the synthesis and characterization of a beta-blocker conjugate of C60[C(PO3H2) 2]2 as a new targeted therapy for osteoporosis. The sympathetic nervous system of mice mediates bone resorption through beta2-adrenergic receptors on bone cells. Thus, the blockage of these receptors could prevent or treat osteoporosis. A non-selective beta-blocker, levobunolol, has been successfully linked to a malonate through a hydrazone formation and then coupled to a C60 via Bingel chemistry. Finally, the beta-blocker malonate compound has been also successfully coupled to C60[C(PO3H 2)2]2 to form the final target compound, a C 60-Bisphosphonate-Beta-blocker conjugate as a new targeted therapy for osteoporosis.