Abstract
Nanocrystalline hydroxyapatite (nanoHA) is the main hard component of bone and has the potential to be used to promote osseointegration of implants and to treat bone defects. Here, using active pharmaceutical ingredients (APIs) such as ibuprofen, we report on the prospects of combining nanoHA with biologically active compounds to improve the clinical performance of these treatments. In this study, we designed and investigated the possibility of API attachment to the surface of nanoHA crystals via the formation of a hydrogen-bonded complex. The mechanistic studies of an ibuprofen/nanoHA complex formation have been performed using a holistic approach encompassing spectroscopic (Fourier transform infrared (FTIR) and Raman) and X-ray diffraction techniques, as well as quantum chemistry calculations, while comparing the behavior of the ibuprofen/nanoHA complex with that of a physical mixture of the two components. Whereas ibuprofen exists in dimeric form both in solid and liquid state, our study showed that the formation of the ibuprofen/nanoHA complex most likely occurs via the dissociation of the ibuprofen dimer into monomeric species promoted by ethanol, with subsequent attachment of a monomer to the HA surface. An adsorption mode for this process is proposed; this includes hydrogen bonding of the hydroxyl group of ibuprofen to the hydroxyl group of the apatite, together with the interaction of the ibuprofen carbonyl group to an HA Ca center. Overall, this mechanistic study provides new insights into the molecular interactions between APIs and the surfaces of bioactive inorganic solids and sheds light on the relationship between the noncovalent bonding and drug release properties.
Highlights
Hydroxyapatite, with its chemical formula Ca10(PO4)6(OH)[2], is a major inorganic component of bone and, along with collagen fibrils, it accounts for up to 65% of the hard tissue of vertebrates
We elucidated the mechanism of the ibuprofen adsorption onto the surface of nanohydroxyapatite and its effects on the drug dissolution rate, explaining earlier findings on the shift of the Fourier transform infrared (FTIR) signal of the carbonyl group of the active pharmaceutical ingredients (APIs) in the presence of ceramics
Using an array of characterization tools, we demonstrated that, when synthesizing an ibuprofen/ceramic complex, hydrogen bonding occurs between the carbonyl group of the API and a Ca center of hydroxyapatite (HA)
Summary
Hydroxyapatite (abbreviated as HA), with its chemical formula Ca10(PO4)6(OH)[2], is a major inorganic component of bone and, along with collagen fibrils, it accounts for up to 65% of the hard tissue of vertebrates. HA-based ceramic drug carriers, in turn, have been studied as prospective drug delivery systems for the treatment of bone infection,[12,13] as well as arthritis.[14] Osteoarthritis and rheumatoid arthritis, despite having different causes behind the diseases, share similar symptoms of chronic pain due to associated peripheral inflammation. Both are considered to be important public health concerns,[15] with osteoarthritis being the most common cause for total hip or knee replacement. The results of total arthroplasty in arthritic patients shows that HA-coated prostheses have excellent medium-term efficacy,[16] promoting osseointegration and, in turn, opening up the prospects of using bioactive ceramics as drug carriers for the treatment of bone diseases
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