Surfactant free rapid synthesis of hydroxyapatite nanorods by a microwave irradiationmethod for the treatment of bone infection

Abstract

Mesoporous nanocrystalline hydroxyapatite (nHAp) rods of size 40–75 nm long and 25 nm wide(resembling bone mineral) were synthesized under microwave irradiation without using anysurfactants or modifiers. The surface area and average pore size of the nHAp were found to be32 m2 g − 1 and 4 nm, respectively. Rifampicin (RIF) and ciprofloxacin (CPF) loaded nHAp displayedan initial burst followed by controlled release (zero order kinetics). Combination of CPFand RIF loaded nHAp showed enhanced bacterial growth inhibition against Staphylococcusaureus (S aureus), Staphylococcus epidermidis (S epidermidis) and Escherichia coli (E coli)compared to individual agent loaded nHAp and pure nHAp. In addition, decreasedbacterial adhesion (90%) was observed on the surface of CPF plus RIF loaded nHAp. Thebiocompatibility test toward MG63 cells infected with micro-organisms showed better cellviability and alkaline phosphatase activity (ALP) for the combination of CPF and RIFloaded nHAp. The influence on cell viability of infected MG63 cells was attributedto the simultaneous and controlled release of CPF and RIF from nHAp, whichprevented the emergence of subpopulations that were resistant to each other.Hence, apart from the issue of the rapid synthesis of nHAp without surfactantsor modifiers, the simultaneous and controlled release of dual drugs from nHApwould be a simple, non-toxic and cost-effective method to treat bone infections.