Gentamicin-loaded strontium-containing hydroxyapatite bioactive bone cement--an efficient bioactive antibiotic drug delivery system.

Modified strontium-containing hydroxyapatite (Sr-HA) bone cement was loaded with gentamicin sulfate to generate an efficient bioactive antibiotic drug delivery system for treatment of bone defects. Gentamicin release and its antibacterial property were determined by fluorometric method and inhibition of Staphylococcus aureus (S. aureus) growth. Gentamicin was released from Sr-HA bone cement during the entire period of study and reached around 38% (w/w) cumulatively after 30 days. Antibacterial activity of the gentamicin loaded in the cements is clearly confirmed by the growth inhibition of S. aureus. The results of the amount and duration of gentamicin release suggest a better drug delivery efficiency in Sr-HA bone cement over polymethylmethacrylate bone cement. Bioactivity of the gentamicin-loaded Sr-HA bone cement was confirmed with the formation of apatite layer with 1.836 ± 0.037 μm thick on day 1 and 5.177 ± 1.355 μm thick on day 7 after immersion in simulated body fluid. Compressive strengths of the gentamicin-loaded Sr-HA cement reached 132.60 ± 10.08 MPa, with a slight decrease from the unloaded groups by 4-9%. Bending moduli of Sr-HA cements with and without gentamicin were 1.782 ± 0.072 GPa and 1.681 ± 0.208 GPa, respectively. On the contrary, unloaded Sr-HA cement obtained slightly larger bending strength of 35.48 ± 2.63 MPa comparing with 33.00 ± 1.65 MPa for loaded cement. No statistical difference was found on the bending strengths and modulus of gentamicin-loaded and -unloaded Sr-HA cements. Sr-HA bone cement loaded with gentamicin was proven to be an efficient drug delivery system with uncompromised mechanical properties and bioactivity.