Incorporation of different antibiotics into carbonated hydroxyapatite coatings on titanium implants, release and antibiotic efficacy

Carbonated hydroxyapatite (CHA) coatings were applied onto titanium implants by using a biomimetic precipitation method. Different antibiotics were incorporated into the CHA coatings and their release and efficacy against bacteria growth were studied in vitro. The following antibiotics were used within this study: cephalothin, carbenicillin, amoxicillin, cefamandol, tobramycin, gentamicin and vancomycin. Increased concentrations of antibiotics in the coating solution led to a higher quantity of antibiotic incorporated into the CHA coating. Some antibiotics were better incorporated than others depending on their chemical structure. Antibiotics, containing carboxylic groups such as cephalothin, carbenicillin and cefamandol, were better incorporated than antibiotics lacking these groups. A bacterial inhibition test on Staphylococcus aureus bacteria showed inhibition of growth for all antibiotics that were released from the CHA coating. A release test was conducted in phosphate buffer saline PBS at pH 7.4 and 37 °C and showed that antibiotics containing carboxylic groups like cephalothin were slower released from the CHA coating than others. These results suggest that certain antibiotics are able to bind/chelate with calcium, resulting in a better incorporation into the CHA coating and a slower release. Antibiotics incorporated in CHA coatings on titanium implants might be used to prevent post-surgical infections and to promote bone-bonding of orthopedic devices.