Evaluation of fluorinated hydroxyapatite nanoparticles as an antibacterial material for catheter coating

Catheter-related infection of peritoneal dialysis (PD) is one of the serious factors of peritonitis. However, an antibacterial PD catheter has not been commercially available in Japan yet. From an infection control viewpoint, it is necessary to develop an antibacterial coating material for catheters with a long-term effectiveness. Fluorinated hydroxyapatite (F-HAp) nanoparticles were prepared by a wet chemical process. F-HAps with different F substitution contents were prepared by adjusting the feed ratio of F ions versus sites of OH groups in HAp structures. The characterization and evaluation of F-HAps were conducted using several analytical equipment and an antibacterial powder assay. The F-HAp nanoparticles possessed highly crystalline and dispersibility. The F-HAps were named as F(30)-HAp, F(50)-HAp, and F(100)-HAp and were 24, 52, and 84% of the actual F substitution content, respectively. The nanomaterials showed acidic resistance, i.e., chemical stability, compared to normal HAp. In an antibacterial assay of F(100)-HAp with 50 mg in 0.2 mL of NaCl aqueous solution, four types of causative bacteria of catheter-related infections, Pseudomonas aeruginosa, Staphylococcus aureus, Enterobacter aerogenes, and Klebsiella pneumoniae were used. The antibacterial activities of F(100)-HAp showed 50–60% against the microorganisms. F ions were gradually released and finally plateaued at 24 weeks. The retention possibility of the antibacterial effect of F(100)-HAp potentially lasted for 24 weeks based on the F ions release behavior. It is expected that the antibacterial performance can be improved by the precise control of material engineering technology, although the duration of the effect has not yet been satisfactory for a PD catheter.