Background and purpose: Commercial gentamicin-loaded bone cement beads (Septopal®) constitute an effective delivery system for local antibiotic therapy. However, these beads are not commercially available in all parts of the world, and are too expensive for common use in others. Therefore, orthopedic surgeons worldwide make antibiotic-loaded beads themselves. However, these beads are usually not as effective as the commercial beads because of inadequate release kinetics. The aim of this study was to develop a simple, cheap and effective formulation to prepare gentamicin-loaded beads with release properties and antibacterial efficacy similar to the ones of commercially available beads.
Methods: Acrylic beads were first prepared with variable monomer contents: 500 μl/g polymer (100%), 375 μl/g polymer (75%), and 250 μl/g polymer (50%) to increase gentamicin release through the creation of a less dense polymer matrix. After optimal monomer content was defined, different gel-forming polymeric fillers were added to enhance the permeation of fluids into the beads. Polyvinylpyrrolidone (PVP) 17 was selected as a suitable filler, its concentration was varied and the antibiotic release and antibacterial efficacy of the final beads were compared with the ones of Septopal® beads.
Results: Gentamicin release rate and extend of release from beads prepared with 50% monomer increased upon increasing the PVP 17 content in the beads. Beads with 15 w/w% PVP 17 released 87% of their antibiotic content within 336 h. Importantly, this is significantly more than the gentamicin-release from Septopal® beads, that appeared confined to only 59% within 336 h. In addition, acrylic beads with 15 w/w% PVP 17 reduced bacterial growth up to 93%, which is a similar reduction as achieved with Septopal®.
Interpretation: A simple, cheap and effective formulation and preparation process has been described for hand-made gentamicin-releasing acrylic beads, with release kinetics and antibacterial efficacy similar to the ones of commercially available Septopal® beads.
