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Biomaterials and Biomedical Engineering
  Volume 2, Number 3, September 2015, pages 159-172
open access

Elution of amikacin and vancomycin from a calcium sulfate/chitosan bone scaffold
Heather A. Doty, Harry S. Courtney, Jessica A. Jennings, Warren O. Haggard and Joel D. Bumgardner

    Treatment of polymicrobial infected musculoskeletal defects continues to be a challenge in orthopaedics. This research investigated single and dual-delivery of two antibiotics, vancomycin and amikacin, targeting different classes of microorganism from a biodegradable calcium sulfate-chitosan-nHA microsphere composite scaffold. The addition of chitosan-nHA was included to provide additional structure for cellular attachment and as a secondary drug-loading device. All scaffolds exhibited an initial burst of antibiotics, but groups containing chitosan reduced the burst for amikacin at 1hr by 50%, and vancomycin by 14-25% over the first 2 days. Extended elution was present in groups containing chitosan; amikacin was above MIC (2-4 µg/mL, Pseudomonas aeruginosa) for 7-42 days and vancomycin was above MIC (0.5-1 µg/mL Staphylococcus aureus) for 42 days. The antibiotic activity of the eluates was tested against S. aureus and P. aeruginosa. The elution from the dual-loaded scaffold was most effective against S. aureus (bacteriostatic 34 days and bactericidal 27 days), compared to vancomycin-loaded scaffolds (bacteriostatic and bactericidal 14 days). The dual- and amikacin-loaded scaffolds were effective against P. aeruginosa, but eluates exhibited very short antibacterial properties; only 24 hours bacteriostatic and 1-5 hours bactericidal activity. For all groups, vancomycin recovery was near 100% whereas the amikacin recovery was 41%. In conclusion, in the presence of chitosan-nHA microspheres, the dual-antibiotic loaded scaffold was able to sustain an extended vancomycin elution longer than individually loaded scaffolds. The composite scaffold shows promise as a dual-drug delivery system for infected orthopaedic wounds and overcomes some deficits of other dual-delivery systems by extending the antibiotic release.
Key Words
    drug delivery; biodegradable scaffolds; chitosan; calcium sulfate; bone regeneration
Heather A. Doty, Jessica A. Jennings, Warren O. Haggard and Joel D. Bumgardner: Joint Program in Biomedical Engineering, University of Memphis and University of Tennessee Health
Science Center, 330 Engineering Technology Building, Memphis, Tennessee 38152, USA

Harry S. Courtney: Veterans Affairs Medical Center and Department of Medicine, University of Tennessee Health Science
Center, Memphis, Tennessee 38104, USA

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