International Journal of Pharmaceutics 317 (2006) 127–135 Characterization of biodegradable chitosan microspheres containing vancomycin and treatment of experimental osteomyelitis caused by methicillin-resistant Staphylococcus aureus with prepared microspheres Erdal Cevher a,∗ , Zafer Orhan b ,L¨ utfiye M ¨ ulazımo˘ glu c , Demet S ¸ ensoy a , Murat Alper d , Ayca Yıldız a , Yıldız ¨ Ozsoy a a Istanbul University, Faculty of Pharmacy, Department of Pharmaceutical Technology, Istanbul, Turkey b Abant Izzet Baysal University, School of Medicine, Department of Orthopaedics, D¨ uzce, Turkey c Marmara University, School of Medicine, Department of Infectious Diseases and Clinical Microbiology, Istanbul, Turkey d Abant Izzet Baysal University, School of Medicine, Department of Pathology, D¨ uzce, Turkey Received 27 October 2005; received in revised form 28 February 2006; accepted 2 March 2006 Available online 19 April 2006 Abstract The biodegradable chitosan microspheres containing vancomycin hydrochloride (VANCO) were prepared by spray drying method with different polymer:drug ratios (1:1, 2:1, 3:1 and 4:1). Thermal behaviour, particle size and distribution, morphological characteristics, drug content, encap- sulation efficiency, in vitro release assessments of formulations have been carried out to obtain suitable formulation which shows sustained-release effect when implanted. Sterilized VANCO loaded microspheres were implanted to proximal tibia of rats with methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. Intramuscular (IM) injection of VANCO for 21 days was applied to another group for comparison. After 3 weeks of treatment, bone samples were analysed with a microbiological assay. According to the results, encapsulation efficiency and yield of microspheres in all formulations were higher than 98% and 47%, respectively. Particle sizes of microspheres were smaller than 6 m. All microsphere formulations have shown sustained-release effect. In vitro drug release rate decreased due to the increase in polymer:drug ratio but no significant difference was seen between these results (p > 0.05). Based on our in vivo data, rats implanted VANCO-loaded chitosan microspheres and administered IM injection showed 3354 ± 3366 and 52500 ± 25635 colony forming unit of MRSA in 1 g bone samples (CFU/g), respectively. As a result, implanted VANCO-loaded microspheres were found to be more effective than IM route for the treatment of experimental osteomyelitis. © 2006 Elsevier B.V. All rights reserved. Keywords: Vancomycin; Biodegradable microspheres; Chitosan; Spray drying method; Methicillin-resistant Staphylococcus aureus; Experimental osteomyelitis 1. Introduction Osteomyelitis being a difficult infection to treat and erad- icate creates a challenging clinical problem in orthopaedics (Waldvogel et al., 1970). Increasing incidences of open fractures due to high-energy trauma from gunshot wounds, open injuries of high-speed motor vehicle accidents, bone and joint infec- tion after total joint arthroplasty, antibiotic resistant pathogenic ∗ Corresponding author at: Istanbul University, Faculty of Pharmacy, Depart- ment of Pharmaceutical Technology, 34116, Universite, Istanbul, Turkey. Tel.: +90 212 4400000/13496; fax: +90 212 440 02 52. E-mail address: erdalcevher@superonline.com (E. Cevher). organism and hospital infections and different implants may increase the incidence of osteomyelitis. The treatment of osteomyelitis can be applied in cases of modalities, surgical debridement, hyperbaric oxygen, soft tissue coverage and various methods of administration of antibiotics. Systemic antimicrobial treatments gave rise to the need of high serum concentration of the antibiotics for extended periods and thereby causing the drawbacks such as higher incidence of side effects, cost and low patient compliance. Local antibiotic treatment seems to be an ideal method with providing better patient compliance and with avoiding adverse effects such as ototoxicity and nephrotoxicity. Local antibi- otics may be given by various ways such as irrigation systems (Compere et al., 1967); venous or arterial perfusion (Finsterbush 0378-5173/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpharm.2006.03.014