332 Volume 2, Issue 3, 2012, 332-338 Received: 15.04.2012 / Accepted: 18.05.2012 / Published on-line: 15.06.2012 In vitro efficacy of antibiotic magnetic dextran microspheres complexes against Staphylococcus aureus and Pseudomonas aeruginosa strains Ecaterina Andronescu 1 , Alexandru Mihai Grumezescu 1 *, Anton Ficai 1 , Irina Gheorghe 2 , Mariana Chifiriuc 2 , Dan Eduard Mihaiescu 3 This paper describes the direct precipitation of magnetite on the surface of dextran as a method to improve the efficiency of this polymer in delivering antibiotics in active forms. FT-IR, SEM, XRD and in vitro biological assay were used to characterize the structure, composition, and the capacity of the magnetic polymeric microspheres to improve the antimicrobial activity of some antistaphylococcal and apntipseudomonal drugs. Our results demonstrated that the magnetic dextran microspheres could be used as macromolecular carriers for large-spectrum antibiotics, particularly for those with small, polar molecules belonging to penicillins, aminoglycosides, rifampicines and quinolones classes. The obtained results are suggesting that the size and the electric charge of the active drugs are influencing the specific interactions between the drug carrier and the active substance. , Veronica Lazǎr 2 Abstract Keywords: magnetic microspheres, antimicrobial activity, S. aureus, P aeuruginosa 1. INTRODUCTION_________________________________________ In the last years, magnetic nanoparticles have found an increasing interest in biomedical and engineering applications [1,2,3]. The reactivity of iron oxide particles has been shown to greatly increase as their dimensions are reduced, and they may undergo rapid biodegradation when they are directly exposed to the biological system [4,5]. Magnetic materials are used for delivering the drug carrier, represented by inorganic materials (ussualy magnetite, maghemite, cobalt ferrite, chromium dioxide) [6, 7] or polymers [8, 9, 10], to the specific site. Thermal stability, resistance to solvents and microbial attack, ease of manufacture and excellent shelf life make inorganic materials ideal supports. But they have limited functional groups for selective binding [11,12]. The substances with biological activity are thus connected to the magnetite core through an organic or polymeric shell. The shells are biocompatible in general [13] or possess active groups which can be conjugated to biomolecules [14]. Dextran is a polysaccharide and has many significant biological advantages such as being biodegradable, biocompatible and bioactive. Dextran is water soluble, inert in biological systems and does not in fluence cell viability [ 15,16 1 Department of Science and Engineering of Oxidic Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Romania *Corresponding author e-mail address: grumezescu@yahoo.com 2 Department of Microbiology and Imunology, Faculty of Biology, University of Bucharest, Romania 3 Department of Organic Chemistry, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Romania ]. This paper describes the direct precipitation of magnetite on the surface of dextran as a method to improve the efficiency of dextran in delivering antibiotics in active forms. FT-IR, SEM, XRD and in vitro biological assay were used to characterize Biointerface research in applied chemistry www.BiointerfaceResearch.com OPEN access JOURNAL ISSN 2069-5837 ORIGINAL ARTICLE