title: Improvement of the antibacterial activity of daptomycin-loaded polymeric microparticles by Eudragit RL 100: an assessment by isothermal microcalorimetry.
abstract: The aim of the present study was to develop novel daptomycin-loaded acrylic microparticles with improved release profiles and antibacterial activity against two clinically relevant methicillin-susceptible and methicillin-resistant Staphylococcus aureus strains (MSSA and MRSA, respectively). Daptomycin was encapsulated into poly(methyl methacrylate) (PMMA) and PMMA-Eudragit RL 100 (EUD) microparticles by a double emulsion-solvent evaporation method. For comparison purposes similar formulations were prepared with vancomycin. Particle morphology, size distribution, encapsulation efficiency, surface charge, physicochemical properties, in vitro release and biocompatibility were assessed. Particles exhibited a micrometer size and a spherical morphology. The addition of EUD to the formulation caused a shift in the surface charge of the particles from negative zeta potential values (100% PMMA formulations) to strongly positive. It also improved daptomycin encapsulation efficiency and release, whereas vancomycin encapsulation and release were strongly hindered. Plain and antibiotic-loaded particles presented comparable biocompatibility profiles. The antibacterial activity of the particles was assessed by isothermal microcalorimetry against both MSSA and MRSA. Daptomycin-loaded PMMA-EUD particles presented the highest antibacterial activity against both strains. The addition of 30% EUD to the daptomycin-loaded PMMA particles caused a 40- and 20-fold decrease in the minimum inhibitory (MIC) and bactericidal concentration (MBC) values, respectively, when compared to the 100% PMMA formulations. On the other hand, vancomycin-loaded microparticles presented the highest antibacterial activity in PMMA particles. Unlike conventional methods, isothermal microcalorimetry proved to be a real-time, sensitive and accurate method for assessment of antibacterial activity of antibiotic-loaded polymeric microparticles. Finally, the addition of EUD to formulations proved to be a powerful strategy to improve daptomycin encapsulation efficiency and release, and consequently improving the microparticles activity against two relevant S. aureus strains.
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Portugal.
authors.forename: Inês Santos
authors.initials: IS
authors.lastname: Ferreira
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Bettencourt
authors.affiliation: Infectious Diseases Service, Department of Medicine, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Bétrisey
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Portugal.
authors.forename: Lídia M D
authors.initials: LM
authors.lastname: Gonçalves
authors.affiliation: Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Free and Humboldt-University of Berlin, Berlin, Germany.
authors.forename: Andrej
authors.initials: A
authors.lastname: Trampuz
authors.affiliation: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Portugal. Electronic address: aalmeida@ff.ulisboa.pt.
authors.forename: António J
authors.initials: AJ
authors.lastname: Almeida
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry* / Q000633:toxicity; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D002151:Calorimetry / Q000379:methods*; D002152:Calorimetry, Differential Scanning; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002626:Chemistry, Pharmaceutical; D017576:Daptomycin / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D007700:Kinetics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D051379:Mice; D008826:Microbial Sensitivity Tests; D010316:Particle Size; D019904:Polymethyl Methacrylate / Q000737:chemistry* / Q000633:toxicity; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D013499:Surface Properties; D013678:Technology, Pharmaceutical / Q000379:methods*; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000180:Acrylic Resins; D000900:Anti-Bacterial Agents; D003692:Delayed-Action Preparations; D004337:Drug Carriers; C050528:Eudragit RS; D014640:Vancomycin; D019904:Polymethyl Methacrylate; D017576:Daptomycin
keywords: Controlled release; Daptomycin; Eudragit; Isothermal microcalorimetry; Microencapsulation; PMMA; Vancomycin