title: Magnetically retainable microparticles for drug delivery to the joint: efficacy studies in an antigen-induced arthritis model in mice.
abstract: BACKGROUND
  Conventional corticosteroid suspensions for the intra-articular treatment of arthritis suffer from limitations such as crystal formation or rapid clearance from the joint. The purpose of this study was to investigate an innovative alternative consisting of corticosteroid encapsulation into magnetically retainable microparticles.
  
  
  METHODS
  Microparticles (1 or 10 microm) containing both superparamagnetic iron oxide nanoparticles (SPIONs) and dexamethasone 21-acetate (DXM) were prepared. In a preliminary study, we compared the persistence of microparticles of both sizes in the joint. A second study evaluated the influence of a subcutaneously implanted magnet near the knee on the retention of magnetic microparticles in the joint by in vivo imaging. Finally, the efficacy of 10-microm microparticles was investigated using a model of antigen-induced arthritis (AIA) in mice. Phosphate-buffered saline, DXM suspension, SPION suspension, blank microparticles and microparticles containing only SPIONs were used as controls. Arthritis severity was assessed using 99mTc accumulation and histological scoring.
  
  
  RESULTS
  Due to their capacity of encapsulating more corticosteroid and their increased joint retention, the 10-microm microparticles were more suitable vectors than the 1-microm microparticles for corticosteroid delivery to the joint. The presence of a magnet resulted in higher magnetic retention in the joint, as demonstrated by a higher fluorescence signal. The therapeutic efficacy in AIA of 10-microm microparticles containing DXM and SPIONs was similar to that of the DXM suspension, proving that the bioactive agent is released. Moreover, the anti-inflammatory effect of DXM-containing microparticles was more important than that of blank microparticles or microparticles containing only SPIONs. The presence of a magnet did not induce a greater inflammatory reaction.
  
  
  CONCLUSIONS
  This study confirms the effectiveness of an innovative approach of using magnetically retainable microparticles as intra-articular drug delivery systems. A major advantage comes from a versatile polymer matrix, which allows the encapsulation of many classes of therapeutic agents (for example, p38 mitogen-activated protein kinase inhibitors), which may reduce systemic side effects.
authors.affiliation: School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Quai Ernest-Ansermet 30, 1211 Geneva, Switzerland. nicoleta.butoescu@unige.ch
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Butoescu
authors.forename: Christian A
authors.initials: CA
authors.lastname: Seemayer
authors.forename: Gaby
authors.initials: G
authors.lastname: Palmer
authors.forename: Pierre-André
authors.initials: PA
authors.lastname: Guerne
authors.forename: Cem
authors.initials: C
authors.lastname: Gabay
authors.forename: Eric
authors.initials: E
authors.lastname: Doelker
authors.forename: Olivier
authors.initials: O
authors.lastname: Jordan
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism*; D002214:Capsules; D003907:Dexamethasone / Q000008:administration & dosage / Q000493:pharmacokinetics; D004195:Disease Models, Animal; D016503:Drug Delivery Systems / Q000379:methods*; D005620:Freund's Adjuvant / Q000633:toxicity; D007719:Knee Joint / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008280:Magnetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D002214:Capsules; D003907:Dexamethasone; D005620:Freund's Adjuvant