title: Charge based intra-cartilage delivery of single dose dexamethasone using Avidin nano-carriers suppresses cytokine-induced catabolism long term.
abstract: OBJECTIVE
  Avidin exhibits ideal characteristics for targeted intra-cartilage drug delivery: its small size and optimal positive charge enable rapid penetration through full-thickness cartilage and electrostatic binding interactions that give long half-lives in vivo. Here we conjugated Avidin with dexamethasone (DEX) and tested the hypothesis that single-dose Avidin-delivered DEX can ameliorate catabolic effects in cytokine-challenged cartilage relevant to post-traumatic OA.
  
  
  METHODS
  Avidin was covalently conjugated with DEX using fast (ester) and slow, pH-sensitive release (hydrazone) linkers. DEX release kinetics from these conjugates was characterized using (3)H-DEX-Avidin (scintillation counting). Cartilage explants treated with IL-1α were cultured with or without Avidin-DEX conjugates and compared to soluble DEX. Sulfated-glycosaminoglycan (sGAG) loss and biosynthesis rates were measured using DMMB assay and (35)S-incorporation, respectively. Chondrocyte viability was measured using fluorescence staining.
  
  
  RESULTS
  Ester linker released DEX from Avidin significantly faster than hydrazone under physiological buffer conditions. Single dose Avidin-DEX suppressed cytokine-induced sGAG loss over 3-weeks, rescued IL-1α-induced cell death, and restored sGAG synthesis levels without causing cytotoxicity. The two Avidin-DEX conjugates in 1:1 combination (fast:slow) had the most prominent bioactivity compared to single dose soluble-DEX, which had a shorter-lived effect and thus needed continuous replenishment throughout the culture period to ameliorate catabolic effects.
  
  
  CONCLUSIONS
  Intra-cartilage drug delivery remains inadequate as drugs rapidly clear from the joint, requiring multiple injections or sustained release of high doses in synovial fluid. A single dose of Avidin-conjugated drug enables rapid uptake and sustained delivery inside cartilage at low intratissue doses, and potentially can minimize unwanted drug exposure to other joint tissues.
authors.affiliation: Department of Mechanical Engineering, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
authors.forename: A G
authors.initials: AG
authors.lastname: Bajpayee
authors.affiliation: Department of Chemical Engineering and Koch Institute of Integrative Cancer Research, MIT, Cambridge, MA 02139, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Quadir
authors.affiliation: Department of Chemical Engineering and Koch Institute of Integrative Cancer Research, MIT, Cambridge, MA 02139, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Hammond
authors.affiliation: Department of Mechanical Engineering, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Department of Biological Engineering, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Department of Electrical Engineering & Computer Science, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. Electronic address: alg@mit.edu.
authors.forename: A J
authors.initials: AJ
authors.lastname: Grodzinsky
mesh_terms: D000818:Animals; D001360:Avidin; D002358:Cartilage, Articular / Q000187:drug effects* / Q000378:metabolism; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D004337:Drug Carriers; D005938:Glucocorticoids / Q000008:administration & dosage / Q000494:pharmacology*; D006025:Glycosaminoglycans / Q000378:metabolism; D066298:In Vitro Techniques; D053582:Interleukin-1alpha / Q000494:pharmacology*; D008660:Metabolism / Q000187:drug effects; D053758:Nanoparticles
chemical_list: D004337:Drug Carriers; D005938:Glucocorticoids; D006025:Glycosaminoglycans; D053582:Interleukin-1alpha; D001360:Avidin; D003907:Dexamethasone
keywords: Avidin; Cartilage repair; Cytokine; Dexamethasone; Electrostatic interactions; Intra-cartilage delivery