title: Applicability of a newly developed bioassay for determining bioactivity of anti-inflammatory compounds in release studies--celecoxib and triamcinolone acetonide released from novel PLGA-based microspheres.
abstract: OBJECTIVE
  To develop a bio-assay for measuring long-term bioactivity of released anti-inflammatory compounds and to test the bioactivity of celecoxib (CXB) and triamcinolone acetonide (TA) released from a new PLGA-based microsphere platform.
  
  
  METHODS
  Human osteoarthritic chondrocytes were plated according to standardized procedures after batch-wise harvest and cultured for 3 days to prevent cell confluency and changes in cell behaviour. Prostaglandin E2 (PGE2) production stimulated by TNFα was used as a parameter of inflammation. A novel microsphere platform based on PTE-functionalised PLGA was used to incorporate CXB and TA. Loaded microspheres were added to transwells overlying the cells, with transfer of the wells to new cell cultures every 3 days. Inhibition of PGE2 production was determined over a period of 21 days.
  
  
  RESULTS
  PLGA(75:25)-PTE microspheres were prepared and loaded with CXB and TA at 86 and 97% loading efficiency, respectively. In the bioactivity assay, PGE2 levels induced by TNFα were reduced to an average of 30% using microspheres loaded with 0.1 nmol CXB per transwell; with microspheres loaded with 0.1 nmol TA, PGE2 production was initially reduced to 3% and gradually recovered to 30% reduction. At 1 nmol loading, PGE2 was inhibited to 0-7% for CXB-loaded microspheres, and 0-28% for TA-loaded microspheres.
  
  
  CONCLUSIONS
  We present a novel sustained release bioactivity assay which provides an essential link between in vitro buffer-based release kinetics and in vivo application. Novel PLGA-based microspheres loaded with TA and CXB showed efficient anti-inflammatory effects over time.
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, Heidelberglaan 100, PO Box 85500, 3508 GA, Utrecht, The Netherlands.
authors.forename: Hsiao-yin
authors.initials: HY
authors.lastname: Yang
authors.forename: Maarten
authors.initials: M
authors.lastname: van Dijk
authors.forename: Ruud
authors.initials: R
authors.lastname: Licht
authors.forename: Michiel
authors.initials: M
authors.lastname: Beekhuizen
authors.forename: Mattie
authors.initials: M
authors.lastname: van Rijen
authors.forename: Martina Källrot
authors.initials: MK
authors.lastname: Janstål
authors.forename: F Cumhur
authors.initials: FC
authors.lastname: Öner
authors.forename: Wouter J A
authors.initials: WJ
authors.lastname: Dhert
authors.forename: Detlef
authors.initials: D
authors.lastname: Schumann
authors.forename: Laura B
authors.initials: LB
authors.lastname: Creemers
mesh_terms: D000893:Anti-Inflammatory Agents / Q000737:chemistry / Q000378:metabolism*; D001681:Biological Assay / Q000379:methods; D000068579:Celecoxib; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism; D004337:Drug Carriers / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D019344:Lactic Acid / Q000737:chemistry / Q000378:metabolism*; D008863:Microspheres; D011100:Polyglycolic Acid / Q000737:chemistry / Q000378:metabolism*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011720:Pyrazoles / Q000737:chemistry / Q000378:metabolism*; D013449:Sulfonamides / Q000737:chemistry / Q000378:metabolism*; D014222:Triamcinolone Acetonide / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; D004337:Drug Carriers; D011720:Pyrazoles; D013449:Sulfonamides; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D014222:Triamcinolone Acetonide; D000068579:Celecoxib