title: Cell attachment and response to photocured, degradable bone adhesives containing tricalcium phosphate and purmorphamine.
abstract: The aim of this study was to quantify and provide evidence as to how addition of tricalcium phosphate (β-TCP) and the Hedgehog agonist purmorphamine to a degradable bone adhesive affects cell attachment/proliferation and Hedgehog pathway activation. Fourier transform infrared spectroscopy demonstrated that high levels (75 wt.%) of β-TCP addition reduced the photocure rate of the chosen poly(propylene glycol-co-lactide) dimethacrylate (PPLM) bone adhesive, but this problem was overcome by increased light exposure. In phosphate-buffered saline the total surface mass loss of set 15 mm diameter PPLM films was ∼3.2 mg in 12 weeks, irrespective of thickness (200 or 400 μm) or β-TCP level (50 or 75 wt.%). With 400 μm samples there was additional bulk material loss. Proliferation of pre-osteoblast cells (MC3T3-E1) on the set adhesive surfaces was enhanced by decreased sample thickness or filler content increase. Degradation evidence suggested that both effects were due to reduced acidic polymeric degradation products. Activation of the Hedgehog pathway was quantified by measuring Gli expression in Light II reporter cells. The 0.01 and 0.1 wt.% purmorphamine in composite discs (400 μm, 75 wt.% β-TCP) enhanced Gli expression of attached cells 2- and 5-fold, respectively, without influencing their number. Pre-storage of the composite samples in culture medium had no detrimental effect on this response. Furthermore, sample storage medium gave no enhanced Gli expression in cells on tissue culture plastic. This suggests drug release levels were very low. Purmorphamine and β-TCP incorporation in PPLM adhesives might, therefore, provide prolonged enhancement of in vivo bone repair without systemic drug side-effects.
authors.affiliation: Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, 256 Gray's Inn Road, London WC1X 8LD, UK.
authors.forename: Kris
authors.initials: K
authors.lastname: Gellynck
authors.forename: Ensanya A Abou
authors.initials: EA
authors.lastname: Neel
authors.forename: Haoying
authors.initials: H
authors.lastname: Li
authors.forename: Nikos
authors.initials: N
authors.lastname: Mardas
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Donos
authors.forename: Paul
authors.initials: P
authors.lastname: Buxton
authors.forename: Anne M
authors.initials: AM
authors.lastname: Young
mesh_terms: D016475:3T3 Cells; D000269:Adhesives / Q000494:pharmacology*; D000818:Animals; D002130:Calcium Phosphates / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D051379:Mice; D009025:Morpholines / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology*
chemical_list: D000269:Adhesives; D002130:Calcium Phosphates; D009025:Morpholines; D011687:Purines; C018392:tricalcium phosphate; C470893:purmorphamine