title: Poly(N-isopropylacrylamide) copolymer films as vehicles for the sustained delivery of proteins to vascular endothelial cells.
abstract: The aim of this study was to establish the capacity of thermoresponsive poly(N-isopropylacrylamide) copolymer films to deliver bioactive concentrations of vascular endothelial growth factor (VEGF165) to human aortic endothelial cells (HAEC) over an extended time period. Films were prepared using a 50:50 (w/w) mixture of non-crosslinkable and crosslinkable copolymers of the following monomer compositions (w/w): 85:15, N-isopropylacrylamide (NiPAAm):N-tert-butylacrylamide (NtBAAm); and 85:13:2 NiPAAm:NtBAAm:acrylamidobenzophenone (ABzPh, crosslinking agent), respectively. After crosslinking by UV irradiation, the ability of films to incorporate a fluorescently labeled carrier protein (FITC-labeled BSA, 1 mg loaded per film), at 4 degrees C, was first established. Incorporation into the matrix was confirmed by the observation that increasing film thickness from 5 to 10 microm increased release from collapsed films at 37 degrees C (1.76 +/- 0.15 and 10.98 +/- 3.38 microg/mL, respectively, at 24 h postloading) and that this difference was maintained at 5 days postloading (1.81 +/- 0.25 and 13.8 +/- 2.3 microg/mL, respectively). Incorporation was also confirmed by visualization using confocal microscopy. When 10-microm films were loaded with a BSA solution (1 mg/mL) containing VEGF165 (3 microg/mL), sustained release of VEGF165 was observed (10.75 +/- 3.11 ng at 24 h; a total of 31.32 +/- 8.50 ng over 7 days). Furthermore, eluted VEGF165 increased HAEC proliferation by 18.2% over control. The absence of cytotoxic species in medium released from the copolymer films was confirmed by the lack of effect of medium (incubated with copolymer films for 3 days) on HAEC viability. In conclusion this study has shown that NiPAAm:NtBAAm copolymers can be loaded with a therapeutic protein and can deliver bioactive concentrations to human vascular endothelial cells over an extended time period.
authors.affiliation: Department of Pharmacology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland.
authors.forename: C A
authors.initials: CA
authors.lastname: Kavanagh
authors.forename: T A
authors.initials: TA
authors.lastname: Gorelova
authors.forename: I I
authors.initials: II
authors.lastname: Selezneva
authors.forename: Y A
authors.initials: YA
authors.lastname: Rochev
authors.forename: K A
authors.initials: KA
authors.lastname: Dawson
authors.forename: W M
authors.initials: WM
authors.lastname: Gallagher
authors.forename: A V
authors.initials: AV
authors.lastname: Gorelov
authors.forename: A K
authors.initials: AK
authors.lastname: Keenan
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001011:Aorta / Q000166:cytology; D049109:Cell Proliferation / Q000187:drug effects; D016503:Drug Delivery Systems; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology*; D006801:Humans; D010539:Permeability; D011506:Proteins / Q000493:pharmacokinetics*; D042461:Vascular Endothelial Growth Factor A / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D000180:Acrylic Resins; D011506:Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C052970:poly-N-isopropylacrylamide