title: Engineering temperature-sensitive poly(N-isopropylacrylamide) polymers as carriers of therapeutic proteins.
abstract: This study was carried out to engineer N-isopropylacrylamide (NiPAM) polymers that contain protein-reactive N-acryloxysuccinimide (NASI) and hydrophobic alkylmethacrylates (AMAs). These thermoreversible, protein-conjugating polymers hold potential for retention of therapeutic proteins at an application site where tissue regeneration is desired. The lower critical solution temperatures (LCST) of the polymers were effectively controlled by the AMA mole content. The AMAs with longer side-chains were more effective in lowering the LCST. Polymers without NASI exhibited a stable LCST in phosphate buffer and in serum over a 10-day study period. The LCST of polymers containing NASI was found to increase over time in phosphate buffer, but not in serum-containing medium. The LCST increase in phosphate buffer was proportional to the AMA content. The feasibility of localizing a therapeutic protein, recombinant human bone morphogenetic protein-2 (rhBMP-2), to a site of application was explored in a rat intramuscular injection model. The results indicated that polymers capable of conjugating to rhBMP-2 were most effective in localizing the protein irrespective of the LCST (13-25 degrees C). For polymers with no NASI groups, a lower LCST resulted in a better rhBMP-2 localization. We conclude that thermosensitive polymers can be engineered for delivery of therapeutic proteins to improve their therapeutic efficacy.
authors.affiliation: Department of Biomedical Engineering, Faculty of Medicine and Dentistry, 1098 EDC Building, University of Alberta, Edmonton, Alberta T6G 2V2 Canada. hasan.uludag@ualberta.ca
authors.forename: H
authors.initials: H
authors.lastname: Uludag
authors.forename: B
authors.initials: B
authors.lastname: Norrie
authors.forename: N
authors.initials: N
authors.lastname: Kousinioris
authors.forename: T
authors.initials: T
authors.lastname: Gao
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000818:Animals; D001709:Biotechnology / Q000379:methods*; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D004337:Drug Carriers / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D007273:Injections, Intramuscular; D008970:Molecular Weight; D010012:Osteogenesis / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry* / Q000494:pharmacology; D013696:Temperature; D016212:Transforming Growth Factor beta
chemical_list: D000180:Acrylic Resins; C525718:BMP2 protein, human; C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004337:Drug Carriers; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; C052970:poly-N-isopropylacrylamide