title: A pilot study of poly(N-isopropylacrylamide)-g-polyethylene glycol and poly(N-isopropylacrylamide)-g-methylcellulose branched copolymers as injectable scaffolds for local delivery of neurotrophins and cellular transplants into the injured spinal cord.
abstract: OBJECTIVE
  The authors investigated the feasibility of using injectable hydrogels, based on poly(N-isopropylacrylamide) (PNIPAAm), lightly cross-linked with polyethylene glycol (PEG) or methylcellulose (MC), to serve as injectable scaffolds for local delivery of neurotrophins and cellular transplants into the injured spinal cord. The primary aims of this work were to assess the biocompatibility of the scaffolds by evaluating graft cell survival and the host tissue immune response. The scaffolds were also evaluated for their ability to promote axonal growth through the action of released brain-derived neurotrophic factor (BDNF).
  
  
  METHODS
  The in vivo performance of PNIPAAm-g-PEG and PNIPAAm-g-MC was evaluated using a rodent model of spinal cord injury (SCI). The hydrogels were injected as viscous liquids into the injury site and formed space-filling hydrogels. The host immune response and biocompatibility of the scaffolds were evaluated at 2 weeks by histological and fluorescent immunohistochemical analysis. Commercially available matrices were used as a control and examined for comparison.
  
  
  RESULTS
  Experiments showed that the scaffolds did not contribute to an injury-related inflammatory response. PNIPAAm-g-PEG was also shown to be an effective vehicle for delivery of cellular transplants and supported graft survival. Additionally, PNIPAAm-g-PEG and PNIPAAm-g-MC are permissive to axonal growth and can serve as injectable scaffolds for local delivery of BDNF.
  
  
  CONCLUSIONS
  Based on the results, the authors suggest that these copolymers are feasible injectable scaffolds for cell grafting into the injured spinal cord and for delivery of therapeutic factors.
authors: Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Lauren
authors: L
authors: Conova
authors: Jennifer
authors: J
authors: Vernengo
authors: Ying
authors: Y
authors: Jin
authors: B Timothy
authors: BT
authors: Himes
authors: Birgit
authors: B
authors: Neuhuber
authors: Itzhak
authors: I
authors: Fischer
authors: Anthony
authors: A
authors: Lowman
authors: Jennifer
authors: J
authors: Vernengo
authors: Ying
authors: Y
authors: Jin
authors: B Timothy
authors: BT
authors: Himes
authors: Birgit
authors: B
authors: Neuhuber
authors: Itzhak
authors: I
authors: Fischer
authors: Anthony
authors: A
authors: Lowman
mesh_terms: D000178:Acrylamides / Q000494:pharmacology*; D000180:Acrylic Resins; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D017690:Cell Transplantation / Q000379:methods*; D002921:Cicatrix / Q000503:physiopathology; D004195:Disease Models, Animal; D016503:Drug Delivery Systems / Q000379:methods; D005260:Female; D006085:Graft Survival / Q000502:physiology; D020100:Hydrogels / Q000494:pharmacology; D015552:Injections, Intralesional; D008747:Methylcellulose / Q000494:pharmacology*; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology; D010865:Pilot Projects; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011108:Polymers / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000628:therapy*; D054457:Tissue Scaffolds
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D019208:Brain-Derived Neurotrophic Factor; D020100:Hydrogels; D011108:Polymers; C052970:poly-N-isopropylacrylamide; D011092:Polyethylene Glycols; D008747:Methylcellulose