Extended and sequential delivery of protein from injectable thermoresponsive hydrogels

The unique versatility of injectable biomaterials has led to their use in many biomedical applications including tissue engineering and drug delivery. One primary advantage of this class of materials is that material injection may avoid the morbidity associated with the large incisions required for implantation of a pre-formed material. N-isopropylacrylamide has been incorporated into many biomaterials due to its favorable sol-gel behavior. Below its lower critical solution temperature of 32°C, an aqueous solution of polyNIPAAm is liquid and can be injected through a small diameter needle

Devin M. Nelson

2012

Scholarcy highlights

  • The unique versatility of injectable biomaterials has led to their use in many biomedical applications including tissue engineering and drug delivery. One primary advantage of this class of materials is that material injection may avoid the morbidity associated with the large incisions required for implantation of a pre-formed material. N-isopropylacrylamide has been incorporated into many biomaterials due to its favorable sol-gel behavior. Below its lower critical solution temperature of 32°C, an aqueous solution of polyNIPAAm is liquid and can be injected through a small diameter needle
  • Thermoresponsive hydrogels were successfully synthesized with yields >75%
  • The degradation of the copolymer, which occurs as hydrolysable methacrylate polylactide side chains are cleaved leaving a more hydrophilic polymer chain that becomes soluble at 37°C, is complete after approximately 4 to 6 months
  • The degradation profile remained similar to the 80/10/10 copolymer wherein mass loss was slow in the first few months of gel formation followed by a rapid loss of mass as MAPLA side chains were cleaved to increase hydrophilicity and allow solubilization at 37°C.8
  • Protein loaded microspheres entrapped in the hydrogel network during gel formation released protein in a delayed fashion relative to microspheres in saline
  • This composite material combines the advantages of injectability, degradability, extended release, and sequential release into a single delivery system

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