Enhanced neurotrophin-3 bioactivity and release from a nanoparticle-loaded composite hydrogel

J Control Release. 2012 Jun 28;160(3):666-75. doi: 10.1016/j.jconrel.2012.03.024. Epub 2012 Apr 4.


Neurotrophin-3 (NT-3) has shown promise in regenerative strategies after spinal cord injury; however, sustained local delivery is difficult to achieve by conventional methods. Controlled release from poly(lactic-co-glycolic acid) (PLGA) nanoparticles has been studied for numerous proteins, yet achieving sustained release of bioactive proteins remains a challenge. To address these issues, we designed a composite drug delivery system comprised of NT-3 encapsulated in PLGA nanoparticles dispersed in an injectable hydrogel of hyaluronan and methyl cellulose (HAMC). A continuum model was used to fit the in vitro release kinetics of an NT-3 analog from a nanoparticle formulation. Interestingly, the model suggested that the linear drug release observed from composite HAMC was due to a diffusion-limiting layer of methyl cellulose on the particle surface. We then studied the effects of processing parameters and excipient selection on NT-3 release, stability, and bioactivity. Trehalose was shown to be the most effective additive for stabilizing NT-3 during sonication and lyophilization and PLGA itself was shown to stabilize NT-3 during these processes. Of four excipients tested, 400g/mol poly(ethylene glycol) was the most effective during nanoparticle fabrication, with 74% of NT-3 detected by ELISA. Conversely, co-encapsulation of magnesium carbonate with NT-3 was the most effective in maintaining NT-3 bioactivity over 28 days according to a cell-based axonal outgrowth assay. Together, the modeling and optimized processing parameters provide insight critical to designing a controlled bioactive release formulation for ultimate testing in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Embryo, Mammalian
  • Female
  • Ganglia, Spinal / drug effects*
  • Ganglia, Spinal / growth & development
  • Humans
  • Hyaluronic Acid / administration & dosage
  • Hyaluronic Acid / chemistry
  • Hydrogels / administration & dosage*
  • Hydrogels / chemistry
  • Hydrogen-Ion Concentration
  • Lactic Acid / administration & dosage
  • Lactic Acid / chemistry
  • Magnesium / administration & dosage
  • Magnesium / chemistry
  • Methylcellulose / administration & dosage
  • Methylcellulose / chemistry
  • Nanoparticles / administration & dosage*
  • Nanoparticles / chemistry
  • Neurites / drug effects
  • Neurites / physiology
  • Neurotrophin 3 / administration & dosage*
  • Neurotrophin 3 / chemistry
  • Polyglycolic Acid / administration & dosage
  • Polyglycolic Acid / chemistry
  • Polylactic Acid-Polyglycolic Acid Copolymer
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Proteins / administration & dosage
  • Recombinant Proteins / chemistry


  • Hydrogels
  • Neurotrophin 3
  • Recombinant Proteins
  • magnesium carbonate
  • Polylactic Acid-Polyglycolic Acid Copolymer
  • Polyglycolic Acid
  • Lactic Acid
  • Hyaluronic Acid
  • Methylcellulose
  • Magnesium