Tunable Surface Charge Enables the Electrostatic Adsorption-Controlled Release of Neuroprotective Peptides from a Hydrogel–Nanoparticle Drug Delivery System

Abstract

We exploit the electrostatic interactions between the positively charged neuroprotective peptide, pituitary adenylate cyclase-activating polypeptide (PACAP), and negatively charged poly(lactic-co-glycolic acid) (PLGA) nanoparticles to control PACAP release from the surface of nanoparticles dispersed in a hyaluronan-methylcellulose (HAMC) hydrogel composite. PACAP is a promising therapeutic for the treatment of neurological disorders, yet it has been difficult to deliver in vivo. Herein, the PACAP release rate was tuned by manipulating peptide adsorption onto the surface of blank nanoparticles by modifying either nanoparticle loading in the hydrogel or nanoparticle surface charge. This peptide–nanoparticle interaction was controlled by the pH-responsive carboxylic acid end terminal groups of PLGA. We further validated this system with the controlled release of a novel stabilized PACAP analog: Ac-[Ala15, Ala20]PACAP-propylamide, which masks its recognition to peptidases in circulation. Both wild-type and stabilized PACAP released from the vehicle increased the production of neuroprotective Interleukin-6 from cultured primary astrocytes. Using computational fluid dynamics methods, PACAP release from the composite was predicted based on experimentally derived adsorption isotherms, which exhibited similar release profiles to experimental data. This versatile adsorption-based system was used to deliver PACAP locally to the brains of stroke-injured mice over a 10 day period in vivo, highlighting its effectiveness for the controlled release of PACAP to the central nervous system.

Protein Release by Controlled Desorption from Transiently Cationic Nanoparticles

“…Notwithstanding these exciting results, we recognize the importance of testing this system in vivo, where the release conditions are significantly more complex than those described herein. As adsorption-based controlled protein release has previously been used successfully in murine models with positively charged proteins from negatively charged polymeric nanoparticles, 73 we are confident that our release mechanism of negatively charged proteins from positively charged polymeric nanoparticles will also be feasible in vivo.…”

Engineering Hydrogels for Affinity-Based Release of Therapeutic Proteins

“…Using this strategy, release of stromal cell-derived factor 1 (SDF-1α), neurotrophin-3 (NT-3), and BDNF from hydrogels was sustained . More recently, Ho and co-workers utilized this strategy to control the release of pituitary adenylate cyclase-activating polypeptide (PACAP), a small neuroprotective peptide, over the course of 14 days . Cheung and co-workers further developed this strategy by producing zwitterionic poly­(lactide- block -carboxybetaine) co-polymer derivative nanoparticles to enable the controlled release of negatively charged proteins …”

Biomaterial strategies for regulating the neuroinflammatory response

“…Hydrogels can also be loaded with peptides to enhance cellmaterial interactions, nanoparticles that can control the release of anti-inflammatory therapeutics, or nanoparticles that are responsive to specific stimuli. For instance, PLGA nanoparticles have been used for sustained release of anti-inflammatory drugs and growth factors 218,223,224 and are regularly loaded into HAMC hydrogels for the sustained delivery of antiinflammatory molecules for stroke treatment. 207,224 A HAMC hydrogel loaded with PLGA nanoparticles was used for the codelivery of cyclosporine and erythropoietin to modulate the inflammatory response after stroke.…”

“…For instance, PLGA nanoparticles have been used for sustained release of anti-inflammatory drugs and growth factors 218,223,224 and are regularly loaded into HAMC hydrogels for the sustained delivery of antiinflammatory molecules for stroke treatment. 207,224 A HAMC hydrogel loaded with PLGA nanoparticles was used for the codelivery of cyclosporine and erythropoietin to modulate the inflammatory response after stroke. 207 Cyclosporine is an immunosuppressant that is used to treat autoimmune diseases and has the ability to stimulate stem cells in the brain by creating a growth-permissive environment.…”