Targeting reactive astrocytes by pH-responsive ligand-bonded polymeric nanoparticles in spinal cord injury.

In spinal cord injuries, axonal regeneration decreases with the activation of astrocytes followed by glial scar formation. Targeting reactive astrocytes has been recently performed by unsafe viral vectors to inhibit gliosis. In the current study, biocompatible polymeric nanoparticles were selected as an alternative for viruses to target reactive astrocytes for further drug/gene delivery applications. Lipopolysaccharide-bonded chitosan-quantum dots/poly acrylic acid nanoparticles were prepared by ionic gelation method to target reactive astrocytes both in vitro and in spinal cord-injured rats. Owing to their biocompatibility and pH-responsive behavior, chitosan and poly acrylic acid were the main components of nanoparticles. Nanoparticles were then chemically labeled with quantum dots to track the cell uptake and electrostatically interacted with lipopolysaccharide as a targeting ligand. In vitro and in vivo studies were performed in triplicate and all data were expressed as the mean ± the standard error of the mean. Smart nanoparticles with optimum size (61.9 nm) and surface charge (+ 12.5 mV) successfully targeted primary reactive astrocytes extracted from the rat cerebral cortex. In vitro studies represented high cell viability (96%) in the exposure of biocompatible nanoparticles. The pH-responsive behavior of nanoparticles was proved by their internalization into the cell's nuclei due to the swelling and endosomal escape of nanoparticles in acidic pH. In vivo studies demonstrated higher transfection of nanoparticles into reactive astrocytes compared to the neurons. pH-responsive ligand-bonded chitosan-based nanoparticles are good alternatives for viral vectors in targeted delivery applications for the treatment of spinal cord injuries.