Targeting peptide homes to spinal cord injury in a rat model.

Abstract

BACKGROUND: CAQK (cysteine-alanine-lysine glutamine) is a homing peptide shown to selectively target injured regions of the brain. This study evaluated CAQK in a rodent model of spinal cord injury (SCI) to determine its localization capacity, dose-response characteristics, and temporal binding properties. METHODS: This is a preclinical pharmacology study of a nanotherapeutic drug delivery system. Twenty-four adult rats underwent C6 right-sided spinal cord hemicontusion. Animals received a tail vein injection of cyanine5-labeled CAQK (CAQK-Cy5) at low (0.5 mg/kg), medium (1.0 mg/kg), or high dose (2.5 mg/kg) or matched doses of free Cy5 dye as a control (n = 3 per group). Localization was monitored via in vivo fluorescence imaging at 1 and 24 hours in all animals and up to 7 days in an additional cohort of high-dose CAQK-Cy5 and Cy5 animals. Spinal cords were harvested for ex vivo imaging and histological confirmation of CAQK-Cy5 accumulation. RESULTS: In vivo imaging demonstrated CAQK-Cy5 signal at the SCI site within 1-hour postinjection, which persisted up to 7 days in the high-dose group. Signal intensity was dose dependent and declined over time. No significant localization was observed in control animals or uninjured spinal regions. CONCLUSION: CAQK rapidly and selectively localizes to injured spinal cord tissue in a dose-responsive manner, with peak accumulation observed within 24 hours. These findings support its potential as a targeted delivery vector for injectable therapeutics in acute SCI.