Delayed injection of polypyrrole doped with iodine particle suspension after spinal cord injury in rats improves functional recovery and decreased tissue damage evaluated by 3.0 Tesla in vivo magnetic resonance imaging

Abstract

Background context: Traumatic spinal cord injury (SCI) causes irreversible damage with loss of motor, sensory, and autonomic functions. Currently, there is not an effective treatment to restore the lost neurologic functions.

Purpose: Injection of polypyrrole-iodine(PPy-I) particle suspension is proposed as a therapeutic strategy.

Study design: This is an in vivo animal study.

Methods: This study evaluates the use of such particles in rats after SCI by examining spared nervous tissue and the Basso, Beattie, and Bresnahan (BBB) scale to evaluate the functional outcome. Diffusive magnetic resonance imaging (MRI) was employed to measure the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) as non-invasive biomarkers of damage after SCI.

Results: Fractional anisotropy decreased, whereas ADC increased in all groups after the lesion. There were significant differences in FA when compared with the SCI-PPy-I group versus the SCI group (p<.05). Significant positive correlations between BBB and FA (r²=0.449, p<.05) and between FA and preserved tissue (r²=0.395, p<.05) were observed, whereas significant negative associations between BBB and ADC (r²=0.367, p<.05) and between ADC and preserved tissue (r²=0.421, p<.05) were observed.

Conclusions: The results suggested that PPy-I is neuroprotective as it decreased the amount of damaged tissue while improving the motor function. Non-invasive MRI proved to be useful in the characterization of SCI and recovery.

Keywords: Apparent diffusion coefficient; Fraction anisotropy; Magnetic resonance imaging; Polypyrrole-Iodine particles; Spinal cord injury.