Research into the use of nanotechnology in treating stroke has produced evidence of significant motor function recovery. The use of carbon nanotubes to deliver short strands of RNA – called siRNA – and induce gene silencing of specific target areas in the brain responsible for motor functions has allowed scientists to ‘switch off’ proteins that contribute to neuronal tissue loss. This collaborative and highly multidisciplinary project offers the possibility of a new treatment for stroke.
Stroke is the second most common cause of death worldwide with over 80% of all stroke cases occurring as a result of an obstruction within a blood vessel supplying blood to the brain. Ischemic or traumatic brain injury can lead to the unwanted activation of a protein, caspase 3, which contributes to brain tissue loss. This "executioner" protein can be “switched off” through the use of siRNA – a molecule that obstructs the expression of genes. The challenge of delivering siRNA in sufficient quantities to specific brain regions was achieved through the use of nanotubes injected directly into the brain by high precision neurosurgical techniques.
These extraordinary nanometer-scale tubes of graphitic carbon are among the stiffest and strongest fibers known and have a structure that can have a length-to-diameter ratio as large as 28,000,000:1. Similar to a syringe at the nanometer scale, nanotubes were used to transport siRNA and silence genes in the brain in an effective manner. A combination of this promising gene therapy approach with a cutting-edge nanoscale delivery system was able to demonstrate functional recovery in stroke-ridden animals.
Nanotubes carrying siRNA against Caspase-3 were injected in the part of cerebral cortex controlling the movement of the forelimb and stroke was induced in the treated cortex. The authors found that the treatment protected neuronal cells from death and promoted recovery in a behavioral test of motor coordination that is normally affected by this type of lesion. A similar dose of siRNA administered alone, without nanotubes, was not effective on neuronal death or motor performance indicating that nanotubes were responsible for the activity and functional recovery obtained.
Professor Kostas Kostarelos (pictured), Chair of Nanomedicine and Head of the Centre for Drug Delivery Research said:
‘’We are delighted to see carbon nanotubes offer therapeutic options at the pre-clinical level, for debilitating and extremely challenging to intervene pathologies such as stroke. Still at very early stages towards their clinical development, carbon nanomaterials encourage us with their capabilities to transport biologically-active molecules intracellularly, even in the notoriously difficult to transfect neuronal tissue.’’
Illustration: The School of Pharmacy, University of London.
The School of Pharmacy, University of London News Release (06/20/11)
Medical News Today (06/19/11)
Abstract (Proceedings of the National Academy of Sciences of the United States of America; (06/20/11))