Contents

29 August 2012
Vol 4, Issue 149

About The Cover

Cover image expansion

ONLINE COVER Brain-Penetrating Particles. Nanoparticles (green) injected directly into the cortex of the brain can disperse freely throughout the brain's extracellular space (ECS), weaving in between neurons (blue) as well as other tissue components. It was previously thought that such particles needed to be very small (<40 nanometers) to diffuse throughout the brain. But now, Nance et al. show that a dense coating of the bio-inert, hydrophilic polymer poly(ethylene glycol) allows particles up to 100 nanometers to travel unobstructed through the ECS. This is in sharp contrast to uncoated particles of the same size (in red). The use of larger nanoparticles has exciting implications for drug delivery to and imaging in the brain. [CREDIT: K. SAILOR, E. NANCE, G. SUN/JOHNS HOPKINS UNIVERSITY]