In vivo imaging and biodistribution of multimodal polymeric nanoparticles delivered to the optic nerve.

The use of nanoparticles for targeted delivery of therapeutic agents to sites of injury or disease in the central nervous system (CNS) holds great promise. However, the biodistribution of nanoparticles following in vivo administration is often unknown, and concerns have been raised regarding potential toxicity. Using poly(glycidyl methacrylate) (PGMA) nanoparticles coated with polyethylenimine (PEI) and containing superparamagnetic iron oxide nanoparticles as a magnetic resonance imaging (MRI) contrast agent and rhodamine B as a fluorophore, whole animal MRI and fluorescence analyses are used to demonstrate that these nanoparticles (NP) remain close to the site of injection into a partial injury of the optic nerve, a CNS white matter tract. In addition, some of these NP enter axons and are transported to parent neuronal somata. NP also remain in the eye following intravitreal injection, a non-injury model. Considerable infiltration of activated microglia/macrophages occurs in both models. Using magnetic concentration and fluorescence visualization of tissue homogenates, no dissemination of the NP into peripheral tissues is observed. Histopathological analysis reveals no toxicity in organs other than at the injection sites. Multifunctional nanoparticles may be a useful mechanism to deliver therapeutic agents to the injury site and somata of injured CNS neurons and thus may be of therapeutic value following brain or spinal cord trauma.

The effects of concentration-dependent morphology of self-assembling RADA16 nanoscaffolds on mixed retinal cultures.

RADA16 self-assembling peptide nanofiber scaffolds (SAPNSs) have been shown to have positive effects on neural regeneration following injury to the central nervous system in vivo, but mechanisms are unclear. Here we show that RADA16 SAPNSs form scaffolds of increasing fiber density with increasing peptide concentration which in turn has a concentration-dependent effect on neurons and astrocytes in mixed retinal cultures. Importantly, we report that the final nanoscale fiber architecture is an important factor to consider in designing scaffolds to promote regeneration in the central nervous system.

Regiospecific assembly of gold nanoparticles around the pores of diatoms: toward three-dimensional nanoarrays.

The templated growth of gold nanoparticles in 3D arrays within the nanopores of unicellular diatoms involves pretreament of the skeletons with poly(vinylpyridine) which has a unique dewetting property. This self-assembly provides a nanochemical analogue of lithography for engineering complex nanostructures. The process can be universally applied to the many types of diatom skeletons which vary in size and structure.