Stroke is the second cause of death worldwide with ischemic stroke accounting for 80% of all stroke insults. Caspase-3 activation contributes to brain tissue loss and downstream biochemical events that lead to programmed cell death after traumatic brain injury. Alleviation of symptoms following ischemic neuronal injury can be potentially achieved by either genetic disruption or pharmacological inhibition of caspases. Here, we studied whether silencing of Caspase-3 using carbon nanotube-mediated in vivo RNA interference (RNAi) could offer a therapeutic opportunity against stroke. Effective delivery of siRNA directly to the CNS has been shown to normalize phenotypes in animal models of several neurological diseases. It is shown here that peri-lesional stereotactic administration of a Caspase-3 siRNA (siCas 3) delivered by functionalized carbon nanotubes (f-CNT) reduced neurodegeneration and promoted functional preservation before and after focal ischemic damage of the rodent motor cortex using an endothelin-1 induced stroke model. These observations illustrate the opportunity offered by carbon nanotube-mediated siRNA delivery and gene silencing of neuronal tissue applicable to a variety of different neuropathological conditions where intervention at well localized brain foci may offer therapeutic and functional benefits.

The cytolytic ionotropic ATP receptor P2X₇ has several important roles in immune cell regulation, such as cytokine release, apoptosis, and microbial killing. Although P2X₇ receptors are frequently coexpressed with another subtype of P2X receptor, P2X₄, they are believed not to form heteromeric assemblies but to function only as homomers. Both receptors play a role in neuropathic pain; therefore, understanding how they coordinate the cellular response to ATP is important for the development of effective pain therapies. Here, we provide biochemical and electrophysiological evidence for an association between P2X₄ and P2X₇ that increases the diversity of receptor currents mediated via these two subtypes. The heterologously expressed receptors were coimmunoprecipitated from human embryonic kidney (HEK) 293 cells, and the endogenous P2X₄ and P2X₇ receptors were similarly coimmunoprecipitated from bone marrow-derived macrophages. In HEK293 cells, the fraction of P2X₄ receptors biotinylated at the plasma membrane increased 2-fold in the presence of P2X₇ although there was no change in overall expression. Coexpression of a dominant-negative P2X₄ mutant (C353W) with P2X₇, inhibited P2X₇ receptor mediated currents by greater than 2-fold, whereas a nonfunctional but non–dominant-negative mutant (S341W) did not. Coexpression of P2X₄S341W with P2X₇ produced a current that was potentiated by ivermectin and inhibited by 2′,3′-O-(2,4,6-trinitrophenyl) adenosine 5-triphosphate (TNP-ATP), whereas expression of P2X₇ alone produced a current that was insensitive to both of these compounds at the concentrations used. These results demonstrate a structural and functional interaction between P2X₄ and P2X₇, which suggests that they associate to form heteromeric receptors.

Methotrexate was tethered to multi-walled carbon nanotubes through different cleavable linkers exploiting the ammonium functionalities introduced by 1,3-dipolar cycloaddition reaction of azomethine ylides to the nanotubes. The new nanobio-hybrid conjugates were internalized into human breast cancer cells and it was shown that the cytotoxic activity was strongly dependent on the presence and type of linker.

Asthma is a chronic respiratory disease known for its high susceptibility to environmental exposure. Inadvertent inhalation of engineered or incidental nanomaterials is a concern for human health, particularly for those with underlying disease susceptibility. In this review we provide a comprehensive analysis of those studies focussed on safety assessment of different nanomaterials and their unique characteristics on asthma and allergic airway disease. These include in vivo and in vitro approaches as well as human and population studies. The weight of evidence presented supports a modifying role for nanomaterial exposure on established asthma as well as the development of the condition. Due to the variability in modelling approaches, nanomaterial characterisation and endpoints used for assessment in these studies, there is insufficient information for how one may assign relative hazard potential to individual nanoscale properties. New developments including the adoption of standardised models and focussed in vitro and in silico approaches have the potential to more reliably identify properties of concern through comparative analysis across robust and select testing systems. Importantly, key to refinement and choice of the most appropriate testing systems is a more complete understanding of how these materials may influence disease at the cellular and molecular level. Detailed mechanistic insight also brings with it opportunities to build important population and exposure susceptibilities into models. Ultimately, such approaches have the potential to more clearly extrapolate relevant toxicological information, which can be used to improve nanomaterial safety assessment for human disease susceptibility.