Nanosize Titanium Dioxide Stimulates Reactive Oxygen Species in Brain Microglia and Damages Neurons in Vitro

BackgroundTitanium dioxide is a widely used nanomaterial whose photo-reactivity suggests that it could damage biological targets (e.g., brain) through oxidative stress (OS).ObjectivesBrain cultures of immortalized mouse microglia (BV2), rat dopaminergic (DA) neurons (N27), and primary cultures of embryonic rat striatum, were exposed to Degussa P25, a commercially available TiO2 nanomaterial. Physical properties of P25 were measured under conditions that paralleled biological measures.FindingsP25 rapidly aggregated in physiological buffer (800–1,900 nm; 25°C) and exposure media (~ 330 nm; 37°C), and maintained a negative zeta potential in both buffer (–12.2 ± 1.6 mV) and media (–9.1 ± 1.2 mV). BV2 microglia exposed to P25 (2.5–120 ppm) responded with an immediate and prolonged release of reactive oxygen species (ROS). Hoechst nuclear stain was reduced after 24-hr (≥100 ppm) and 48-hr (≥2.5 ppm) exposure. Microarray analysis on P25-exposed BV2 microglia indicated up-regulation of inflammatory, apoptotic, and cell cycling pathways and down-regulation of energy metabolism. P25 (2.5–120 ppm) stimulated increases of intracellular ATP and caspase 3/7 activity in isolated N27 neurons (24–48 hr) but did not produce cytotoxicity after 72-hr exposure. Primary cultures of rat striatum exposed to P25 (5 ppm) showed a reduction of immunohistochemically stained neurons and microscopic evidence of neuronal apoptosis after 6-hr exposure. These findings indicate that P25 stimulates ROS in BV2 microglia and is nontoxic to isolated N27 neurons. However, P25 rapidly damages neurons at low concentrations in complex brain cultures, plausibly though microglial generated ROS

Users as Innovators: Implications for Patent Doctrine

User innovators range from commercial firms, which invent new production methods in expectation of competitive advantage, to individual hobbyists motivated entirely by their enjoyment of the inventive process. In this Article, I consider the implications for patent doctrine of the fact that many user innovators derive sufficient benefit simply from developing and using their inventions to motivate them to invest the effort necessary to invent them. Moreover, user innovators often benefit from freely revealing their innovations to others. Trade secrecy and patenting are not central to motivating this inventive activity. This picture of user innovation contrasts sharply with the seller innovator picture which dominates patent policy. In that picture, incentives for inventing, disclosing, and disseminating new technologies arise from the potential for recouping innovative investments through commercial sales. Because user innovators have different incentives, we should consider modifying patent doctrine so as to avoid the social costs of unnecessarily broad protection in contexts in which user innovation predominates. This Article lays out a framework for thinking about patent doctrine in the context of user innovation. It then explores one context in which user innovation plays a significant role-the development of inventions that can be used as research tools. Considering the specific incentives to invent, disclose, and disseminate research tools of different classes of research tool inventors leads to a proposal for a blanket exemption from infringement liability for research use. The Article also proposes an alternative, more modest, double-edged sword exemption, which would excuse noncommercial research use of all patented inventions and all research use of inventions made by non-profit inventors