Mechanisms of bioreactivity of engineered nanoparticles with pulmonary gas exchange barrier

Nanotechnology is a rapidly emerging area of science involving synthesis of engineered nanoparticles that are less that the width of a hair (ie less than 100 nanometres in size). Nanoparticles are processed to form larger products which are not harmful; they are used in engineering, medicine, cosmetics and many other day-to-day products. Nanoparticles have unique properties which make them very attractive and useful in producing new products; however, the properties that make them unique may unfortunately have health effects. We know very little about the hazards or risks associated with exposure to these materials because they are so new. As nanotechnology is moving so fast it is important to establish whether nanoparticles are likely to be toxic or to have unwanted health or environmental effects. If we know this we can protect people and the environment from exposure. We know that when susceptible individuals are exposed to high levels of air pollution which contains nano-sized particles they may develop heart and lung problems and have to go to hospital and might even die. This suggests that inhalation of very small, nanosized engineered particles might cause heart and lung problems, although they have very different properties to air pollution particles. The aim is to discover whether inhaled engineered nanoparticles are harmful and whether they cause breathing or heart problems if they reach the delicate air sacs of the lung. We will use cells that line human lungs and the blood vessels of the lung. These cells will be exposed to the nanoparticles to discover whether the they are toxic and if so, how toxic and why? Do the exposed cells release molecules that might cause inflammation or blood clotting? We want to know what properties of the particles make them dangerous - are they sharp, or do they pass into the cells, or between the cells or are any particular surface chemicals responsible for nanoparticle toxicity? We will watch nanoparticles under a unique microscope to see how they alter cell behaviour. We hope to learn whether inhaled, engineered nanoparticles are likely to be harmful. If they are, is it possible to make particles that are not harmful? This information will allow us to provide guidelines on the possible risks of inhaling engineered nanoparticles, as well as preventing exposure, particularly at work, where levels may be high.

There has been a rapid emergence and expansion of nanotechnology - hundreds of products utilise nanoparticles. Unfortunately, the properties that make nanomaterials so attractive for use eg in electronics, cosmetics, textiles and medicine may have negative health effects. There are serious, urgent concerns that research on possible toxicity and risk of nano- sized materials to human health is insufficient compared to their current rate of production and use; recent reports describe the situation as urgent. Epidemiological studies of particulate air pollution suggest that inhalation of high levels of nano-sized particles causes increased cardiorespiratory morbidity and mortality, particularly in those with existing disease. This may be because the alveolar units are easily accessible by inhaled nano-sized particles ( 100nm), and delivery of large numbers (but low mass) of nanosized particles, with a large reactive surface area, to the alveolar epithelial-endothelial barrier of the lung may elicit pulmonary inflammation, release of pro-thrombotic factors and facilitate particle translocation into the vasculature. We hypothesise that the degree of bioreactivity and translocation of inhaled nanoparticles at the alveolar epithelial-endothelial blood-gas barrier depends on the physicochemical properties of the particles and nature/response of the target cell. In this cross-disciplinary study, materials scientists, a lung cell biologist, a cardiovascular cell biologist and biophysicist will collaborate to address this hypothesis. Materials scientists will synthesise and fully characterise a series of designer nanoparticles initially using silver and titanium dioxide, as well as carbon nanotubes. These particles have been chosen because their production and use is increasing fast; other particles may be used depending on the early findings. The chemists can strictly control nanoparticle synthesis and functionalisation for in vitro studies. Primary human pulmonary alveolar epithelial cells, capillary endothelial cells as well as monocyte-derived macrophages and dendritic cells will be exposed to the particles in both monoculture and co-culture to represent the alveolar-endothelial membrane in vivo. Effects will be assessed using conventional toxicology as well as determining more subtle molecular-biochemical changes, mechanisms of particle internalisation and intracellular localisation. Living cells will be examined at the level of the electron microscope by scanning ion conductance microscopy and scanning surface confocal microscopy to discover the exact features controlling particle uptake and how particles might affect the integrity of the epithelial-endothelial barrier. Any effects of test particles will be related to their physicochemistry and functionalisation to establish possible patterns or trends that predict reactivity or non-reactivity which will help in determining risk factors.