2. Toxicity Assessment of Nanomaterials. The wide range of applications of engineered nanomaterials or nanoparticles increases opportunities for their release into the environment. Much evidence shows that novel nanomaterials are highly toxic to bacteria, aquatic organisms, and mammalian cells, which raises concerns about the unintended biological and ecological impacts. For example, the persistence of nanomaterials may adversely affect beneficial bacteria and disrupt important ecological functions. We perform microbe-based toxicity tests (mostly, bacteria) but also examine mammalian cell lines or aquatic organisms (phytoplankton) in collaboration with partner researchers. Our recent interests are to link the reactive oxygen species (ROS) with the antibacterial activities of nanomaterials and the results would provide fundamental insight into the toxic mechanisms of nanomaterials and the search and development of environmentally benign or functional nanomaterials for antimicrobial applications.

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1.Aquatic Behavior and Physicochemical Processes for Nanomaterials. Nanomaterials or nanoparticles in aquatic environment undergo complex and dynamic processes such as aggregation, disaggregation, dissolution, sorption, photocatalytic reactions, and surface coating. These processes are often interdependent and interrelated, substantially affecting the environmental fate, transport, biological interactions, and ecotoxicity of nanomaterials. In this aspect, our previous work aimed at investigating the kinetics of aggregation, dissolution, sorption and oxygen radical production at different interfaces as well as the biological implications such as toxicity or antibacterial or antiviral activities.

3. Molecular Level Imaging and Characterization. Imaging, quantifying, and characterizing the nanoparticle interactions at cellular, subcellular, and molecular levels will facilitate the applications of nanotechnology such as  biomedical diagnostics and drug delivery, and prevent potential adverse impacts on human health and ecosystems. Dr. Zhang has expertise in manipulating atomic force microscope (AFM) for submicrometer or nanometer scale imaging and surface characteristics measurements on inorganic nanoparticles, microbial cells, proteins, and DNA.