What does the term 'toxic' refer to?

The term 'toxic' specifically refers to substances that can cause harm to living cells. In the context of nanotechnology, understanding toxicity is crucial because nanoparticles can interact with biological systems in unique ways. Some nanoparticles may lead to adverse effects such as cellular damage, inflammation, or even genotoxicity, depending on their composition, size, shape, and surface properties. This aspect of toxicity is particularly important when evaluating the safety and potential risks associated with nanomaterials in various applications, including medicine, environmental science, and consumer products. The implications of toxicity highlight the need for rigorous testing and assessment protocols to ensure that nanomaterials are safe for use in their intended applications.

The other choices describe different concepts unrelated to the definition of 'toxic.' Imaging at atomic levels pertains to characterization techniques rather than toxicity; self-repairing materials refer to innovative material properties; and nanoscale sensors are devices that rely on nanoscale phenomena for detection purposes.