• Carbon nanotubes (CNTs) are cylindrical large molecules consisting of a hexagonal arrangement of hybridized carbon atoms, which may by formed by rolling up a single sheet of graphene (single-walled carbon nanotubes, SWCNTs) or by rolling up multiple sheets of graphene (multiwalled carbon nanotubes, MWCNTs).
• Hence structurally, carbon nanotubes (CNTs) can be viewed as wrapped from graphene sheets. Carbon nanotubes were once considered to be resistant to chemical damage due to their rigid and perfect chemical structure, which rendered them immune to biodegradation.
• However, enzymes like peroxidase were found to play an important role in the process of biodegradation of carbon nanotubes. Hence option 4 is correct. NASA has demonstrated the use of carbon nanotube arrays as biosensors. Hence option 3 is correct.
• Carbon nanotubes (CNTs) are characterized by unique chemical and biological properties. CNTs have a large surface area that allows them to attach a wide range of biological substances. In addition, CNTs are able to penetrate through cell membranes, capillaries, and accumulated in cells and tissues.
• It is expected that enabling technology would facilitate the making of nanodevices using these blood -compatible nanomaterials as building blocks for biomedical applications such as artificial implants, including structural tissue replacements, that is, artificial blood vessels, or functional devices such as drug delivery matrixes. Hence statements 1 and 2 are correct.

Source: CSP2020