With reference to carbon nanotubes, consider the following statements: 1. They can be used as carriers of drugs and antigens in the human body. 2. They can be made into artificial blood capillaries for an injured part of human body. 3. They can be used in biochemical sensors. 4. Carbon nanotubes are biodegradable. Which of the statements given above are correct?

1. Correct. Carbon nanotubes are used as drug/antigen delivery carriers because they can be functionalized and enter cells.

2. Correct. Carbon nanotubes have been explored in tissue engineering and vascular graft/microtube applications, including making artificial capillary-like structures for damaged tissues.

3. Correct. They are used in biochemical/biosensors due to high conductivity, sensitivity, and large surface area.

4. Correct. Carbon nanotubes can be biodegraded under biological/enzymatic conditions (for example by certain peroxidase enzymes), so the statement is taken as correct.

Hence, all four statements are correct.