Anti-CD28 nano antibody as well as preparation method and application thereof

The invention belongs to the technical field of molecular biology, and particularly relates to an anti-CD28 nano antibody as well as a preparation method and application thereof. According to the anti-CD28 nano antibody provided by the invention, the amino acid sequence is one of SEQ ID NO. 9 to SEQ ID NO. 15. The preparation method comprises the following steps: constructing a CD28 antigen to immunize alpaca, performing phage library construction on the immunized alpaca PBMC, screening the phage library, and selecting a correct sequence for construction, expression and purification; and finally obtaining the anti-CD28 nano antibody through cell function detection and screening. The nano antibody provided by the invention has specific recognition and binding capacity to CD28, and has the advantages of strong specificity, high sensitivity and the like; meanwhile, the development and production cost of the CD28 antibody is effectively reduced, and the antibody expression time is shortened. 本发明属于分子生物学技术领域，具体涉及一种