Bruce Banner’s inhibitor in Spider-Man: Brand New Day uses siRNA, or small interfering RNA. The device suppresses his super-powered alter ego, the Hulk, by targeting biological processes involved in his transformation.
Banner becomes an important scientific resource for Peter Parker because Peter’s own powers are evolving uncontrollably. After seeing Banner’s technology, Peter builds an inhibitor to suppress his new abilities while he tries to understand what is happening to him.
siRNA is a real biological mechanism used by cells to regulate gene expression. In laboratory and medical research, designed siRNA molecules can reduce the production of specific proteins. The film uses that scientific concept as fictional superhero technology rather than presenting a real-world Hulk-suppression treatment.