A nanoparticle including an amphiphilic chitosan and a contrast agent is provided. The contrast agent is grafted to the amphiphilic chitosan. The chemical bonding between the amphiphilic chitosan and the contrast agent has a synergistic effect to further improve the contrasting ability of the contrast agent.一種自組裝奈米結構,包括雙性幾丁聚醣以及顯影劑化合物。顯影劑化合物嫁接於雙性幾丁聚醣上。雙性幾丁聚醣與顯影劑化合物之間的化學鍵結具有加乘作用,可進一步提高顯影劑化合物的顯影效果。100‧‧‧自組裝奈米結構102‧‧‧雙性幾丁聚醣104‧‧‧顯影劑化合物