There is provided a nanocomplex having a core-shell structure. The shell of the nanocomplex comprises a functionalized hyaluronic acid while the core of the nanocomplex comprises a flavonoid encapsulating a metal-containing compound. Preferably, the flavonoid is epigallocatechin gallate (EGCG) and the hyaluronic acid is thiol-functionalized and subsequently conjugated to the flavonoid. There is also provided a method of forming the nanocomplex, a pharmaceutical composition comprising the nanocomplex, medical uses of the nanocomplex and a method of treating a patient, preferably with cancer using the nanocomplex.