Amorphous iron nanoparticles: special structural and physicochemical features enable chemical dynamic therapy for tumors.

Abstract

Amorphous metals or alloys, also known as the metallic glasses with a disordered structure on atomic level, have attracted great attentions owing to their special physical properties and extraordinary prosperities [1– 5]. In addition to the excellent plasticity upon heating for easy processing, the absence of grain boundaries leads the bulk metallic glasses (BMGs) to higher strength and better corrosion resistance than conventional metals or alloys, which stimulated widespread researches to hurry their potential as advanced structural materials. However, the severe synthesis conditions, typically the superhigh cooling rate (usually higher than 10 K s) to freeze the molten metal and to suppress the nucleation of crystalline phases, have been being one of the main bottlenecks for the widespread applications of BMGs [6]. Compared with BMGs, nanosized amorphous materials such as amorphous nanoparticles, which combine the advantages of both random arrangement of atoms in amorphous state and nanodimension and are therefore expected to exhibit even more unique and diverse properties, have been rarely explored, most probably due to the difficulties in the successful syntheses of such materials which leaves rooms for researches and developments. Taking amorphous iron nanoparticles (AFe-NPs) as an example, not to mention the possible specificities in electromagnetism such as soft magnetic characteristics and others, it is expected that the randomly arranged iron atoms are active enough to be ionized in mild acidic conditions for on-demand Fe (II) release and to initiate subsequent localized Fenton reaction under the presence of hydrogen peroxide. On the other hand, most solid tumors feature acidic nature (pH = 6.5–6.9) and overproduced hydrogen peroxide, and such a special microenvironment has attracted great interest for the exploration of so-called microenvironment-responsive cancer therapy [7–11]. In fact, acidic microenvironment in tumor has triggered the development of numerous strategies of pHstimuli-responsible controlled drug releases, in which drug is expected to release in acidic tumor but not in neutral normal tissues or blood stream; while cumulative H 2 O 2 in cancer has been exploited to implement specific therapeutic strategies, such as to act as a spontaneous trigger for responsive-drugreleasing chemotherapy or an endogenous O 2 producer for enhanced photodynamic therapy [12–14]. Thus, seemly totally different fields of metallic glasses and cancer therapies find their common points for combination. Amorphous iron nanoparticles: special structural and physicochemical features enable chemical dynamic therapy for tumors