BSA-assisted synthesis of ultrasmall gallic acid–Fe(III) coordination polymer nanoparticles for cancer theranostics

Protein-related nanotheranostic agents hold great promise as tools to serve many clinical applications. Proteins such as BSA are used to regulate the synthesis of nondegradable inorganic nanoparticles (NPs). To fully employ the potential of such proteins, a new type of biosafe nanotheranostic agent must be designed to optimize BSA as a biomineralization agent. Here, a straightforward BSA-assisted biomineralization method was developed to prepare gallic acid (GA)–Fe(III) coordination polymer NPs. BSA-coated GA-Fe (GA-Fe@BSA) NPs were ultrasmall (3.5 nm) and showed good biocompatibility, a lower r(2):r(1) ratio (1.06), and strong absorption in the visible near-infrared region. T(1)-weighted magnetic resonance imaging of tumor-bearing mice before and after intratumoral injection with GA-Fe@BSA NPs definitively demonstrated positive change. In a subsequent in vivo study, antitumor activity was precipitated by intratumoral injection of GA-Fe@BSA NPs combined with laser treatment, suggesting excellent outcomes with this treatment method. These results describe a successful protocol in which BSA regulated the synthesis of benign organic polymer NPs. GA-Fe@BSA NPs have the potential to be ideal agents to be used in clinical theranostic nanoplatforms.