Preparation of Fetal Bovine Serum–Copper Phosphate Hybrid Particles under Cell Culture Conditions for Cancer Cell Treatment

[Image: see text] Fetal bovine serum (FBS) particles, which mainly consist of bovine serum albumin, have the potential for biological and medical applications as drug carriers. The coacervation of albumin is a common technique for preparing albumin-based particles. The replacement of salt with novel metal salts such as Cu is an affordable way to embed the metal ion in the albumin-based particles. Further, increased Cu distribution is prevalent in many cancers. Here, we prepared adhesive cell-like FBS–copper phosphate hybrid particles [FBS-Cu(3)(PO(4))(2)], which exhibited toxicity toward cancer cells, with a narrow size distribution under cell culture conditions for preventing tumor progression. FBS-Cu(3)(PO(4))(2) showed peroxidase-like activity. In addition, FBS-Cu(3)(PO(4))(2) was successfully loaded with rhodamine B and conjugated with fluorescein isothiocyanate as models of drugs by coincubation. Thus, we designed a simple preparation method for optimizing FBS-Cu(3)(PO(4))(2) synthesis under cell culture conditions. FBS-Cu(3)(PO(4))(2) has significant potential as an efficient reactive oxygen species generator and drug-delivery agent against cancer cells. Furthermore, the RhoB-loaded FBS-Cu(3)(PO(4))(2) successfully interacted with 4T1 mouse mammary tumor cells and were confirmed to exhibit toxicity.