Figure 2: Cell viability study in vitro with 4T1: untreated cells (C), nanoparticle-treated cells (C+N), ERBB2 siRNA-treated cells (C+N+ERBB2), p53 plasmid-treated cells (C+N+p53) and ERBB2 siRNA/p53 plasmidtreated cells (C+N+ERBB2+p53). ERBB2 siRNA and/or p53 plasmid-loaded carbonate apatite particles were generated by exogenous addition of 4 µl of 1 M calcium chloride and ERBB2 siRNA (40 nM) and/or p53 plasmid (100 ng) to 1mL bicarbonate-buffered DMEM (pH7.4), followed by incubation at 37°C for 30min and supplementation with 10% FBS prior to incubation with MCF-7 cells for a consecutive period of 48 h. MTT assay was subsequently performed with the absorbance being taken at wave length of 570 nm with reference to 630 nm.