Fig. 4: In vitro nanoparticle toxicity.

A Schematic diagram of the in vitro induction of acquired platinum resistance. B Baseline cisplatin sensitivity of A2780 and A2780^DDP cell lines. C The IC₅₀ of A2780 and A2780^DDP were 4.71 ± 0.26 and 13.95 ± 1.18 µg/ml, respectively. D Bar graph showing normalized baseline SOD1 mRNA levels (n = 6). E Western blot showing the SOD1 protein levels in A2780 and A2780^DDP cell lines in vivo in Q1 and Q3. F Bar graph showing normalized baseline SOD1 mRNA (n = 3). G Schematic illustration of xenograft tumour sample preparation for immunoblotting and qRT-PCR. H Western blot showing the SOD1 protein levels in A2780 and A2780^DDP cell-derived xenograft tumour tissue samples. I Cisplatin treatment of A2780^DDP cells (n = 6) induced SOD1 mRNA overexpression in a concentration-dependent manner measured by RT-qPCR. J Time-course evaluation SOD1 mRNA induction by GO^PEI treatment in A2780^DDP cells (n = 6) measured by qRT-PCR. K Cytotoxicity of GO, PEI, GO^PEI and GO^PEI-mPEG were determined at the following concentrations: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 30, 35 and 40 µg/mL, respectively. L MTT assay showing relative cell viability after A2780 cells were treated with 9 µg/mL of GO^PEI for 48 h followed by cisplatin treatment at 14 different concentrations (2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 and 28 µg/mL respectively). IC₅₀ values were compared with that of A2780 cells (n = 6). M Volcano plot showing the transcriptional activation of the mitochondrial unfolded protein response by 15 µM cisplatin in A2780 cell line. N, O GO^PEI and GO^PEI-mPEG treatment-induced differential in vitro activation of the UPR^mt in (N) A2780 and (O) A2780^DDP cell lines. P Schematic diagram illustrating UPR^mt activation by cisplatin, graphene and cationic polymers leading to mitochondrial dysfunction and subsequent mito-nuclear signalling.