It is notable that in the literature, a similar level of decrease in cancer cell viability and proliferation is reached following treatment with free cetuximab, at doses up to the molar range.46,53,54 Covalently bound Ab-GNPs did not affect viability of 3T3 fibroblast cells, similar to free antibodies (Fig. S4†), indicating the specificity of Ab-GNPs to the cancer cells, and no cytotoxicity towards non-cancerous cells with low EGFR expression. Here, EGFR is linked to cancer.