Moreover, the sensor platform not only detected Cu2+ in tap and lake water samples (recoveries: 98.7–103%) but also in HeLa and cisplatin-resistant tumor cells (less uptake of Cu2+ in the resistant tumor cells compared to tumor (HeLa) cells due to the down regulation of human copper transporter-1 expression).259 The visible light-induced photoelectrochemical (PEC) detection of Cu2+ using a ternary CdS/AuNPs/GQDs@ITO electrode system is also beneficial for good sensitivity (Table 4). Here, SLC31A1 is linked to neoplasm.