CdSe/CdS/ZnS nanocrystals decorated with Fe3O4 nanoparticles for point-of-care optomagnetic detection of cancer biomarker in serum

Early diagnosis of a progressive cancer disease is currently limited due to lack of adequate point-of-care (PoC) diagnostic tools. PoC diagnosis enables detecting early signs of a disease and pave way to disease prevention. Here, we developed an immuno-optomagnetic quantum dots based PoC assay for early detection of a cancer biomarker, human epidermal growth factor receptor-2 (hErbB2) protein in serum. This assay utilizes immunooptomagnetic quantum dots (MQDs-Ab2) nanoarchitectures with unique orientation comprised of core CdSe/CdS/ZnS QD nanocrystals surrounded by layers of magnetic Fe3O4 nanoparticles (MNPs) and a bioactivated borofloat PoC-chip (Ab1). The MQDs-Ab2 and the PoC-chips were designed to bind same hErbB2 analyte, but both bind with distinct epitopes. First, free hErbB2 protein from serum was captured by MQDs-Ab2 forming immuno-optomagnetic MQDs-Ab2-hErbB2 complex, which was isolated and presented to bioactivated PoCchips. The immuno-optomagnetic signal from chips was directly visualized by naked-eye after exposing chips with a UV-torch and the signal was directly measured within 30 min by computing RGB intensities using a smartphone camera and a colorimeter-app. The immuno-optomagnetic QDs based PoC-chip exhibited the detection range of 620 pg mL(-1) similar to 5 ng mL(-1) hErbB2 protein in serum. The MQDs-Ab2 rendered biospecificty, magnetic and optical functionality to PoC detection and provided advantages of speed, sensitivity, portability and low-cost, which is most desired in resource limited settings. The developed PoC chip assay provided an accurate quantitative cancer biomarker detection with high sensitivity and specificity that required no laboratory equipment and is also potentially applicable to the detection of many other biomarkers.