3D printed microcell featuring a disposable nanocomposite Sb/Sn immunosensor for quantum dot-based electrochemical determination of adulteration of ewe/goat’s cheese with cow’s milk

This work describes a new type of electrochemical immunosensing device which consists of a 3D printed mini cell integrating two thermoplastic electrodes and a disposable graphite screen-printed working electrode modified with Sb2O5/SnO2. The applicability of the immunodevice to the analysis of complex matrices is demonstrated through the assessment of adulteration of cheese produced from ewe/goat’s milk with cow’s milk. The operation of the device is based on: (i) the development of a competitive immunoassay onto the surface of the screen-printed working electrode using biotinylated anti-bovine k-casein labeled with streptavidin-conjugated CdSe/ZnS quantum dots (QDs) and (ii) the stripping voltammetric detection of Cd(II) released after the acidic dissolution of Cd-based QDs. Determination is carried out at the screen-printed working electrode covered with Sb/Sn nanoparticles formed in-situ by reduction of the embedded precursors (Sb2O5/SnO2) simultaneously with the deposition of Cd on the surface of the working electrode. Under the selected experimental variables, the limit of detection was 0.07 % (v/v) cow’s milk in ewe/goat’s cheese. The synergistic combination of 3D printing, QD labeling and in-situ formation of nanostructured sensing surface, establishes the proposed sensor as an easy-constructed and ultrasensitive immunodetection device with wide scope of applicability to other QDs-based bioassays.