Figure 4. Rapid and ultrasensitive detection of DSG3 in human HNSCC samples using nanosensors.

A. Scheme used for the ultrasensitive detection by the microfluidic immunoarray showing a single sensor in the array with capture DSG3 antibodies attached. Proteins are captured off-line on Ab₂-magnetic bead (MB)-HRP bioconjugates, and after magnetic separation and washes, the MBs are injected into the immunoarray containing 8 sensors. A single immunoarray sensor is depicted. Following incubation, amperometric signals are generated by applying −0.3 V vs Ag/AgCl to the sensors by injecting a mixture of HRP-activator H₂O₂ and mediator hydroquinone (HQ). B. Varying recombinant DSG3 protein concentrations were used to generate a calibration plot. The sensitivity of DSG3 sensor using recombinant protein was 5646 nA mL [fg protein]⁻¹ cm⁻². C. Protein extracts of primary human oral squamous carcinomas (T 1–4) made with RIPA buffer were processed for detection of DSG3. High DSG3 levels were found to be present in all the samples, and this was confirmed by Western blot analysis of the same extracts for DSG3 (D). Tubulin was used as loading control.