Vertically aligned multi-walled carbon nanotubes based flexible immunosensor for extreme low level detection of multidrug resistant leukemia cells

[Display omitted] •Pattern transfer with high end technique to make it flexible.•Sensing is done by vertically aligned flexible MWCNT electrode.•Lower detection limit- 10 cells mL−1.•Correlations of charge transfer induced Fermi level shift with sensitivity of the order of μeV per molecule. We report an advanced flexible immunosensor for extreme low level detection of multidrug resistant myeloid leukemia cells. The detection mechanism is analyzed in terms of novel nanoscale interactions of target molecules with vertically aligned multi-walled carbon nanotubes (VA-MWNT). The immunosensor is fabricated by transferring VA-MWNTs on a polyethylene terephthalate substrate by hot press technique without losing CNTs’ pristine character. Sensing is performed using doxorubicin treated leukemia K562 cells in varying concentrations from 1.5 × 102 cells mL–1 to 1.5 × 107 cells mL–1 and sensor showed detection limit of 10 cells mL–1. The calibration plot of peak current versus logarithmic concentration of DOX/leukemia K562 cells exhibited good linearity with a regression coefficient of ˜0.98. Sensing mechanism is explained in terms of charge transfer induced Fermi level shift of sub μeV order, causing band bending at the interface of CNT-molecular species; and it is reflected in lowering detection limit of the fabricated sensor. Theoretical analysis is done to correlate Fermi energy shift with sensitivity of the device on cancer cell immobilization. Additionally, the developed immunosensor shows good stability, reproducibility and fast detection vis-à-vis the devices reported so far. The notable advantages of proposed flexible sensor are its durability, chemical and moisture resistance, making it a potentially competitive device for point-of-care diagnostics.