Development of multiwalled carbon nanotube integrated field eEffect transistor for highly sensitive HIV-1 tat protein biosensor

Human immunodeficiency virus (HIV) has infected almost 35 million people worldwide. Various tests have been developed to detect the presence of HIV during the early stages of the disease in order to reduce the risk of transmission to other humans. The HIV-1 Tat protein is one of the proteins present in HIV that are released abundantly approximately 2 to 4 weeks after infection. Early stage detection of the disease can be achieved by detecting Tat protein in high risk individuals. This mitigates the risk of a HIV pandemic. A back gated field effect transistor (BGFET) has been developed to be a biosensor for the early detection of HIV. Tat protein has been used as the target while split RNA aptamer has been chosen as the detection probe. The binding interactions between split RNA aptamer and HIV-1 Tat protein on a biosensor device was validated using colorimetric assay. The assay successfully demonstrated the interaction occurred between split RNA aptamer and HIV-1 Tat indicated by the changes of gold nanoparticles color from pink to purple. BGFET was made biocompatible by using carbon nanomaterials like multiwalled carbon nanotube (MWCNT) as biomolecules immobilization site. Acid oxidation treatment was conducted to functionalize MWCNT with carboxyl functional groups and subsequently characterized through field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) analysis had profound ~2.91% increment in overall oxygen group and ~1% increment was noticed with a specific carboxyl content owing to C=O and O–C=O bonding. The binding interaction between split RNA aptamer and HIV-1 Tat protein was characterized by Fourier transform infrared (FTIR) binding analysis and electrical quantification of current signal (Ids) over a gate voltage (Vgs). The attainment of sensitivity with aptamer and HIV-1 Tat interaction on the fabricated device was 600 pM. To ensure the genuine interaction of aptamer with HIV-1 Tat, other HIV-1 proteins, Nef and p24 were interacted with aptamer and they displayed the negligible interferences with gate voltage shift of 3.5 mV and 5.7 mV, which shows 4 and 2.5 folds lesser than HIV-1 Tat interaction, respectively.