Single wall carbon nanotube electrode system capable of quantitative detection of CD4⁺ T cells

Development of CNT-based CD4⁺ T cell imunosensors remains in its infancy due to the poor immobilization efficiency, lack of reproducibility, and difficulty in providing linear quantification. Here, we developed a fully-integrated single wall carbon nanotube (SWCNT)-based immunosensor capable of selective capture and linear quantification of CD4⁺ T cells with greater dynamic range. By employing repeated two-step oxygen (O₂) plasma treatment processes with 35 days of recovery periods, we achieved the enhanced functionalization of the CNT surface and the removal of the byproduct of spray-coated SWCNTs that hinders charge transfer and stable CD4⁺ T cell sensing. As a result, a linear electrochemical signal was generated in direct proportion to the bound cells. The slope of a SWCNT electrode in a target concentration range (10²~10⁶cells/mL) was 4.55×10^-2μA per concentration decade, with the lowest detection limit of 1×10²cells/mL. Since the reduced number of CD4⁺ T cell counts in patients' peripheral blood corresponds to the progression of HIV disease, our CD4⁺ T cell-immunosensor provides a simple and low-cost platform which can fulfill the requirement for the development of point-of-care (POC) diagnostic technologies for human immunodeficiency virus (HIV) patients in resource-limited countries.