Ultrasensitive detection of HIV-1 p24 antigen using nanofunctionalized surfaces in a capacitive immunosensor.

The HIV-1 capsid protein, p24 antigen, is of considerable diagnostic interest because following HIV exposure it is detectable several days earlier than host-generated HIV antibodies (which are the target of almost all current tests used in the field) and can be used to design very sensitive assays without the need for PCR. Here, we present an ultrasensitive capacitive immunosensor that is capable of detecting subattogram per milliliter concentrations of p24 antigen, which to our knowledge is the lowest level of detection ever reported. Dilution studies using p24-spiked human plasma samples indicate that the immunosensor is robust against the interfering effects of a complex biological matrix. Moreover, the capacitive immunosensor assay is rapid (<20 min), label-free, and generates data in real-time, with a portable format in development. Additional optimization of the capture agents and/or surface chemistries may further improve performance, highlighting the potential of this platform to serve as a diagnostic tool for early detection of HIV in field settings.