Nanoparticle-based immunoassays for sensitive and early detection of HIV-1 capsid (p24) antigen.

We evaluated the feasibility of using nanoparticle (NP)-based assays for improving detection sensitivity of human immunodeficiency virus type 1 (HIV-1) p24 antigen. One assay that was evaluated is a gold NP-based biobarcode amplification (BCA) assay, which can detect HIV-1 p24 antigen at levels as low as 0.1 pg/mL. The lower limit of detection for an enzyme-linked immunosorbent assay (ELISA) is 10-15 pg/mL. These results demonstrate that the HIV-1 p24 BCA assay offers 100-150-fold enhancement in the detection limit over the traditional colorimetric ELISA. Furthermore, the BCA assay detected HIV-1 infection 3 days earlier than did ELISA in samples from patients who had experienced seroconversion. The other assay that we tested is the europium NP-based immunoassay, which uses europium NPs to replace gold NPs in the BCA assay to further simplify the detection method and decrease the incubation time. For detection of HIV-1 p24, the lower limit of detection for the europium NP-based immunoassay was 0.5 pg/mL. These results indicate that the universal labeling technology based on NPs and its application may provide a rapid and sensitive testing platform for clinical diagnosis and laboratory research.