We have developed an immuno-PCR based diagnostic platform which couples detection antibodies to self-assembled, ultra-detectable DNA-avidin nanoparticles stabilized with poly(ethylene glycol) to link DNA amplification to target protein concentration. Electrostatic neutralization and cloaking of the PCR-amplifiable DNA labels by avidin and PEG coating reduces non-specific "stickiness" and enhances assay sensitivity. We further optimized the detectability of the nanoparticles by incorporating four repeats of a unique synthetic DNA PCR target into each nanoparticle. Using human chorionic gonadotropin hormone (hCG) as a model analyte, this platform was able to quantitate the target hCG protein in femtomolar concentrations using only standard laboratory equipment.