PCR-like sensitivity for proteins with bio-bar-code amplification.

Extract: The polymerase chain reaction (PCR) made it possible to detect and amplify nucleic acid target sequences of interest when present in extremely dilute quantities. Comparable target detection and signal amplification methods for proteins could dramatically improve medical diagnostics and the developing field of proteomics. In order to improve upon the sensitivity limitations of conventional ELISA assays, researchers turned to oligonucleotide-antibody conjugates where a DNA strand replaced the enzyme as the molecule responsible for the amplification of detection events. The DNA sequence bound to the antibody (Ab) becomes the surrogate for protein detection, and can be amplified with PCR in a process termed immuno-PCR. Although a significant advance in protein detection, this approach and others have several drawbacks: 1) a low ratio of DNA identification sequence to detection Ab, which limits sensitivity; 2) inefficient target capture and slow target binding kinetics because of the heterogeneous nature of the target capture procedure, which increases assay time and decreases assay sensitivity; 3) complex conjugation chemistries that are required to link the Ab and DNA-markers; and 4) they require PCR.