Amplified protein detection and identification through DNA-conjugated M13 bacteriophage

Sensitive protein detection and accurate identification continues to be in great demand for disease screening in clinical and laboratory settings. For these diagnostics to be of clinical value, it is necessary to develop sensors that have high sensitivity but favorable cost-to-benefit ratios. However, many of these sensing platforms are thermally unstable or require significant materials synthesis, engineering, or fabrication. Recently, we demonstrated that naturally occurring M13 bacteriophage can serve as biological scaffolds for engineering protein diagnostics. These viruses have five copies of the pIII protein, which can bind specifically to target antigens, and thousands of pVIII coat proteins, which can be genetically or chemically modified to react with signal-producing materials, such as plasmon-shifting gold nanoparticles (Au NPs). In this report, we show that DNA-conjugated M13 bacteriophage can act as inexpensive protein sensors that can rapidly induce a color change in the presence of a target protein yet also offer the ability to identify the detected antigen in a separate step. Many copies of a specific DNA oligonucleotide were appended to each virus to create phage-DNA conjugates that can hybridize with DNA-conjugated gold nanoparticles. In the case of a colorimetric positive result, the identity of the antigen can also be easily determined by using a DNA microarray. This saves precious resources by establishing a rapid, quantitative method to first screen for the presence of antigen followed by a highly specific typing assay if necessary.