Ultrasensitive IgG quantification using DNA nano-pyramids

In addition to being a repository of genetic information, DNA is a bio-polymer that can be formed into various nanostructures. This profound ability to engineer various moieties has expanded its role from data storage to a structural biomaterial for sensing applications. In this study, we anchored DNA nano-pyramids (DPs) to gold electrodes for the electrochemical sensing of immunoglobulin G (IgG), an important antibody produced in response to infection. The pyramidal DNA structure not only avoids entanglement with neighboring probes through the use of spatially separating pendant probes but also reduces the local overcrowding effect with the overall enhanced packing of targets. The results from electrochemical impedance spectroscopy measurements also show that DP layer has better conductivity, with the hollow structure further facilitating electron transfer and increasing the sensitivity of electrochemical detection. We are able to selectively detect IgG in the presence of other proteins in an analyte solution. The limit of detection was 2.8 pg ml(-1). Our ferrocene-labeled sandwich immunoassay works at 37 degrees C under a neutral pH environment. It also produces stable and reproducible signals even after storage for 1 week at 4 degrees C, further demonstrating the potential of this sensing system for clinical applications.