Glycan-Evoked Silver Deposition for Highly Sensitive Electrochemical Assay of Anti-dsDNA Antibodies.

Anti-dsDNA antibodies are of great value in the diagnosis of systemic lupus erythematosus (SLE). Here, we report the development of an amplification-free electrochemical method for the signal-on assay of anti-dsDNA antibodies at low abundance levels, taking advantage of the silver deposition evoked by the target's glycan chains. Briefly, the method involves (i) the capture of anti-dsDNA antibodies by the double-stranded DNA (dsDNA) recognition probes, (ii) the cleavage of the diol sites in glycan chains into aldehyde groups by periodate oxidation, (iii) the reduction of silver ions into the metallic deposits, and (iv) Ag/AgX solid-state voltammetric stripping analysis. As each anti-dsDNA antibody has two N-linked biantennary glycan chains, the capture of an anti-dsDNA antibody can bring about the reduction of tens of silver ions into metallic silver. Thus, the glycan-evoked silver deposition can enable an amplification-free assay of anti-dsDNA antibodies with high sensitivity. Under optimal conditions, the method permitted the signal-on assay of anti-dsDNA antibodies down to 0.13 IU/mL (∼31.2 ng/mL), with the assay time as short as ∼69 min (from sample addition to signal readout). Moreover, it can selectively discriminate anti-dsDNA antibodies from other glycoproteins, and the voltammetric responses toward the assay of serum samples from patients with SLE had a good quantitative correlation with the clinical chemiluminescent immunoassay. By virtue of the simple operation, low cost, mild reaction conditions, and rapid readout, the glycan-evoked silver deposition shows good promise in the point-of-care electrochemical assay of anti-dsDNA antibodies at low abundance levels.