Ultrasensitive chemiluminescence biosensors using nucleic acid-functionalized silver–cysteine nanowires as signal amplifying labels

Abstract

Ultrasensitive chemiluminescence (CL) sensors for biomolecules (DNA and proteins) have been developed by adopting DNA-functionalized silver–cysteine hybrid nanowires (p-SCNWs) as signal amplifying labels. The sensing is established from a sandwich-type DNA hybridization, where the target DNA strands are initially hybridized with the capture DNA located at paramagnetic microspheres (PMs) and subsequently hybridized with p-SCNWs functionalized with the signal DNA probe. After magnetic separation, p-SCNWs on the hybrids were completely decomposed with HNO₃ to release numerous silver ions. The powerful catalysis of silver ions toward the redox reaction of K₂S₂O₈–Mn²⁺–H₃PO₄ causes the generation of KMnO₄ that is capable of oxidizing luminol at high pH, triggering an amplified chemiluminescent signal emission. The sensing combines the extraordinary sensitivity of the catalytic chemiluminescence technology and the amplifying strategy via releasing large quantities of silver ions as the catalyst from each hybrid, enabling the assay of target DNA strands at a concentration as low as 0.34 fM. The CL signals associated with single-base pair mismatched DNA strands and non-complementary DNA strands are able to be discriminated well from the CL signal related to the complementary DNA hybridization. Likewise, the combination of p-SCNWs functionalized with an aptamer and PMs/aptamer/thrombin complex allowed the chemiluminescence sensing of thrombin with a low limit of detection corresponding to 0.17 pM.