Abstract

Herein, biomodification-free Pt nanoparticles (Pt NPs) were directly employed to construct new single-particle collision electrochemical biosensors, which were based on rational control of sulfhydryl group onto the magnetic beads (MBs) surface for Pt NPs capture. As proof of concept, human immunodeficiency virus DNA (HIV-DNA) was chosen as a model target. The hairpin-like DNA probes were conjugated onto the MBs and the sulfhydryl groups labeled at the end of hairpins were confined onto the MBs. The target recognition induced the exposure of the caged sulfhydryl groups for efficient capture of Pt NPs and polymerase-powered target recycling contributed for signal amplification. After magnetic separation, the amount of freely diffusing Pt NPs in solution for electrocatalytic hydrazine oxidation decreased, resulting in target-dependent collision frequency change. With the developed sensing mode, the sensitive detection of target DNA with a low detection limit of 0.13?pM could be achieved. It also demonstrated a good detection selectivity toward other nucleotide sequences and could be applied for target detection in serum system. An extended application of current collision-based sensing mode for protein kinase (PKA) activity was also proposed, which was based on PKA-catalyzed peptide phosphorylation to introduce new sulfhydryl groups onto MBs for Pt NPs capture. By monitoring the changes in the collision of Pt NPs, the activity of PKA and its inhibitor were well determined. Thus, this work provides new avenue toward the development of single-particle collision-based biosensors for highly sensitive and accurate bioanalysis by integrating specific biorecognition and/or amplification process and biomodification-free nanoparticles.