Dendrimer-encapsulated silver nanoparticles as a novel electrochemical label for sensitive immunosensors

This paper reports on the synthesis and characterization of a novel electrochemical label for sensitive electrochemical stripping metalloimmunoassays based on silver dendrimer-encapsulated nanoparticles (NPs). Silver dendrimer nanocomposites (Ag-DNCs) were synthesized from a generation 5–7 (G5–7) hydroxyl-terminated ethylenediamine-core-type (2-carbon core) PAMAM dendrimer. Several fixed ratios of Ag+/dendrimer were prepared with the aim to obtain stable nanocomposites with maximal silver loading in the interior of a polymeric shell. Synthesized Ag-DNCs were characterized by UV–vis spectrophotometry, atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The G7 Ag-DNC synthesized in 2000 molar excess of silver (1/4 ratio of tertiary amine/Ag+) turned out a more suitable candidate for the label development. By combination of the differential pulse voltammetry (DPV) and the anodic stripping analysis (ASV) on a carbon electrode, down to 1.35 × 10+10 of individual Ag-DNCs (LOD = 0.9 pM, 25 ml volume) was detected after the dissolution of silver nanoparticles in a diluted nitric acid. The potential advantages of proposed electrochemical label are discussed.