Gold nanoparticle-assembled capsules and their application as hydrogen peroxide biosensor based on hemoglobin

Gold nanoparticle-assembled capsules (GNACs) with controllable size and tunable morphology were fabricated through a simple two-step mixing procedure. Cationic polyelectrolyte was first induced to self-assemble into spherical aggregates in the presence of multivalent anions. Then, the aggregates served as an effective template for the self-assembly of gold nanoparticles to form size-controllable capsules. By adjusting the quantity of gold nanoparticles, capsules with various morphologies could be obtained. Because of their unique nanoporous features, the capsules with intact shells were further used to load hemoglobin (Hb) for the fabrication of a novel H2O2 biosensor. The results of UV-vis spectroscopy and cyclic voltammetry indicated that the capsules provided a suitable matrix for the immobilization of Hb. Additionally, the resulting biosensor showed a high affinity and good catalytic activity to H2O2. With the advantages of the large surface area, good conductivity and biocompatibility, the GNACs can offer a promising platform for the development of biosensors. Moreover, on the basis of the capsule structure, this material may also be expected to apply in some fields such as drug delivery, medical diagnostics and bio-encapsulation. (C) 2011 Elsevier B.V. All rights reserved.