We report a relatively simple electrostatic method for modifying sub-micron size latex spheres with gold nanoparticles (AuNPs) based on layer-by-layer modification of the latex by polyelectrolytes. The AuNP coverages for 343 nm and 501 nm diameter spheres were 4.0 × 1010 + 1.3 × 1010 particles cm-2 and 8.2 × 1010 + 2.7 × 1010 particles cm-2 respectively, which is an increase of one order of magnitude on the previously reported coverage at latex-AuNPs using streptavidin-biotin binding [Kawde, A.N.; Wang, J. Electroanalysis 2004, 16, 101-107]. Due to the fact that the AuNPs used here are also of a larger size (mean diameter = 15.47 + 1.55 nm c.f. 5 nm), this represents an increase of two orders of magnitude in the number of Au atoms delivered per sphere. The spheres were attached to DNA probes specific to E. coli and used to detect probe hybridization by dissolution of the AuNPs, followed by measurement of Au3+ ions by anodic stripping voltammetry (ASV). Use of differential pulse voltammetry for the stripping step, along with optimization of the ASV conditions, enabled a detection limit of 0.5 fM, which is, to the best of our knowledge, equal or lower than previous voltammetric nanoparticle methods for detection of DNA hybridization.