A ruthenium complex served as an ECL tag. Hybridization was induced by exposure of the target ssDNA gold electrode to the solution of ECL probe consisting of complementary ssDNA tagged with ruthenium complex. The detection limit of target ssDNA on a gold nanoparticle modified gold electrode (6.7��10-12 M) is much lower than that on a bare gold electrode (1.2��10-10 M). Sensitivity enhancements of 18-fold were obtained with Au nanoparticle amplification for DNA over their direct immobilization on an electrode.Another possible reason for the enhancement of ECL signals on Au N
Hydrogels have demonstrated their potential as a useful platform for the development of immunoassays [1�C8]. These porous materials can be tailored to possess high surface areas and inter-penetrating networks that can be readily functionalized with receptor ligands for the immobilization of biomolecules.

In addition to the increased surface area, hydrogels have been recognized as substrates capable of preserving the integrity of a protein secondary structure during most immobilization procedures. This is critical in a biomolecule’s ability to bind targeted antigens with high efficiency in order to achieve the highest degree of immunoassay sensitivity. So as researchers continue to investigate the utility of hydrogels and attempt to understand their intricate internal three-dimensional (3-D) porous microstructure, they also recognize its limitless potential for improving biomolecular interactions for the development of highly sensitive sensor systems.Several platforms have been developed using hydrogels as a research tool.

DNA as well as other proteins have been successfully incorporated into hydrogel networks [9�C11] GSK-3 and have demonstrated that these materials can improve hybridization protocols and biosensor detection systems [12]. Hydrogels have provided networks for drug delivery and cell transplantation applications [13] and served as cryoprotectant scaffolds for cellular arrays [14]. The versatility of these porous materials renders them amenable to an array of applications that extend from biomedical to pharmaceutical.Although most hydrogels can be tailored to possess large pores, it remains nonetheless a network that is heterogeneous where ��pockets�� and ��channels�� are of different dimensions. This heterogeneity provides a greater opportunity for proteins to non-specifically adsorb to pores walls.

Non-specific protein interactions as a result of hydrogen bonding, charge interactions, or non-polar interactions [15] can prove quite challenging in many assay systems. Although the inherent characteristics and hydrophilic nature of the hydrogel is beneficial in minimizing non-specific protein adsorption it rarely eliminates the problem. As a result, blocking agents (e.g.