Abstract
Hydrogel-functionalized surface-based transducers demonstrate fluid-like kinetics, non-fouling properties, and superior biocompatibility. The integration of such properties of three-dimensional (3D) micro- or macrostructure of hydrogels into a mesoporous platform provides a favorable moiety for incorporating biomolecule for adsorption or hybridization with a capture agent. Herein, we report a novel kappa-carrageenan hydrogel-coated mesoporous gold (Au) electrode (abbreviated as MPGE/gel) for chronocoulometric (CC) detection of microRNA (miRNA). The kappa-carrageenan gel provides a 3D porous network on Au electrode surface to enable higher adsorption of target miRNA for CC interrogation of miRNA in presence of a redox molecule-ruthenium hexaammine (III) chloride ([Ru(NH3)(6)](3+), RuHex). Magnetically isolated and purified target miR-9-2 is adsorbed onto the MPGE via Au-RNA affinity interaction through the porous 3D network of the gel followed by the CC detection. The enhanced miRNA adsorption and electrocatalytic activity of MPGE/gel provide attomolar (50 aM) level of detection of miRNA with a dynamic range from 100pM to 10 aM. The good reproducibility (% RSD <= 5%, for n = 3) and high specificity of the developed biosensor demonstrates its excellent translational potential toward developing precisely controlled sensing devices for current clinical needs.