An amperometric immunoprobe based on multifunctional nanogel for sensitive detection of tumor marker

Nanogel as a multifunctional carrier was used to fabricate immunoprobe. The obtained immunoprobe was applied in a competitive amperometric immunosensor and exhibited an excellent analytical performance for the detection of tumor marker. The nanogel was easily fabricated by irradiation of the mixture of glucose, sodium citrate and sodium alginate by microwave, which exhibits excellent adsorbent ability for multivalence metal ions. The immunoprobe was constructed by functionalizing such uniform nanogels with multivalence metal ions (Cu 2+ as model) as redox species and gold nanoparticles for immobilizing antibody. The signal of Cu 2+ from the nanogel can be directly measured without acid dissolution and pre-concentration, which substantially simplified the detection steps. Besides, the response current can be amplified by glucose because Cu 2+ is an electro-catalyst for the oxidation of glucose. Polyaniline hydrogel with a three dimensional network structure and π–π conjugated structure was used to fabricate immunosensing substrate, which extremely improved the specific surface area and conductivity of the modified electrode. Under optimal conditions, the current changes of square wave voltammetry were used to detect neuron specific enolase (as a model analyte) with a broad linear ranging from 0.01 to 1000 ng mL −1 and a ultralow detection limit of 4.6 pg mL -1 (S/N = 3). This work provides a new strategy for designing multifunctional immunoprobes.