An ultrasensitive aptamer biosensor for the detection of codeine based on a Au nanoparticle/polyamidoamine dendrimer-modified screen-printed carbon electrode

This paper reports a novel aptamer biosensor for the ultrasensitive detection of codeine in aqueous solutions by the special interactions between codeine-binding aptamers. Polyamidoamine dendrimers (PAMAM) were used to absorb gold nanoparticles (AuNPs) and modify the surface of screen-printed carbon electrodes (SPCEs). The codeine aptamer was immobilized on the PAMAM/glutaraldehyde (GA)/chitosan (CHIT)-modified electrode through Au-SH affinity. The specific combination between the aptamer and codeine can obstruct the electron transfer of electrochemical probe K3Fe(CN)(6)/K4Fe(CN)(6), which can be used to detect codeine. The linear range covered from 1 x 10(-12) mol L-1 to 1 x 10(-7) mol L-1, and the detection limit was 3 x 10(-13) mol L-1. The new aptamer biosensor is sensitive and selective enough to detect codeine directly in blood serum and other aqueous solutions. Compared with other conventional methods, it has several advantages, such as a lower detection limit, a broader detection range and a fast detection process.