Sequential acoustic detection of atrazine herbicide and carbofuran insecticide using a single micro-structured gold quartz crystal microbalance

In this work, a cost-effective protocol to fabricate acoustic micro-immunosensors based on a quartz crystal microbalance (QCM) is reported. Specifically, the patterned quartz crystal is prepared via an electron beam evaporation of gold through a commercial transmission electron microscope (TEM) grid as a mask. Two different patterned zones on the crystal electrode surface were functionalized either with the monoclonal anti-carbofuran or with anti-atrazine IgG antibody by using thiol chemistry. Different concentrations of antigens (carbofuran or atrazine) were deposited onto their corresponding antibody modified zones monitoring in situ the specific interaction between antibody and its antigen from both resonant frequency and resistance changes versus time. Two sets of control experiments, including antigen interactions with non-specific antibody and simple antigen deposition onto thiolated-QCM quartz crystal were also investigated. It was found that the proposed methodology allows sequential specific detection of 4.5 μM carbofuran and 4.6 μM atrazine, respectively.