A Piezoelectric Biosensor as a Direct Affinity Sensor

Conclusions

We have demonstrated the potential of the piezoelectric detector for real-time monitoring of adsorption process and affinity-immunoreactions in liquid phase. Results for h-Ig G adsorption indicates the relation between the surface mass and the frequency shift. The adsorption process does not bind covalently the molecules to the surface. In the case of a stable binding for the receptor to the surface is needed, a covalent immobilization is recommended. A pesticide, the 2,4-D, has been bound to the surface and an affinity reaction between the bound 2,4-D and antibodies anti-2,4-D was performed. The stability of the interaction was evident. A qualitative comparison between two different clones is provided suggesting a possible application of this device to studies of affinity constant in the analysis where a ligand and a receptor are involved. A quantitative evaluation is given for the 2,4-D analysis in tap water. The pesticide could be detected at ppb levels. What characterise the adsorption and the affinity experiments are the analysis time. When the protein adsorption occurs the process requests hours, on the contrary, when the interaction between the antigen and the antibody takes place the decrease in frequency is rapidly evident.