Copper UPD as non-specific adsorption barrier in electrochemical displacement immunosensors.

Non-specific adsorption events are responsible to a large extent for the lack of reliability and applicability of electrochemical immunosensors. In the particular case of displacement-based immunosensors, as an approach to achieve reagentless, labelless and easy to use immunosensors, the hindering effect of then non-specific adsorption is amplified when the system presents a low affinity constant between biorecognition element and target. The application of Copper UPD as non-specific adsorption barrier in combination with the use of self-assembled monolayers (SAM) to provide efficient binding of biomolecules to the immunosensor electrode surface is shown to be a very promising mechanism to construct protein resistant surfaces with no harming effects on the electrochemical transducing mechanism. The electrochemical immunodetection of TCA (2,4,6-Trichloroanisole) has been chosen as example for a real case study. A monoclonal antibody to detect the target TCA and an appropriate sub-optimum antigen were used. In addition to a rational strategy for displacement immunosensor development, the decrease of non-specific adsorption phenomena by introducing Copper UPD is reported here. With such strategy an electrochemical displacement immunosensor with a limit of detection of 200ppb and response time of 10min is achieved.

Cadmium uptake by floating macrophytes.

Cd uptake capacity of a group of floating macrophytes (Salvinia herzogii, Pistia stratiotes, Hydromistia stolonifera and Eichhornia crassipes) was determined in outdoors experiments during the lowest temperature period of the year. Although all studied species were highly efficient in the Cd uptake, Pistia stratiotes was selected for further research because of its superior performance and its higher average relative growth rate. Cadmium% removal by Pistia stratiotes was greater in the first 24 h of the experiments (63, 65, 72 and 74% of the added Cd for 1, 2, 4 and 6 mg Cd 1(-1), respectively). After 31 days of growth, Pistia statiotes efficiently removed Cd at the studied concentrations. The macrophyte was able to keep its capacity for Cd removal even though some toxicity symptoms appeared at 4 and 6 mg Cd 1(-1). The greater the initial concentration, the greater Cd bioaccumulation rates. The increase of Cd concentration in plant tissues occurred especially in roots and was linearly related to the quantity of Cd added. Cd sorption by roots is faster than translocation to the plant aerial part and it occurs mainly during the first 24h.