Distance layer

Figure 18. Spectral response of a SEA-chip with increasing distance layer.

Another way to use the technique is to fix the colloid onto the distance layer s surface. If the height of distance layer itself is changed specifically via. an enzymatic assay shrinking or swelling the distance layer, for example, a color shift is observed. By this, the presence of an enzyme substrate or a reactive chemical is transduced by the system into an optical signal. The effect of moderate to high analyte concentrations can be observed with the naked eye. Applications and details of this technique are discussed below. 

To attach (mostly covalently) biomolecules onto the distance layer s surface a chemical activation is needed. One way to achieve that activation is the etching of... 

For medical application ion variations were established using parameters and buffer systems comparable to the human blood. Variations of chloride induced within the pathological concentration could be monitored, whereby no or minor pH-induced changes were observed at blood-pH. Therefore ion effects could be well separated from pH effects. To prove the applicability of the sensor, more than 500 measurement cycles were performed, whereby the reversibility of the polyvinylpyrrolidone distance layer was fully sustained. 

As discussed above biochips based on metal particles layers are among the best in enhancing fluorescence. The REF -chip is a slide with a coating of designed metal nanoparticles and an overcoat of a transparent inert non-metal distance layer and topmost an array of biorecognitive components, which do bind the fluorophores in the proper distance during an assay. 

The biorecognitive components are arrayed and bound onto the chips distance layer surface using standard arrayers, for the binding process practically all immobili tion methods can be used, like silane or carbodiimide chemistry. 

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