Physical Mechanisms of Detection

A better understanding of the physical mechanisms involved in the field-effect detection of DNA is fundamental in the development of reliable DNA microarrays based on FETs. Several aspects play a role in the detection mechanism. Counterion condensation theory can be used to evaluate the effective charge density of the DNA layer in contact with an electrol3d e, which partly screens its charge, its dependence on the ionic strength of the electrolyte, and the reduction of the charge fraction observed upon hybridization. Mathematical models have been used to describe the observed shifts in the I-V curves of the field-effect transistors. 

The immobilization of the nucleic acid probe is crucial in determining the performance of the biosensor. To achieve high sensitivity and selectivity, the hybridization efficiency must be maximized and the non-specific adsorption minimized. Immobilization should produce a stable layer of well-defined probe orientation, readily accessible to the target. There are a wide variety of immobilization methods, depending on the transducer surface and application. For 

The net charge density p x) is related to the potential by the Poisson equation 

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