Noncovalent immobilization site-specific

Not only the components of the sensing layer are important but also the strategies of integration between them and with the primary transducer are of paramount importance. Passive adsorption is one of the simplest and most frequently used immobilization techniques, based mainly on weak noncovalent bindings. However, random protein orientation can lead to the obstruction of functional binding sites and can result in the loss of affinity or activity. Thus, covalent attachment of a protein layer on a chemically functionalized surface produces a more stable layer with correct orientation. This influences sensitivity and specificity of the immunoassay as density of immobilized protein can be better controlled and nonspecific adsorption may be decreased [155]. On the other hand, covalent procedures are usually longer and more tedious and are less justified when disposable surfaces can be used. 

---